~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/workqueue.c

Version: ~ [ linux-4.18 ] ~ [ linux-4.17.14 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.62 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.119 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.147 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.118 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.57 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.27.62 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~ [ linux-next-20180810 ] ~ [ linux-next-20180813 ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * kernel/workqueue.c - generic async execution with shared worker pool
  3  *
  4  * Copyright (C) 2002           Ingo Molnar
  5  *
  6  *   Derived from the taskqueue/keventd code by:
  7  *     David Woodhouse <dwmw2@infradead.org>
  8  *     Andrew Morton
  9  *     Kai Petzke <wpp@marie.physik.tu-berlin.de>
 10  *     Theodore Ts'o <tytso@mit.edu>
 11  *
 12  * Made to use alloc_percpu by Christoph Lameter.
 13  *
 14  * Copyright (C) 2010           SUSE Linux Products GmbH
 15  * Copyright (C) 2010           Tejun Heo <tj@kernel.org>
 16  *
 17  * This is the generic async execution mechanism.  Work items as are
 18  * executed in process context.  The worker pool is shared and
 19  * automatically managed.  There are two worker pools for each CPU (one for
 20  * normal work items and the other for high priority ones) and some extra
 21  * pools for workqueues which are not bound to any specific CPU - the
 22  * number of these backing pools is dynamic.
 23  *
 24  * Please read Documentation/core-api/workqueue.rst for details.
 25  */
 26 
 27 #include <linux/export.h>
 28 #include <linux/kernel.h>
 29 #include <linux/sched.h>
 30 #include <linux/init.h>
 31 #include <linux/signal.h>
 32 #include <linux/completion.h>
 33 #include <linux/workqueue.h>
 34 #include <linux/slab.h>
 35 #include <linux/cpu.h>
 36 #include <linux/notifier.h>
 37 #include <linux/kthread.h>
 38 #include <linux/hardirq.h>
 39 #include <linux/mempolicy.h>
 40 #include <linux/freezer.h>
 41 #include <linux/debug_locks.h>
 42 #include <linux/lockdep.h>
 43 #include <linux/idr.h>
 44 #include <linux/jhash.h>
 45 #include <linux/hashtable.h>
 46 #include <linux/rculist.h>
 47 #include <linux/nodemask.h>
 48 #include <linux/moduleparam.h>
 49 #include <linux/uaccess.h>
 50 #include <linux/sched/isolation.h>
 51 #include <linux/nmi.h>
 52 
 53 #include "workqueue_internal.h"
 54 
 55 enum {
 56         /*
 57          * worker_pool flags
 58          *
 59          * A bound pool is either associated or disassociated with its CPU.
 60          * While associated (!DISASSOCIATED), all workers are bound to the
 61          * CPU and none has %WORKER_UNBOUND set and concurrency management
 62          * is in effect.
 63          *
 64          * While DISASSOCIATED, the cpu may be offline and all workers have
 65          * %WORKER_UNBOUND set and concurrency management disabled, and may
 66          * be executing on any CPU.  The pool behaves as an unbound one.
 67          *
 68          * Note that DISASSOCIATED should be flipped only while holding
 69          * wq_pool_attach_mutex to avoid changing binding state while
 70          * worker_attach_to_pool() is in progress.
 71          */
 72         POOL_MANAGER_ACTIVE     = 1 << 0,       /* being managed */
 73         POOL_DISASSOCIATED      = 1 << 2,       /* cpu can't serve workers */
 74 
 75         /* worker flags */
 76         WORKER_DIE              = 1 << 1,       /* die die die */
 77         WORKER_IDLE             = 1 << 2,       /* is idle */
 78         WORKER_PREP             = 1 << 3,       /* preparing to run works */
 79         WORKER_CPU_INTENSIVE    = 1 << 6,       /* cpu intensive */
 80         WORKER_UNBOUND          = 1 << 7,       /* worker is unbound */
 81         WORKER_REBOUND          = 1 << 8,       /* worker was rebound */
 82 
 83         WORKER_NOT_RUNNING      = WORKER_PREP | WORKER_CPU_INTENSIVE |
 84                                   WORKER_UNBOUND | WORKER_REBOUND,
 85 
 86         NR_STD_WORKER_POOLS     = 2,            /* # standard pools per cpu */
 87 
 88         UNBOUND_POOL_HASH_ORDER = 6,            /* hashed by pool->attrs */
 89         BUSY_WORKER_HASH_ORDER  = 6,            /* 64 pointers */
 90 
 91         MAX_IDLE_WORKERS_RATIO  = 4,            /* 1/4 of busy can be idle */
 92         IDLE_WORKER_TIMEOUT     = 300 * HZ,     /* keep idle ones for 5 mins */
 93 
 94         MAYDAY_INITIAL_TIMEOUT  = HZ / 100 >= 2 ? HZ / 100 : 2,
 95                                                 /* call for help after 10ms
 96                                                    (min two ticks) */
 97         MAYDAY_INTERVAL         = HZ / 10,      /* and then every 100ms */
 98         CREATE_COOLDOWN         = HZ,           /* time to breath after fail */
 99 
100         /*
101          * Rescue workers are used only on emergencies and shared by
102          * all cpus.  Give MIN_NICE.
103          */
104         RESCUER_NICE_LEVEL      = MIN_NICE,
105         HIGHPRI_NICE_LEVEL      = MIN_NICE,
106 
107         WQ_NAME_LEN             = 24,
108 };
109 
110 /*
111  * Structure fields follow one of the following exclusion rules.
112  *
113  * I: Modifiable by initialization/destruction paths and read-only for
114  *    everyone else.
115  *
116  * P: Preemption protected.  Disabling preemption is enough and should
117  *    only be modified and accessed from the local cpu.
118  *
119  * L: pool->lock protected.  Access with pool->lock held.
120  *
121  * X: During normal operation, modification requires pool->lock and should
122  *    be done only from local cpu.  Either disabling preemption on local
123  *    cpu or grabbing pool->lock is enough for read access.  If
124  *    POOL_DISASSOCIATED is set, it's identical to L.
125  *
126  * A: wq_pool_attach_mutex protected.
127  *
128  * PL: wq_pool_mutex protected.
129  *
130  * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.
131  *
132  * PW: wq_pool_mutex and wq->mutex protected for writes.  Either for reads.
133  *
134  * PWR: wq_pool_mutex and wq->mutex protected for writes.  Either or
135  *      sched-RCU for reads.
136  *
137  * WQ: wq->mutex protected.
138  *
139  * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.
140  *
141  * MD: wq_mayday_lock protected.
142  */
143 
144 /* struct worker is defined in workqueue_internal.h */
145 
146 struct worker_pool {
147         spinlock_t              lock;           /* the pool lock */
148         int                     cpu;            /* I: the associated cpu */
149         int                     node;           /* I: the associated node ID */
150         int                     id;             /* I: pool ID */
151         unsigned int            flags;          /* X: flags */
152 
153         unsigned long           watchdog_ts;    /* L: watchdog timestamp */
154 
155         struct list_head        worklist;       /* L: list of pending works */
156 
157         int                     nr_workers;     /* L: total number of workers */
158         int                     nr_idle;        /* L: currently idle workers */
159 
160         struct list_head        idle_list;      /* X: list of idle workers */
161         struct timer_list       idle_timer;     /* L: worker idle timeout */
162         struct timer_list       mayday_timer;   /* L: SOS timer for workers */
163 
164         /* a workers is either on busy_hash or idle_list, or the manager */
165         DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
166                                                 /* L: hash of busy workers */
167 
168         struct worker           *manager;       /* L: purely informational */
169         struct list_head        workers;        /* A: attached workers */
170         struct completion       *detach_completion; /* all workers detached */
171 
172         struct ida              worker_ida;     /* worker IDs for task name */
173 
174         struct workqueue_attrs  *attrs;         /* I: worker attributes */
175         struct hlist_node       hash_node;      /* PL: unbound_pool_hash node */
176         int                     refcnt;         /* PL: refcnt for unbound pools */
177 
178         /*
179          * The current concurrency level.  As it's likely to be accessed
180          * from other CPUs during try_to_wake_up(), put it in a separate
181          * cacheline.
182          */
183         atomic_t                nr_running ____cacheline_aligned_in_smp;
184 
185         /*
186          * Destruction of pool is sched-RCU protected to allow dereferences
187          * from get_work_pool().
188          */
189         struct rcu_head         rcu;
190 } ____cacheline_aligned_in_smp;
191 
192 /*
193  * The per-pool workqueue.  While queued, the lower WORK_STRUCT_FLAG_BITS
194  * of work_struct->data are used for flags and the remaining high bits
195  * point to the pwq; thus, pwqs need to be aligned at two's power of the
196  * number of flag bits.
197  */
198 struct pool_workqueue {
199         struct worker_pool      *pool;          /* I: the associated pool */
200         struct workqueue_struct *wq;            /* I: the owning workqueue */
201         int                     work_color;     /* L: current color */
202         int                     flush_color;    /* L: flushing color */
203         int                     refcnt;         /* L: reference count */
204         int                     nr_in_flight[WORK_NR_COLORS];
205                                                 /* L: nr of in_flight works */
206         int                     nr_active;      /* L: nr of active works */
207         int                     max_active;     /* L: max active works */
208         struct list_head        delayed_works;  /* L: delayed works */
209         struct list_head        pwqs_node;      /* WR: node on wq->pwqs */
210         struct list_head        mayday_node;    /* MD: node on wq->maydays */
211 
212         /*
213          * Release of unbound pwq is punted to system_wq.  See put_pwq()
214          * and pwq_unbound_release_workfn() for details.  pool_workqueue
215          * itself is also sched-RCU protected so that the first pwq can be
216          * determined without grabbing wq->mutex.
217          */
218         struct work_struct      unbound_release_work;
219         struct rcu_head         rcu;
220 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
221 
222 /*
223  * Structure used to wait for workqueue flush.
224  */
225 struct wq_flusher {
226         struct list_head        list;           /* WQ: list of flushers */
227         int                     flush_color;    /* WQ: flush color waiting for */
228         struct completion       done;           /* flush completion */
229 };
230 
231 struct wq_device;
232 
233 /*
234  * The externally visible workqueue.  It relays the issued work items to
235  * the appropriate worker_pool through its pool_workqueues.
236  */
237 struct workqueue_struct {
238         struct list_head        pwqs;           /* WR: all pwqs of this wq */
239         struct list_head        list;           /* PR: list of all workqueues */
240 
241         struct mutex            mutex;          /* protects this wq */
242         int                     work_color;     /* WQ: current work color */
243         int                     flush_color;    /* WQ: current flush color */
244         atomic_t                nr_pwqs_to_flush; /* flush in progress */
245         struct wq_flusher       *first_flusher; /* WQ: first flusher */
246         struct list_head        flusher_queue;  /* WQ: flush waiters */
247         struct list_head        flusher_overflow; /* WQ: flush overflow list */
248 
249         struct list_head        maydays;        /* MD: pwqs requesting rescue */
250         struct worker           *rescuer;       /* I: rescue worker */
251 
252         int                     nr_drainers;    /* WQ: drain in progress */
253         int                     saved_max_active; /* WQ: saved pwq max_active */
254 
255         struct workqueue_attrs  *unbound_attrs; /* PW: only for unbound wqs */
256         struct pool_workqueue   *dfl_pwq;       /* PW: only for unbound wqs */
257 
258 #ifdef CONFIG_SYSFS
259         struct wq_device        *wq_dev;        /* I: for sysfs interface */
260 #endif
261 #ifdef CONFIG_LOCKDEP
262         struct lockdep_map      lockdep_map;
263 #endif
264         char                    name[WQ_NAME_LEN]; /* I: workqueue name */
265 
266         /*
267          * Destruction of workqueue_struct is sched-RCU protected to allow
268          * walking the workqueues list without grabbing wq_pool_mutex.
269          * This is used to dump all workqueues from sysrq.
270          */
271         struct rcu_head         rcu;
272 
273         /* hot fields used during command issue, aligned to cacheline */
274         unsigned int            flags ____cacheline_aligned; /* WQ: WQ_* flags */
275         struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
276         struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
277 };
278 
279 static struct kmem_cache *pwq_cache;
280 
281 static cpumask_var_t *wq_numa_possible_cpumask;
282                                         /* possible CPUs of each node */
283 
284 static bool wq_disable_numa;
285 module_param_named(disable_numa, wq_disable_numa, bool, 0444);
286 
287 /* see the comment above the definition of WQ_POWER_EFFICIENT */
288 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
289 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
290 
291 static bool wq_online;                  /* can kworkers be created yet? */
292 
293 static bool wq_numa_enabled;            /* unbound NUMA affinity enabled */
294 
295 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
296 static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
297 
298 static DEFINE_MUTEX(wq_pool_mutex);     /* protects pools and workqueues list */
299 static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
300 static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
301 static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
302 
303 static LIST_HEAD(workqueues);           /* PR: list of all workqueues */
304 static bool workqueue_freezing;         /* PL: have wqs started freezing? */
305 
306 /* PL: allowable cpus for unbound wqs and work items */
307 static cpumask_var_t wq_unbound_cpumask;
308 
309 /* CPU where unbound work was last round robin scheduled from this CPU */
310 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
311 
312 /*
313  * Local execution of unbound work items is no longer guaranteed.  The
314  * following always forces round-robin CPU selection on unbound work items
315  * to uncover usages which depend on it.
316  */
317 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
318 static bool wq_debug_force_rr_cpu = true;
319 #else
320 static bool wq_debug_force_rr_cpu = false;
321 #endif
322 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
323 
324 /* the per-cpu worker pools */
325 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
326 
327 static DEFINE_IDR(worker_pool_idr);     /* PR: idr of all pools */
328 
329 /* PL: hash of all unbound pools keyed by pool->attrs */
330 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
331 
332 /* I: attributes used when instantiating standard unbound pools on demand */
333 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
334 
335 /* I: attributes used when instantiating ordered pools on demand */
336 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
337 
338 struct workqueue_struct *system_wq __read_mostly;
339 EXPORT_SYMBOL(system_wq);
340 struct workqueue_struct *system_highpri_wq __read_mostly;
341 EXPORT_SYMBOL_GPL(system_highpri_wq);
342 struct workqueue_struct *system_long_wq __read_mostly;
343 EXPORT_SYMBOL_GPL(system_long_wq);
344 struct workqueue_struct *system_unbound_wq __read_mostly;
345 EXPORT_SYMBOL_GPL(system_unbound_wq);
346 struct workqueue_struct *system_freezable_wq __read_mostly;
347 EXPORT_SYMBOL_GPL(system_freezable_wq);
348 struct workqueue_struct *system_power_efficient_wq __read_mostly;
349 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
350 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
351 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
352 
353 static int worker_thread(void *__worker);
354 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
355 
356 #define CREATE_TRACE_POINTS
357 #include <trace/events/workqueue.h>
358 
359 #define assert_rcu_or_pool_mutex()                                      \
360         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&                 \
361                          !lockdep_is_held(&wq_pool_mutex),              \
362                          "sched RCU or wq_pool_mutex should be held")
363 
364 #define assert_rcu_or_wq_mutex(wq)                                      \
365         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&                 \
366                          !lockdep_is_held(&wq->mutex),                  \
367                          "sched RCU or wq->mutex should be held")
368 
369 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)                        \
370         RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() &&                 \
371                          !lockdep_is_held(&wq->mutex) &&                \
372                          !lockdep_is_held(&wq_pool_mutex),              \
373                          "sched RCU, wq->mutex or wq_pool_mutex should be held")
374 
375 #define for_each_cpu_worker_pool(pool, cpu)                             \
376         for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];               \
377              (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
378              (pool)++)
379 
380 /**
381  * for_each_pool - iterate through all worker_pools in the system
382  * @pool: iteration cursor
383  * @pi: integer used for iteration
384  *
385  * This must be called either with wq_pool_mutex held or sched RCU read
386  * locked.  If the pool needs to be used beyond the locking in effect, the
387  * caller is responsible for guaranteeing that the pool stays online.
388  *
389  * The if/else clause exists only for the lockdep assertion and can be
390  * ignored.
391  */
392 #define for_each_pool(pool, pi)                                         \
393         idr_for_each_entry(&worker_pool_idr, pool, pi)                  \
394                 if (({ assert_rcu_or_pool_mutex(); false; })) { }       \
395                 else
396 
397 /**
398  * for_each_pool_worker - iterate through all workers of a worker_pool
399  * @worker: iteration cursor
400  * @pool: worker_pool to iterate workers of
401  *
402  * This must be called with wq_pool_attach_mutex.
403  *
404  * The if/else clause exists only for the lockdep assertion and can be
405  * ignored.
406  */
407 #define for_each_pool_worker(worker, pool)                              \
408         list_for_each_entry((worker), &(pool)->workers, node)           \
409                 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
410                 else
411 
412 /**
413  * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
414  * @pwq: iteration cursor
415  * @wq: the target workqueue
416  *
417  * This must be called either with wq->mutex held or sched RCU read locked.
418  * If the pwq needs to be used beyond the locking in effect, the caller is
419  * responsible for guaranteeing that the pwq stays online.
420  *
421  * The if/else clause exists only for the lockdep assertion and can be
422  * ignored.
423  */
424 #define for_each_pwq(pwq, wq)                                           \
425         list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)          \
426                 if (({ assert_rcu_or_wq_mutex(wq); false; })) { }       \
427                 else
428 
429 #ifdef CONFIG_DEBUG_OBJECTS_WORK
430 
431 static struct debug_obj_descr work_debug_descr;
432 
433 static void *work_debug_hint(void *addr)
434 {
435         return ((struct work_struct *) addr)->func;
436 }
437 
438 static bool work_is_static_object(void *addr)
439 {
440         struct work_struct *work = addr;
441 
442         return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
443 }
444 
445 /*
446  * fixup_init is called when:
447  * - an active object is initialized
448  */
449 static bool work_fixup_init(void *addr, enum debug_obj_state state)
450 {
451         struct work_struct *work = addr;
452 
453         switch (state) {
454         case ODEBUG_STATE_ACTIVE:
455                 cancel_work_sync(work);
456                 debug_object_init(work, &work_debug_descr);
457                 return true;
458         default:
459                 return false;
460         }
461 }
462 
463 /*
464  * fixup_free is called when:
465  * - an active object is freed
466  */
467 static bool work_fixup_free(void *addr, enum debug_obj_state state)
468 {
469         struct work_struct *work = addr;
470 
471         switch (state) {
472         case ODEBUG_STATE_ACTIVE:
473                 cancel_work_sync(work);
474                 debug_object_free(work, &work_debug_descr);
475                 return true;
476         default:
477                 return false;
478         }
479 }
480 
481 static struct debug_obj_descr work_debug_descr = {
482         .name           = "work_struct",
483         .debug_hint     = work_debug_hint,
484         .is_static_object = work_is_static_object,
485         .fixup_init     = work_fixup_init,
486         .fixup_free     = work_fixup_free,
487 };
488 
489 static inline void debug_work_activate(struct work_struct *work)
490 {
491         debug_object_activate(work, &work_debug_descr);
492 }
493 
494 static inline void debug_work_deactivate(struct work_struct *work)
495 {
496         debug_object_deactivate(work, &work_debug_descr);
497 }
498 
499 void __init_work(struct work_struct *work, int onstack)
500 {
501         if (onstack)
502                 debug_object_init_on_stack(work, &work_debug_descr);
503         else
504                 debug_object_init(work, &work_debug_descr);
505 }
506 EXPORT_SYMBOL_GPL(__init_work);
507 
508 void destroy_work_on_stack(struct work_struct *work)
509 {
510         debug_object_free(work, &work_debug_descr);
511 }
512 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
513 
514 void destroy_delayed_work_on_stack(struct delayed_work *work)
515 {
516         destroy_timer_on_stack(&work->timer);
517         debug_object_free(&work->work, &work_debug_descr);
518 }
519 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
520 
521 #else
522 static inline void debug_work_activate(struct work_struct *work) { }
523 static inline void debug_work_deactivate(struct work_struct *work) { }
524 #endif
525 
526 /**
527  * worker_pool_assign_id - allocate ID and assing it to @pool
528  * @pool: the pool pointer of interest
529  *
530  * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
531  * successfully, -errno on failure.
532  */
533 static int worker_pool_assign_id(struct worker_pool *pool)
534 {
535         int ret;
536 
537         lockdep_assert_held(&wq_pool_mutex);
538 
539         ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
540                         GFP_KERNEL);
541         if (ret >= 0) {
542                 pool->id = ret;
543                 return 0;
544         }
545         return ret;
546 }
547 
548 /**
549  * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
550  * @wq: the target workqueue
551  * @node: the node ID
552  *
553  * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
554  * read locked.
555  * If the pwq needs to be used beyond the locking in effect, the caller is
556  * responsible for guaranteeing that the pwq stays online.
557  *
558  * Return: The unbound pool_workqueue for @node.
559  */
560 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
561                                                   int node)
562 {
563         assert_rcu_or_wq_mutex_or_pool_mutex(wq);
564 
565         /*
566          * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
567          * delayed item is pending.  The plan is to keep CPU -> NODE
568          * mapping valid and stable across CPU on/offlines.  Once that
569          * happens, this workaround can be removed.
570          */
571         if (unlikely(node == NUMA_NO_NODE))
572                 return wq->dfl_pwq;
573 
574         return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
575 }
576 
577 static unsigned int work_color_to_flags(int color)
578 {
579         return color << WORK_STRUCT_COLOR_SHIFT;
580 }
581 
582 static int get_work_color(struct work_struct *work)
583 {
584         return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
585                 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
586 }
587 
588 static int work_next_color(int color)
589 {
590         return (color + 1) % WORK_NR_COLORS;
591 }
592 
593 /*
594  * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
595  * contain the pointer to the queued pwq.  Once execution starts, the flag
596  * is cleared and the high bits contain OFFQ flags and pool ID.
597  *
598  * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
599  * and clear_work_data() can be used to set the pwq, pool or clear
600  * work->data.  These functions should only be called while the work is
601  * owned - ie. while the PENDING bit is set.
602  *
603  * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
604  * corresponding to a work.  Pool is available once the work has been
605  * queued anywhere after initialization until it is sync canceled.  pwq is
606  * available only while the work item is queued.
607  *
608  * %WORK_OFFQ_CANCELING is used to mark a work item which is being
609  * canceled.  While being canceled, a work item may have its PENDING set
610  * but stay off timer and worklist for arbitrarily long and nobody should
611  * try to steal the PENDING bit.
612  */
613 static inline void set_work_data(struct work_struct *work, unsigned long data,
614                                  unsigned long flags)
615 {
616         WARN_ON_ONCE(!work_pending(work));
617         atomic_long_set(&work->data, data | flags | work_static(work));
618 }
619 
620 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
621                          unsigned long extra_flags)
622 {
623         set_work_data(work, (unsigned long)pwq,
624                       WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
625 }
626 
627 static void set_work_pool_and_keep_pending(struct work_struct *work,
628                                            int pool_id)
629 {
630         set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
631                       WORK_STRUCT_PENDING);
632 }
633 
634 static void set_work_pool_and_clear_pending(struct work_struct *work,
635                                             int pool_id)
636 {
637         /*
638          * The following wmb is paired with the implied mb in
639          * test_and_set_bit(PENDING) and ensures all updates to @work made
640          * here are visible to and precede any updates by the next PENDING
641          * owner.
642          */
643         smp_wmb();
644         set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
645         /*
646          * The following mb guarantees that previous clear of a PENDING bit
647          * will not be reordered with any speculative LOADS or STORES from
648          * work->current_func, which is executed afterwards.  This possible
649          * reordering can lead to a missed execution on attempt to qeueue
650          * the same @work.  E.g. consider this case:
651          *
652          *   CPU#0                         CPU#1
653          *   ----------------------------  --------------------------------
654          *
655          * 1  STORE event_indicated
656          * 2  queue_work_on() {
657          * 3    test_and_set_bit(PENDING)
658          * 4 }                             set_..._and_clear_pending() {
659          * 5                                 set_work_data() # clear bit
660          * 6                                 smp_mb()
661          * 7                               work->current_func() {
662          * 8                                  LOAD event_indicated
663          *                                 }
664          *
665          * Without an explicit full barrier speculative LOAD on line 8 can
666          * be executed before CPU#0 does STORE on line 1.  If that happens,
667          * CPU#0 observes the PENDING bit is still set and new execution of
668          * a @work is not queued in a hope, that CPU#1 will eventually
669          * finish the queued @work.  Meanwhile CPU#1 does not see
670          * event_indicated is set, because speculative LOAD was executed
671          * before actual STORE.
