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TOMOYO Linux Cross Reference
Linux/kernel/rcu/tree.h

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  1 /*
  2  * Read-Copy Update mechanism for mutual exclusion (tree-based version)
  3  * Internal non-public definitions.
  4  *
  5  * This program is free software; you can redistribute it and/or modify
  6  * it under the terms of the GNU General Public License as published by
  7  * the Free Software Foundation; either version 2 of the License, or
  8  * (at your option) any later version.
  9  *
 10  * This program is distributed in the hope that it will be useful,
 11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13  * GNU General Public License for more details.
 14  *
 15  * You should have received a copy of the GNU General Public License
 16  * along with this program; if not, you can access it online at
 17  * http://www.gnu.org/licenses/gpl-2.0.html.
 18  *
 19  * Copyright IBM Corporation, 2008
 20  *
 21  * Author: Ingo Molnar <mingo@elte.hu>
 22  *         Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 23  */
 24 
 25 #include <linux/cache.h>
 26 #include <linux/spinlock.h>
 27 #include <linux/rtmutex.h>
 28 #include <linux/threads.h>
 29 #include <linux/cpumask.h>
 30 #include <linux/seqlock.h>
 31 #include <linux/swait.h>
 32 #include <linux/stop_machine.h>
 33 #include <linux/rcu_node_tree.h>
 34 
 35 #include "rcu_segcblist.h"
 36 
 37 /*
 38  * Dynticks per-CPU state.
 39  */
 40 struct rcu_dynticks {
 41         long long dynticks_nesting; /* Track irq/process nesting level. */
 42                                     /* Process level is worth LLONG_MAX/2. */
 43         int dynticks_nmi_nesting;   /* Track NMI nesting level. */
 44         atomic_t dynticks;          /* Even value for idle, else odd. */
 45         bool rcu_need_heavy_qs;     /* GP old, need heavy quiescent state. */
 46         unsigned long rcu_qs_ctr;   /* Light universal quiescent state ctr. */
 47         bool rcu_urgent_qs;         /* GP old need light quiescent state. */
 48 #ifdef CONFIG_RCU_FAST_NO_HZ
 49         bool all_lazy;              /* Are all CPU's CBs lazy? */
 50         unsigned long nonlazy_posted;
 51                                     /* # times non-lazy CBs posted to CPU. */
 52         unsigned long nonlazy_posted_snap;
 53                                     /* idle-period nonlazy_posted snapshot. */
 54         unsigned long last_accelerate;
 55                                     /* Last jiffy CBs were accelerated. */
 56         unsigned long last_advance_all;
 57                                     /* Last jiffy CBs were all advanced. */
 58         int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
 59 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 60 };
 61 
 62 /* RCU's kthread states for tracing. */
 63 #define RCU_KTHREAD_STOPPED  0
 64 #define RCU_KTHREAD_RUNNING  1
 65 #define RCU_KTHREAD_WAITING  2
 66 #define RCU_KTHREAD_OFFCPU   3
 67 #define RCU_KTHREAD_YIELDING 4
 68 #define RCU_KTHREAD_MAX      4
 69 
 70 /*
 71  * Definition for node within the RCU grace-period-detection hierarchy.
