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TOMOYO Linux Cross Reference
Linux/kernel/workqueue.c

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

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