672          */
673         smp_mb();
674 }
675 
676 static void clear_work_data(struct work_struct *work)
677 {
678         smp_wmb();      /* see set_work_pool_and_clear_pending() */
679         set_work_data(work, WORK_STRUCT_NO_POOL, 0);
680 }
681 
682 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
683 {
684         unsigned long data = atomic_long_read(&work->data);
685 
686         if (data & WORK_STRUCT_PWQ)
687                 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
688         else
689                 return NULL;
690 }
691 
692 /**
693  * get_work_pool - return the worker_pool a given work was associated with
694  * @work: the work item of interest
695  *
696  * Pools are created and destroyed under wq_pool_mutex, and allows read
697  * access under sched-RCU read lock.  As such, this function should be
698  * called under wq_pool_mutex or with preemption disabled.
699  *
700  * All fields of the returned pool are accessible as long as the above
701  * mentioned locking is in effect.  If the returned pool needs to be used
702  * beyond the critical section, the caller is responsible for ensuring the
703  * returned pool is and stays online.
704  *
705  * Return: The worker_pool @work was last associated with.  %NULL if none.
706  */
707 static struct worker_pool *get_work_pool(struct work_struct *work)
708 {
709         unsigned long data = atomic_long_read(&work->data);
710         int pool_id;
711 
712         assert_rcu_or_pool_mutex();
713 
714         if (data & WORK_STRUCT_PWQ)
715                 return ((struct pool_workqueue *)
716                         (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
717 
718         pool_id = data >> WORK_OFFQ_POOL_SHIFT;
719         if (pool_id == WORK_OFFQ_POOL_NONE)
720                 return NULL;
721 
722         return idr_find(&worker_pool_idr, pool_id);
723 }
724 
725 /**
726  * get_work_pool_id - return the worker pool ID a given work is associated with
727  * @work: the work item of interest
728  *
729  * Return: The worker_pool ID @work was last associated with.
730  * %WORK_OFFQ_POOL_NONE if none.
731  */
732 static int get_work_pool_id(struct work_struct *work)
733 {
734         unsigned long data = atomic_long_read(&work->data);
735 
736         if (data & WORK_STRUCT_PWQ)
737                 return ((struct pool_workqueue *)
738                         (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
739 
740         return data >> WORK_OFFQ_POOL_SHIFT;
741 }
742 
743 static void mark_work_canceling(struct work_struct *work)
744 {
745         unsigned long pool_id = get_work_pool_id(work);
746 
747         pool_id <<= WORK_OFFQ_POOL_SHIFT;
748         set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
749 }
750 
751 static bool work_is_canceling(struct work_struct *work)
752 {
753         unsigned long data = atomic_long_read(&work->data);
754 
755         return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
756 }
757 
758 /*
759  * Policy functions.  These define the policies on how the global worker
760  * pools are managed.  Unless noted otherwise, these functions assume that
761  * they're being called with pool->lock held.
762  */
763 
764 static bool __need_more_worker(struct worker_pool *pool)
765 {
766         return !atomic_read(&pool->nr_running);
767 }
768 
769 /*
770  * Need to wake up a worker?  Called from anything but currently
771  * running workers.
772  *
773  * Note that, because unbound workers never contribute to nr_running, this
774  * function will always return %true for unbound pools as long as the
775  * worklist isn't empty.
776  */
777 static bool need_more_worker(struct worker_pool *pool)
778 {
779         return !list_empty(&pool->worklist) && __need_more_worker(pool);
780 }
781 
782 /* Can I start working?  Called from busy but !running workers. */
783 static bool may_start_working(struct worker_pool *pool)
784 {
785         return pool->nr_idle;
786 }
787 
788 /* Do I need to keep working?  Called from currently running workers. */
789 static bool keep_working(struct worker_pool *pool)
790 {
791         return !list_empty(&pool->worklist) &&
792                 atomic_read(&pool->nr_running) <= 1;
793 }
794 
795 /* Do we need a new worker?  Called from manager. */
796 static bool need_to_create_worker(struct worker_pool *pool)
797 {
798         return need_more_worker(pool) && !may_start_working(pool);
799 }
800 
801 /* Do we have too many workers and should some go away? */
802 static bool too_many_workers(struct worker_pool *pool)
803 {
804         bool managing = pool->flags & POOL_MANAGER_ACTIVE;
805         int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
806         int nr_busy = pool->nr_workers - nr_idle;
807 
808         return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
809 }
810 
811 /*
812  * Wake up functions.
813  */
814 
815 /* Return the first idle worker.  Safe with preemption disabled */
816 static struct worker *first_idle_worker(struct worker_pool *pool)
817 {
818         if (unlikely(list_empty(&pool->idle_list)))
819                 return NULL;
820 
821         return list_first_entry(&pool->idle_list, struct worker, entry);
822 }
823 
824 /**
825  * wake_up_worker - wake up an idle worker
826  * @pool: worker pool to wake worker from
827  *
828  * Wake up the first idle worker of @pool.
829  *
830  * CONTEXT:
831  * spin_lock_irq(pool->lock).
832  */
833 static void wake_up_worker(struct worker_pool *pool)
834 {
835         struct worker *worker = first_idle_worker(pool);
836 
837         if (likely(worker))
838                 wake_up_process(worker->task);
839 }
840 
841 /**
842  * wq_worker_waking_up - a worker is waking up
843  * @task: task waking up
844  * @cpu: CPU @task is waking up to
845  *
846  * This function is called during try_to_wake_up() when a worker is
847  * being awoken.
848  *
849  * CONTEXT:
850  * spin_lock_irq(rq->lock)
851  */
852 void wq_worker_waking_up(struct task_struct *task, int cpu)
853 {
854         struct worker *worker = kthread_data(task);
855 
856         if (!(worker->flags & WORKER_NOT_RUNNING)) {
857                 WARN_ON_ONCE(worker->pool->cpu != cpu);
858                 atomic_inc(&worker->pool->nr_running);
859         }
860 }
861 
862 /**
863  * wq_worker_sleeping - a worker is going to sleep
864  * @task: task going to sleep
865  *
866  * This function is called during schedule() when a busy worker is
867  * going to sleep.  Worker on the same cpu can be woken up by
868  * returning pointer to its task.
869  *
870  * CONTEXT:
871  * spin_lock_irq(rq->lock)
872  *
873  * Return:
874  * Worker task on @cpu to wake up, %NULL if none.
875  */
876 struct task_struct *wq_worker_sleeping(struct task_struct *task)
877 {
878         struct worker *worker = kthread_data(task), *to_wakeup = NULL;
879         struct worker_pool *pool;
880 
881         /*
882          * Rescuers, which may not have all the fields set up like normal
883          * workers, also reach here, let's not access anything before
884          * checking NOT_RUNNING.
885          */
886         if (worker->flags & WORKER_NOT_RUNNING)
887                 return NULL;
888 
889         pool = worker->pool;
890 
891         /* this can only happen on the local cpu */
892         if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
893                 return NULL;
894 
895         /*
896          * The counterpart of the following dec_and_test, implied mb,
897          * worklist not empty test sequence is in insert_work().
898          * Please read comment there.
899          *
900          * NOT_RUNNING is clear.  This means that we're bound to and
901          * running on the local cpu w/ rq lock held and preemption
902          * disabled, which in turn means that none else could be
903          * manipulating idle_list, so dereferencing idle_list without pool
904          * lock is safe.
905          */
906         if (atomic_dec_and_test(&pool->nr_running) &&
907             !list_empty(&pool->worklist))
908                 to_wakeup = first_idle_worker(pool);
909         return to_wakeup ? to_wakeup->task : NULL;
910 }
911 
912 /**
913  * worker_set_flags - set worker flags and adjust nr_running accordingly
914  * @worker: self
915  * @flags: flags to set
916  *
917  * Set @flags in @worker->flags and adjust nr_running accordingly.
918  *
919  * CONTEXT:
920  * spin_lock_irq(pool->lock)
921  */
922 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
923 {
924         struct worker_pool *pool = worker->pool;
925 
926         WARN_ON_ONCE(worker->task != current);
927 
928         /* If transitioning into NOT_RUNNING, adjust nr_running. */
929         if ((flags & WORKER_NOT_RUNNING) &&
930             !(worker->flags & WORKER_NOT_RUNNING)) {
931                 atomic_dec(&pool->nr_running);
932         }
933 
934         worker->flags |= flags;
935 }
936 
937 /**
938  * worker_clr_flags - clear worker flags and adjust nr_running accordingly
939  * @worker: self
940  * @flags: flags to clear
941  *
942  * Clear @flags in @worker->flags and adjust nr_running accordingly.
943  *
944  * CONTEXT:
945  * spin_lock_irq(pool->lock)
946  */
947 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
948 {
949         struct worker_pool *pool = worker->pool;
950         unsigned int oflags = worker->flags;
951 
952         WARN_ON_ONCE(worker->task != current);
953 
954         worker->flags &= ~flags;
955 
956         /*
957          * If transitioning out of NOT_RUNNING, increment nr_running.  Note
958          * that the nested NOT_RUNNING is not a noop.  NOT_RUNNING is mask
959          * of multiple flags, not a single flag.
960          */
961         if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
962                 if (!(worker->flags & WORKER_NOT_RUNNING))
963                         atomic_inc(&pool->nr_running);
964 }
965 
966 /**
967  * find_worker_executing_work - find worker which is executing a work
968  * @pool: pool of interest
969  * @work: work to find worker for
970  *
971  * Find a worker which is executing @work on @pool by searching
972  * @pool->busy_hash which is keyed by the address of @work.  For a worker
973  * to match, its current execution should match the address of @work and
974  * its work function.  This is to avoid unwanted dependency between
975  * unrelated work executions through a work item being recycled while still
976  * being executed.
977  *
978  * This is a bit tricky.  A work item may be freed once its execution
979  * starts and nothing prevents the freed area from being recycled for
980  * another work item.  If the same work item address ends up being reused
981  * before the original execution finishes, workqueue will identify the
982  * recycled work item as currently executing and make it wait until the
983  * current execution finishes, introducing an unwanted dependency.
984  *
985  * This function checks the work item address and work function to avoid
986  * false positives.  Note that this isn't complete as one may construct a
987  * work function which can introduce dependency onto itself through a
988  * recycled work item.  Well, if somebody wants to shoot oneself in the
989  * foot that badly, there's only so much we can do, and if such deadlock
990  * actually occurs, it should be easy to locate the culprit work function.
991  *
992  * CONTEXT:
993  * spin_lock_irq(pool->lock).
994  *
995  * Return:
996  * Pointer to worker which is executing @work if found, %NULL
997  * otherwise.
998  */
999 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1000                                                  struct work_struct *work)
1001 {
1002         struct worker *worker;
1003 
1004         hash_for_each_possible(pool->busy_hash, worker, hentry,
1005                                (unsigned long)work)
1006                 if (worker->current_work == work &&
1007                     worker->current_func == work->func)
1008                         return worker;
1009 
1010         return NULL;
1011 }
1012 
1013 /**
1014  * move_linked_works - move linked works to a list
1015  * @work: start of series of works to be scheduled
1016  * @head: target list to append @work to
1017  * @nextp: out parameter for nested worklist walking
1018  *
1019  * Schedule linked works starting from @work to @head.  Work series to
1020  * be scheduled starts at @work and includes any consecutive work with
1021  * WORK_STRUCT_LINKED set in its predecessor.
1022  *
1023  * If @nextp is not NULL, it's updated to point to the next work of
1024  * the last scheduled work.  This allows move_linked_works() to be
1025  * nested inside outer list_for_each_entry_safe().
1026  *
1027  * CONTEXT:
1028  * spin_lock_irq(pool->lock).
1029  */
1030 static void move_linked_works(struct work_struct *work, struct list_head *head,
1031                               struct work_struct **nextp)
1032 {
1033         struct work_struct *n;
1034 
1035         /*
1036          * Linked worklist will always end before the end of the list,
1037          * use NULL for list head.
1038          */
1039         list_for_each_entry_safe_from(work, n, NULL, entry) {
1040                 list_move_tail(&work->entry, head);
1041                 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1042                         break;
1043         }
1044 
1045         /*
1046          * If we're already inside safe list traversal and have moved
1047          * multiple works to the scheduled queue, the next position
1048          * needs to be updated.
1049          */
1050         if (nextp)
1051                 *nextp = n;
1052 }
1053 
1054 /**
1055  * get_pwq - get an extra reference on the specified pool_workqueue
1056  * @pwq: pool_workqueue to get
1057  *
1058  * Obtain an extra reference on @pwq.  The caller should guarantee that
1059  * @pwq has positive refcnt and be holding the matching pool->lock.
1060  */
1061 static void get_pwq(struct pool_workqueue *pwq)
1062 {
1063         lockdep_assert_held(&pwq->pool->lock);
1064         WARN_ON_ONCE(pwq->refcnt <= 0);
1065         pwq->refcnt++;
1066 }
1067 
1068 /**
1069  * put_pwq - put a pool_workqueue reference
1070  * @pwq: pool_workqueue to put
1071  *
1072  * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
1073  * destruction.  The caller should be holding the matching pool->lock.
1074  */
1075 static void put_pwq(struct pool_workqueue *pwq)
1076 {
1077         lockdep_assert_held(&pwq->pool->lock);
1078         if (likely(--pwq->refcnt))
1079                 return;
1080         if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1081                 return;
1082         /*
1083          * @pwq can't be released under pool->lock, bounce to
1084          * pwq_unbound_release_workfn().  This never recurses on the same
1085          * pool->lock as this path is taken only for unbound workqueues and
1086          * the release work item is scheduled on a per-cpu workqueue.  To
1087          * avoid lockdep warning, unbound pool->locks are given lockdep
1088          * subclass of 1 in get_unbound_pool().
1089          */
1090         schedule_work(&pwq->unbound_release_work);
1091 }
1092 
1093 /**
1094  * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1095  * @pwq: pool_workqueue to put (can be %NULL)
1096  *
1097  * put_pwq() with locking.  This function also allows %NULL @pwq.
1098  */
1099 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1100 {
1101         if (pwq) {
1102                 /*
1103                  * As both pwqs and pools are sched-RCU protected, the
1104                  * following lock operations are safe.
1105                  */
1106                 spin_lock_irq(&pwq->pool->lock);
1107                 put_pwq(pwq);
1108                 spin_unlock_irq(&pwq->pool->lock);
1109         }
1110 }
1111 
1112 static void pwq_activate_delayed_work(struct work_struct *work)
1113 {
1114         struct pool_workqueue *pwq = get_work_pwq(work);
1115 
1116         trace_workqueue_activate_work(work);
1117         if (list_empty(&pwq->pool->worklist))
1118                 pwq->pool->watchdog_ts = jiffies;
1119         move_linked_works(work, &pwq->pool->worklist, NULL);
1120         __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1121         pwq->nr_active++;
1122 }
1123 
1124 static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1125 {
1126         struct work_struct *work = list_first_entry(&pwq->delayed_works,
1127                                                     struct work_struct, entry);
1128 
1129         pwq_activate_delayed_work(work);
1130 }
1131 
1132 /**
1133  * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1134  * @pwq: pwq of interest
1135  * @color: color of work which left the queue
1136  *
1137  * A work either has completed or is removed from pending queue,
1138  * decrement nr_in_flight of its pwq and handle workqueue flushing.
1139  *
1140  * CONTEXT:
1141  * spin_lock_irq(pool->lock).
1142  */
1143 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1144 {
1145         /* uncolored work items don't participate in flushing or nr_active */
1146         if (color == WORK_NO_COLOR)
1147                 goto out_put;
1148 
1149         pwq->nr_in_flight[color]--;
1150 
1151         pwq->nr_active--;
1152         if (!list_empty(&pwq->delayed_works)) {
1153                 /* one down, submit a delayed one */
1154                 if (pwq->nr_active < pwq->max_active)
1155                         pwq_activate_first_delayed(pwq);
1156         }
1157 
1158         /* is flush in progress and are we at the flushing tip? */
1159         if (likely(pwq->flush_color != color))
1160                 goto out_put;
1161 
1162         /* are there still in-flight works? */
1163         if (pwq->nr_in_flight[color])
1164                 goto out_put;
1165 
1166         /* this pwq is done, clear flush_color */
1167         pwq->flush_color = -1;
1168 
1169         /*
1170          * If this was the last pwq, wake up the first flusher.  It
1171          * will handle the rest.
1172          */
1173         if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1174                 complete(&pwq->wq->first_flusher->done);
1175 out_put:
1176         put_pwq(pwq);
1177 }
1178 
1179 /**
1180  * try_to_grab_pending - steal work item from worklist and disable irq
1181  * @work: work item to steal
1182  * @is_dwork: @work is a delayed_work
1183  * @flags: place to store irq state
1184  *
1185  * Try to grab PENDING bit of @work.  This function can handle @work in any
1186  * stable state - idle, on timer or on worklist.
1187  *
1188  * Return:
1189  *  1           if @work was pending and we successfully stole PENDING
1190  *  0           if @work was idle and we claimed PENDING
1191  *  -EAGAIN     if PENDING couldn't be grabbed at the moment, safe to busy-retry
1192  *  -ENOENT     if someone else is canceling @work, this state may persist
1193  *              for arbitrarily long
1194  *
1195  * Note:
1196  * On >= 0 return, the caller owns @work's PENDING bit.  To avoid getting
1197  * interrupted while holding PENDING and @work off queue, irq must be
1198  * disabled on entry.  This, combined with delayed_work->timer being
1199  * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1200  *
1201  * On successful return, >= 0, irq is disabled and the caller is
1202  * responsible for releasing it using local_irq_restore(*@flags).
1203  *
1204  * This function is safe to call from any context including IRQ handler.
1205  */
1206 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1207                                unsigned long *flags)
1208 {
1209         struct worker_pool *pool;
1210         struct pool_workqueue *pwq;
1211 
1212         local_irq_save(*flags);
1213 
1214         /* try to steal the timer if it exists */
1215         if (is_dwork) {
1216                 struct delayed_work *dwork = to_delayed_work(work);
1217 
1218                 /*
1219                  * dwork->timer is irqsafe.  If del_timer() fails, it's
1220                  * guaranteed that the timer is not queued anywhere and not
1221                  * running on the local CPU.
1222                  */
1223                 if (likely(del_timer(&dwork->timer)))
1224                         return 1;
1225         }
1226 
1227         /* try to claim PENDING the normal way */
1228         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1229                 return 0;
1230 
1231         /*
1232          * The queueing is in progress, or it is already queued. Try to
1233          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1234          */
1235         pool = get_work_pool(work);
1236         if (!pool)
1237                 goto fail;
1238 
1239         spin_lock(&pool->lock);
1240         /*
1241          * work->data is guaranteed to point to pwq only while the work
1242          * item is queued on pwq->wq, and both updating work->data to point
1243          * to pwq on queueing and to pool on dequeueing are done under
1244          * pwq->pool->lock.  This in turn guarantees that, if work->data
1245          * points to pwq which is associated with a locked pool, the work
1246          * item is currently queued on that pool.
1247          */
1248         pwq = get_work_pwq(work);
1249         if (pwq && pwq->pool == pool) {
1250                 debug_work_deactivate(work);
1251 
1252                 /*
1253                  * A delayed work item cannot be grabbed directly because
1254                  * it might have linked NO_COLOR work items which, if left
1255                  * on the delayed_list, will confuse pwq->nr_active
1256                  * management later on and cause stall.  Make sure the work
1257                  * item is activated before grabbing.
1258                  */
1259                 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1260                         pwq_activate_delayed_work(work);
1261 
1262                 list_del_init(&work->entry);
1263                 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1264 
1265                 /* work->data points to pwq iff queued, point to pool */
1266                 set_work_pool_and_keep_pending(work, pool->id);
1267 
1268                 spin_unlock(&pool->lock);
1269                 return 1;
1270         }
1271         spin_unlock(&pool->lock);
1272 fail:
1273         local_irq_restore(*flags);
1274         if (work_is_canceling(work))
1275                 return -ENOENT;
1276         cpu_relax();
1277         return -EAGAIN;
1278 }
1279 
1280 /**
1281  * insert_work - insert a work into a pool
1282  * @pwq: pwq @work belongs to
1283  * @work: work to insert
1284  * @head: insertion point
1285  * @extra_flags: extra WORK_STRUCT_* flags to set
1286  *
1287  * Insert @work which belongs to @pwq after @head.  @extra_flags is or'd to
1288  * work_struct flags.
1289  *
1290  * CONTEXT:
1291  * spin_lock_irq(pool->lock).
1292  */
1293 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1294                         struct list_head *head, unsigned int extra_flags)
1295 {
1296         struct worker_pool *pool = pwq->pool;
1297 
1298         /* we own @work, set data and link */
1299         set_work_pwq(work, pwq, extra_flags);
1300         list_add_tail(&work->entry, head);
1301         get_pwq(pwq);
1302 
1303         /*
1304          * Ensure either wq_worker_sleeping() sees the above
1305          * list_add_tail() or we see zero nr_running to avoid workers lying
1306          * around lazily while there are works to be processed.
1307          */
1308         smp_mb();
1309 
1310         if (__need_more_worker(pool))
1311                 wake_up_worker(pool);
1312 }
1313 
1314 /*
1315  * Test whether @work is being queued from another work executing on the
1316  * same workqueue.
1317  */
1318 static bool is_chained_work(struct workqueue_struct *wq)
1319 {
1320         struct worker *worker;
1321 
1322         worker = current_wq_worker();
1323         /*
1324          * Return %true iff I'm a worker execuing a work item on @wq.  If
1325          * I'm @worker, it's safe to dereference it without locking.
1326          */
1327         return worker && worker->current_pwq->wq == wq;
1328 }
1329 
1330 /*
1331  * When queueing an unbound work item to a wq, prefer local CPU if allowed
1332  * by wq_unbound_cpumask.  Otherwise, round robin among the allowed ones to
1333  * avoid perturbing sensitive tasks.
1334  */
1335 static int wq_select_unbound_cpu(int cpu)
1336 {
1337         static bool printed_dbg_warning;
1338         int new_cpu;
1339 
1340         if (likely(!wq_debug_force_rr_cpu)) {
1341                 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1342                         return cpu;
1343         } else if (!printed_dbg_warning) {
1344                 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1345                 printed_dbg_warning = true;
1346         }
1347 
1348         if (cpumask_empty(wq_unbound_cpumask))
1349                 return cpu;
1350 
1351         new_cpu = __this_cpu_read(wq_rr_cpu_last);
1352         new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1353         if (unlikely(new_cpu >= nr_cpu_ids)) {
1354                 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1355                 if (unlikely(new_cpu >= nr_cpu_ids))
1356                         return cpu;
1357         }
1358         __this_cpu_write(wq_rr_cpu_last, new_cpu);
1359 
1360         return new_cpu;
1361 }
1362 
1363 static void __queue_work(int cpu, struct workqueue_struct *wq,
1364                          struct work_struct *work)
1365 {
1366         struct pool_workqueue *pwq;
1367         struct worker_pool *last_pool;
1368         struct list_head *worklist;
1369         unsigned int work_flags;
1370         unsigned int req_cpu = cpu;
1371 
1372         /*
1373          * While a work item is PENDING && off queue, a task trying to
1374          * steal the PENDING will busy-loop waiting for it to either get
1375          * queued or lose PENDING.  Grabbing PENDING and queueing should
1376          * happen with IRQ disabled.
1377          */
1378         lockdep_assert_irqs_disabled();
1379 
1380         debug_work_activate(work);
1381 
1382         /* if draining, only works from the same workqueue are allowed */
1383         if (unlikely(wq->flags & __WQ_DRAINING) &&
1384             WARN_ON_ONCE(!is_chained_work(wq)))
1385                 return;
1386 retry:
1387         if (req_cpu == WORK_CPU_UNBOUND)
1388                 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1389 
1390         /* pwq which will be used unless @work is executing elsewhere */
1391         if (!(wq->flags & WQ_UNBOUND))
1392                 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1393         else
1394                 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1395 
1396         /*
1397          * If @work was previously on a different pool, it might still be
1398          * running there, in which case the work needs to be queued on that
1399          * pool to guarantee non-reentrancy.