 72  */
 73 struct rcu_node {
 74         raw_spinlock_t __private lock;  /* Root rcu_node's lock protects */
 75                                         /*  some rcu_state fields as well as */
 76                                         /*  following. */
 77         unsigned long gpnum;    /* Current grace period for this node. */
 78                                 /*  This will either be equal to or one */
 79                                 /*  behind the root rcu_node's gpnum. */
 80         unsigned long completed; /* Last GP completed for this node. */
 81                                 /*  This will either be equal to or one */
 82                                 /*  behind the root rcu_node's gpnum. */
 83         unsigned long qsmask;   /* CPUs or groups that need to switch in */
 84                                 /*  order for current grace period to proceed.*/
 85                                 /*  In leaf rcu_node, each bit corresponds to */
 86                                 /*  an rcu_data structure, otherwise, each */
 87                                 /*  bit corresponds to a child rcu_node */
 88                                 /*  structure. */
 89         unsigned long qsmaskinit;
 90                                 /* Per-GP initial value for qsmask. */
 91                                 /*  Initialized from ->qsmaskinitnext at the */
 92                                 /*  beginning of each grace period. */
 93         unsigned long qsmaskinitnext;
 94                                 /* Online CPUs for next grace period. */
 95         unsigned long expmask;  /* CPUs or groups that need to check in */
 96                                 /*  to allow the current expedited GP */
 97                                 /*  to complete. */
 98         unsigned long expmaskinit;
 99                                 /* Per-GP initial values for expmask. */
100                                 /*  Initialized from ->expmaskinitnext at the */
101                                 /*  beginning of each expedited GP. */
102         unsigned long expmaskinitnext;
103                                 /* Online CPUs for next expedited GP. */
104                                 /*  Any CPU that has ever been online will */
105                                 /*  have its bit set. */
106         unsigned long ffmask;   /* Fully functional CPUs. */
107         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
108                                 /*  Only one bit will be set in this mask. */
109         int     grplo;          /* lowest-numbered CPU or group here. */
110         int     grphi;          /* highest-numbered CPU or group here. */
111         u8      grpnum;         /* CPU/group number for next level up. */
112         u8      level;          /* root is at level 0. */
113         bool    wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
114                                 /*  exit RCU read-side critical sections */
115                                 /*  before propagating offline up the */
116                                 /*  rcu_node tree? */
117         struct rcu_node *parent;
118         struct list_head blkd_tasks;
119                                 /* Tasks blocked in RCU read-side critical */
120                                 /*  section.  Tasks are placed at the head */
121                                 /*  of this list and age towards the tail. */
122         struct list_head *gp_tasks;
123                                 /* Pointer to the first task blocking the */
124                                 /*  current grace period, or NULL if there */
125                                 /*  is no such task. */
126         struct list_head *exp_tasks;
127                                 /* Pointer to the first task blocking the */
128                                 /*  current expedited grace period, or NULL */
129                                 /*  if there is no such task.  If there */
130                                 /*  is no current expedited grace period, */
131                                 /*  then there can cannot be any such task. */
132         struct list_head *boost_tasks;
133                                 /* Pointer to first task that needs to be */
134                                 /*  priority boosted, or NULL if no priority */
135                                 /*  boosting is needed for this rcu_node */
136                                 /*  structure.  If there are no tasks */
137                                 /*  queued on this rcu_node structure that */
138                                 /*  are blocking the current grace period, */
139                                 /*  there can be no such task. */
140         struct rt_mutex boost_mtx;
141                                 /* Used only for the priority-boosting */
142                                 /*  side effect, not as a lock. */
143         unsigned long boost_time;
144                                 /* When to start boosting (jiffies). */
145         struct task_struct *boost_kthread_task;
146                                 /* kthread that takes care of priority */
147                                 /*  boosting for this rcu_node structure. */
148         unsigned int boost_kthread_status;
149                                 /* State of boost_kthread_task for tracing. */
150         unsigned long n_tasks_boosted;
151                                 /* Total number of tasks boosted. */
152         unsigned long n_exp_boosts;
153                                 /* Number of tasks boosted for expedited GP. */
154         unsigned long n_normal_boosts;
155                                 /* Number of tasks boosted for normal GP. */
156 #ifdef CONFIG_RCU_NOCB_CPU
157         struct swait_queue_head nocb_gp_wq[2];
158                                 /* Place for rcu_nocb_kthread() to wait GP. */
159 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
160         int need_future_gp[2];
161                                 /* Counts of upcoming no-CB GP requests. */
162         raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
163 
164         spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
165         unsigned long exp_seq_rq;
166         wait_queue_head_t exp_wq[4];
167 } ____cacheline_internodealigned_in_smp;
168 
169 /*
170  * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
171  * are indexed relative to this interval rather than the global CPU ID space.