1400          */
1401         last_pool = get_work_pool(work);
1402         if (last_pool && last_pool != pwq->pool) {
1403                 struct worker *worker;
1404 
1405                 spin_lock(&last_pool->lock);
1406 
1407                 worker = find_worker_executing_work(last_pool, work);
1408 
1409                 if (worker && worker->current_pwq->wq == wq) {
1410                         pwq = worker->current_pwq;
1411                 } else {
1412                         /* meh... not running there, queue here */
1413                         spin_unlock(&last_pool->lock);
1414                         spin_lock(&pwq->pool->lock);
1415                 }
1416         } else {
1417                 spin_lock(&pwq->pool->lock);
1418         }
1419 
1420         /*
1421          * pwq is determined and locked.  For unbound pools, we could have
1422          * raced with pwq release and it could already be dead.  If its
1423          * refcnt is zero, repeat pwq selection.  Note that pwqs never die
1424          * without another pwq replacing it in the numa_pwq_tbl or while
1425          * work items are executing on it, so the retrying is guaranteed to
1426          * make forward-progress.
1427          */
1428         if (unlikely(!pwq->refcnt)) {
1429                 if (wq->flags & WQ_UNBOUND) {
1430                         spin_unlock(&pwq->pool->lock);
1431                         cpu_relax();
1432                         goto retry;
1433                 }
1434                 /* oops */
1435                 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1436                           wq->name, cpu);
1437         }
1438 
1439         /* pwq determined, queue */
1440         trace_workqueue_queue_work(req_cpu, pwq, work);
1441 
1442         if (WARN_ON(!list_empty(&work->entry))) {
1443                 spin_unlock(&pwq->pool->lock);
1444                 return;
1445         }
1446 
1447         pwq->nr_in_flight[pwq->work_color]++;
1448         work_flags = work_color_to_flags(pwq->work_color);
1449 
1450         if (likely(pwq->nr_active < pwq->max_active)) {
1451                 trace_workqueue_activate_work(work);
1452                 pwq->nr_active++;
1453                 worklist = &pwq->pool->worklist;
1454                 if (list_empty(worklist))
1455                         pwq->pool->watchdog_ts = jiffies;
1456         } else {
1457                 work_flags |= WORK_STRUCT_DELAYED;
1458                 worklist = &pwq->delayed_works;
1459         }
1460 
1461         insert_work(pwq, work, worklist, work_flags);
1462 
1463         spin_unlock(&pwq->pool->lock);
1464 }
1465 
1466 /**
1467  * queue_work_on - queue work on specific cpu
1468  * @cpu: CPU number to execute work on
1469  * @wq: workqueue to use
1470  * @work: work to queue
1471  *
1472  * We queue the work to a specific CPU, the caller must ensure it
1473  * can't go away.
1474  *
1475  * Return: %false if @work was already on a queue, %true otherwise.
1476  */
1477 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1478                    struct work_struct *work)
1479 {
1480         bool ret = false;
1481         unsigned long flags;
1482 
1483         local_irq_save(flags);
1484 
1485         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1486                 __queue_work(cpu, wq, work);
1487                 ret = true;
1488         }
1489 
1490         local_irq_restore(flags);
1491         return ret;
1492 }
1493 EXPORT_SYMBOL(queue_work_on);
1494 
1495 void delayed_work_timer_fn(struct timer_list *t)
1496 {
1497         struct delayed_work *dwork = from_timer(dwork, t, timer);
1498 
1499         /* should have been called from irqsafe timer with irq already off */
1500         __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1501 }
1502 EXPORT_SYMBOL(delayed_work_timer_fn);
1503 
1504 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1505                                 struct delayed_work *dwork, unsigned long delay)
1506 {
1507         struct timer_list *timer = &dwork->timer;
1508         struct work_struct *work = &dwork->work;
1509 
1510         WARN_ON_ONCE(!wq);
1511         WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1512         WARN_ON_ONCE(timer_pending(timer));
1513         WARN_ON_ONCE(!list_empty(&work->entry));
1514 
1515         /*
1516          * If @delay is 0, queue @dwork->work immediately.  This is for
1517          * both optimization and correctness.  The earliest @timer can
1518          * expire is on the closest next tick and delayed_work users depend
1519          * on that there's no such delay when @delay is 0.
1520          */
1521         if (!delay) {
1522                 __queue_work(cpu, wq, &dwork->work);
1523                 return;
1524         }
1525 
1526         dwork->wq = wq;
1527         dwork->cpu = cpu;
1528         timer->expires = jiffies + delay;
1529 
1530         if (unlikely(cpu != WORK_CPU_UNBOUND))
1531                 add_timer_on(timer, cpu);
1532         else
1533                 add_timer(timer);
1534 }
1535 
1536 /**
1537  * queue_delayed_work_on - queue work on specific CPU after delay
1538  * @cpu: CPU number to execute work on
1539  * @wq: workqueue to use
1540  * @dwork: work to queue
1541  * @delay: number of jiffies to wait before queueing
1542  *
1543  * Return: %false if @work was already on a queue, %true otherwise.  If
1544  * @delay is zero and @dwork is idle, it will be scheduled for immediate
1545  * execution.
1546  */
1547 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1548                            struct delayed_work *dwork, unsigned long delay)
1549 {
1550         struct work_struct *work = &dwork->work;
1551         bool ret = false;
1552         unsigned long flags;
1553 
1554         /* read the comment in __queue_work() */
1555         local_irq_save(flags);
1556 
1557         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1558                 __queue_delayed_work(cpu, wq, dwork, delay);
1559                 ret = true;
1560         }
1561 
1562         local_irq_restore(flags);
1563         return ret;
1564 }
1565 EXPORT_SYMBOL(queue_delayed_work_on);
1566 
1567 /**
1568  * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1569  * @cpu: CPU number to execute work on
1570  * @wq: workqueue to use
1571  * @dwork: work to queue
1572  * @delay: number of jiffies to wait before queueing
1573  *
1574  * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1575  * modify @dwork's timer so that it expires after @delay.  If @delay is
1576  * zero, @work is guaranteed to be scheduled immediately regardless of its
1577  * current state.
1578  *
1579  * Return: %false if @dwork was idle and queued, %true if @dwork was
1580  * pending and its timer was modified.
1581  *
1582  * This function is safe to call from any context including IRQ handler.
1583  * See try_to_grab_pending() for details.
1584  */
1585 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1586                          struct delayed_work *dwork, unsigned long delay)
1587 {
1588         unsigned long flags;
1589         int ret;
1590 
1591         do {
1592                 ret = try_to_grab_pending(&dwork->work, true, &flags);
1593         } while (unlikely(ret == -EAGAIN));
1594 
1595         if (likely(ret >= 0)) {
1596                 __queue_delayed_work(cpu, wq, dwork, delay);
1597                 local_irq_restore(flags);
1598         }
1599 
1600         /* -ENOENT from try_to_grab_pending() becomes %true */
1601         return ret;
1602 }
1603 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1604 
1605 static void rcu_work_rcufn(struct rcu_head *rcu)
1606 {
1607         struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
1608 
1609         /* read the comment in __queue_work() */
1610         local_irq_disable();
1611         __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
1612         local_irq_enable();
1613 }
1614 
1615 /**
1616  * queue_rcu_work - queue work after a RCU grace period
1617  * @wq: workqueue to use
1618  * @rwork: work to queue
1619  *
1620  * Return: %false if @rwork was already pending, %true otherwise.  Note
1621  * that a full RCU grace period is guaranteed only after a %true return.
1622  * While @rwork is guarnateed to be executed after a %false return, the
1623  * execution may happen before a full RCU grace period has passed.
1624  */
1625 bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
1626 {
1627         struct work_struct *work = &rwork->work;
1628 
1629         if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1630                 rwork->wq = wq;
1631                 call_rcu(&rwork->rcu, rcu_work_rcufn);
1632                 return true;
1633         }
1634 
1635         return false;
1636 }
1637 EXPORT_SYMBOL(queue_rcu_work);
1638 
1639 /**
1640  * worker_enter_idle - enter idle state
1641  * @worker: worker which is entering idle state
1642  *
1643  * @worker is entering idle state.  Update stats and idle timer if
1644  * necessary.
1645  *
1646  * LOCKING:
1647  * spin_lock_irq(pool->lock).
1648  */
1649 static void worker_enter_idle(struct worker *worker)
1650 {
1651         struct worker_pool *pool = worker->pool;
1652 
1653         if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1654             WARN_ON_ONCE(!list_empty(&worker->entry) &&
1655                          (worker->hentry.next || worker->hentry.pprev)))
1656                 return;
1657 
1658         /* can't use worker_set_flags(), also called from create_worker() */
1659         worker->flags |= WORKER_IDLE;
1660         pool->nr_idle++;
1661         worker->last_active = jiffies;
1662 
1663         /* idle_list is LIFO */
1664         list_add(&worker->entry, &pool->idle_list);
1665 
1666         if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1667                 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1668 
1669         /*
1670          * Sanity check nr_running.  Because unbind_workers() releases
1671          * pool->lock between setting %WORKER_UNBOUND and zapping
1672          * nr_running, the warning may trigger spuriously.  Check iff
1673          * unbind is not in progress.
1674          */
1675         WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1676                      pool->nr_workers == pool->nr_idle &&
1677                      atomic_read(&pool->nr_running));
1678 }
1679 
1680 /**
1681  * worker_leave_idle - leave idle state
1682  * @worker: worker which is leaving idle state
1683  *
1684  * @worker is leaving idle state.  Update stats.
1685  *
1686  * LOCKING:
1687  * spin_lock_irq(pool->lock).
1688  */
1689 static void worker_leave_idle(struct worker *worker)
1690 {
1691         struct worker_pool *pool = worker->pool;
1692 
1693         if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1694                 return;
1695         worker_clr_flags(worker, WORKER_IDLE);
1696         pool->nr_idle--;
1697         list_del_init(&worker->entry);
1698 }
1699 
1700 static struct worker *alloc_worker(int node)
1701 {
1702         struct worker *worker;
1703 
1704         worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1705         if (worker) {
1706                 INIT_LIST_HEAD(&worker->entry);
1707                 INIT_LIST_HEAD(&worker->scheduled);
1708                 INIT_LIST_HEAD(&worker->node);
1709                 /* on creation a worker is in !idle && prep state */
1710                 worker->flags = WORKER_PREP;
1711         }
1712         return worker;
1713 }
1714 
1715 /**
1716  * worker_attach_to_pool() - attach a worker to a pool
1717  * @worker: worker to be attached
1718  * @pool: the target pool
1719  *
1720  * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and
1721  * cpu-binding of @worker are kept coordinated with the pool across
1722  * cpu-[un]hotplugs.
1723  */
1724 static void worker_attach_to_pool(struct worker *worker,
1725                                    struct worker_pool *pool)
1726 {
1727         mutex_lock(&wq_pool_attach_mutex);
1728 
1729         /*
1730          * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1731          * online CPUs.  It'll be re-applied when any of the CPUs come up.
1732          */
1733         set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1734 
1735         /*
1736          * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
1737          * stable across this function.  See the comments above the flag
1738          * definition for details.
1739          */
1740         if (pool->flags & POOL_DISASSOCIATED)
1741                 worker->flags |= WORKER_UNBOUND;
1742 
1743         list_add_tail(&worker->node, &pool->workers);
1744         worker->pool = pool;
1745 
1746         mutex_unlock(&wq_pool_attach_mutex);
1747 }
1748 
1749 /**
1750  * worker_detach_from_pool() - detach a worker from its pool
1751  * @worker: worker which is attached to its pool
1752  *
1753  * Undo the attaching which had been done in worker_attach_to_pool().  The
1754  * caller worker shouldn't access to the pool after detached except it has
1755  * other reference to the pool.
1756  */
1757 static void worker_detach_from_pool(struct worker *worker)
1758 {
1759         struct worker_pool *pool = worker->pool;
1760         struct completion *detach_completion = NULL;
1761 
1762         mutex_lock(&wq_pool_attach_mutex);
1763 
1764         list_del(&worker->node);
1765         worker->pool = NULL;
1766 
1767         if (list_empty(&pool->workers))
1768                 detach_completion = pool->detach_completion;
1769         mutex_unlock(&wq_pool_attach_mutex);
1770 
1771         /* clear leftover flags without pool->lock after it is detached */
1772         worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1773 
1774         if (detach_completion)
1775                 complete(detach_completion);
1776 }
1777 
1778 /**
1779  * create_worker - create a new workqueue worker
1780  * @pool: pool the new worker will belong to
1781  *
1782  * Create and start a new worker which is attached to @pool.
1783  *
1784  * CONTEXT:
1785  * Might sleep.  Does GFP_KERNEL allocations.
1786  *
1787  * Return:
1788  * Pointer to the newly created worker.
1789  */
1790 static struct worker *create_worker(struct worker_pool *pool)
1791 {
1792         struct worker *worker = NULL;
1793         int id = -1;
1794         char id_buf[16];
1795 
1796         /* ID is needed to determine kthread name */
1797         id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1798         if (id < 0)
1799                 goto fail;
1800 
1801         worker = alloc_worker(pool->node);
1802         if (!worker)
1803                 goto fail;
1804 
1805         worker->id = id;
1806 
1807         if (pool->cpu >= 0)
1808                 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1809                          pool->attrs->nice < 0  ? "H" : "");
1810         else
1811                 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1812 
1813         worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1814                                               "kworker/%s", id_buf);
1815         if (IS_ERR(worker->task))
1816                 goto fail;
1817 
1818         set_user_nice(worker->task, pool->attrs->nice);
1819         kthread_bind_mask(worker->task, pool->attrs->cpumask);
1820 
1821         /* successful, attach the worker to the pool */
1822         worker_attach_to_pool(worker, pool);
1823 
1824         /* start the newly created worker */
1825         spin_lock_irq(&pool->lock);
1826         worker->pool->nr_workers++;
1827         worker_enter_idle(worker);
1828         wake_up_process(worker->task);
1829         spin_unlock_irq(&pool->lock);
1830 
1831         return worker;
1832 
1833 fail:
1834         if (id >= 0)
1835                 ida_simple_remove(&pool->worker_ida, id);
1836         kfree(worker);
1837         return NULL;
1838 }
1839 
1840 /**
1841  * destroy_worker - destroy a workqueue worker
1842  * @worker: worker to be destroyed
1843  *
1844  * Destroy @worker and adjust @pool stats accordingly.  The worker should
1845  * be idle.
1846  *
1847  * CONTEXT:
1848  * spin_lock_irq(pool->lock).
1849  */
1850 static void destroy_worker(struct worker *worker)
1851 {
1852         struct worker_pool *pool = worker->pool;
1853 
1854         lockdep_assert_held(&pool->lock);
1855 
1856         /* sanity check frenzy */
1857         if (WARN_ON(worker->current_work) ||
1858             WARN_ON(!list_empty(&worker->scheduled)) ||
1859             WARN_ON(!(worker->flags & WORKER_IDLE)))
1860                 return;
1861 
1862         pool->nr_workers--;
1863         pool->nr_idle--;
1864 
1865         list_del_init(&worker->entry);
1866         worker->flags |= WORKER_DIE;
1867         wake_up_process(worker->task);
1868 }
1869 
1870 static void idle_worker_timeout(struct timer_list *t)
1871 {
1872         struct worker_pool *pool = from_timer(pool, t, idle_timer);
1873 
1874         spin_lock_irq(&pool->lock);
1875 
1876         while (too_many_workers(pool)) {
1877                 struct worker *worker;
1878                 unsigned long expires;
1879 
1880                 /* idle_list is kept in LIFO order, check the last one */
1881                 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1882                 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1883 
1884                 if (time_before(jiffies, expires)) {
1885                         mod_timer(&pool->idle_timer, expires);
1886                         break;
1887                 }
1888 
1889                 destroy_worker(worker);
1890         }
1891 
1892         spin_unlock_irq(&pool->lock);
1893 }
1894 
1895 static void send_mayday(struct work_struct *work)
1896 {
1897         struct pool_workqueue *pwq = get_work_pwq(work);
1898         struct workqueue_struct *wq = pwq->wq;
1899 
1900         lockdep_assert_held(&wq_mayday_lock);
1901 
1902         if (!wq->rescuer)
1903                 return;
1904 
1905         /* mayday mayday mayday */
1906         if (list_empty(&pwq->mayday_node)) {
1907                 /*
1908                  * If @pwq is for an unbound wq, its base ref may be put at
1909                  * any time due to an attribute change.  Pin @pwq until the
1910                  * rescuer is done with it.
1911                  */
1912                 get_pwq(pwq);
1913                 list_add_tail(&pwq->mayday_node, &wq->maydays);
1914                 wake_up_process(wq->rescuer->task);
1915         }
1916 }
1917 
1918 static void pool_mayday_timeout(struct timer_list *t)
1919 {
1920         struct worker_pool *pool = from_timer(pool, t, mayday_timer);
1921         struct work_struct *work;
1922 
1923         spin_lock_irq(&pool->lock);
1924         spin_lock(&wq_mayday_lock);             /* for wq->maydays */
1925 
1926         if (need_to_create_worker(pool)) {
1927                 /*
1928                  * We've been trying to create a new worker but
1929                  * haven't been successful.  We might be hitting an
1930                  * allocation deadlock.  Send distress signals to
1931                  * rescuers.
1932                  */
1933                 list_for_each_entry(work, &pool->worklist, entry)
1934                         send_mayday(work);
1935         }
1936 
1937         spin_unlock(&wq_mayday_lock);
1938         spin_unlock_irq(&pool->lock);
1939 
1940         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1941 }
1942 
1943 /**
1944  * maybe_create_worker - create a new worker if necessary
1945  * @pool: pool to create a new worker for
1946  *
1947  * Create a new worker for @pool if necessary.  @pool is guaranteed to
1948  * have at least one idle worker on return from this function.  If
1949  * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1950  * sent to all rescuers with works scheduled on @pool to resolve
1951  * possible allocation deadlock.
1952  *
1953  * On return, need_to_create_worker() is guaranteed to be %false and
1954  * may_start_working() %true.
1955  *
1956  * LOCKING:
1957  * spin_lock_irq(pool->lock) which may be released and regrabbed
1958  * multiple times.  Does GFP_KERNEL allocations.  Called only from
1959  * manager.
1960  */
1961 static void maybe_create_worker(struct worker_pool *pool)
1962 __releases(&pool->lock)
1963 __acquires(&pool->lock)
1964 {
1965 restart:
1966         spin_unlock_irq(&pool->lock);
1967 
1968         /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1969         mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1970 
1971         while (true) {
1972                 if (create_worker(pool) || !need_to_create_worker(pool))
1973                         break;
1974 
1975                 schedule_timeout_interruptible(CREATE_COOLDOWN);
1976 
1977                 if (!need_to_create_worker(pool))
1978                         break;
1979         }
1980 
1981         del_timer_sync(&pool->mayday_timer);
1982         spin_lock_irq(&pool->lock);
1983         /*
1984          * This is necessary even after a new worker was just successfully
1985          * created as @pool->lock was dropped and the new worker might have
1986          * already become busy.
1987          */
1988         if (need_to_create_worker(pool))
1989                 goto restart;
1990 }
1991 
1992 /**
1993  * manage_workers - manage worker pool
1994  * @worker: self
1995  *
1996  * Assume the manager role and manage the worker pool @worker belongs
1997  * to.  At any given time, there can be only zero or one manager per
1998  * pool.  The exclusion is handled automatically by this function.
1999  *
2000  * The caller can safely start processing works on false return.  On
2001  * true return, it's guaranteed that need_to_create_worker() is false
2002  * and may_start_working() is true.
2003  *
2004  * CONTEXT:
2005  * spin_lock_irq(pool->lock) which may be released and regrabbed
2006  * multiple times.  Does GFP_KERNEL allocations.
2007  *
2008  * Return:
2009  * %false if the pool doesn't need management and the caller can safely
2010  * start processing works, %true if management function was performed and
2011  * the conditions that the caller verified before calling the function may
2012  * no longer be true.
2013  */
2014 static bool manage_workers(struct worker *worker)
2015 {
2016         struct worker_pool *pool = worker->pool;
2017 
2018         if (pool->flags & POOL_MANAGER_ACTIVE)
2019                 return false;
2020 
2021         pool->flags |= POOL_MANAGER_ACTIVE;
2022         pool->manager = worker;
2023 
2024         maybe_create_worker(pool);
2025 
2026         pool->manager = NULL;
2027         pool->flags &= ~POOL_MANAGER_ACTIVE;
2028         wake_up(&wq_manager_wait);
2029         return true;
2030 }
2031 
2032 /**
2033  * process_one_work - process single work
2034  * @worker: self
2035  * @work: work to process
2036  *
2037  * Process @work.  This function contains all the logics necessary to
2038  * process a single work including synchronization against and
2039  * interaction with other workers on the same cpu, queueing and
2040  * flushing.  As long as context requirement is met, any worker can
2041  * call this function to process a work.
2042  *
2043  * CONTEXT:
2044  * spin_lock_irq(pool->lock) which is released and regrabbed.
2045  */
2046 static void process_one_work(struct worker *worker, struct work_struct *work)
2047 __releases(&pool->lock)
2048 __acquires(&pool->lock)
2049 {
2050         struct pool_workqueue *pwq = get_work_pwq(work);
2051         struct worker_pool *pool = worker->pool;
2052         bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2053         int work_color;
2054         struct worker *collision;
2055 #ifdef CONFIG_LOCKDEP
2056         /*
2057          * It is permissible to free the struct work_struct from
2058          * inside the function that is called from it, this we need to
2059          * take into account for lockdep too.  To avoid bogus "held
2060          * lock freed" warnings as well as problems when looking into
2061          * work->lockdep_map, make a copy and use that here.
2062          */
2063         struct lockdep_map lockdep_map;
2064 
2065         lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2066 #endif
2067         /* ensure we're on the correct CPU */
2068         WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2069                      raw_smp_processor_id() != pool->cpu);
2070 
2071         /*
2072          * A single work shouldn't be executed concurrently by
2073          * multiple workers on a single cpu.  Check whether anyone is
2074          * already processing the work.  If so, defer the work to the
2075          * currently executing one.
2076          */
2077         collision = find_worker_executing_work(pool, work);
2078         if (unlikely(collision)) {
2079                 move_linked_works(work, &collision->scheduled, NULL);
2080                 return;
2081         }
2082 
2083         /* claim and dequeue */
2084         debug_work_deactivate(work);
2085         hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2086         worker->current_work = work;
2087         worker->current_func = work->func;
2088         worker->current_pwq = pwq;
2089         work_color = get_work_color(work);
2090 
2091         /*
2092          * Record wq name for cmdline and debug reporting, may get
2093          * overridden through set_worker_desc().
2094          */
2095         strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2096 
2097         list_del_init(&work->entry);
2098 
2099         /*
2100          * CPU intensive works don't participate in concurrency management.
2101          * They're the scheduler's responsibility.  This takes @worker out
2102          * of concurrency management and the next code block will chain
2103          * execution of the pending work items.
2104          */
2105         if (unlikely(cpu_intensive))
2106                 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2107 
2108         /*
2109          * Wake up another worker if necessary.  The condition is always
2110          * false for normal per-cpu workers since nr_running would always
2111          * be >= 1 at this point.  This is used to chain execution of the
2112          * pending work items for WORKER_NOT_RUNNING workers such as the
2113          * UNBOUND and CPU_INTENSIVE ones.
2114          */
2115         if (need_more_worker(pool))
2116                 wake_up_worker(pool);
2117 
2118         /*
2119          * Record the last pool and clear PENDING which should be the last
2120          * update to @work.  Also, do this inside @pool->lock so that
2121          * PENDING and queued state changes happen together while IRQ is
2122          * disabled.
2123          */
2124         set_work_pool_and_clear_pending(work, pool->id);
2125 
2126         spin_unlock_irq(&pool->lock);
2127 
2128         lock_map_acquire(&pwq->wq->lockdep_map);
2129         lock_map_acquire(&lockdep_map);
2130         /*
2131          * Strictly speaking we should mark the invariant state without holding
2132          * any locks, that is, before these two lock_map_acquire()'s.
2133          *
2134          * However, that would result in:
2135          *
2136          *   A(W1)
2137          *   WFC(C)
2138          *              A(W1)
2139          *              C(C)
2140          *
2141          * Which would create W1->C->W1 dependencies, even though there is no
2142          * actual deadlock possible. There are two solutions, using a
2143          * read-recursive acquire on the work(queue) 'locks', but this will then
2144          * hit the lockdep limitation on recursive locks, or simply discard
2145          * these locks.
2146          *
2147          * AFAICT there is no possible deadlock scenario between the
2148          * flush_work() and complete() primitives (except for single-threaded
2149          * workqueues), so hiding them isn't a problem.
2150          */
2151         lockdep_invariant_state(true);
2152         trace_workqueue_execute_start(work);
2153         worker->current_func(work);
2154         /*
2155          * While we must be careful to not use "work" after this, the trace
2156          * point will only record its address.
2157          */
2158         trace_workqueue_execute_end(work);
2159         lock_map_release(&lockdep_map);
2160         lock_map_release(&pwq->wq->lockdep_map);
2161 
2162         if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2163                 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2164                        "     last function: %pf\n",
2165                        current->comm, preempt_count(), task_pid_nr(current),
2166                        worker->current_func);
2167                 debug_show_held_locks(current);
2168                 dump_stack();
2169         }
2170 
2171         /*
2172          * The following prevents a kworker from hogging CPU on !PREEMPT
2173          * kernels, where a requeueing work item waiting for something to
2174          * happen could deadlock with stop_machine as such work item could
2175          * indefinitely requeue itself while all other CPUs are trapped in
2176          * stop_machine. At the same time, report a quiescent RCU state so
2177          * the same condition doesn't freeze RCU.
2178          */
2179         cond_resched();
2180 
2181         spin_lock_irq(&pool->lock);
2182 
2183         /* clear cpu intensive status */
2184         if (unlikely(cpu_intensive))
2185                 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2186 
2187         /* we're done with it, release */
2188         hash_del(&worker->hentry);
2189         worker->current_work = NULL;
2190         worker->current_func = NULL;
2191         worker->current_pwq = NULL;
2192         pwq_dec_nr_in_flight(pwq, work_color);
2193 }
2194 
2195 /**
2196  * process_scheduled_works - process scheduled works
2197  * @worker: self
2198  *
2199  * Process all scheduled works.  Please note that the scheduled list
2200  * may change while processing a work, so this function repeatedly
2201  * fetches a work from the top and executes it.
2202  *
2203  * CONTEXT:
2204  * spin_lock_irq(pool->lock) which may be released and regrabbed
2205  * multiple times.
2206  */
2207 static void process_scheduled_works(struct worker *worker)
2208 {
2209         while (!list_empty(&worker->scheduled)) {
2210                 struct work_struct *work = list_first_entry(&worker->scheduled,
2211                                                 struct work_struct, entry);
2212                 process_one_work(worker, work);
2213         }
2214 }
2215 
2216 static void set_pf_worker(bool val)
2217 {
2218         mutex_lock(&wq_pool_attach_mutex);
2219         if (val)
2220                 current->flags |= PF_WQ_WORKER;
2221         else
2222                 current->flags &= ~PF_WQ_WORKER;
2223         mutex_unlock(&wq_pool_attach_mutex);
2224 }
2225 
2226 /**
2227  * worker_thread - the worker thread function
2228  * @__worker: self
2229  *
2230  * The worker thread function.  All workers belong to a worker_pool -
2231  * either a per-cpu one or dynamic unbound one.  These workers process all
2232  * work items regardless of their specific target workqueue.  The only
2233  * exception is work items which belong to workqueues with a rescuer which
2234  * will be explained in rescuer_thread().
2235  *
2236  * Return: 0
2237  */
2238 static int worker_thread(void *__worker)
2239 {
2240         struct worker *worker = __worker;
2241         struct worker_pool *pool = worker->pool;
2242 
2243         /* tell the scheduler that this is a workqueue worker */
2244         set_pf_worker(true);
2245 woke_up:
2246         spin_lock_irq(&pool->lock);
2247 
2248         /* am I supposed to die? */
2249         if (unlikely(worker->flags & WORKER_DIE)) {
2250                 spin_unlock_irq(&pool->lock);
2251                 WARN_ON_ONCE(!list_empty(&worker->entry));
2252                 set_pf_worker(false);
2253 
2254                 set_task_comm(worker->task, "kworker/dying");
2255                 ida_simple_remove(&pool->worker_ida, worker->id);
2256                 worker_detach_from_pool(worker);
2257                 kfree(worker);
2258                 return 0;
2259         }
2260 
2261         worker_leave_idle(worker);
2262 recheck:
2263         /* no more worker necessary? */
2264         if (!need_more_worker(pool))
2265                 goto sleep;
2266 
2267         /* do we need to manage? */
2268         if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2269                 goto recheck;
2270 
2271         /*
2272          * ->scheduled list can only be filled while a worker is
2273          * preparing to process a work or actually processing it.
2274          * Make sure nobody diddled with it while I was sleeping.
2275          */
2276         WARN_ON_ONCE(!list_empty(&worker->scheduled));
2277 
2278         /*
2279          * Finish PREP stage.  We're guaranteed to have at least one idle
2280          * worker or that someone else has already assumed the manager
2281          * role.  This is where @worker starts participating in concurrency
2282          * management if applicable and concurrency management is restored
2283          * after being rebound.  See rebind_workers() for details.
2284          */
2285         worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2286 
2287         do {
2288                 struct work_struct *work =
2289                         list_first_entry(&pool->worklist,
2290                                          struct work_struct, entry);
2291 
2292                 pool->watchdog_ts = jiffies;
2293 
2294                 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2295                         /* optimization path, not strictly necessary */
2296                         process_one_work(worker, work);
2297                         if (unlikely(!list_empty(&worker->scheduled)))
2298                                 process_scheduled_works(worker);
2299                 } else {
2300                         move_linked_works(work, &worker->scheduled, NULL);
2301                         process_scheduled_works(worker);
2302                 }
2303         } while (keep_working(pool));
2304 
2305         worker_set_flags(worker, WORKER_PREP);
2306 sleep:
2307         /*
2308          * pool->lock is held and there's no work to process and no need to
2309          * manage, sleep.  Workers are woken up only while holding
2310          * pool->lock or from local cpu, so setting the current state
2311          * before releasing pool->lock is enough to prevent losing any
2312          * event.
2313          */
2314         worker_enter_idle(worker);
2315         __set_current_state(TASK_IDLE);
2316         spin_unlock_irq(&pool->lock);
2317         schedule();
2318         goto woke_up;
2319 }
2320 
2321 /**
2322  * rescuer_thread - the rescuer thread function
2323  * @__rescuer: self
2324  *
2325  * Workqueue rescuer thread function.  There's one rescuer for each
2326  * workqueue which has WQ_MEM_RECLAIM set.
2327  *
2328  * Regular work processing on a pool may block trying to create a new
2329  * worker which uses GFP_KERNEL allocation which has slight chance of
2330  * developing into deadlock if some works currently on the same queue
2331  * need to be processed to satisfy the GFP_KERNEL allocation.  This is
2332  * the problem rescuer solves.
2333  *
2334  * When such condition is possible, the pool summons rescuers of all
2335  * workqueues which have works queued on the pool and let them process
2336  * those works so that forward progress can be guaranteed.
2337  *
2338  * This should happen rarely.
2339  *
2340  * Return: 0
2341  */
2342 static int rescuer_thread(void *__rescuer)
2343 {
2344         struct worker *rescuer = __rescuer;
2345         struct workqueue_struct *wq = rescuer->rescue_wq;
2346         struct list_head *scheduled = &rescuer->scheduled;
2347         bool should_stop;
2348 
2349         set_user_nice(current, RESCUER_NICE_LEVEL);
2350 
2351         /*
2352          * Mark rescuer as worker too.  As WORKER_PREP is never cleared, it
2353          * doesn't participate in concurrency management.
2354          */
2355         set_pf_worker(true);
2356 repeat:
2357         set_current_state(TASK_IDLE);
2358 
2359         /*
2360          * By the time the rescuer is requested to stop, the workqueue
2361          * shouldn't have any work pending, but @wq->maydays may still have
2362          * pwq(s) queued.  This can happen by non-rescuer workers consuming
2363          * all the work items before the rescuer got to them.  Go through
2364          * @wq->maydays processing before acting on should_stop so that the
2365          * list is always empty on exit.
2366          */
2367         should_stop = kthread_should_stop();
2368 
2369         /* see whether any pwq is asking for help */
2370         spin_lock_irq(&wq_mayday_lock);
2371 
2372         while (!list_empty(&wq->maydays)) {
2373                 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2374                                         struct pool_workqueue, mayday_node);
2375                 struct worker_pool *pool = pwq->pool;
2376                 struct work_struct *work, *n;
2377                 bool first = true;
2378 
2379                 __set_current_state(TASK_RUNNING);
2380                 list_del_init(&pwq->mayday_node);
2381 
2382                 spin_unlock_irq(&wq_mayday_lock);
2383 
2384                 worker_attach_to_pool(rescuer, pool);
2385 
2386                 spin_lock_irq(&pool->lock);
2387 
2388                 /*
2389                  * Slurp in all works issued via this workqueue and
2390                  * process'em.
2391                  */
2392                 WARN_ON_ONCE(!list_empty(scheduled));
2393                 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2394                         if (get_work_pwq(work) == pwq) {
2395                                 if (first)
2396                                         pool->watchdog_ts = jiffies;
2397                                 move_linked_works(work, scheduled, &n);
2398                         }
2399                         first = false;
2400                 }
2401 
2402                 if (!list_empty(scheduled)) {
2403                         process_scheduled_works(rescuer);
2404 
2405                         /*
2406                          * The above execution of rescued work items could
2407                          * have created more to rescue through
2408                          * pwq_activate_first_delayed() or chained
2409                          * queueing.  Let's put @pwq back on mayday list so
2410                          * that such back-to-back work items, which may be
2411                          * being used to relieve memory pressure, don't
2412                          * incur MAYDAY_INTERVAL delay inbetween.
2413                          */
2414                         if (need_to_create_worker(pool)) {
2415                                 spin_lock(&wq_mayday_lock);
2416                                 get_pwq(pwq);
2417                                 list_move_tail(&pwq->mayday_node, &wq->maydays);
2418                                 spin_unlock(&wq_mayday_lock);
2419                         }
2420                 }
2421 
2422                 /*
2423                  * Put the reference grabbed by send_mayday().  @pool won't
2424                  * go away while we're still attached to it.
2425                  */
2426                 put_pwq(pwq);
2427 
2428                 /*
2429                  * Leave this pool.  If need_more_worker() is %true, notify a
2430                  * regular worker; otherwise, we end up with 0 concurrency
2431                  * and stalling the execution.
2432                  */
2433                 if (need_more_worker(pool))
2434                         wake_up_worker(pool);
2435 
2436                 spin_unlock_irq(&pool->lock);
2437 
2438                 worker_detach_from_pool(rescuer);
2439 
2440                 spin_lock_irq(&wq_mayday_lock);
2441         }
2442 
2443         spin_unlock_irq(&wq_mayday_lock);
2444 
2445         if (should_stop) {
2446                 __set_current_state(TASK_RUNNING);
2447                 set_pf_worker(false);
2448                 return 0;
2449         }
2450 
2451         /* rescuers should never participate in concurrency management */
2452         WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2453         schedule();
2454         goto repeat;
2455 }
2456 
2457 /**
2458  * check_flush_dependency - check for flush dependency sanity
2459  * @target_wq: workqueue being flushed
2460  * @target_work: work item being flushed (NULL for workqueue flushes)
2461  *
2462  * %current is trying to flush the whole @target_wq or @target_work on it.
2463  * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2464  * reclaiming memory or running on a workqueue which doesn't have
2465  * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2466  * a deadlock.
2467  */
2468 static void check_flush_dependency(struct workqueue_struct *target_wq,
2469                                    struct work_struct *target_work)
2470 {
2471         work_func_t target_func = target_work ? target_work->func : NULL;
2472         struct worker *worker;
2473 
2474         if (target_wq->flags & WQ_MEM_RECLAIM)
2475                 return;
2476 
2477         worker = current_wq_worker();
2478 
2479         WARN_ONCE(current->flags & PF_MEMALLOC,
2480                   "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2481                   current->pid, current->comm, target_wq->name, target_func);
2482         WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2483                               (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2484                   "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2485                   worker->current_pwq->wq->name, worker->current_func,
2486                   target_wq->name, target_func);
2487 }
2488 
2489 struct wq_barrier {
2490         struct work_struct      work;
2491         struct completion       done;
2492         struct task_struct      *task;  /* purely informational */
2493 };
2494 
2495 static void wq_barrier_func(struct work_struct *work)
2496 {
2497         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2498         complete(&barr->done);
2499 }
2500 
2501 /**
2502  * insert_wq_barrier - insert a barrier work
2503  * @pwq: pwq to insert barrier into
2504  * @barr: wq_barrier to insert
2505  * @target: target work to attach @barr to
2506  * @worker: worker currently executing @target, NULL if @target is not executing
2507  *
2508  * @barr is linked to @target such that @barr is completed only after
2509  * @target finishes execution.  Please note that the ordering
2510  * guarantee is observed only with respect to @target and on the local
2511  * cpu.
2512  *
2513  * Currently, a queued barrier can't be canceled.  This is because
2514  * try_to_grab_pending() can't determine whether the work to be
2515  * grabbed is at the head of the queue and thus can't clear LINKED
2516  * flag of the previous work while there must be a valid next work
2517  * after a work with LINKED flag set.
2518  *
2519  * Note that when @worker is non-NULL, @target may be modified
2520  * underneath us, so we can't reliably determine pwq from @target.
2521  *
2522  * CONTEXT:
2523  * spin_lock_irq(pool->lock).
2524  */
2525 static void insert_wq_barrier(struct pool_workqueue *pwq,
2526                               struct wq_barrier *barr,
2527                               struct work_struct *target, struct worker *worker)
2528 {
2529         struct list_head *head;
2530         unsigned int linked = 0;
2531 
2532         /*
2533          * debugobject calls are safe here even with pool->lock locked
2534          * as we know for sure that this will not trigger any of the
2535          * checks and call back into the fixup functions where we
2536          * might deadlock.
2537          */
2538         INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2539         __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2540 
2541         init_completion_map(&barr->done, &target->lockdep_map);
2542 
2543         barr->task = current;
2544 
2545         /*
2546          * If @target is currently being executed, schedule the
2547          * barrier to the worker; otherwise, put it after @target.
2548          */
2549         if (worker)
2550                 head = worker->scheduled.next;
2551         else {
2552                 unsigned long *bits = work_data_bits(target);
2553 
2554                 head = target->entry.next;
2555                 /* there can already be other linked works, inherit and set */
2556                 linked = *bits & WORK_STRUCT_LINKED;
2557                 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2558         }
2559 
2560         debug_work_activate(&barr->work);
2561         insert_work(pwq, &barr->work, head,
2562                     work_color_to_flags(WORK_NO_COLOR) | linked);
2563 }
2564 
2565 /**
2566  * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2567  * @wq: workqueue being flushed
2568  * @flush_color: new flush color, < 0 for no-op
2569  * @work_color: new work color, < 0 for no-op
2570  *
2571  * Prepare pwqs for workqueue flushing.
2572  *
2573  * If @flush_color is non-negative, flush_color on all pwqs should be
2574  * -1.  If no pwq has in-flight commands at the specified color, all
2575  * pwq->flush_color's stay at -1 and %false is returned.  If any pwq
2576  * has in flight commands, its pwq->flush_color is set to
2577  * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2578  * wakeup logic is armed and %true is returned.
2579  *
2580  * The caller should have initialized @wq->first_flusher prior to
2581  * calling this function with non-negative @flush_color.  If
2582  * @flush_color is negative, no flush color update is done and %false
2583  * is returned.
2584  *
2585  * If @work_color is non-negative, all pwqs should have the same
2586  * work_color which is previous to @work_color and all will be
2587  * advanced to @work_color.
2588  *
2589  * CONTEXT:
2590  * mutex_lock(wq->mutex).
2591  *
2592  * Return:
2593  * %true if @flush_color >= 0 and there's something to flush.  %false
2594  * otherwise.
2595  */
2596 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2597                                       int flush_color, int work_color)
2598 {
2599         bool wait = false;
2600         struct pool_workqueue *pwq;
2601 
2602         if (flush_color >= 0) {
2603                 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2604                 atomic_set(&wq->nr_pwqs_to_flush, 1);
2605         }
2606 
2607         for_each_pwq(pwq, wq) {
2608                 struct worker_pool *pool = pwq->pool;
2609 
2610                 spin_lock_irq(&pool->lock);
2611 
2612                 if (flush_color >= 0) {
2613                         WARN_ON_ONCE(pwq->flush_color != -1);
2614 
2615                         if (pwq->nr_in_flight[flush_color]) {
2616                                 pwq->flush_color = flush_color;
2617                                 atomic_inc(&wq->nr_pwqs_to_flush);
2618                                 wait = true;
2619                         }
2620                 }
2621 
2622                 if (work_color >= 0) {
2623                         WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2624                         pwq->work_color = work_color;
2625                 }
2626 
2627                 spin_unlock_irq(&pool->lock);
2628         }
2629 
2630         if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2631                 complete(&wq->first_flusher->done);
2632 
2633         return wait;
2634 }
2635 
2636 /**
2637  * flush_workqueue - ensure that any scheduled work has run to completion.
2638  * @wq: workqueue to flush
2639  *
2640  * This function sleeps until all work items which were queued on entry
2641  * have finished execution, but it is not livelocked by new incoming ones.
2642  */
2643 void flush_workqueue(struct workqueue_struct *wq)
2644 {
2645         struct wq_flusher this_flusher = {
2646                 .list = LIST_HEAD_INIT(this_flusher.list),
2647                 .flush_color = -1,
2648                 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
2649         };
2650         int next_color;
2651 
2652         if (WARN_ON(!wq_online))
2653                 return;
2654 
2655         mutex_lock(&wq->mutex);
2656 
2657         /*
2658          * Start-to-wait phase
2659          */
2660         next_color = work_next_color(wq->work_color);
2661 
2662         if (next_color != wq->flush_color) {
2663                 /*
2664                  * Color space is not full.  The current work_color
2665                  * becomes our flush_color and work_color is advanced
2666                  * by one.
2667                  */
2668                 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2669                 this_flusher.flush_color = wq->work_color;
2670                 wq->work_color = next_color;
2671 
2672                 if (!wq->first_flusher) {
2673                         /* no flush in progress, become the first flusher */
2674                         WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2675 
2676                         wq->first_flusher = &this_flusher;
2677 
2678                         if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2679                                                        wq->work_color)) {
2680                                 /* nothing to flush, done */
2681                                 wq->flush_color = next_color;
2682                                 wq->first_flusher = NULL;
2683                                 goto out_unlock;
2684                         }
2685                 } else {
2686                         /* wait in queue */
2687                         WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2688                         list_add_tail(&this_flusher.list, &wq->flusher_queue);
2689                         flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2690                 }
2691         } else {
2692                 /*
2693                  * Oops, color space is full, wait on overflow queue.
2694                  * The next flush completion will assign us
2695                  * flush_color and transfer to flusher_queue.
2696                  */
2697                 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2698         }
2699 
2700         check_flush_dependency(wq, NULL);
2701 
2702         mutex_unlock(&wq->mutex);
2703 
2704         wait_for_completion(&this_flusher.done);
2705 
2706         /*
2707          * Wake-up-and-cascade phase
2708          *
2709          * First flushers are responsible for cascading flushes and
2710          * handling overflow.  Non-first flushers can simply return.
2711          */
2712         if (wq->first_flusher != &this_flusher)
2713                 return;
2714 
2715         mutex_lock(&wq->mutex);
2716 
2717         /* we might have raced, check again with mutex held */
2718         if (wq->first_flusher != &this_flusher)
2719                 goto out_unlock;
2720 
2721         wq->first_flusher = NULL;
2722 
2723         WARN_ON_ONCE(!list_empty(&this_flusher.list));
2724         WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2725 
2726         while (true) {
2727                 struct wq_flusher *next, *tmp;
2728 
2729                 /* complete all the flushers sharing the current flush color */
2730                 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2731                         if (next->flush_color != wq->flush_color)
2732                                 break;
2733                         list_del_init(&next->list);
2734                         complete(&next->done);
2735                 }
2736 
2737                 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2738                              wq->flush_color != work_next_color(wq->work_color));
2739 
2740                 /* this flush_color is finished, advance by one */
2741                 wq->flush_color = work_next_color(wq->flush_color);
2742 
2743                 /* one color has been freed, handle overflow queue */
2744                 if (!list_empty(&wq->flusher_overflow)) {
2745                         /*
2746                          * Assign the same color to all overflowed
2747                          * flushers, advance work_color and append to
2748                          * flusher_queue.  This is the start-to-wait
2749                          * phase for these overflowed flushers.
2750                          */
2751                         list_for_each_entry(tmp, &wq->flusher_overflow, list)
2752                                 tmp->flush_color = wq->work_color;
2753 
2754                         wq->work_color = work_next_color(wq->work_color);
2755 
2756                         list_splice_tail_init(&wq->flusher_overflow,
2757                                               &wq->flusher_queue);
2758                         flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2759                 }
2760 
2761                 if (list_empty(&wq->flusher_queue)) {
2762                         WARN_ON_ONCE(wq->flush_color != wq->work_color);
2763                         break;
2764                 }
2765 
2766                 /*
2767                  * Need to flush more colors.  Make the next flusher
2768                  * the new first flusher and arm pwqs.
2769                  */
2770                 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2771                 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2772 
2773                 list_del_init(&next->list);
2774                 wq->first_flusher = next;
2775 
2776                 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2777                         break;
2778 
2779                 /*
2780                  * Meh... this color is already done, clear first
2781                  * flusher and repeat cascading.
2782                  */
2783                 wq->first_flusher = NULL;
2784         }
2785 
2786 out_unlock:
2787         mutex_unlock(&wq->mutex);
2788 }
2789 EXPORT_SYMBOL(flush_workqueue);
2790 
2791 /**
2792  * drain_workqueue - drain a workqueue
2793  * @wq: workqueue to drain
2794  *
2795  * Wait until the workqueue becomes empty.  While draining is in progress,
2796  * only chain queueing is allowed.  IOW, only currently pending or running
2797  * work items on @wq can queue further work items on it.  @wq is flushed
2798  * repeatedly until it becomes empty.  The number of flushing is determined
2799  * by the depth of chaining and should be relatively short.  Whine if it
2800  * takes too long.
2801  */
2802 void drain_workqueue(struct workqueue_struct *wq)
2803 {
2804         unsigned int flush_cnt = 0;
2805         struct pool_workqueue *pwq;
2806 
2807         /*
2808          * __queue_work() needs to test whether there are drainers, is much
2809          * hotter than drain_workqueue() and already looks at @wq->flags.