172  * This generates the bit for a CPU in node-local masks.
173  */
174 #define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo))
175 
176 /*
177  * Union to allow "aggregate OR" operation on the need for a quiescent
178  * state by the normal and expedited grace periods.
179  */
180 union rcu_noqs {
181         struct {
182                 u8 norm;
183                 u8 exp;
184         } b; /* Bits. */
185         u16 s; /* Set of bits, aggregate OR here. */
186 };
187 
188 /* Index values for nxttail array in struct rcu_data. */
189 #define RCU_DONE_TAIL           0       /* Also RCU_WAIT head. */
190 #define RCU_WAIT_TAIL           1       /* Also RCU_NEXT_READY head. */
191 #define RCU_NEXT_READY_TAIL     2       /* Also RCU_NEXT head. */
192 #define RCU_NEXT_TAIL           3
193 #define RCU_NEXT_SIZE           4
194 
195 /* Per-CPU data for read-copy update. */
196 struct rcu_data {
197         /* 1) quiescent-state and grace-period handling : */
198         unsigned long   completed;      /* Track rsp->completed gp number */
199                                         /*  in order to detect GP end. */
200         unsigned long   gpnum;          /* Highest gp number that this CPU */
201                                         /*  is aware of having started. */
202         unsigned long   rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
203                                         /*  for rcu_all_qs() invocations. */
204         union rcu_noqs  cpu_no_qs;      /* No QSes yet for this CPU. */
205         bool            core_needs_qs;  /* Core waits for quiesc state. */
206         bool            beenonline;     /* CPU online at least once. */
207         bool            gpwrap;         /* Possible gpnum/completed wrap. */
208         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
209         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
210         unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
211                                         /*  ticks this CPU has handled */
212                                         /*  during and after the last grace */
213                                         /* period it is aware of. */
214 
215         /* 2) batch handling */
216         struct rcu_segcblist cblist;    /* Segmented callback list, with */
217                                         /* different callbacks waiting for */
218                                         /* different grace periods. */
219         long            qlen_last_fqs_check;
220                                         /* qlen at last check for QS forcing */
221         unsigned long   n_cbs_invoked;  /* count of RCU cbs invoked. */
222         unsigned long   n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
223         unsigned long   n_force_qs_snap;
224                                         /* did other CPU force QS recently? */
225         long            blimit;         /* Upper limit on a processed batch */
226 
227         /* 3) dynticks interface. */
228         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
229         int dynticks_snap;              /* Per-GP tracking for dynticks. */
230 
231         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
232         unsigned long dynticks_fqs;     /* Kicked due to dynticks idle. */
233         unsigned long offline_fqs;      /* Kicked due to being offline. */
234         unsigned long cond_resched_completed;
235                                         /* Grace period that needs help */
236                                         /*  from cond_resched(). */
237 
238         /* 5) __rcu_pending() statistics. */
239         unsigned long n_rcu_pending;    /* rcu_pending() calls since boot. */
240         unsigned long n_rp_core_needs_qs;
241         unsigned long n_rp_report_qs;
242         unsigned long n_rp_cb_ready;
243         unsigned long n_rp_cpu_needs_gp;
244         unsigned long n_rp_gp_completed;
245         unsigned long n_rp_gp_started;
246         unsigned long n_rp_nocb_defer_wakeup;
247         unsigned long n_rp_need_nothing;
248 
249         /* 6) _rcu_barrier(), OOM callbacks, and expediting. */
250         struct rcu_head barrier_head;
251 #ifdef CONFIG_RCU_FAST_NO_HZ
252         struct rcu_head oom_head;
253 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
254         atomic_long_t exp_workdone0;    /* # done by workqueue. */
255         atomic_long_t exp_workdone1;    /* # done by others #1. */