2810          * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2811          */
2812         mutex_lock(&wq->mutex);
2813         if (!wq->nr_drainers++)
2814                 wq->flags |= __WQ_DRAINING;
2815         mutex_unlock(&wq->mutex);
2816 reflush:
2817         flush_workqueue(wq);
2818 
2819         mutex_lock(&wq->mutex);
2820 
2821         for_each_pwq(pwq, wq) {
2822                 bool drained;
2823 
2824                 spin_lock_irq(&pwq->pool->lock);
2825                 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2826                 spin_unlock_irq(&pwq->pool->lock);
2827 
2828                 if (drained)
2829                         continue;
2830 
2831                 if (++flush_cnt == 10 ||
2832                     (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2833                         pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2834                                 wq->name, flush_cnt);
2835 
2836                 mutex_unlock(&wq->mutex);
2837                 goto reflush;
2838         }
2839 
2840         if (!--wq->nr_drainers)
2841                 wq->flags &= ~__WQ_DRAINING;
2842         mutex_unlock(&wq->mutex);
2843 }
2844 EXPORT_SYMBOL_GPL(drain_workqueue);
2845 
2846 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2847 {
2848         struct worker *worker = NULL;
2849         struct worker_pool *pool;
2850         struct pool_workqueue *pwq;
2851 
2852         might_sleep();
2853 
2854         local_irq_disable();
2855         pool = get_work_pool(work);
2856         if (!pool) {
2857                 local_irq_enable();
2858                 return false;
2859         }
2860 
2861         spin_lock(&pool->lock);
2862         /* see the comment in try_to_grab_pending() with the same code */
2863         pwq = get_work_pwq(work);
2864         if (pwq) {
2865                 if (unlikely(pwq->pool != pool))
2866                         goto already_gone;
2867         } else {
2868                 worker = find_worker_executing_work(pool, work);
2869                 if (!worker)
2870                         goto already_gone;
2871                 pwq = worker->current_pwq;
2872         }
2873 
2874         check_flush_dependency(pwq->wq, work);
2875 
2876         insert_wq_barrier(pwq, barr, work, worker);
2877         spin_unlock_irq(&pool->lock);
2878 
2879         /*
2880          * Force a lock recursion deadlock when using flush_work() inside a
2881          * single-threaded or rescuer equipped workqueue.
2882          *
2883          * For single threaded workqueues the deadlock happens when the work
2884          * is after the work issuing the flush_work(). For rescuer equipped
2885          * workqueues the deadlock happens when the rescuer stalls, blocking
2886          * forward progress.
2887          */
2888         if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) {
2889                 lock_map_acquire(&pwq->wq->lockdep_map);
2890                 lock_map_release(&pwq->wq->lockdep_map);
2891         }
2892 
2893         return true;
2894 already_gone:
2895         spin_unlock_irq(&pool->lock);
2896         return false;
2897 }
2898 
2899 /**
2900  * flush_work - wait for a work to finish executing the last queueing instance
2901  * @work: the work to flush
2902  *
2903  * Wait until @work has finished execution.  @work is guaranteed to be idle
2904  * on return if it hasn't been requeued since flush started.
2905  *
2906  * Return:
2907  * %true if flush_work() waited for the work to finish execution,
2908  * %false if it was already idle.
2909  */
2910 bool flush_work(struct work_struct *work)
2911 {
2912         struct wq_barrier barr;
2913 
2914         if (WARN_ON(!wq_online))
2915                 return false;
2916 
2917         if (start_flush_work(work, &barr)) {
2918                 wait_for_completion(&barr.done);
2919                 destroy_work_on_stack(&barr.work);
2920                 return true;
2921         } else {
2922                 return false;
2923         }
2924 }
2925 EXPORT_SYMBOL_GPL(flush_work);
2926 
2927 struct cwt_wait {
2928         wait_queue_entry_t              wait;
2929         struct work_struct      *work;
2930 };
2931 
2932 static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
2933 {
2934         struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2935 
2936         if (cwait->work != key)
2937                 return 0;
2938         return autoremove_wake_function(wait, mode, sync, key);
2939 }
2940 
2941 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2942 {
2943         static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2944         unsigned long flags;
2945         int ret;
2946 
2947         do {
2948                 ret = try_to_grab_pending(work, is_dwork, &flags);
2949                 /*
2950                  * If someone else is already canceling, wait for it to
2951                  * finish.  flush_work() doesn't work for PREEMPT_NONE
2952                  * because we may get scheduled between @work's completion
2953                  * and the other canceling task resuming and clearing
2954                  * CANCELING - flush_work() will return false immediately
2955                  * as @work is no longer busy, try_to_grab_pending() will
2956                  * return -ENOENT as @work is still being canceled and the
2957                  * other canceling task won't be able to clear CANCELING as
2958                  * we're hogging the CPU.
2959                  *
2960                  * Let's wait for completion using a waitqueue.  As this
2961                  * may lead to the thundering herd problem, use a custom
2962                  * wake function which matches @work along with exclusive
2963                  * wait and wakeup.
2964                  */
2965                 if (unlikely(ret == -ENOENT)) {
2966                         struct cwt_wait cwait;
2967 
2968                         init_wait(&cwait.wait);
2969                         cwait.wait.func = cwt_wakefn;
2970                         cwait.work = work;
2971 
2972                         prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2973                                                   TASK_UNINTERRUPTIBLE);
2974                         if (work_is_canceling(work))
2975                                 schedule();
2976                         finish_wait(&cancel_waitq, &cwait.wait);
2977                 }
2978         } while (unlikely(ret < 0));
2979 
2980         /* tell other tasks trying to grab @work to back off */
2981         mark_work_canceling(work);
2982         local_irq_restore(flags);
2983 
2984         /*
2985          * This allows canceling during early boot.  We know that @work
2986          * isn't executing.
2987          */
2988         if (wq_online)
2989                 flush_work(work);
2990 
2991         clear_work_data(work);
2992 
2993         /*
2994          * Paired with prepare_to_wait() above so that either
2995          * waitqueue_active() is visible here or !work_is_canceling() is
2996          * visible there.
2997          */
2998         smp_mb();
2999         if (waitqueue_active(&cancel_waitq))
3000                 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3001 
3002         return ret;
3003 }
3004 
3005 /**
3006  * cancel_work_sync - cancel a work and wait for it to finish
3007  * @work: the work to cancel
3008  *
3009  * Cancel @work and wait for its execution to finish.  This function
3010  * can be used even if the work re-queues itself or migrates to
3011  * another workqueue.  On return from this function, @work is
3012  * guaranteed to be not pending or executing on any CPU.
3013  *
3014  * cancel_work_sync(&delayed_work->work) must not be used for
3015  * delayed_work's.  Use cancel_delayed_work_sync() instead.
3016  *
3017  * The caller must ensure that the workqueue on which @work was last
3018  * queued can't be destroyed before this function returns.
3019  *
3020  * Return:
3021  * %true if @work was pending, %false otherwise.
3022  */
3023 bool cancel_work_sync(struct work_struct *work)
3024 {
3025         return __cancel_work_timer(work, false);
3026 }
3027 EXPORT_SYMBOL_GPL(cancel_work_sync);
3028 
3029 /**
3030  * flush_delayed_work - wait for a dwork to finish executing the last queueing
3031  * @dwork: the delayed work to flush
3032  *
3033  * Delayed timer is cancelled and the pending work is queued for
3034  * immediate execution.  Like flush_work(), this function only
3035  * considers the last queueing instance of @dwork.
3036  *
3037  * Return:
3038  * %true if flush_work() waited for the work to finish execution,
3039  * %false if it was already idle.
3040  */
3041 bool flush_delayed_work(struct delayed_work *dwork)
3042 {
3043         local_irq_disable();
3044         if (del_timer_sync(&dwork->timer))
3045                 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3046         local_irq_enable();
3047         return flush_work(&dwork->work);
3048 }
3049 EXPORT_SYMBOL(flush_delayed_work);
3050 
3051 /**
3052  * flush_rcu_work - wait for a rwork to finish executing the last queueing
3053  * @rwork: the rcu work to flush
3054  *
3055  * Return:
3056  * %true if flush_rcu_work() waited for the work to finish execution,
3057  * %false if it was already idle.
3058  */
3059 bool flush_rcu_work(struct rcu_work *rwork)
3060 {
3061         if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3062                 rcu_barrier();
3063                 flush_work(&rwork->work);
3064                 return true;
3065         } else {
3066                 return flush_work(&rwork->work);
3067         }
3068 }
3069 EXPORT_SYMBOL(flush_rcu_work);
3070 
3071 static bool __cancel_work(struct work_struct *work, bool is_dwork)
3072 {
3073         unsigned long flags;
3074         int ret;
3075 
3076         do {
3077                 ret = try_to_grab_pending(work, is_dwork, &flags);
3078         } while (unlikely(ret == -EAGAIN));
3079 
3080         if (unlikely(ret < 0))
3081                 return false;
3082 
3083         set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3084         local_irq_restore(flags);
3085         return ret;
3086 }
3087 
3088 /**
3089  * cancel_delayed_work - cancel a delayed work
3090  * @dwork: delayed_work to cancel
3091  *
3092  * Kill off a pending delayed_work.
3093  *
3094  * Return: %true if @dwork was pending and canceled; %false if it wasn't
3095  * pending.
3096  *
3097  * Note:
3098  * The work callback function may still be running on return, unless
3099  * it returns %true and the work doesn't re-arm itself.  Explicitly flush or
3100  * use cancel_delayed_work_sync() to wait on it.
3101  *
3102  * This function is safe to call from any context including IRQ handler.
3103  */
3104 bool cancel_delayed_work(struct delayed_work *dwork)
3105 {
3106         return __cancel_work(&dwork->work, true);
3107 }
3108 EXPORT_SYMBOL(cancel_delayed_work);
3109 
3110 /**
3111  * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3112  * @dwork: the delayed work cancel
3113  *
3114  * This is cancel_work_sync() for delayed works.
3115  *
3116  * Return:
3117  * %true if @dwork was pending, %false otherwise.
3118  */
3119 bool cancel_delayed_work_sync(struct delayed_work *dwork)
3120 {
3121         return __cancel_work_timer(&dwork->work, true);
3122 }
3123 EXPORT_SYMBOL(cancel_delayed_work_sync);
3124 
3125 /**
3126  * schedule_on_each_cpu - execute a function synchronously on each online CPU
3127  * @func: the function to call
3128  *
3129  * schedule_on_each_cpu() executes @func on each online CPU using the
3130  * system workqueue and blocks until all CPUs have completed.
3131  * schedule_on_each_cpu() is very slow.
3132  *
3133  * Return:
3134  * 0 on success, -errno on failure.
3135  */
3136 int schedule_on_each_cpu(work_func_t func)
3137 {
3138         int cpu;
3139         struct work_struct __percpu *works;
3140 
3141         works = alloc_percpu(struct work_struct);
3142         if (!works)
3143                 return -ENOMEM;
3144 
3145         get_online_cpus();
3146 
3147         for_each_online_cpu(cpu) {
3148                 struct work_struct *work = per_cpu_ptr(works, cpu);
3149 
3150                 INIT_WORK(work, func);
3151                 schedule_work_on(cpu, work);
3152         }
3153 
3154         for_each_online_cpu(cpu)
3155                 flush_work(per_cpu_ptr(works, cpu));
3156 
3157         put_online_cpus();
3158         free_percpu(works);
3159         return 0;
3160 }
3161 
3162 /**
3163  * execute_in_process_context - reliably execute the routine with user context
3164  * @fn:         the function to execute
3165  * @ew:         guaranteed storage for the execute work structure (must
3166  *              be available when the work executes)
3167  *
3168  * Executes the function immediately if process context is available,
3169  * otherwise schedules the function for delayed execution.
3170  *
3171  * Return:      0 - function was executed
3172  *              1 - function was scheduled for execution
3173  */
3174 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3175 {
3176         if (!in_interrupt()) {
3177                 fn(&ew->work);
3178                 return 0;
3179         }
3180 
3181         INIT_WORK(&ew->work, fn);
3182         schedule_work(&ew->work);
3183 
3184         return 1;
3185 }
3186 EXPORT_SYMBOL_GPL(execute_in_process_context);
3187 
3188 /**
3189  * free_workqueue_attrs - free a workqueue_attrs
3190  * @attrs: workqueue_attrs to free
3191  *
3192  * Undo alloc_workqueue_attrs().
3193  */
3194 void free_workqueue_attrs(struct workqueue_attrs *attrs)
3195 {
3196         if (attrs) {
3197                 free_cpumask_var(attrs->cpumask);
3198                 kfree(attrs);
3199         }
3200 }
3201 
3202 /**
3203  * alloc_workqueue_attrs - allocate a workqueue_attrs
3204  * @gfp_mask: allocation mask to use
3205  *
3206  * Allocate a new workqueue_attrs, initialize with default settings and
3207  * return it.
3208  *
3209  * Return: The allocated new workqueue_attr on success. %NULL on failure.
3210  */
3211 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3212 {
3213         struct workqueue_attrs *attrs;
3214 
3215         attrs = kzalloc(sizeof(*attrs), gfp_mask);
3216         if (!attrs)
3217                 goto fail;
3218         if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3219                 goto fail;
3220 
3221         cpumask_copy(attrs->cpumask, cpu_possible_mask);
3222         return attrs;
3223 fail:
3224         free_workqueue_attrs(attrs);
3225         return NULL;
3226 }
3227 
3228 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3229                                  const struct workqueue_attrs *from)
3230 {
3231         to->nice = from->nice;
3232         cpumask_copy(to->cpumask, from->cpumask);
3233         /*
3234          * Unlike hash and equality test, this function doesn't ignore
3235          * ->no_numa as it is used for both pool and wq attrs.  Instead,
3236          * get_unbound_pool() explicitly clears ->no_numa after copying.
3237          */
3238         to->no_numa = from->no_numa;
3239 }
3240 
3241 /* hash value of the content of @attr */
3242 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3243 {
3244         u32 hash = 0;
3245 
3246         hash = jhash_1word(attrs->nice, hash);
3247         hash = jhash(cpumask_bits(attrs->cpumask),
3248                      BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3249         return hash;
3250 }
3251 
3252 /* content equality test */
3253 static bool wqattrs_equal(const struct workqueue_attrs *a,
3254                           const struct workqueue_attrs *b)
3255 {
3256         if (a->nice != b->nice)
3257                 return false;
3258         if (!cpumask_equal(a->cpumask, b->cpumask))
3259                 return false;
3260         return true;
3261 }
3262 
3263 /**
3264  * init_worker_pool - initialize a newly zalloc'd worker_pool
3265  * @pool: worker_pool to initialize
3266  *
3267  * Initialize a newly zalloc'd @pool.  It also allocates @pool->attrs.
3268  *
3269  * Return: 0 on success, -errno on failure.  Even on failure, all fields
3270  * inside @pool proper are initialized and put_unbound_pool() can be called
3271  * on @pool safely to release it.
3272  */
3273 static int init_worker_pool(struct worker_pool *pool)
3274 {
3275         spin_lock_init(&pool->lock);
3276         pool->id = -1;
3277         pool->cpu = -1;
3278         pool->node = NUMA_NO_NODE;
3279         pool->flags |= POOL_DISASSOCIATED;
3280         pool->watchdog_ts = jiffies;
3281         INIT_LIST_HEAD(&pool->worklist);
3282         INIT_LIST_HEAD(&pool->idle_list);
3283         hash_init(pool->busy_hash);
3284 
3285         timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3286 
3287         timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3288 
3289         INIT_LIST_HEAD(&pool->workers);
3290 
3291         ida_init(&pool->worker_ida);
3292         INIT_HLIST_NODE(&pool->hash_node);
3293         pool->refcnt = 1;
3294 
3295         /* shouldn't fail above this point */
3296         pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3297         if (!pool->attrs)
3298                 return -ENOMEM;
3299         return 0;
3300 }
3301 
3302 static void rcu_free_wq(struct rcu_head *rcu)
3303 {
3304         struct workqueue_struct *wq =
3305                 container_of(rcu, struct workqueue_struct, rcu);
3306 
3307         if (!(wq->flags & WQ_UNBOUND))
3308                 free_percpu(wq->cpu_pwqs);
3309         else
3310                 free_workqueue_attrs(wq->unbound_attrs);
3311 
3312         kfree(wq->rescuer);
3313         kfree(wq);
3314 }
3315 
3316 static void rcu_free_pool(struct rcu_head *rcu)
3317 {
3318         struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3319 
3320         ida_destroy(&pool->worker_ida);
3321         free_workqueue_attrs(pool->attrs);
3322         kfree(pool);
3323 }
3324 
3325 /**
3326  * put_unbound_pool - put a worker_pool
3327  * @pool: worker_pool to put
3328  *
3329  * Put @pool.  If its refcnt reaches zero, it gets destroyed in sched-RCU
3330  * safe manner.  get_unbound_pool() calls this function on its failure path
3331  * and this function should be able to release pools which went through,
3332  * successfully or not, init_worker_pool().
3333  *
3334  * Should be called with wq_pool_mutex held.
3335  */
3336 static void put_unbound_pool(struct worker_pool *pool)
3337 {
3338         DECLARE_COMPLETION_ONSTACK(detach_completion);
3339         struct worker *worker;
3340 
3341         lockdep_assert_held(&wq_pool_mutex);
3342 
3343         if (--pool->refcnt)
3344                 return;
3345 
3346         /* sanity checks */
3347         if (WARN_ON(!(pool->cpu < 0)) ||
3348             WARN_ON(!list_empty(&pool->worklist)))
3349                 return;
3350 
3351         /* release id and unhash */
3352         if (pool->id >= 0)
3353                 idr_remove(&worker_pool_idr, pool->id);
3354         hash_del(&pool->hash_node);
3355 
3356         /*
3357          * Become the manager and destroy all workers.  This prevents
3358          * @pool's workers from blocking on attach_mutex.  We're the last
3359          * manager and @pool gets freed with the flag set.
3360          */
3361         spin_lock_irq(&pool->lock);
3362         wait_event_lock_irq(wq_manager_wait,
3363                             !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock);
3364         pool->flags |= POOL_MANAGER_ACTIVE;
3365 
3366         while ((worker = first_idle_worker(pool)))
3367                 destroy_worker(worker);
3368         WARN_ON(pool->nr_workers || pool->nr_idle);
3369         spin_unlock_irq(&pool->lock);
3370 
3371         mutex_lock(&wq_pool_attach_mutex);
3372         if (!list_empty(&pool->workers))
3373                 pool->detach_completion = &detach_completion;
3374         mutex_unlock(&wq_pool_attach_mutex);
3375 
3376         if (pool->detach_completion)
3377                 wait_for_completion(pool->detach_completion);
3378 
3379         /* shut down the timers */
3380         del_timer_sync(&pool->idle_timer);
3381         del_timer_sync(&pool->mayday_timer);
3382 
3383         /* sched-RCU protected to allow dereferences from get_work_pool() */
3384         call_rcu_sched(&pool->rcu, rcu_free_pool);
3385 }
3386 
3387 /**
3388  * get_unbound_pool - get a worker_pool with the specified attributes
3389  * @attrs: the attributes of the worker_pool to get
3390  *
3391  * Obtain a worker_pool which has the same attributes as @attrs, bump the
3392  * reference count and return it.  If there already is a matching
3393  * worker_pool, it will be used; otherwise, this function attempts to
3394  * create a new one.
3395  *
3396  * Should be called with wq_pool_mutex held.
3397  *
3398  * Return: On success, a worker_pool with the same attributes as @attrs.
3399  * On failure, %NULL.
3400  */
3401 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3402 {
3403         u32 hash = wqattrs_hash(attrs);
3404         struct worker_pool *pool;
3405         int node;
3406         int target_node = NUMA_NO_NODE;
3407 
3408         lockdep_assert_held(&wq_pool_mutex);
3409 
3410         /* do we already have a matching pool? */
3411         hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3412                 if (wqattrs_equal(pool->attrs, attrs)) {
3413                         pool->refcnt++;
3414                         return pool;
3415                 }
3416         }
3417 
3418         /* if cpumask is contained inside a NUMA node, we belong to that node */
3419         if (wq_numa_enabled) {
3420                 for_each_node(node) {
3421                         if (cpumask_subset(attrs->cpumask,
3422                                            wq_numa_possible_cpumask[node])) {
3423                                 target_node = node;
3424                                 break;
3425                         }
3426                 }
3427         }
3428 
3429         /* nope, create a new one */
3430         pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3431         if (!pool || init_worker_pool(pool) < 0)
3432                 goto fail;
3433 
3434         lockdep_set_subclass(&pool->lock, 1);   /* see put_pwq() */
3435         copy_workqueue_attrs(pool->attrs, attrs);
3436         pool->node = target_node;
3437 
3438         /*
3439          * no_numa isn't a worker_pool attribute, always clear it.  See
3440          * 'struct workqueue_attrs' comments for detail.
3441          */
3442         pool->attrs->no_numa = false;
3443 
3444         if (worker_pool_assign_id(pool) < 0)
3445                 goto fail;
3446 
3447         /* create and start the initial worker */
3448         if (wq_online && !create_worker(pool))
3449                 goto fail;
3450 
3451         /* install */
3452         hash_add(unbound_pool_hash, &pool->hash_node, hash);
3453 
3454         return pool;
3455 fail:
3456         if (pool)
3457                 put_unbound_pool(pool);
3458         return NULL;
3459 }
3460 
3461 static void rcu_free_pwq(struct rcu_head *rcu)
3462 {
3463         kmem_cache_free(pwq_cache,
3464                         container_of(rcu, struct pool_workqueue, rcu));
3465 }
3466 
3467 /*
3468  * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3469  * and needs to be destroyed.
3470  */
3471 static void pwq_unbound_release_workfn(struct work_struct *work)
3472 {
3473         struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3474                                                   unbound_release_work);
3475         struct workqueue_struct *wq = pwq->wq;
3476         struct worker_pool *pool = pwq->pool;
3477         bool is_last;
3478 
3479         if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3480                 return;
3481 
3482         mutex_lock(&wq->mutex);
3483         list_del_rcu(&pwq->pwqs_node);
3484         is_last = list_empty(&wq->pwqs);
3485         mutex_unlock(&wq->mutex);
3486 
3487         mutex_lock(&wq_pool_mutex);
3488         put_unbound_pool(pool);
3489         mutex_unlock(&wq_pool_mutex);
3490 
3491         call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3492 
3493         /*
3494          * If we're the last pwq going away, @wq is already dead and no one
3495          * is gonna access it anymore.  Schedule RCU free.
3496          */
3497         if (is_last)
3498                 call_rcu_sched(&wq->rcu, rcu_free_wq);
3499 }
3500 
3501 /**
3502  * pwq_adjust_max_active - update a pwq's max_active to the current setting
3503  * @pwq: target pool_workqueue
3504  *
3505  * If @pwq isn't freezing, set @pwq->max_active to the associated
3506  * workqueue's saved_max_active and activate delayed work items
3507  * accordingly.  If @pwq is freezing, clear @pwq->max_active to zero.
3508  */
3509 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3510 {
3511         struct workqueue_struct *wq = pwq->wq;
3512         bool freezable = wq->flags & WQ_FREEZABLE;
3513         unsigned long flags;
3514 
3515         /* for @wq->saved_max_active */
3516         lockdep_assert_held(&wq->mutex);
3517 
3518         /* fast exit for non-freezable wqs */
3519         if (!freezable && pwq->max_active == wq->saved_max_active)
3520                 return;
3521 
3522         /* this function can be called during early boot w/ irq disabled */
3523         spin_lock_irqsave(&pwq->pool->lock, flags);
3524 
3525         /*
3526          * During [un]freezing, the caller is responsible for ensuring that
3527          * this function is called at least once after @workqueue_freezing
3528          * is updated and visible.
3529          */
3530         if (!freezable || !workqueue_freezing) {
3531                 pwq->max_active = wq->saved_max_active;
3532 
3533                 while (!list_empty(&pwq->delayed_works) &&
3534                        pwq->nr_active < pwq->max_active)
3535                         pwq_activate_first_delayed(pwq);
3536 
3537                 /*
3538                  * Need to kick a worker after thawed or an unbound wq's
3539                  * max_active is bumped.  It's a slow path.  Do it always.