256         atomic_long_t exp_workdone2;    /* # done by others #2. */
257         atomic_long_t exp_workdone3;    /* # done by others #3. */
258         int exp_dynticks_snap;          /* Double-check need for IPI. */
259 
260         /* 7) Callback offloading. */
261 #ifdef CONFIG_RCU_NOCB_CPU
262         struct rcu_head *nocb_head;     /* CBs waiting for kthread. */
263         struct rcu_head **nocb_tail;
264         atomic_long_t nocb_q_count;     /* # CBs waiting for nocb */
265         atomic_long_t nocb_q_count_lazy; /*  invocation (all stages). */
266         struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
267         struct rcu_head **nocb_follower_tail;
268         struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
269         struct task_struct *nocb_kthread;
270         raw_spinlock_t nocb_lock;       /* Guard following pair of fields. */
271         int nocb_defer_wakeup;          /* Defer wakeup of nocb_kthread. */
272         struct timer_list nocb_timer;   /* Enforce finite deferral. */
273 
274         /* The following fields are used by the leader, hence own cacheline. */
275         struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
276                                         /* CBs waiting for GP. */
277         struct rcu_head **nocb_gp_tail;
278         bool nocb_leader_sleep;         /* Is the nocb leader thread asleep? */
279         struct rcu_data *nocb_next_follower;
280                                         /* Next follower in wakeup chain. */
281 
282         /* The following fields are used by the follower, hence new cachline. */
283         struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
284                                         /* Leader CPU takes GP-end wakeups. */
285 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
286 
287         /* 8) RCU CPU stall data. */
288         unsigned int softirq_snap;      /* Snapshot of softirq activity. */
289         /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
290         struct irq_work rcu_iw;         /* Check for non-irq activity. */
291         bool rcu_iw_pending;            /* Is ->rcu_iw pending? */
292         unsigned long rcu_iw_gpnum;     /* ->gpnum associated with ->rcu_iw. */
293 
294         int cpu;
295         struct rcu_state *rsp;
296 };
297 
298 /* Values for nocb_defer_wakeup field in struct rcu_data. */
299 #define RCU_NOCB_WAKE_NOT       0
300 #define RCU_NOCB_WAKE           1
301 #define RCU_NOCB_WAKE_FORCE     2
302 
303 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
304                                         /* For jiffies_till_first_fqs and */
305                                         /*  and jiffies_till_next_fqs. */
306 
307 #define RCU_JIFFIES_FQS_DIV     256     /* Very large systems need more */
308                                         /*  delay between bouts of */
309                                         /*  quiescent-state forcing. */
310 
311 #define RCU_STALL_RAT_DELAY     2       /* Allow other CPUs time to take */
312                                         /*  at least one scheduling clock */
313                                         /*  irq before ratting on them. */
314 
315 #define rcu_wait(cond)                                                  \
316 do {                                                                    \
317         for (;;) {                                                      \
318                 set_current_state(TASK_INTERRUPTIBLE);                  \
319                 if (cond)                                               \
320                         break;                                          \
321                 schedule();                                             \
322         }                                                               \
323         __set_current_state(TASK_RUNNING);                              \
324 } while (0)
325 
326 /*
327  * RCU global state, including node hierarchy.  This hierarchy is
328  * represented in "heap" form in a dense array.  The root (first level)
329  * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
330  * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
331  * and the third level in ->node[m+1] and following (->node[m+1] referenced
332  * by ->level[2]).  The number of levels is determined by the number of
333  * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
334  * consisting of a single rcu_node.
335  */
336 struct rcu_state {
337         struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
338         struct rcu_node *level[RCU_NUM_LVLS + 1];
339                                                 /* Hierarchy levels (+1 to */
340                                                 /*  shut bogus gcc warning) */
341         struct rcu_data __percpu *rda;          /* pointer of percu rcu_data. */
342         call_rcu_func_t call;                   /* call_rcu() flavor. */
343         int ncpus;                              /* # CPUs seen so far. */
344 
345         /* The following fields are guarded by the root rcu_node's lock. */
346 
347         u8      boost ____cacheline_internodealigned_in_smp;
348                                                 /* Subject to priority boost. */
349         unsigned long gpnum;                    /* Current gp number. */
350         unsigned long completed;                /* # of last completed gp. */
351         struct task_struct *gp_kthread;         /* Task for grace periods. */
352         struct swait_queue_head gp_wq;          /* Where GP task waits. */
353         short gp_flags;                         /* Commands for GP task. */
354         short gp_state;                         /* GP kthread sleep state. */
355 
356         /* End of fields guarded by root rcu_node's lock. */
357 
358         struct mutex barrier_mutex;             /* Guards barrier fields. */
359         atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
360         struct completion barrier_completion;   /* Wake at barrier end. */
361         unsigned long barrier_sequence;         /* ++ at start and end of */
362                                                 /*  _rcu_barrier(). */
363         /* End of fields guarded by barrier_mutex. */
364 
365         struct mutex exp_mutex;                 /* Serialize expedited GP. */
366         struct mutex exp_wake_mutex;            /* Serialize wakeup. */
367         unsigned long expedited_sequence;       /* Take a ticket. */
368         atomic_t expedited_need_qs;             /* # CPUs left to check in. */
369         struct swait_queue_head expedited_wq;   /* Wait for check-ins. */
370         int ncpus_snap;                         /* # CPUs seen last time. */
371 
372         unsigned long jiffies_force_qs;         /* Time at which to invoke */
373                                                 /*  force_quiescent_state(). */
374         unsigned long jiffies_kick_kthreads;    /* Time at which to kick */
375                                                 /*  kthreads, if configured. */
376         unsigned long n_force_qs;               /* Number of calls to */
377                                                 /*  force_quiescent_state(). */
378         unsigned long n_force_qs_lh;            /* ~Number of calls leaving */
379                                                 /*  due to lock unavailable. */
380         unsigned long n_force_qs_ngp;           /* Number of calls leaving */
381                                                 /*  due to no GP active. */
382         unsigned long gp_start;                 /* Time at which GP started, */
383                                                 /*  but in jiffies. */
384         unsigned long gp_activity;              /* Time of last GP kthread */
385                                                 /*  activity in jiffies. */
386         unsigned long jiffies_stall;            /* Time at which to check */
387                                                 /*  for CPU stalls. */
388         unsigned long jiffies_resched;          /* Time at which to resched */
389                                                 /*  a reluctant CPU. */
390         unsigned long n_force_qs_gpstart;       /* Snapshot of n_force_qs at */
391                                                 /*  GP start. */
392         unsigned long gp_max;                   /* Maximum GP duration in */
393                                                 /*  jiffies. */
394         const char *name;                       /* Name of structure. */
395         char abbr;                              /* Abbreviated name. */
396         struct list_head flavors;               /* List of RCU flavors. */
397 };
398 
399 /* Values for rcu_state structure's gp_flags field. */
400 #define RCU_GP_FLAG_INIT 0x1    /* Need grace-period initialization. */
401 #define RCU_GP_FLAG_FQS  0x2    /* Need grace-period quiescent-state forcing. */
402 
403 /* Values for rcu_state structure's gp_state field. */
404 #define RCU_GP_IDLE      0      /* Initial state and no GP in progress. */
405 #define RCU_GP_WAIT_GPS  1      /* Wait for grace-period start. */
406 #define RCU_GP_DONE_GPS  2      /* Wait done for grace-period start. */
407 #define RCU_GP_WAIT_FQS  3      /* Wait for force-quiescent-state time. */
408 #define RCU_GP_DOING_FQS 4      /* Wait done for force-quiescent-state time. */
409 #define RCU_GP_CLEANUP   5      /* Grace-period cleanup started. */