3540                  */
3541                 wake_up_worker(pwq->pool);
3542         } else {
3543                 pwq->max_active = 0;
3544         }
3545 
3546         spin_unlock_irqrestore(&pwq->pool->lock, flags);
3547 }
3548 
3549 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3550 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3551                      struct worker_pool *pool)
3552 {
3553         BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3554 
3555         memset(pwq, 0, sizeof(*pwq));
3556 
3557         pwq->pool = pool;
3558         pwq->wq = wq;
3559         pwq->flush_color = -1;
3560         pwq->refcnt = 1;
3561         INIT_LIST_HEAD(&pwq->delayed_works);
3562         INIT_LIST_HEAD(&pwq->pwqs_node);
3563         INIT_LIST_HEAD(&pwq->mayday_node);
3564         INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3565 }
3566 
3567 /* sync @pwq with the current state of its associated wq and link it */
3568 static void link_pwq(struct pool_workqueue *pwq)
3569 {
3570         struct workqueue_struct *wq = pwq->wq;
3571 
3572         lockdep_assert_held(&wq->mutex);
3573 
3574         /* may be called multiple times, ignore if already linked */
3575         if (!list_empty(&pwq->pwqs_node))
3576                 return;
3577 
3578         /* set the matching work_color */
3579         pwq->work_color = wq->work_color;
3580 
3581         /* sync max_active to the current setting */
3582         pwq_adjust_max_active(pwq);
3583 
3584         /* link in @pwq */
3585         list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3586 }
3587 
3588 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3589 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3590                                         const struct workqueue_attrs *attrs)
3591 {
3592         struct worker_pool *pool;
3593         struct pool_workqueue *pwq;
3594 
3595         lockdep_assert_held(&wq_pool_mutex);
3596 
3597         pool = get_unbound_pool(attrs);
3598         if (!pool)
3599                 return NULL;
3600 
3601         pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3602         if (!pwq) {
3603                 put_unbound_pool(pool);
3604                 return NULL;
3605         }
3606 
3607         init_pwq(pwq, wq, pool);
3608         return pwq;
3609 }
3610 
3611 /**
3612  * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3613  * @attrs: the wq_attrs of the default pwq of the target workqueue
3614  * @node: the target NUMA node
3615  * @cpu_going_down: if >= 0, the CPU to consider as offline
3616  * @cpumask: outarg, the resulting cpumask
3617  *
3618  * Calculate the cpumask a workqueue with @attrs should use on @node.  If
3619  * @cpu_going_down is >= 0, that cpu is considered offline during
3620  * calculation.  The result is stored in @cpumask.
3621  *
3622  * If NUMA affinity is not enabled, @attrs->cpumask is always used.  If
3623  * enabled and @node has online CPUs requested by @attrs, the returned
3624  * cpumask is the intersection of the possible CPUs of @node and
3625  * @attrs->cpumask.
3626  *
3627  * The caller is responsible for ensuring that the cpumask of @node stays
3628  * stable.
3629  *
3630  * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3631  * %false if equal.
3632  */
3633 static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3634                                  int cpu_going_down, cpumask_t *cpumask)
3635 {
3636         if (!wq_numa_enabled || attrs->no_numa)
3637                 goto use_dfl;
3638 
3639         /* does @node have any online CPUs @attrs wants? */
3640         cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3641         if (cpu_going_down >= 0)
3642                 cpumask_clear_cpu(cpu_going_down, cpumask);
3643 
3644         if (cpumask_empty(cpumask))
3645                 goto use_dfl;
3646 
3647         /* yeap, return possible CPUs in @node that @attrs wants */
3648         cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3649 
3650         if (cpumask_empty(cpumask)) {
3651                 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3652                                 "possible intersect\n");
3653                 return false;
3654         }
3655 
3656         return !cpumask_equal(cpumask, attrs->cpumask);
3657 
3658 use_dfl:
3659         cpumask_copy(cpumask, attrs->cpumask);
3660         return false;
3661 }
3662 
3663 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3664 static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3665                                                    int node,
3666                                                    struct pool_workqueue *pwq)
3667 {
3668         struct pool_workqueue *old_pwq;
3669 
3670         lockdep_assert_held(&wq_pool_mutex);
3671         lockdep_assert_held(&wq->mutex);
3672 
3673         /* link_pwq() can handle duplicate calls */
3674         link_pwq(pwq);
3675 
3676         old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3677         rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3678         return old_pwq;
3679 }
3680 
3681 /* context to store the prepared attrs & pwqs before applying */
3682 struct apply_wqattrs_ctx {
3683         struct workqueue_struct *wq;            /* target workqueue */
3684         struct workqueue_attrs  *attrs;         /* attrs to apply */
3685         struct list_head        list;           /* queued for batching commit */
3686         struct pool_workqueue   *dfl_pwq;
3687         struct pool_workqueue   *pwq_tbl[];
3688 };
3689 
3690 /* free the resources after success or abort */
3691 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3692 {
3693         if (ctx) {
3694                 int node;
3695 
3696                 for_each_node(node)
3697                         put_pwq_unlocked(ctx->pwq_tbl[node]);
3698                 put_pwq_unlocked(ctx->dfl_pwq);
3699 
3700                 free_workqueue_attrs(ctx->attrs);
3701 
3702                 kfree(ctx);
3703         }
3704 }
3705 
3706 /* allocate the attrs and pwqs for later installation */
3707 static struct apply_wqattrs_ctx *
3708 apply_wqattrs_prepare(struct workqueue_struct *wq,
3709                       const struct workqueue_attrs *attrs)
3710 {
3711         struct apply_wqattrs_ctx *ctx;
3712         struct workqueue_attrs *new_attrs, *tmp_attrs;
3713         int node;
3714 
3715         lockdep_assert_held(&wq_pool_mutex);
3716 
3717         ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_node_ids), GFP_KERNEL);
3718 
3719         new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3720         tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3721         if (!ctx || !new_attrs || !tmp_attrs)
3722                 goto out_free;
3723 
3724         /*
3725          * Calculate the attrs of the default pwq.
3726          * If the user configured cpumask doesn't overlap with the
3727          * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3728          */
3729         copy_workqueue_attrs(new_attrs, attrs);
3730         cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3731         if (unlikely(cpumask_empty(new_attrs->cpumask)))
3732                 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3733 
3734         /*
3735          * We may create multiple pwqs with differing cpumasks.  Make a
3736          * copy of @new_attrs which will be modified and used to obtain
3737          * pools.
3738          */
3739         copy_workqueue_attrs(tmp_attrs, new_attrs);
3740 
3741         /*
3742          * If something goes wrong during CPU up/down, we'll fall back to
3743          * the default pwq covering whole @attrs->cpumask.  Always create
3744          * it even if we don't use it immediately.
3745          */
3746         ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3747         if (!ctx->dfl_pwq)
3748                 goto out_free;
3749 
3750         for_each_node(node) {
3751                 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3752                         ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3753                         if (!ctx->pwq_tbl[node])
3754                                 goto out_free;
3755                 } else {
3756                         ctx->dfl_pwq->refcnt++;
3757                         ctx->pwq_tbl[node] = ctx->dfl_pwq;
3758                 }
3759         }
3760 
3761         /* save the user configured attrs and sanitize it. */
3762         copy_workqueue_attrs(new_attrs, attrs);
3763         cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3764         ctx->attrs = new_attrs;
3765 
3766         ctx->wq = wq;
3767         free_workqueue_attrs(tmp_attrs);
3768         return ctx;
3769 
3770 out_free:
3771         free_workqueue_attrs(tmp_attrs);
3772         free_workqueue_attrs(new_attrs);
3773         apply_wqattrs_cleanup(ctx);
3774         return NULL;
3775 }
3776 
3777 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3778 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3779 {
3780         int node;
3781 
3782         /* all pwqs have been created successfully, let's install'em */
3783         mutex_lock(&ctx->wq->mutex);
3784 
3785         copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3786 
3787         /* save the previous pwq and install the new one */
3788         for_each_node(node)
3789                 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3790                                                           ctx->pwq_tbl[node]);
3791 
3792         /* @dfl_pwq might not have been used, ensure it's linked */
3793         link_pwq(ctx->dfl_pwq);
3794         swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3795 
3796         mutex_unlock(&ctx->wq->mutex);
3797 }
3798 
3799 static void apply_wqattrs_lock(void)
3800 {
3801         /* CPUs should stay stable across pwq creations and installations */
3802         get_online_cpus();
3803         mutex_lock(&wq_pool_mutex);
3804 }
3805 
3806 static void apply_wqattrs_unlock(void)
3807 {
3808         mutex_unlock(&wq_pool_mutex);
3809         put_online_cpus();
3810 }
3811 
3812 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3813                                         const struct workqueue_attrs *attrs)
3814 {
3815         struct apply_wqattrs_ctx *ctx;
3816 
3817         /* only unbound workqueues can change attributes */
3818         if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3819                 return -EINVAL;
3820 
3821         /* creating multiple pwqs breaks ordering guarantee */
3822         if (!list_empty(&wq->pwqs)) {
3823                 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
3824                         return -EINVAL;
3825 
3826                 wq->flags &= ~__WQ_ORDERED;
3827         }
3828 
3829         ctx = apply_wqattrs_prepare(wq, attrs);
3830         if (!ctx)
3831                 return -ENOMEM;
3832 
3833         /* the ctx has been prepared successfully, let's commit it */
3834         apply_wqattrs_commit(ctx);
3835         apply_wqattrs_cleanup(ctx);
3836 
3837         return 0;
3838 }
3839 
3840 /**
3841  * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3842  * @wq: the target workqueue
3843  * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3844  *
3845  * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA
3846  * machines, this function maps a separate pwq to each NUMA node with
3847  * possibles CPUs in @attrs->cpumask so that work items are affine to the
3848  * NUMA node it was issued on.  Older pwqs are released as in-flight work
3849  * items finish.  Note that a work item which repeatedly requeues itself
3850  * back-to-back will stay on its current pwq.
3851  *
3852  * Performs GFP_KERNEL allocations.
3853  *
3854  * Return: 0 on success and -errno on failure.
3855  */
3856 int apply_workqueue_attrs(struct workqueue_struct *wq,
3857                           const struct workqueue_attrs *attrs)
3858 {
3859         int ret;
3860 
3861         apply_wqattrs_lock();
3862         ret = apply_workqueue_attrs_locked(wq, attrs);
3863         apply_wqattrs_unlock();
3864 
3865         return ret;
3866 }
3867 EXPORT_SYMBOL_GPL(apply_workqueue_attrs);
3868 
3869 /**
3870  * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3871  * @wq: the target workqueue
3872  * @cpu: the CPU coming up or going down
3873  * @online: whether @cpu is coming up or going down
3874  *
3875  * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3876  * %CPU_DOWN_FAILED.  @cpu is being hot[un]plugged, update NUMA affinity of
3877  * @wq accordingly.
3878  *
3879  * If NUMA affinity can't be adjusted due to memory allocation failure, it
3880  * falls back to @wq->dfl_pwq which may not be optimal but is always
3881  * correct.
3882  *
3883  * Note that when the last allowed CPU of a NUMA node goes offline for a
3884  * workqueue with a cpumask spanning multiple nodes, the workers which were
3885  * already executing the work items for the workqueue will lose their CPU
3886  * affinity and may execute on any CPU.  This is similar to how per-cpu
3887  * workqueues behave on CPU_DOWN.  If a workqueue user wants strict
3888  * affinity, it's the user's responsibility to flush the work item from
3889  * CPU_DOWN_PREPARE.
3890  */
3891 static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3892                                    bool online)
3893 {
3894         int node = cpu_to_node(cpu);
3895         int cpu_off = online ? -1 : cpu;
3896         struct pool_workqueue *old_pwq = NULL, *pwq;
3897         struct workqueue_attrs *target_attrs;
3898         cpumask_t *cpumask;
3899 
3900         lockdep_assert_held(&wq_pool_mutex);
3901 
3902         if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3903             wq->unbound_attrs->no_numa)
3904                 return;
3905 
3906         /*
3907          * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3908          * Let's use a preallocated one.  The following buf is protected by
3909          * CPU hotplug exclusion.
3910          */
3911         target_attrs = wq_update_unbound_numa_attrs_buf;
3912         cpumask = target_attrs->cpumask;
3913 
3914         copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3915         pwq = unbound_pwq_by_node(wq, node);
3916 
3917         /*
3918          * Let's determine what needs to be done.  If the target cpumask is
3919          * different from the default pwq's, we need to compare it to @pwq's
3920          * and create a new one if they don't match.  If the target cpumask
3921          * equals the default pwq's, the default pwq should be used.
3922          */
3923         if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3924                 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3925                         return;
3926         } else {
3927                 goto use_dfl_pwq;
3928         }
3929 
3930         /* create a new pwq */
3931         pwq = alloc_unbound_pwq(wq, target_attrs);
3932         if (!pwq) {
3933                 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3934                         wq->name);
3935                 goto use_dfl_pwq;
3936         }
3937 
3938         /* Install the new pwq. */
3939         mutex_lock(&wq->mutex);
3940         old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3941         goto out_unlock;
3942 
3943 use_dfl_pwq:
3944         mutex_lock(&wq->mutex);
3945         spin_lock_irq(&wq->dfl_pwq->pool->lock);
3946         get_pwq(wq->dfl_pwq);
3947         spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3948         old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3949 out_unlock:
3950         mutex_unlock(&wq->mutex);
3951         put_pwq_unlocked(old_pwq);
3952 }
3953 
3954 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3955 {
3956         bool highpri = wq->flags & WQ_HIGHPRI;
3957         int cpu, ret;
3958 
3959         if (!(wq->flags & WQ_UNBOUND)) {
3960                 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3961                 if (!wq->cpu_pwqs)
3962                         return -ENOMEM;
3963 
3964                 for_each_possible_cpu(cpu) {
3965                         struct pool_workqueue *pwq =
3966                                 per_cpu_ptr(wq->cpu_pwqs, cpu);
3967                         struct worker_pool *cpu_pools =
3968                                 per_cpu(cpu_worker_pools, cpu);
3969 
3970                         init_pwq(pwq, wq, &cpu_pools[highpri]);
3971 
3972                         mutex_lock(&wq->mutex);
3973                         link_pwq(pwq);
3974                         mutex_unlock(&wq->mutex);
3975                 }
3976                 return 0;
3977         } else if (wq->flags & __WQ_ORDERED) {
3978                 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3979                 /* there should only be single pwq for ordering guarantee */
3980                 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3981                               wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3982                      "ordering guarantee broken for workqueue %s\n", wq->name);
3983                 return ret;
3984         } else {
3985                 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3986         }
3987 }
3988 
3989 static int wq_clamp_max_active(int max_active, unsigned int flags,
3990                                const char *name)
3991 {
3992         int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3993 
3994         if (max_active < 1 || max_active > lim)
3995                 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3996                         max_active, name, 1, lim);
3997 
3998         return clamp_val(max_active, 1, lim);
3999 }
4000 
4001 /*
4002  * Workqueues which may be used during memory reclaim should have a rescuer
4003  * to guarantee forward progress.
4004  */
4005 static int init_rescuer(struct workqueue_struct *wq)
4006 {
4007         struct worker *rescuer;
4008         int ret;
4009 
4010         if (!(wq->flags & WQ_MEM_RECLAIM))
4011                 return 0;
4012 
4013         rescuer = alloc_worker(NUMA_NO_NODE);
4014         if (!rescuer)
4015                 return -ENOMEM;
4016 
4017         rescuer->rescue_wq = wq;
4018         rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
4019         ret = PTR_ERR_OR_ZERO(rescuer->task);
4020         if (ret) {
4021                 kfree(rescuer);
4022                 return ret;
4023         }
4024 
4025         wq->rescuer = rescuer;
4026         kthread_bind_mask(rescuer->task, cpu_possible_mask);
4027         wake_up_process(rescuer->task);
4028 
4029         return 0;
4030 }
4031 
4032 struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
4033                                                unsigned int flags,
4034                                                int max_active,
4035                                                struct lock_class_key *key,
4036                                                const char *lock_name, ...)
4037 {
4038         size_t tbl_size = 0;
4039         va_list args;
4040         struct workqueue_struct *wq;
4041         struct pool_workqueue *pwq;
4042 
4043         /*
4044          * Unbound && max_active == 1 used to imply ordered, which is no
4045          * longer the case on NUMA machines due to per-node pools.  While
4046          * alloc_ordered_workqueue() is the right way to create an ordered
4047          * workqueue, keep the previous behavior to avoid subtle breakages
4048          * on NUMA.
4049          */
4050         if ((flags & WQ_UNBOUND) && max_active == 1)
4051                 flags |= __WQ_ORDERED;
4052 
4053         /* see the comment above the definition of WQ_POWER_EFFICIENT */
4054         if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4055                 flags |= WQ_UNBOUND;
4056 
4057         /* allocate wq and format name */
4058         if (flags & WQ_UNBOUND)
4059                 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
4060 
4061         wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4062         if (!wq)
4063                 return NULL;
4064 
4065         if (flags & WQ_UNBOUND) {
4066                 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
4067                 if (!wq->unbound_attrs)
4068                         goto err_free_wq;
4069         }
4070 
4071         va_start(args, lock_name);
4072         vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4073         va_end(args);
4074 
4075         max_active = max_active ?: WQ_DFL_ACTIVE;
4076         max_active = wq_clamp_max_active(max_active, flags, wq->name);
4077 
4078         /* init wq */
4079         wq->flags = flags;
4080         wq->saved_max_active = max_active;
4081         mutex_init(&wq->mutex);
4082         atomic_set(&wq->nr_pwqs_to_flush, 0);
4083         INIT_LIST_HEAD(&wq->pwqs);
4084         INIT_LIST_HEAD(&wq->flusher_queue);
4085         INIT_LIST_HEAD(&wq->flusher_overflow);
4086         INIT_LIST_HEAD(&wq->maydays);
4087 
4088         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
4089         INIT_LIST_HEAD(&wq->list);
4090 
4091         if (alloc_and_link_pwqs(wq) < 0)
4092                 goto err_free_wq;
4093 
4094         if (wq_online && init_rescuer(wq) < 0)
4095                 goto err_destroy;
4096 
4097         if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4098                 goto err_destroy;
4099 
4100         /*
4101          * wq_pool_mutex protects global freeze state and workqueues list.
4102          * Grab it, adjust max_active and add the new @wq to workqueues
4103          * list.
4104          */
4105         mutex_lock(&wq_pool_mutex);
4106 
4107         mutex_lock(&wq->mutex);
4108         for_each_pwq(pwq, wq)
4109                 pwq_adjust_max_active(pwq);
4110         mutex_unlock(&wq->mutex);
4111 
4112         list_add_tail_rcu(&wq->list, &workqueues);
4113 
4114         mutex_unlock(&wq_pool_mutex);
4115 
4116         return wq;
4117 
4118 err_free_wq:
4119         free_workqueue_attrs(wq->unbound_attrs);
4120         kfree(wq);
4121         return NULL;
4122 err_destroy:
4123         destroy_workqueue(wq);
4124         return NULL;
4125 }
4126 EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4127 
4128 /**
4129  * destroy_workqueue - safely terminate a workqueue
4130  * @wq: target workqueue
4131  *
4132  * Safely destroy a workqueue. All work currently pending will be done first.
4133  */
4134 void destroy_workqueue(struct workqueue_struct *wq)
4135 {
4136         struct pool_workqueue *pwq;
4137         int node;
4138 
4139         /* drain it before proceeding with destruction */
4140         drain_workqueue(wq);
4141 
4142         /* sanity checks */
4143         mutex_lock(&wq->mutex);
4144         for_each_pwq(pwq, wq) {
4145                 int i;
4146 
4147                 for (i = 0; i < WORK_NR_COLORS; i++) {
4148                         if (WARN_ON(pwq->nr_in_flight[i])) {
4149                                 mutex_unlock(&wq->mutex);
4150                                 show_workqueue_state();
4151                                 return;
4152                         }
4153                 }
4154 
4155                 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4156                     WARN_ON(pwq->nr_active) ||
4157                     WARN_ON(!list_empty(&pwq->delayed_works))) {
4158                         mutex_unlock(&wq->mutex);
4159                         show_workqueue_state();
4160                         return;
4161                 }
4162         }
4163         mutex_unlock(&wq->mutex);
4164 
4165         /*
4166          * wq list is used to freeze wq, remove from list after
4167          * flushing is complete in case freeze races us.
4168          */
4169         mutex_lock(&wq_pool_mutex);
4170         list_del_rcu(&wq->list);
4171         mutex_unlock(&wq_pool_mutex);
4172 
4173         workqueue_sysfs_unregister(wq);
4174 
4175         if (wq->rescuer)
4176                 kthread_stop(wq->rescuer->task);
4177 
4178         if (!(wq->flags & WQ_UNBOUND)) {
4179                 /*
4180                  * The base ref is never dropped on per-cpu pwqs.  Directly
4181                  * schedule RCU free.
4182                  */
4183                 call_rcu_sched(&wq->rcu, rcu_free_wq);
4184         } else {
4185                 /*
4186                  * We're the sole accessor of @wq at this point.  Directly
4187                  * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4188                  * @wq will be freed when the last pwq is released.
4189                  */
4190                 for_each_node(node) {
4191                         pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4192                         RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4193                         put_pwq_unlocked(pwq);
4194                 }
4195 
4196                 /*
4197                  * Put dfl_pwq.  @wq may be freed any time after dfl_pwq is
4198                  * put.  Don't access it afterwards.
4199                  */
4200                 pwq = wq->dfl_pwq;
4201                 wq->dfl_pwq = NULL;
4202                 put_pwq_unlocked(pwq);
4203         }
4204 }
4205 EXPORT_SYMBOL_GPL(destroy_workqueue);
4206 
4207 /**
4208  * workqueue_set_max_active - adjust max_active of a workqueue
4209  * @wq: target workqueue
4210  * @max_active: new max_active value.
4211  *
4212  * Set max_active of @wq to @max_active.
4213  *
4214  * CONTEXT:
4215  * Don't call from IRQ context.
4216  */
4217 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4218 {
4219         struct pool_workqueue *pwq;
4220 
4221         /* disallow meddling with max_active for ordered workqueues */
4222         if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4223                 return;
4224 
4225         max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4226 
4227         mutex_lock(&wq->mutex);
4228 
4229         wq->flags &= ~__WQ_ORDERED;
4230         wq->saved_max_active = max_active;
4231 
4232         for_each_pwq(pwq, wq)
4233                 pwq_adjust_max_active(pwq);
4234 
4235         mutex_unlock(&wq->mutex);
4236 }
4237 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4238 
4239 /**
4240  * current_work - retrieve %current task's work struct
4241  *
4242  * Determine if %current task is a workqueue worker and what it's working on.
4243  * Useful to find out the context that the %current task is running in.
4244  *
4245  * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4246  */
4247 struct work_struct *current_work(void)
4248 {
4249         struct worker *worker = current_wq_worker();
4250 
4251         return worker ? worker->current_work : NULL;
4252 }
4253 EXPORT_SYMBOL(current_work);
4254 
4255 /**
4256  * current_is_workqueue_rescuer - is %current workqueue rescuer?
4257  *
4258  * Determine whether %current is a workqueue rescuer.  Can be used from
4259  * work functions to determine whether it's being run off the rescuer task.
4260  *
4261  * Return: %true if %current is a workqueue rescuer. %false otherwise.
4262  */
4263 bool current_is_workqueue_rescuer(void)
4264 {
4265         struct worker *worker = current_wq_worker();
4266 
4267         return worker && worker->rescue_wq;
4268 }
4269 
4270 /**
4271  * workqueue_congested - test whether a workqueue is congested
4272  * @cpu: CPU in question
4273  * @wq: target workqueue
4274  *
4275  * Test whether @wq's cpu workqueue for @cpu is congested.  There is
4276  * no synchronization around this function and the test result is
4277  * unreliable and only useful as advisory hints or for debugging.
4278  *
4279  * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4280  * Note that both per-cpu and unbound workqueues may be associated with
4281  * multiple pool_workqueues which have separate congested states.  A
4282  * workqueue being congested on one CPU doesn't mean the workqueue is also
4283  * contested on other CPUs / NUMA nodes.
4284  *
4285  * Return:
4286  * %true if congested, %false otherwise.
4287  */
4288 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4289 {
4290         struct pool_workqueue *pwq;
4291         bool ret;
4292 
4293         rcu_read_lock_sched();
4294 
4295         if (cpu == WORK_CPU_UNBOUND)
4296                 cpu = smp_processor_id();
4297 
4298         if (!(wq->flags & WQ_UNBOUND))
4299                 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4300         else
4301                 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4302 
4303         ret = !list_empty(&pwq->delayed_works);
4304         rcu_read_unlock_sched();
4305 
4306         return ret;
4307 }
4308 EXPORT_SYMBOL_GPL(workqueue_congested);
4309 
4310 /**
4311  * work_busy - test whether a work is currently pending or running
4312  * @work: the work to be tested
4313  *
4314  * Test whether @work is currently pending or running.  There is no
4315  * synchronization around this function and the test result is
4316  * unreliable and only useful as advisory hints or for debugging.
4317  *
4318  * Return:
4319  * OR'd bitmask of WORK_BUSY_* bits.
4320  */
4321 unsigned int work_busy(struct work_struct *work)
4322 {
4323         struct worker_pool *pool;
4324         unsigned long flags;
4325         unsigned int ret = 0;
4326 
4327         if (work_pending(work))
4328                 ret |= WORK_BUSY_PENDING;
4329 
4330         local_irq_save(flags);
4331         pool = get_work_pool(work);
4332         if (pool) {
4333                 spin_lock(&pool->lock);
4334                 if (find_worker_executing_work(pool, work))
4335                         ret |= WORK_BUSY_RUNNING;
4336                 spin_unlock(&pool->lock);
4337         }
4338         local_irq_restore(flags);
4339 
4340         return ret;
4341 }
4342 EXPORT_SYMBOL_GPL(work_busy);
4343 
4344 /**
4345  * set_worker_desc - set description for the current work item
4346  * @fmt: printf-style format string
4347  * @...: arguments for the format string
4348  *
4349  * This function can be called by a running work function to describe what
4350  * the work item is about.  If the worker task gets dumped, this
4351  * information will be printed out together to help debugging.  The
4352  * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4353  */
4354 void set_worker_desc(const char *fmt, ...)
4355 {
4356         struct worker *worker = current_wq_worker();
4357         va_list args;
4358 
4359         if (worker) {
4360                 va_start(args, fmt);
4361                 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4362                 va_end(args);
4363         }
4364 }
4365 EXPORT_SYMBOL_GPL(set_worker_desc);
4366 
4367 /**
4368  * print_worker_info - print out worker information and description
4369  * @log_lvl: the log level to use when printing
4370  * @task: target task
4371  *
4372  * If @task is a worker and currently executing a work item, print out the
4373  * name of the workqueue being serviced and worker description set with
4374  * set_worker_desc() by the currently executing work item.
4375  *
4376  * This function can be safely called on any task as long as the
4377  * task_struct itself is accessible.  While safe, this function isn't
4378  * synchronized and may print out mixups or garbages of limited length.
4379  */
4380 void print_worker_info(const char *log_lvl, struct task_struct *task)
4381 {
4382         work_func_t *fn = NULL;
4383         char name[WQ_NAME_LEN] = { };
4384         char desc[WORKER_DESC_LEN] = { };
4385         struct pool_workqueue *pwq = NULL;
4386         struct workqueue_struct *wq = NULL;
4387         struct worker *worker;
4388 
4389         if (!(task->flags & PF_WQ_WORKER))
4390                 return;
4391 
4392         /*
4393          * This function is called without any synchronization and @task
4394          * could be in any state.  Be careful with dereferences.
4395          */
4396         worker = kthread_probe_data(task);
4397 
4398         /*
4399          * Carefully copy the associated workqueue's workfn, name and desc.
4400          * Keep the original last '\0' in case the original is garbage.
4401          */
4402         probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4403         probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4404         probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4405         probe_kernel_read(name, wq->name, sizeof(name) - 1);
4406         probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4407 
4408         if (fn || name[0] || desc[0]) {
4409                 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4410                 if (strcmp(name, desc))
4411                         pr_cont(" (%s)", desc);
4412                 pr_cont("\n");
4413         }
4414 }
4415 
4416 static void pr_cont_pool_info(struct worker_pool *pool)
4417 {
4418         pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4419         if (pool->node != NUMA_NO_NODE)
4420                 pr_cont(" node=%d", pool->node);
4421         pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4422 }
4423 
4424 static void pr_cont_work(bool comma, struct work_struct *work)
4425 {
4426         if (work->func == wq_barrier_func) {
4427                 struct wq_barrier *barr;
4428 
4429                 barr = container_of(work, struct wq_barrier, work);
4430 
4431                 pr_cont("%s BAR(%d)", comma ? "," : "",
4432                         task_pid_nr(barr->task));
4433         } else {
4434                 pr_cont("%s %pf", comma ? "," : "", work->func);
4435         }
4436 }
4437 
4438 static void show_pwq(struct pool_workqueue *pwq)
4439 {
4440         struct worker_pool *pool = pwq->pool;
4441         struct work_struct *work;
4442         struct worker *worker;
4443         bool has_in_flight = false, has_pending = false;
4444         int bkt;
4445 
4446         pr_info("  pwq %d:", pool->id);
4447         pr_cont_pool_info(pool);
4448 
4449         pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4450                 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4451 
4452         hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4453                 if (worker->current_pwq == pwq) {
4454                         has_in_flight = true;
4455                         break;
4456                 }
4457         }
4458         if (has_in_flight) {
4459                 bool comma = false;
4460 
4461                 pr_info("    in-flight:");
4462                 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4463                         if (worker->current_pwq != pwq)
4464                                 continue;
4465 
4466                         pr_cont("%s %d%s:%pf", comma ? "," : "",
4467                                 task_pid_nr(worker->task),
4468                                 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4469                                 worker->current_func);
4470                         list_for_each_entry(work, &worker->scheduled, entry)
4471                                 pr_cont_work(false, work);
4472                         comma = true;
4473                 }
4474                 pr_cont("\n");
4475         }
4476 
4477         list_for_each_entry(work, &pool->worklist, entry) {
4478                 if (get_work_pwq(work) == pwq) {
4479                         has_pending = true;
4480                         break;
4481                 }
4482         }
4483         if (has_pending) {
4484                 bool comma = false;
4485 
4486                 pr_info("    pending:");
4487                 list_for_each_entry(work, &pool->worklist, entry) {
4488                         if (get_work_pwq(work) != pwq)
4489                                 continue;
4490 
4491                         pr_cont_work(comma, work);
4492                         comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4493                 }
4494                 pr_cont("\n");
4495         }
4496 
4497         if (!list_empty(&pwq->delayed_works)) {
4498                 bool comma = false;
4499 
4500                 pr_info("    delayed:");
4501                 list_for_each_entry(work, &pwq->delayed_works, entry) {
4502                         pr_cont_work(comma, work);
4503                         comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4504                 }
4505                 pr_cont("\n");
4506         }
4507 }
4508 
4509 /**
4510  * show_workqueue_state - dump workqueue state
4511  *
4512  * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4513  * all busy workqueues and pools.
4514  */
4515 void show_workqueue_state(void)
4516 {
4517         struct workqueue_struct *wq;
4518         struct worker_pool *pool;
4519         unsigned long flags;
4520         int pi;
4521 
4522         rcu_read_lock_sched();
4523 
4524         pr_info("Showing busy workqueues and worker pools:\n");
4525 
4526         list_for_each_entry_rcu(wq, &workqueues, list) {
4527                 struct pool_workqueue *pwq;
4528                 bool idle = true;
4529 
4530                 for_each_pwq(pwq, wq) {
4531                         if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4532                                 idle = false;
4533                                 break;
4534                         }
4535                 }
4536                 if (idle)
4537                         continue;
4538 
4539                 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4540 
4541                 for_each_pwq(pwq, wq) {
4542                         spin_lock_irqsave(&pwq->pool->lock, flags);
4543                         if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4544                                 show_pwq(pwq);
4545                         spin_unlock_irqrestore(&pwq->pool->lock, flags);
4546                         /*
4547                          * We could be printing a lot from atomic context, e.g.
4548                          * sysrq-t -> show_workqueue_state(). Avoid triggering
4549                          * hard lockup.
4550                          */
4551                         touch_nmi_watchdog();
4552                 }
4553         }
4554 
4555         for_each_pool(pool, pi) {
4556                 struct worker *worker;
4557                 bool first = true;
4558 
4559                 spin_lock_irqsave(&pool->lock, flags);
4560                 if (pool->nr_workers == pool->nr_idle)
4561                         goto next_pool;
4562 
4563                 pr_info("pool %d:", pool->id);
4564                 pr_cont_pool_info(pool);
4565                 pr_cont(" hung=%us workers=%d",
4566                         jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4567                         pool->nr_workers);
4568                 if (pool->manager)
4569                         pr_cont(" manager: %d",
4570                                 task_pid_nr(pool->manager->task));
4571                 list_for_each_entry(worker, &pool->idle_list, entry) {
4572                         pr_cont(" %s%d", first ? "idle: " : "",
4573                                 task_pid_nr(worker->task));
4574                         first = false;
4575                 }
4576                 pr_cont("\n");
4577         next_pool:
4578                 spin_unlock_irqrestore(&pool->lock, flags);
4579                 /*
4580                  * We could be printing a lot from atomic context, e.g.
4581                  * sysrq-t -> show_workqueue_state(). Avoid triggering
4582                  * hard lockup.
4583                  */
4584                 touch_nmi_watchdog();
4585         }
4586 
4587         rcu_read_unlock_sched();
4588 }
4589 
4590 /* used to show worker information through /proc/PID/{comm,stat,status} */
4591 void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
4592 {
4593         int off;
4594 
4595         /* always show the actual comm */
4596         off = strscpy(buf, task->comm, size);
4597         if (off < 0)
4598                 return;
4599 
4600         /* stabilize PF_WQ_WORKER and worker pool association */
4601         mutex_lock(&wq_pool_attach_mutex);
4602 
4603         if (task->flags & PF_WQ_WORKER) {
4604                 struct worker *worker = kthread_data(task);
4605                 struct worker_pool *pool = worker->pool;
4606 
4607                 if (pool) {
4608                         spin_lock_irq(&pool->lock);
4609                         /*
4610                          * ->desc tracks information (wq name or
4611                          * set_worker_desc()) for the latest execution.  If
4612                          * current, prepend '+', otherwise '-'.
4613                          */
4614                         if (worker->desc[0] != '\0') {
4615                                 if (worker->current_work)
4616                                         scnprintf(buf + off, size - off, "+%s",
4617                                                   worker->desc);
4618                                 else
4619                                         scnprintf(buf + off, size - off, "-%s",
4620                                                   worker->desc);
4621                         }
4622                         spin_unlock_irq(&pool->lock);
4623                 }
4624         }
4625 
4626         mutex_unlock(&wq_pool_attach_mutex);
4627 }
4628 
4629 #ifdef CONFIG_SMP
4630 
4631 /*
4632  * CPU hotplug.
4633  *
4634  * There are two challenges in supporting CPU hotplug.  Firstly, there
4635  * are a lot of assumptions on strong associations among work, pwq and
4636  * pool which make migrating pending and scheduled works very
4637  * difficult to implement without impacting hot paths.  Secondly,
4638  * worker pools serve mix of short, long and very long running works making
4639  * blocked draining impractical.
4640  *
4641  * This is solved by allowing the pools to be disassociated from the CPU
4642  * running as an unbound one and allowing it to be reattached later if the
4643  * cpu comes back online.
4644  */
4645 
4646 static void unbind_workers(int cpu)
4647 {
4648         struct worker_pool *pool;
4649         struct worker *worker;
4650 
4651         for_each_cpu_worker_pool(pool, cpu) {
4652                 mutex_lock(&wq_pool_attach_mutex);
4653                 spin_lock_irq(&pool->lock);
4654 
4655                 /*
4656                  * We've blocked all attach/detach operations. Make all workers
4657                  * unbound and set DISASSOCIATED.  Before this, all workers
4658                  * except for the ones which are still executing works from
4659                  * before the last CPU down must be on the cpu.  After
4660                  * this, they may become diasporas.
4661                  */
4662                 for_each_pool_worker(worker, pool)
4663                         worker->flags |= WORKER_UNBOUND;
4664 
4665                 pool->flags |= POOL_DISASSOCIATED;
4666 
4667                 spin_unlock_irq(&pool->lock);
4668                 mutex_unlock(&wq_pool_attach_mutex);
4669 
4670                 /*
4671                  * Call schedule() so that we cross rq->lock and thus can
4672                  * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4673                  * This is necessary as scheduler callbacks may be invoked
4674                  * from other cpus.
4675                  */
4676                 schedule();
4677 
4678                 /*
4679                  * Sched callbacks are disabled now.  Zap nr_running.
4680                  * After this, nr_running stays zero and need_more_worker()
4681                  * and keep_working() are always true as long as the
4682                  * worklist is not empty.  This pool now behaves as an
4683                  * unbound (in terms of concurrency management) pool which
4684                  * are served by workers tied to the pool.
4685                  */
4686                 atomic_set(&pool->nr_running, 0);
4687 
4688                 /*
4689                  * With concurrency management just turned off, a busy
4690                  * worker blocking could lead to lengthy stalls.  Kick off
4691                  * unbound chain execution of currently pending work items.
4692                  */
4693                 spin_lock_irq(&pool->lock);
4694                 wake_up_worker(pool);
4695                 spin_unlock_irq(&pool->lock);
4696         }
4697 }
4698 
4699 /**
4700  * rebind_workers - rebind all workers of a pool to the associated CPU
4701  * @pool: pool of interest
4702  *
4703  * @pool->cpu is coming online.  Rebind all workers to the CPU.
4704  */
4705 static void rebind_workers(struct worker_pool *pool)
4706 {
4707         struct worker *worker;
4708 
4709         lockdep_assert_held(&wq_pool_attach_mutex);
4710 
4711         /*
4712          * Restore CPU affinity of all workers.  As all idle workers should
4713          * be on the run-queue of the associated CPU before any local
4714          * wake-ups for concurrency management happen, restore CPU affinity
4715          * of all workers first and then clear UNBOUND.  As we're called
4716          * from CPU_ONLINE, the following shouldn't fail.
4717          */
4718         for_each_pool_worker(worker, pool)
4719                 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4720                                                   pool->attrs->cpumask) < 0);
4721 
4722         spin_lock_irq(&pool->lock);
4723 
4724         pool->flags &= ~POOL_DISASSOCIATED;
4725 
4726         for_each_pool_worker(worker, pool) {
4727                 unsigned int worker_flags = worker->flags;
4728 
4729                 /*
4730                  * A bound idle worker should actually be on the runqueue
4731                  * of the associated CPU for local wake-ups targeting it to
4732                  * work.  Kick all idle workers so that they migrate to the
4733                  * associated CPU.  Doing this in the same loop as
4734                  * replacing UNBOUND with REBOUND is safe as no worker will
4735                  * be bound before @pool->lock is released.
4736                  */
4737                 if (worker_flags & WORKER_IDLE)
4738                         wake_up_process(worker->task);
4739 
4740                 /*
4741                  * We want to clear UNBOUND but can't directly call
4742                  * worker_clr_flags() or adjust nr_running.  Atomically
4743                  * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4744                  * @worker will clear REBOUND using worker_clr_flags() when
4745                  * it initiates the next execution cycle thus restoring
4746                  * concurrency management.  Note that when or whether
4747                  * @worker clears REBOUND doesn't affect correctness.
4748                  *
4749                  * WRITE_ONCE() is necessary because @worker->flags may be
4750                  * tested without holding any lock in
4751                  * wq_worker_waking_up().  Without it, NOT_RUNNING test may
4752                  * fail incorrectly leading to premature concurrency
4753                  * management operations.
4754                  */
4755                 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4756                 worker_flags |= WORKER_REBOUND;
4757                 worker_flags &= ~WORKER_UNBOUND;
4758                 WRITE_ONCE(worker->flags, worker_flags);
4759         }
4760 
4761         spin_unlock_irq(&pool->lock);
4762 }
4763 
4764 /**
4765  * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4766  * @pool: unbound pool of interest
4767  * @cpu: the CPU which is coming up
4768  *
4769  * An unbound pool may end up with a cpumask which doesn't have any online
4770  * CPUs.  When a worker of such pool get scheduled, the scheduler resets
4771  * its cpus_allowed.  If @cpu is in @pool's cpumask which didn't have any
4772  * online CPU before, cpus_allowed of all its workers should be restored.
4773  */
4774 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4775 {
4776         static cpumask_t cpumask;
4777         struct worker *worker;
4778 
4779         lockdep_assert_held(&wq_pool_attach_mutex);
4780 
4781         /* is @cpu allowed for @pool? */
4782         if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4783                 return;
4784 
4785         cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4786 
4787         /* as we're called from CPU_ONLINE, the following shouldn't fail */
4788         for_each_pool_worker(worker, pool)
4789                 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
4790 }
4791 
4792 int workqueue_prepare_cpu(unsigned int cpu)
4793 {
4794         struct worker_pool *pool;
4795 
4796         for_each_cpu_worker_pool(pool, cpu) {
4797                 if (pool->nr_workers)
4798                         continue;
4799                 if (!create_worker(pool))
4800                         return -ENOMEM;
4801         }
4802         return 0;
4803 }
4804 
4805 int workqueue_online_cpu(unsigned int cpu)
4806 {
4807         struct worker_pool *pool;
4808         struct workqueue_struct *wq;
4809         int pi;
4810 
4811         mutex_lock(&wq_pool_mutex);
4812 
4813         for_each_pool(pool, pi) {
4814                 mutex_lock(&wq_pool_attach_mutex);
4815 
4816                 if (pool->cpu == cpu)
4817                         rebind_workers(pool);
4818                 else if (pool->cpu < 0)
4819                         restore_unbound_workers_cpumask(pool, cpu);
4820 
4821                 mutex_unlock(&wq_pool_attach_mutex);
4822         }
4823 
4824         /* update NUMA affinity of unbound workqueues */
4825         list_for_each_entry(wq, &workqueues, list)
4826                 wq_update_unbound_numa(wq, cpu, true);
4827 
4828         mutex_unlock(&wq_pool_mutex);
4829         return 0;
4830 }
4831 
4832 int workqueue_offline_cpu(unsigned int cpu)
4833 {
4834         struct workqueue_struct *wq;
4835 
4836         /* unbinding per-cpu workers should happen on the local CPU */
4837         if (WARN_ON(cpu != smp_processor_id()))
4838                 return -1;
4839 
4840         unbind_workers(cpu);
4841 
4842         /* update NUMA affinity of unbound workqueues */
4843         mutex_lock(&wq_pool_mutex);
4844         list_for_each_entry(wq, &workqueues, list)
4845                 wq_update_unbound_numa(wq, cpu, false);
4846         mutex_unlock(&wq_pool_mutex);
4847 
4848         return 0;
4849 }
4850 
4851 struct work_for_cpu {
4852         struct work_struct work;
4853         long (*fn)(void *);
4854         void *arg;
4855         long ret;
4856 };
4857 
4858 static void work_for_cpu_fn(struct work_struct *work)
4859 {
4860         struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4861 
4862         wfc->ret = wfc->fn(wfc->arg);
4863 }
4864 
4865 /**
4866  * work_on_cpu - run a function in thread context on a particular cpu
4867  * @cpu: the cpu to run on
4868  * @fn: the function to run
4869  * @arg: the function arg
4870  *
4871  * It is up to the caller to ensure that the cpu doesn't go offline.
4872  * The caller must not hold any locks which would prevent @fn from completing.
4873  *
4874  * Return: The value @fn returns.
4875  */
4876 long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4877 {
4878         struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4879 
4880         INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4881         schedule_work_on(cpu, &wfc.work);
4882         flush_work(&wfc.work);
4883         destroy_work_on_stack(&wfc.work);
4884         return wfc.ret;
4885 }
4886 EXPORT_SYMBOL_GPL(work_on_cpu);
4887 
4888 /**
4889  * work_on_cpu_safe - run a function in thread context on a particular cpu
4890  * @cpu: the cpu to run on
4891  * @fn:  the function to run
4892  * @arg: the function argument
4893  *
4894  * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
4895  * any locks which would prevent @fn from completing.
4896  *
4897  * Return: The value @fn returns.
4898  */
4899 long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
4900 {
4901         long ret = -ENODEV;
4902 
4903         get_online_cpus();
4904         if (cpu_online(cpu))
4905                 ret = work_on_cpu(cpu, fn, arg);
4906         put_online_cpus();
4907         return ret;
4908 }
4909 EXPORT_SYMBOL_GPL(work_on_cpu_safe);
4910 #endif /* CONFIG_SMP */
4911 
4912 #ifdef CONFIG_FREEZER
4913 
4914 /**
4915  * freeze_workqueues_begin - begin freezing workqueues
4916  *
4917  * Start freezing workqueues.  After this function returns, all freezable
4918  * workqueues will queue new works to their delayed_works list instead of
4919  * pool->worklist.
4920  *
4921  * CONTEXT:
4922  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4923  */
4924 void freeze_workqueues_begin(void)
4925 {
4926         struct workqueue_struct *wq;
4927         struct pool_workqueue *pwq;
4928 
4929         mutex_lock(&wq_pool_mutex);
4930 
4931         WARN_ON_ONCE(workqueue_freezing);
4932         workqueue_freezing = true;
4933 
4934         list_for_each_entry(wq, &workqueues, list) {
4935                 mutex_lock(&wq->mutex);
4936                 for_each_pwq(pwq, wq)
4937                         pwq_adjust_max_active(pwq);
4938                 mutex_unlock(&wq->mutex);
4939         }
4940 
4941         mutex_unlock(&wq_pool_mutex);
4942 }
4943 
4944 /**
4945  * freeze_workqueues_busy - are freezable workqueues still busy?
4946  *
4947  * Check whether freezing is complete.  This function must be called
4948  * between freeze_workqueues_begin() and thaw_workqueues().
4949  *
4950  * CONTEXT:
4951  * Grabs and releases wq_pool_mutex.
4952  *
4953  * Return:
4954  * %true if some freezable workqueues are still busy.  %false if freezing
4955  * is complete.
4956  */
4957 bool freeze_workqueues_busy(void)
4958 {
4959         bool busy = false;
4960         struct workqueue_struct *wq;
4961         struct pool_workqueue *pwq;
4962 
4963         mutex_lock(&wq_pool_mutex);
4964 
4965         WARN_ON_ONCE(!workqueue_freezing);
4966 
4967         list_for_each_entry(wq, &workqueues, list) {
4968                 if (!(wq->flags & WQ_FREEZABLE))
4969                         continue;
4970                 /*
4971                  * nr_active is monotonically decreasing.  It's safe
4972                  * to peek without lock.
4973                  */
4974                 rcu_read_lock_sched();
4975                 for_each_pwq(pwq, wq) {
4976                         WARN_ON_ONCE(pwq->nr_active < 0);
4977                         if (pwq->nr_active) {
4978                                 busy = true;
4979                                 rcu_read_unlock_sched();
4980                                 goto out_unlock;
4981                         }
4982                 }
4983                 rcu_read_unlock_sched();
4984         }
4985 out_unlock:
4986         mutex_unlock(&wq_pool_mutex);
4987         return busy;
4988 }
4989 
4990 /**
4991  * thaw_workqueues - thaw workqueues
4992  *
4993  * Thaw workqueues.  Normal queueing is restored and all collected
4994  * frozen works are transferred to their respective pool worklists.
4995  *
4996  * CONTEXT:
4997  * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4998  */
4999 void thaw_workqueues(void)
5000 {
5001         struct workqueue_struct *wq;
5002         struct pool_workqueue *pwq;
5003 
5004         mutex_lock(&wq_pool_mutex);
5005 
5006         if (!workqueue_freezing)
5007                 goto out_unlock;
5008 
5009         workqueue_freezing = false;
5010 
5011         /* restore max_active and repopulate worklist */
5012         list_for_each_entry(wq, &workqueues, list) {
5013                 mutex_lock(&wq->mutex);
5014                 for_each_pwq(pwq, wq)
5015                         pwq_adjust_max_active(pwq);
5016                 mutex_unlock(&wq->mutex);
5017         }
5018 
5019 out_unlock:
5020         mutex_unlock(&wq_pool_mutex);
5021 }
5022 #endif /* CONFIG_FREEZER */
5023 
5024 static int workqueue_apply_unbound_cpumask(void)
5025 {
5026         LIST_HEAD(ctxs);
5027         int ret = 0;
5028         struct workqueue_struct *wq;
5029         struct apply_wqattrs_ctx *ctx, *n;
5030 
5031         lockdep_assert_held(&wq_pool_mutex);
5032 
5033         list_for_each_entry(wq, &workqueues, list) {
5034                 if (!(wq->flags & WQ_UNBOUND))
5035                         continue;
5036                 /* creating multiple pwqs breaks ordering guarantee */
5037                 if (wq->flags & __WQ_ORDERED)
5038                         continue;
5039 
5040                 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
5041                 if (!ctx) {
5042                         ret = -ENOMEM;
5043                         break;
5044                 }
5045 
5046                 list_add_tail(&ctx->list, &ctxs);
5047         }
5048 
5049         list_for_each_entry_safe(ctx, n, &ctxs, list) {
5050                 if (!ret)
5051                         apply_wqattrs_commit(ctx);
5052                 apply_wqattrs_cleanup(ctx);
5053         }
5054 
5055         return ret;
5056 }
5057 
5058 /**
5059  *  workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5060  *  @cpumask: the cpumask to set
5061  *
5062  *  The low-level workqueues cpumask is a global cpumask that limits
5063  *  the affinity of all unbound workqueues.  This function check the @cpumask
5064  *  and apply it to all unbound workqueues and updates all pwqs of them.