410 #define RCU_GP_CLEANED   6      /* Grace-period cleanup complete. */
411 
412 #ifndef RCU_TREE_NONCORE
413 static const char * const gp_state_names[] = {
414         "RCU_GP_IDLE",
415         "RCU_GP_WAIT_GPS",
416         "RCU_GP_DONE_GPS",
417         "RCU_GP_WAIT_FQS",
418         "RCU_GP_DOING_FQS",
419         "RCU_GP_CLEANUP",
420         "RCU_GP_CLEANED",
421 };
422 #endif /* #ifndef RCU_TREE_NONCORE */
423 
424 extern struct list_head rcu_struct_flavors;
425 
426 /* Sequence through rcu_state structures for each RCU flavor. */
427 #define for_each_rcu_flavor(rsp) \
428         list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
429 
430 /*
431  * RCU implementation internal declarations:
432  */
433 extern struct rcu_state rcu_sched_state;
434 
435 extern struct rcu_state rcu_bh_state;
436 
437 #ifdef CONFIG_PREEMPT_RCU
438 extern struct rcu_state rcu_preempt_state;
439 #endif /* #ifdef CONFIG_PREEMPT_RCU */
440 
441 int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
442 bool rcu_eqs_special_set(int cpu);
443 
444 #ifdef CONFIG_RCU_BOOST
445 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
446 DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
447 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
448 DECLARE_PER_CPU(char, rcu_cpu_has_work);
449 #endif /* #ifdef CONFIG_RCU_BOOST */
450 
451 #ifndef RCU_TREE_NONCORE
452 
453 /* Forward declarations for rcutree_plugin.h */
454 static void rcu_bootup_announce(void);
455 static void rcu_preempt_note_context_switch(bool preempt);
456 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
457 #ifdef CONFIG_HOTPLUG_CPU
458 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
459 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
460 static void rcu_print_detail_task_stall(struct rcu_state *rsp);
461 static int rcu_print_task_stall(struct rcu_node *rnp);
462 static int rcu_print_task_exp_stall(struct rcu_node *rnp);
463 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
464 static void rcu_preempt_check_callbacks(void);
465 void call_rcu(struct rcu_head *head, rcu_callback_t func);
466 static void __init __rcu_init_preempt(void);
467 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
468 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
469 static void invoke_rcu_callbacks_kthread(void);
470 static bool rcu_is_callbacks_kthread(void);
471 #ifdef CONFIG_RCU_BOOST
472 static void rcu_preempt_do_callbacks(void);
473 static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
474                                                  struct rcu_node *rnp);
475 #endif /* #ifdef CONFIG_RCU_BOOST */
476 static void __init rcu_spawn_boost_kthreads(void);
477 static void rcu_prepare_kthreads(int cpu);
478 static void rcu_cleanup_after_idle(void);
479 static void rcu_prepare_for_idle(void);
480 static void rcu_idle_count_callbacks_posted(void);
481 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
482 static void print_cpu_stall_info_begin(void);
483 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
484 static void print_cpu_stall_info_end(void);
485 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
486 static void increment_cpu_stall_ticks(void);
487 static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
488 static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
489 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
490 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
491 static void rcu_init_one_nocb(struct rcu_node *rnp);
492 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
493                             bool lazy, unsigned long flags);
494 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
495                                       struct rcu_data *rdp,
496                                       unsigned long flags);
497 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
498 static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
499 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
500 static void rcu_spawn_all_nocb_kthreads(int cpu);
501 static void __init rcu_spawn_nocb_kthreads(void);
502 #ifdef CONFIG_RCU_NOCB_CPU
503 static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
504 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
505 static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
506 static bool init_nocb_callback_list(struct rcu_data *rdp);
507 static void rcu_bind_gp_kthread(void);
508 static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
509 static void rcu_dynticks_task_enter(void);
510 static void rcu_dynticks_task_exit(void);
511 
512 #ifdef CONFIG_SRCU
513 void srcu_online_cpu(unsigned int cpu);
514 void srcu_offline_cpu(unsigned int cpu);
515 #else /* #ifdef CONFIG_SRCU */
516 void srcu_online_cpu(unsigned int cpu) { }
517 void srcu_offline_cpu(unsigned int cpu) { }
518 #endif /* #else #ifdef CONFIG_SRCU */
519 
520 #endif /* #ifndef RCU_TREE_NONCORE */
521 

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