5065  *
5066  *  Retun:      0       - Success
5067  *              -EINVAL - Invalid @cpumask
5068  *              -ENOMEM - Failed to allocate memory for attrs or pwqs.
5069  */
5070 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5071 {
5072         int ret = -EINVAL;
5073         cpumask_var_t saved_cpumask;
5074 
5075         if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
5076                 return -ENOMEM;
5077 
5078         /*
5079          * Not excluding isolated cpus on purpose.
5080          * If the user wishes to include them, we allow that.
5081          */
5082         cpumask_and(cpumask, cpumask, cpu_possible_mask);
5083         if (!cpumask_empty(cpumask)) {
5084                 apply_wqattrs_lock();
5085 
5086                 /* save the old wq_unbound_cpumask. */
5087                 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
5088 
5089                 /* update wq_unbound_cpumask at first and apply it to wqs. */
5090                 cpumask_copy(wq_unbound_cpumask, cpumask);
5091                 ret = workqueue_apply_unbound_cpumask();
5092 
5093                 /* restore the wq_unbound_cpumask when failed. */
5094                 if (ret < 0)
5095                         cpumask_copy(wq_unbound_cpumask, saved_cpumask);
5096 
5097                 apply_wqattrs_unlock();
5098         }
5099 
5100         free_cpumask_var(saved_cpumask);
5101         return ret;
5102 }
5103 
5104 #ifdef CONFIG_SYSFS
5105 /*
5106  * Workqueues with WQ_SYSFS flag set is visible to userland via
5107  * /sys/bus/workqueue/devices/WQ_NAME.  All visible workqueues have the
5108  * following attributes.
5109  *
5110  *  per_cpu     RO bool : whether the workqueue is per-cpu or unbound
5111  *  max_active  RW int  : maximum number of in-flight work items
5112  *
5113  * Unbound workqueues have the following extra attributes.
5114  *
5115  *  pool_ids    RO int  : the associated pool IDs for each node
5116  *  nice        RW int  : nice value of the workers
5117  *  cpumask     RW mask : bitmask of allowed CPUs for the workers
5118  *  numa        RW bool : whether enable NUMA affinity
5119  */
5120 struct wq_device {
5121         struct workqueue_struct         *wq;
5122         struct device                   dev;
5123 };
5124 
5125 static struct workqueue_struct *dev_to_wq(struct device *dev)
5126 {
5127         struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5128 
5129         return wq_dev->wq;
5130 }
5131 
5132 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5133                             char *buf)
5134 {
5135         struct workqueue_struct *wq = dev_to_wq(dev);
5136 
5137         return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5138 }
5139 static DEVICE_ATTR_RO(per_cpu);
5140 
5141 static ssize_t max_active_show(struct device *dev,
5142                                struct device_attribute *attr, char *buf)
5143 {
5144         struct workqueue_struct *wq = dev_to_wq(dev);
5145 
5146         return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5147 }
5148 
5149 static ssize_t max_active_store(struct device *dev,
5150                                 struct device_attribute *attr, const char *buf,
5151                                 size_t count)
5152 {
5153         struct workqueue_struct *wq = dev_to_wq(dev);
5154         int val;
5155 
5156         if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5157                 return -EINVAL;
5158 
5159         workqueue_set_max_active(wq, val);
5160         return count;
5161 }
5162 static DEVICE_ATTR_RW(max_active);
5163 
5164 static struct attribute *wq_sysfs_attrs[] = {
5165         &dev_attr_per_cpu.attr,
5166         &dev_attr_max_active.attr,
5167         NULL,
5168 };
5169 ATTRIBUTE_GROUPS(wq_sysfs);
5170 
5171 static ssize_t wq_pool_ids_show(struct device *dev,
5172                                 struct device_attribute *attr, char *buf)
5173 {
5174         struct workqueue_struct *wq = dev_to_wq(dev);
5175         const char *delim = "";
5176         int node, written = 0;
5177 
5178         rcu_read_lock_sched();
5179         for_each_node(node) {
5180                 written += scnprintf(buf + written, PAGE_SIZE - written,
5181                                      "%s%d:%d", delim, node,
5182                                      unbound_pwq_by_node(wq, node)->pool->id);
5183                 delim = " ";
5184         }
5185         written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5186         rcu_read_unlock_sched();
5187 
5188         return written;
5189 }
5190 
5191 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5192                             char *buf)
5193 {
5194         struct workqueue_struct *wq = dev_to_wq(dev);
5195         int written;
5196 
5197         mutex_lock(&wq->mutex);
5198         written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5199         mutex_unlock(&wq->mutex);
5200 
5201         return written;
5202 }
5203 
5204 /* prepare workqueue_attrs for sysfs store operations */
5205 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5206 {
5207         struct workqueue_attrs *attrs;
5208 
5209         lockdep_assert_held(&wq_pool_mutex);
5210 
5211         attrs = alloc_workqueue_attrs(GFP_KERNEL);
5212         if (!attrs)
5213                 return NULL;
5214 
5215         copy_workqueue_attrs(attrs, wq->unbound_attrs);
5216         return attrs;
5217 }
5218 
5219 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5220                              const char *buf, size_t count)
5221 {
5222         struct workqueue_struct *wq = dev_to_wq(dev);
5223         struct workqueue_attrs *attrs;
5224         int ret = -ENOMEM;
5225 
5226         apply_wqattrs_lock();
5227 
5228         attrs = wq_sysfs_prep_attrs(wq);
5229         if (!attrs)
5230                 goto out_unlock;
5231 
5232         if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5233             attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5234                 ret = apply_workqueue_attrs_locked(wq, attrs);
5235         else
5236                 ret = -EINVAL;
5237 
5238 out_unlock:
5239         apply_wqattrs_unlock();
5240         free_workqueue_attrs(attrs);
5241         return ret ?: count;
5242 }
5243 
5244 static ssize_t wq_cpumask_show(struct device *dev,
5245                                struct device_attribute *attr, char *buf)
5246 {
5247         struct workqueue_struct *wq = dev_to_wq(dev);
5248         int written;
5249 
5250         mutex_lock(&wq->mutex);
5251         written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5252                             cpumask_pr_args(wq->unbound_attrs->cpumask));
5253         mutex_unlock(&wq->mutex);
5254         return written;
5255 }
5256 
5257 static ssize_t wq_cpumask_store(struct device *dev,
5258                                 struct device_attribute *attr,
5259                                 const char *buf, size_t count)
5260 {
5261         struct workqueue_struct *wq = dev_to_wq(dev);
5262         struct workqueue_attrs *attrs;
5263         int ret = -ENOMEM;
5264 
5265         apply_wqattrs_lock();
5266 
5267         attrs = wq_sysfs_prep_attrs(wq);
5268         if (!attrs)
5269                 goto out_unlock;
5270 
5271         ret = cpumask_parse(buf, attrs->cpumask);
5272         if (!ret)
5273                 ret = apply_workqueue_attrs_locked(wq, attrs);
5274 
5275 out_unlock:
5276         apply_wqattrs_unlock();
5277         free_workqueue_attrs(attrs);
5278         return ret ?: count;
5279 }
5280 
5281 static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5282                             char *buf)
5283 {
5284         struct workqueue_struct *wq = dev_to_wq(dev);
5285         int written;
5286 
5287         mutex_lock(&wq->mutex);
5288         written = scnprintf(buf, PAGE_SIZE, "%d\n",
5289                             !wq->unbound_attrs->no_numa);
5290         mutex_unlock(&wq->mutex);
5291 
5292         return written;
5293 }
5294 
5295 static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5296                              const char *buf, size_t count)
5297 {
5298         struct workqueue_struct *wq = dev_to_wq(dev);
5299         struct workqueue_attrs *attrs;
5300         int v, ret = -ENOMEM;
5301 
5302         apply_wqattrs_lock();
5303 
5304         attrs = wq_sysfs_prep_attrs(wq);
5305         if (!attrs)
5306                 goto out_unlock;
5307 
5308         ret = -EINVAL;
5309         if (sscanf(buf, "%d", &v) == 1) {
5310                 attrs->no_numa = !v;
5311                 ret = apply_workqueue_attrs_locked(wq, attrs);
5312         }
5313 
5314 out_unlock:
5315         apply_wqattrs_unlock();
5316         free_workqueue_attrs(attrs);
5317         return ret ?: count;
5318 }
5319 
5320 static struct device_attribute wq_sysfs_unbound_attrs[] = {
5321         __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5322         __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5323         __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5324         __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5325         __ATTR_NULL,
5326 };
5327 
5328 static struct bus_type wq_subsys = {
5329         .name                           = "workqueue",
5330         .dev_groups                     = wq_sysfs_groups,
5331 };
5332 
5333 static ssize_t wq_unbound_cpumask_show(struct device *dev,
5334                 struct device_attribute *attr, char *buf)
5335 {
5336         int written;
5337 
5338         mutex_lock(&wq_pool_mutex);
5339         written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5340                             cpumask_pr_args(wq_unbound_cpumask));
5341         mutex_unlock(&wq_pool_mutex);
5342 
5343         return written;
5344 }
5345 
5346 static ssize_t wq_unbound_cpumask_store(struct device *dev,
5347                 struct device_attribute *attr, const char *buf, size_t count)
5348 {
5349         cpumask_var_t cpumask;
5350         int ret;
5351 
5352         if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5353                 return -ENOMEM;
5354 
5355         ret = cpumask_parse(buf, cpumask);
5356         if (!ret)
5357                 ret = workqueue_set_unbound_cpumask(cpumask);
5358 
5359         free_cpumask_var(cpumask);
5360         return ret ? ret : count;
5361 }
5362 
5363 static struct device_attribute wq_sysfs_cpumask_attr =
5364         __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5365                wq_unbound_cpumask_store);
5366 
5367 static int __init wq_sysfs_init(void)
5368 {
5369         int err;
5370 
5371         err = subsys_virtual_register(&wq_subsys, NULL);
5372         if (err)
5373                 return err;
5374 
5375         return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5376 }
5377 core_initcall(wq_sysfs_init);
5378 
5379 static void wq_device_release(struct device *dev)
5380 {
5381         struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5382 
5383         kfree(wq_dev);
5384 }
5385 
5386 /**
5387  * workqueue_sysfs_register - make a workqueue visible in sysfs
5388  * @wq: the workqueue to register
5389  *
5390  * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5391  * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5392  * which is the preferred method.
5393  *
5394  * Workqueue user should use this function directly iff it wants to apply
5395  * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5396  * apply_workqueue_attrs() may race against userland updating the
5397  * attributes.
5398  *
5399  * Return: 0 on success, -errno on failure.
5400  */
5401 int workqueue_sysfs_register(struct workqueue_struct *wq)
5402 {
5403         struct wq_device *wq_dev;
5404         int ret;
5405 
5406         /*
5407          * Adjusting max_active or creating new pwqs by applying
5408          * attributes breaks ordering guarantee.  Disallow exposing ordered
5409          * workqueues.
5410          */
5411         if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
5412                 return -EINVAL;
5413 
5414         wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5415         if (!wq_dev)
5416                 return -ENOMEM;
5417 
5418         wq_dev->wq = wq;
5419         wq_dev->dev.bus = &wq_subsys;
5420         wq_dev->dev.release = wq_device_release;
5421         dev_set_name(&wq_dev->dev, "%s", wq->name);
5422 
5423         /*
5424          * unbound_attrs are created separately.  Suppress uevent until
5425          * everything is ready.
5426          */
5427         dev_set_uevent_suppress(&wq_dev->dev, true);
5428 
5429         ret = device_register(&wq_dev->dev);
5430         if (ret) {
5431                 put_device(&wq_dev->dev);
5432                 wq->wq_dev = NULL;
5433                 return ret;
5434         }
5435 
5436         if (wq->flags & WQ_UNBOUND) {
5437                 struct device_attribute *attr;
5438 
5439                 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5440                         ret = device_create_file(&wq_dev->dev, attr);
5441                         if (ret) {
5442                                 device_unregister(&wq_dev->dev);
5443                                 wq->wq_dev = NULL;
5444                                 return ret;
5445                         }
5446                 }
5447         }
5448 
5449         dev_set_uevent_suppress(&wq_dev->dev, false);
5450         kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5451         return 0;
5452 }
5453 
5454 /**
5455  * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5456  * @wq: the workqueue to unregister
5457  *
5458  * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5459  */
5460 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5461 {
5462         struct wq_device *wq_dev = wq->wq_dev;
5463 
5464         if (!wq->wq_dev)
5465                 return;
5466 
5467         wq->wq_dev = NULL;
5468         device_unregister(&wq_dev->dev);
5469 }
5470 #else   /* CONFIG_SYSFS */
5471 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)     { }
5472 #endif  /* CONFIG_SYSFS */
5473 
5474 /*
5475  * Workqueue watchdog.
5476  *
5477  * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5478  * flush dependency, a concurrency managed work item which stays RUNNING
5479  * indefinitely.  Workqueue stalls can be very difficult to debug as the
5480  * usual warning mechanisms don't trigger and internal workqueue state is
5481  * largely opaque.
5482  *
5483  * Workqueue watchdog monitors all worker pools periodically and dumps
5484  * state if some pools failed to make forward progress for a while where
5485  * forward progress is defined as the first item on ->worklist changing.
5486  *
5487  * This mechanism is controlled through the kernel parameter
5488  * "workqueue.watchdog_thresh" which can be updated at runtime through the
5489  * corresponding sysfs parameter file.
5490  */
5491 #ifdef CONFIG_WQ_WATCHDOG
5492 
5493 static unsigned long wq_watchdog_thresh = 30;
5494 static struct timer_list wq_watchdog_timer;
5495 
5496 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5497 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5498 
5499 static void wq_watchdog_reset_touched(void)
5500 {
5501         int cpu;
5502 
5503         wq_watchdog_touched = jiffies;
5504         for_each_possible_cpu(cpu)
5505                 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5506 }
5507 
5508 static void wq_watchdog_timer_fn(struct timer_list *unused)
5509 {
5510         unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5511         bool lockup_detected = false;
5512         struct worker_pool *pool;
5513         int pi;
5514 
5515         if (!thresh)
5516                 return;
5517 
5518         rcu_read_lock();
5519 
5520         for_each_pool(pool, pi) {
5521                 unsigned long pool_ts, touched, ts;
5522 
5523                 if (list_empty(&pool->worklist))
5524                         continue;
5525 
5526                 /* get the latest of pool and touched timestamps */
5527                 pool_ts = READ_ONCE(pool->watchdog_ts);
5528                 touched = READ_ONCE(wq_watchdog_touched);
5529 
5530                 if (time_after(pool_ts, touched))
5531                         ts = pool_ts;
5532                 else
5533                         ts = touched;
5534 
5535                 if (pool->cpu >= 0) {
5536                         unsigned long cpu_touched =
5537                                 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5538                                                   pool->cpu));
5539                         if (time_after(cpu_touched, ts))
5540                                 ts = cpu_touched;
5541                 }
5542 
5543                 /* did we stall? */
5544                 if (time_after(jiffies, ts + thresh)) {
5545                         lockup_detected = true;
5546                         pr_emerg("BUG: workqueue lockup - pool");
5547                         pr_cont_pool_info(pool);
5548                         pr_cont(" stuck for %us!\n",
5549                                 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5550                 }
5551         }
5552 
5553         rcu_read_unlock();
5554 
5555         if (lockup_detected)
5556                 show_workqueue_state();
5557 
5558         wq_watchdog_reset_touched();
5559         mod_timer(&wq_watchdog_timer, jiffies + thresh);
5560 }
5561 
5562 void wq_watchdog_touch(int cpu)
5563 {
5564         if (cpu >= 0)
5565                 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5566         else
5567                 wq_watchdog_touched = jiffies;
5568 }
5569 
5570 static void wq_watchdog_set_thresh(unsigned long thresh)
5571 {
5572         wq_watchdog_thresh = 0;
5573         del_timer_sync(&wq_watchdog_timer);
5574 
5575         if (thresh) {
5576                 wq_watchdog_thresh = thresh;
5577                 wq_watchdog_reset_touched();
5578                 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5579         }
5580 }
5581 
5582 static int wq_watchdog_param_set_thresh(const char *val,
5583                                         const struct kernel_param *kp)
5584 {
5585         unsigned long thresh;
5586         int ret;
5587 
5588         ret = kstrtoul(val, 0, &thresh);
5589         if (ret)
5590                 return ret;
5591 
5592         if (system_wq)
5593                 wq_watchdog_set_thresh(thresh);
5594         else
5595                 wq_watchdog_thresh = thresh;
5596 
5597         return 0;
5598 }
5599 
5600 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5601         .set    = wq_watchdog_param_set_thresh,
5602         .get    = param_get_ulong,
5603 };
5604 
5605 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5606                 0644);
5607 
5608 static void wq_watchdog_init(void)
5609 {
5610         timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
5611         wq_watchdog_set_thresh(wq_watchdog_thresh);
5612 }
5613 
5614 #else   /* CONFIG_WQ_WATCHDOG */
5615 
5616 static inline void wq_watchdog_init(void) { }
5617 
5618 #endif  /* CONFIG_WQ_WATCHDOG */
5619 
5620 static void __init wq_numa_init(void)
5621 {
5622         cpumask_var_t *tbl;
5623         int node, cpu;
5624 
5625         if (num_possible_nodes() <= 1)
5626                 return;
5627 
5628         if (wq_disable_numa) {
5629                 pr_info("workqueue: NUMA affinity support disabled\n");
5630                 return;
5631         }
5632 
5633         wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5634         BUG_ON(!wq_update_unbound_numa_attrs_buf);
5635 
5636         /*
5637          * We want masks of possible CPUs of each node which isn't readily
5638          * available.  Build one from cpu_to_node() which should have been
5639          * fully initialized by now.
5640          */
5641         tbl = kcalloc(nr_node_ids, sizeof(tbl[0]), GFP_KERNEL);
5642         BUG_ON(!tbl);
5643 
5644         for_each_node(node)
5645                 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5646                                 node_online(node) ? node : NUMA_NO_NODE));
5647 
5648         for_each_possible_cpu(cpu) {
5649                 node = cpu_to_node(cpu);
5650                 if (WARN_ON(node == NUMA_NO_NODE)) {
5651                         pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5652                         /* happens iff arch is bonkers, let's just proceed */
5653                         return;
5654                 }
5655                 cpumask_set_cpu(cpu, tbl[node]);
5656         }
5657 
5658         wq_numa_possible_cpumask = tbl;
5659         wq_numa_enabled = true;
5660 }
5661 
5662 /**
5663  * workqueue_init_early - early init for workqueue subsystem
5664  *
5665  * This is the first half of two-staged workqueue subsystem initialization
5666  * and invoked as soon as the bare basics - memory allocation, cpumasks and
5667  * idr are up.  It sets up all the data structures and system workqueues
5668  * and allows early boot code to create workqueues and queue/cancel work
5669  * items.  Actual work item execution starts only after kthreads can be
5670  * created and scheduled right before early initcalls.
5671  */
5672 int __init workqueue_init_early(void)
5673 {
5674         int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5675         int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
5676         int i, cpu;
5677 
5678         WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5679 
5680         BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5681         cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
5682 
5683         pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5684 
5685         /* initialize CPU pools */
5686         for_each_possible_cpu(cpu) {
5687                 struct worker_pool *pool;
5688 
5689                 i = 0;
5690                 for_each_cpu_worker_pool(pool, cpu) {
5691                         BUG_ON(init_worker_pool(pool));
5692                         pool->cpu = cpu;
5693                         cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5694                         pool->attrs->nice = std_nice[i++];
5695                         pool->node = cpu_to_node(cpu);
5696 
5697                         /* alloc pool ID */
5698                         mutex_lock(&wq_pool_mutex);
5699                         BUG_ON(worker_pool_assign_id(pool));
5700                         mutex_unlock(&wq_pool_mutex);
5701                 }
5702         }
5703 
5704         /* create default unbound and ordered wq attrs */
5705         for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5706                 struct workqueue_attrs *attrs;
5707 
5708                 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5709                 attrs->nice = std_nice[i];
5710                 unbound_std_wq_attrs[i] = attrs;
5711 
5712                 /*
5713                  * An ordered wq should have only one pwq as ordering is
5714                  * guaranteed by max_active which is enforced by pwqs.
5715                  * Turn off NUMA so that dfl_pwq is used for all nodes.
5716                  */
5717                 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5718                 attrs->nice = std_nice[i];
5719                 attrs->no_numa = true;
5720                 ordered_wq_attrs[i] = attrs;
5721         }
5722 
5723         system_wq = alloc_workqueue("events", 0, 0);
5724         system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5725         system_long_wq = alloc_workqueue("events_long", 0, 0);
5726         system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5727                                             WQ_UNBOUND_MAX_ACTIVE);
5728         system_freezable_wq = alloc_workqueue("events_freezable",
5729                                               WQ_FREEZABLE, 0);
5730         system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5731                                               WQ_POWER_EFFICIENT, 0);
5732         system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5733                                               WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5734                                               0);
5735         BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5736                !system_unbound_wq || !system_freezable_wq ||
5737                !system_power_efficient_wq ||
5738                !system_freezable_power_efficient_wq);
5739 
5740         return 0;
5741 }
5742 
5743 /**
5744  * workqueue_init - bring workqueue subsystem fully online
5745  *
5746  * This is the latter half of two-staged workqueue subsystem initialization
5747  * and invoked as soon as kthreads can be created and scheduled.
5748  * Workqueues have been created and work items queued on them, but there
5749  * are no kworkers executing the work items yet.  Populate the worker pools
5750  * with the initial workers and enable future kworker creations.
5751  */
5752 int __init workqueue_init(void)
5753 {
5754         struct workqueue_struct *wq;
5755         struct worker_pool *pool;
5756         int cpu, bkt;
5757 
5758         /*
5759          * It'd be simpler to initialize NUMA in workqueue_init_early() but
5760          * CPU to node mapping may not be available that early on some
5761          * archs such as power and arm64.  As per-cpu pools created
5762          * previously could be missing node hint and unbound pools NUMA
5763          * affinity, fix them up.
5764          *
5765          * Also, while iterating workqueues, create rescuers if requested.
5766          */
5767         wq_numa_init();
5768 
5769         mutex_lock(&wq_pool_mutex);
5770 
5771         for_each_possible_cpu(cpu) {
5772                 for_each_cpu_worker_pool(pool, cpu) {
5773                         pool->node = cpu_to_node(cpu);
5774                 }
5775         }
5776 
5777         list_for_each_entry(wq, &workqueues, list) {
5778                 wq_update_unbound_numa(wq, smp_processor_id(), true);
5779                 WARN(init_rescuer(wq),
5780                      "workqueue: failed to create early rescuer for %s",
5781                      wq->name);
5782         }
5783 
5784         mutex_unlock(&wq_pool_mutex);
5785 
5786         /* create the initial workers */
5787         for_each_online_cpu(cpu) {
5788                 for_each_cpu_worker_pool(pool, cpu) {
5789                         pool->flags &= ~POOL_DISASSOCIATED;
5790                         BUG_ON(!create_worker(pool));
5791                 }
5792         }
5793 
5794         hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
5795                 BUG_ON(!create_worker(pool));
5796 
5797         wq_online = true;
5798         wq_watchdog_init();
5799 
5800         return 0;
5801 }
5802 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp