aboutsummaryrefslogtreecommitdiff
path: root/kernel/rcu/tree.h
blob: 9af0f31d6847a0893e1d9070e08096281e806e63 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
/*
 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
 * Internal non-public definitions.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright IBM Corporation, 2008
 *
 * Author: Ingo Molnar <mingo@elte.hu>
 *	   Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */

#include <linux/cache.h>
#include <linux/spinlock.h>
#include <linux/rtmutex.h>
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/swait.h>
#include <linux/stop_machine.h>
#include <linux/rcu_node_tree.h>

#include "rcu_segcblist.h"

/*
 * Dynticks per-CPU state.
 */
struct rcu_dynticks {
	long long dynticks_nesting; /* Track irq/process nesting level. */
				    /* Process level is worth LLONG_MAX/2. */
	int dynticks_nmi_nesting;   /* Track NMI nesting level. */
	atomic_t dynticks;	    /* Even value for idle, else odd. */
	bool rcu_need_heavy_qs;     /* GP old, need heavy quiescent state. */
	unsigned long rcu_qs_ctr;   /* Light universal quiescent state ctr. */
	bool rcu_urgent_qs;	    /* GP old need light quiescent state. */
#ifdef CONFIG_RCU_FAST_NO_HZ
	bool all_lazy;		    /* Are all CPU's CBs lazy? */
	unsigned long nonlazy_posted;
				    /* # times non-lazy CBs posted to CPU. */
	unsigned long nonlazy_posted_snap;
				    /* idle-period nonlazy_posted snapshot. */
	unsigned long last_accelerate;
				    /* Last jiffy CBs were accelerated. */
	unsigned long last_advance_all;
				    /* Last jiffy CBs were all advanced. */
	int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
};

/* RCU's kthread states for tracing. */
#define RCU_KTHREAD_STOPPED  0
#define RCU_KTHREAD_RUNNING  1
#define RCU_KTHREAD_WAITING  2
#define RCU_KTHREAD_OFFCPU   3
#define RCU_KTHREAD_YIELDING 4
#define RCU_KTHREAD_MAX      4

/*
 * Definition for node within the RCU grace-period-detection hierarchy.
 */
struct rcu_node {
	raw_spinlock_t __private lock;	/* Root rcu_node's lock protects */
					/*  some rcu_state fields as well as */
					/*  following. */
	unsigned long gpnum;	/* Current grace period for this node. */
				/*  This will either be equal to or one */
				/*  behind the root rcu_node's gpnum. */
	unsigned long completed; /* Last GP completed for this node. */
				/*  This will either be equal to or one */
				/*  behind the root rcu_node's gpnum. */
	unsigned long qsmask;	/* CPUs or groups that need to switch in */
				/*  order for current grace period to proceed.*/
				/*  In leaf rcu_node, each bit corresponds to */
				/*  an rcu_data structure, otherwise, each */
				/*  bit corresponds to a child rcu_node */
				/*  structure. */
	unsigned long qsmaskinit;
				/* Per-GP initial value for qsmask. */
				/*  Initialized from ->qsmaskinitnext at the */
				/*  beginning of each grace period. */
	unsigned long qsmaskinitnext;
				/* Online CPUs for next grace period. */
	unsigned long expmask;	/* CPUs or groups that need to check in */
				/*  to allow the current expedited GP */
				/*  to complete. */
	unsigned long expmaskinit;
				/* Per-GP initial values for expmask. */
				/*  Initialized from ->expmaskinitnext at the */
				/*  beginning of each expedited GP. */
	unsigned long expmaskinitnext;
				/* Online CPUs for next expedited GP. */
				/*  Any CPU that has ever been online will */
				/*  have its bit set. */
	unsigned long grpmask;	/* Mask to apply to parent qsmask. */
				/*  Only one bit will be set in this mask. */
	int	grplo;		/* lowest-numbered CPU or group here. */
	int	grphi;		/* highest-numbered CPU or group here. */
	u8	grpnum;		/* CPU/group number for next level up. */
	u8	level;		/* root is at level 0. */
	bool	wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
				/*  exit RCU read-side critical sections */
				/*  before propagating offline up the */
				/*  rcu_node tree? */
	struct rcu_node *parent;
	struct list_head blkd_tasks;
				/* Tasks blocked in RCU read-side critical */
				/*  section.  Tasks are placed at the head */
				/*  of this list and age towards the tail. */
	struct list_head *gp_tasks;
				/* Pointer to the first task blocking the */
				/*  current grace period, or NULL if there */
				/*  is no such task. */
	struct list_head *exp_tasks;
				/* Pointer to the first task blocking the */
				/*  current expedited grace period, or NULL */
				/*  if there is no such task.  If there */
				/*  is no current expedited grace period, */
				/*  then there can cannot be any such task. */
	struct list_head *boost_tasks;
				/* Pointer to first task that needs to be */
				/*  priority boosted, or NULL if no priority */
				/*  boosting is needed for this rcu_node */
				/*  structure.  If there are no tasks */
				/*  queued on this rcu_node structure that */
				/*  are blocking the current grace period, */
				/*  there can be no such task. */
	struct rt_mutex boost_mtx;
				/* Used only for the priority-boosting */
				/*  side effect, not as a lock. */
	unsigned long boost_time;
				/* When to start boosting (jiffies). */
	struct task_struct *boost_kthread_task;
				/* kthread that takes care of priority */
				/*  boosting for this rcu_node structure. */
	unsigned int boost_kthread_status;
				/* State of boost_kthread_task for tracing. */
	unsigned long n_tasks_boosted;
				/* Total number of tasks boosted. */
	unsigned long n_exp_boosts;
				/* Number of tasks boosted for expedited GP. */
	unsigned long n_normal_boosts;
				/* Number of tasks boosted for normal GP. */
#ifdef CONFIG_RCU_NOCB_CPU
	struct swait_queue_head nocb_gp_wq[2];
				/* Place for rcu_nocb_kthread() to wait GP. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
	int need_future_gp[2];
				/* Counts of upcoming no-CB GP requests. */
	raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;

	spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
	unsigned long exp_seq_rq;
	wait_queue_head_t exp_wq[4];
} ____cacheline_internodealigned_in_smp;

/*
 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
 * are indexed relative to this interval rather than the global CPU ID space.
 * This generates the bit for a CPU in node-local masks.
 */
#define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo))

/*
 * Union to allow "aggregate OR" operation on the need for a quiescent
 * state by the normal and expedited grace periods.
 */
union rcu_noqs {
	struct {
		u8 norm;
		u8 exp;
	} b; /* Bits. */
	u16 s; /* Set of bits, aggregate OR here. */
};

/* Index values for nxttail array in struct rcu_data. */
#define RCU_DONE_TAIL		0	/* Also RCU_WAIT head. */
#define RCU_WAIT_TAIL		1	/* Also RCU_NEXT_READY head. */
#define RCU_NEXT_READY_TAIL	2	/* Also RCU_NEXT head. */
#define RCU_NEXT_TAIL		3
#define RCU_NEXT_SIZE		4

/* Per-CPU data for read-copy update. */
struct rcu_data {
	/* 1) quiescent-state and grace-period handling : */
	unsigned long	completed;	/* Track rsp->completed gp number */
					/*  in order to detect GP end. */
	unsigned long	gpnum;		/* Highest gp number that this CPU */
					/*  is aware of having started. */
	unsigned long	rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
					/*  for rcu_all_qs() invocations. */
	union rcu_noqs	cpu_no_qs;	/* No QSes yet for this CPU. */
	bool		core_needs_qs;	/* Core waits for quiesc state. */
	bool		beenonline;	/* CPU online at least once. */
	bool		gpwrap;		/* Possible gpnum/completed wrap. */
	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */
	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */
					/*  ticks this CPU has handled */
					/*  during and after the last grace */
					/* period it is aware of. */

	/* 2) batch handling */
	struct rcu_segcblist cblist;	/* Segmented callback list, with */
					/* different callbacks waiting for */
					/* different grace periods. */
	long		qlen_last_fqs_check;
					/* qlen at last check for QS forcing */
	unsigned long	n_cbs_invoked;	/* count of RCU cbs invoked. */
	unsigned long	n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
	unsigned long   n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
	unsigned long   n_cbs_adopted;  /* RCU cbs adopted from dying CPU */
	unsigned long	n_force_qs_snap;
					/* did other CPU force QS recently? */
	long		blimit;		/* Upper limit on a processed batch */

	/* 3) dynticks interface. */
	struct rcu_dynticks *dynticks;	/* Shared per-CPU dynticks state. */
	int dynticks_snap;		/* Per-GP tracking for dynticks. */

	/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
	unsigned long dynticks_fqs;	/* Kicked due to dynticks idle. */
	unsigned long offline_fqs;	/* Kicked due to being offline. */
	unsigned long cond_resched_completed;
					/* Grace period that needs help */
					/*  from cond_resched(). */

	/* 5) __rcu_pending() statistics. */
	unsigned long n_rcu_pending;	/* rcu_pending() calls since boot. */
	unsigned long n_rp_core_needs_qs;
	unsigned long n_rp_report_qs;
	unsigned long n_rp_cb_ready;
	unsigned long n_rp_cpu_needs_gp;
	unsigned long n_rp_gp_completed;
	unsigned long n_rp_gp_started;
	unsigned long n_rp_nocb_defer_wakeup;
	unsigned long n_rp_need_nothing;

	/* 6) _rcu_barrier(), OOM callbacks, and expediting. */
	struct rcu_head barrier_head;
#ifdef CONFIG_RCU_FAST_NO_HZ
	struct rcu_head oom_head;
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
	atomic_long_t exp_workdone0;	/* # done by workqueue. */
	atomic_long_t exp_workdone1;	/* # done by others #1. */
	atomic_long_t exp_workdone2;	/* # done by others #2. */
	atomic_long_t exp_workdone3;	/* # done by others #3. */
	int exp_dynticks_snap;		/* Double-check need for IPI. */

	/* 7) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU
	struct rcu_head *nocb_head;	/* CBs waiting for kthread. */
	struct rcu_head **nocb_tail;
	atomic_long_t nocb_q_count;	/* # CBs waiting for nocb */
	atomic_long_t nocb_q_count_lazy; /*  invocation (all stages). */
	struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
	struct rcu_head **nocb_follower_tail;
	struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
	struct task_struct *nocb_kthread;
	int nocb_defer_wakeup;		/* Defer wakeup of nocb_kthread. */

	/* The following fields are used by the leader, hence own cacheline. */
	struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
					/* CBs waiting for GP. */
	struct rcu_head **nocb_gp_tail;
	bool nocb_leader_sleep;		/* Is the nocb leader thread asleep? */
	struct rcu_data *nocb_next_follower;
					/* Next follower in wakeup chain. */

	/* The following fields are used by the follower, hence new cachline. */
	struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
					/* Leader CPU takes GP-end wakeups. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */

	/* 8) RCU CPU stall data. */
	unsigned int softirq_snap;	/* Snapshot of softirq activity. */

	int cpu;
	struct rcu_state *rsp;
};

/* Values for nocb_defer_wakeup field in struct rcu_data. */
#define RCU_NOCB_WAKE_NOT	0
#define RCU_NOCB_WAKE		1
#define RCU_NOCB_WAKE_FORCE	2

#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
					/* For jiffies_till_first_fqs and */
					/*  and jiffies_till_next_fqs. */

#define RCU_JIFFIES_FQS_DIV	256	/* Very large systems need more */
					/*  delay between bouts of */
					/*  quiescent-state forcing. */

#define RCU_STALL_RAT_DELAY	2	/* Allow other CPUs time to take */
					/*  at least one scheduling clock */
					/*  irq before ratting on them. */

#define rcu_wait(cond)							\
do {									\
	for (;;) {							\
		set_current_state(TASK_INTERRUPTIBLE);			\
		if (cond)						\
			break;						\
		schedule();						\
	}								\
	__set_current_state(TASK_RUNNING);				\
} while (0)

/*
 * RCU global state, including node hierarchy.  This hierarchy is
 * represented in "heap" form in a dense array.  The root (first level)
 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 * and the third level in ->node[m+1] and following (->node[m+1] referenced
 * by ->level[2]).  The number of levels is determined by the number of
 * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 * consisting of a single rcu_node.
 */
struct rcu_state {
	struct rcu_node node[NUM_RCU_NODES];	/* Hierarchy. */
	struct rcu_node *level[RCU_NUM_LVLS + 1];
						/* Hierarchy levels (+1 to */
						/*  shut bogus gcc warning) */
	struct rcu_data __percpu *rda;		/* pointer of percu rcu_data. */
	call_rcu_func_t call;			/* call_rcu() flavor. */
	int ncpus;				/* # CPUs seen so far. */

	/* The following fields are guarded by the root rcu_node's lock. */

	u8	boost ____cacheline_internodealigned_in_smp;
						/* Subject to priority boost. */
	unsigned long gpnum;			/* Current gp number. */
	unsigned long completed;		/* # of last completed gp. */
	struct task_struct *gp_kthread;		/* Task for grace periods. */
	struct swait_queue_head gp_wq;		/* Where GP task waits. */
	short gp_flags;				/* Commands for GP task. */
	short gp_state;				/* GP kthread sleep state. */

	/* End of fields guarded by root rcu_node's lock. */

	raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;
						/* Protect following fields. */
	struct rcu_cblist orphan_pend;		/* Orphaned callbacks that */
						/*  need a grace period. */
	struct rcu_cblist orphan_done;		/* Orphaned callbacks that */
						/*  are ready to invoke. */
						/* (Contains counts.) */
	/* End of fields guarded by orphan_lock. */

	struct mutex barrier_mutex;		/* Guards barrier fields. */
	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */
	struct completion barrier_completion;	/* Wake at barrier end. */
	unsigned long barrier_sequence;		/* ++ at start and end of */
						/*  _rcu_barrier(). */
	/* End of fields guarded by barrier_mutex. */

	struct mutex exp_mutex;			/* Serialize expedited GP. */
	struct mutex exp_wake_mutex;		/* Serialize wakeup. */
	unsigned long expedited_sequence;	/* Take a ticket. */
	atomic_t expedited_need_qs;		/* # CPUs left to check in. */
	struct swait_queue_head expedited_wq;	/* Wait for check-ins. */
	int ncpus_snap;				/* # CPUs seen last time. */

	unsigned long jiffies_force_qs;		/* Time at which to invoke */
						/*  force_quiescent_state(). */
	unsigned long jiffies_kick_kthreads;	/* Time at which to kick */
						/*  kthreads, if configured. */
	unsigned long n_force_qs;		/* Number of calls to */
						/*  force_quiescent_state(). */
	unsigned long n_force_qs_lh;		/* ~Number of calls leaving */
						/*  due to lock unavailable. */
	unsigned long n_force_qs_ngp;		/* Number of calls leaving */
						/*  due to no GP active. */
	unsigned long gp_start;			/* Time at which GP started, */
						/*  but in jiffies. */
	unsigned long gp_activity;		/* Time of last GP kthread */
						/*  activity in jiffies. */
	unsigned long jiffies_stall;		/* Time at which to check */
						/*  for CPU stalls. */
	unsigned long jiffies_resched;		/* Time at which to resched */
						/*  a reluctant CPU. */
	unsigned long n_force_qs_gpstart;	/* Snapshot of n_force_qs at */
						/*  GP start. */
	unsigned long gp_max;			/* Maximum GP duration in */
						/*  jiffies. */
	const char *name;			/* Name of structure. */
	char abbr;				/* Abbreviated name. */
	struct list_head flavors;		/* List of RCU flavors. */
};

/* Values for rcu_state structure's gp_flags field. */
#define RCU_GP_FLAG_INIT 0x1	/* Need grace-period initialization. */
#define RCU_GP_FLAG_FQS  0x2	/* Need grace-period quiescent-state forcing. */

/* Values for rcu_state structure's gp_state field. */
#define RCU_GP_IDLE	 0	/* Initial state and no GP in progress. */
#define RCU_GP_WAIT_GPS  1	/* Wait for grace-period start. */
#define RCU_GP_DONE_GPS  2	/* Wait done for grace-period start. */
#define RCU_GP_WAIT_FQS  3	/* Wait for force-quiescent-state time. */
#define RCU_GP_DOING_FQS 4	/* Wait done for force-quiescent-state time. */
#define RCU_GP_CLEANUP   5	/* Grace-period cleanup started. */
#define RCU_GP_CLEANED   6	/* Grace-period cleanup complete. */

#ifndef RCU_TREE_NONCORE
static const char * const gp_state_names[] = {
	"RCU_GP_IDLE",
	"RCU_GP_WAIT_GPS",
	"RCU_GP_DONE_GPS",
	"RCU_GP_WAIT_FQS",
	"RCU_GP_DOING_FQS",
	"RCU_GP_CLEANUP",
	"RCU_GP_CLEANED",
};
#endif /* #ifndef RCU_TREE_NONCORE */

extern struct list_head rcu_struct_flavors;

/* Sequence through rcu_state structures for each RCU flavor. */
#define for_each_rcu_flavor(rsp) \
	list_for_each_entry((rsp), &rcu_struct_flavors, flavors)

/*
 * RCU implementation internal declarations:
 */
extern struct rcu_state rcu_sched_state;

extern struct rcu_state rcu_bh_state;

#ifdef CONFIG_PREEMPT_RCU
extern struct rcu_state rcu_preempt_state;
#endif /* #ifdef CONFIG_PREEMPT_RCU */

int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
bool rcu_eqs_special_set(int cpu);

#ifdef CONFIG_RCU_BOOST
DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
DECLARE_PER_CPU(char, rcu_cpu_has_work);
#endif /* #ifdef CONFIG_RCU_BOOST */

#ifndef RCU_TREE_NONCORE

/* Forward declarations for rcutree_plugin.h */
static void rcu_bootup_announce(void);
static void rcu_preempt_note_context_switch(bool preempt);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
static int rcu_print_task_stall(struct rcu_node *rnp);
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
static void rcu_preempt_check_callbacks(void);
void call_rcu(struct rcu_head *head, rcu_callback_t func);
static void __init __rcu_init_preempt(void);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
static void invoke_rcu_callbacks_kthread(void);
static bool rcu_is_callbacks_kthread(void);
#ifdef CONFIG_RCU_BOOST
static void rcu_preempt_do_callbacks(void);
static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
						 struct rcu_node *rnp);
#endif /* #ifdef CONFIG_RCU_BOOST */
static void __init rcu_spawn_boost_kthreads(void);
static void rcu_prepare_kthreads(int cpu);
static void rcu_cleanup_after_idle(void);
static void rcu_prepare_for_idle(void);
static void rcu_idle_count_callbacks_posted(void);
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
static void print_cpu_stall_info_begin(void);
static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
static void print_cpu_stall_info_end(void);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
static void rcu_init_one_nocb(struct rcu_node *rnp);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
			    bool lazy, unsigned long flags);
static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
				      struct rcu_data *rdp,
				      unsigned long flags);
static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void rcu_spawn_all_nocb_kthreads(int cpu);
static void __init rcu_spawn_nocb_kthreads(void);
#ifdef CONFIG_RCU_NOCB_CPU
static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
static bool init_nocb_callback_list(struct rcu_data *rdp);
static void rcu_bind_gp_kthread(void);
static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
static void rcu_dynticks_task_enter(void);
static void rcu_dynticks_task_exit(void);

#ifdef CONFIG_SRCU
void srcu_online_cpu(unsigned int cpu);
void srcu_offline_cpu(unsigned int cpu);
#else /* #ifdef CONFIG_SRCU */
void srcu_online_cpu(unsigned int cpu) { }
void srcu_offline_cpu(unsigned int cpu) { }
#endif /* #else #ifdef CONFIG_SRCU */

#endif /* #ifndef RCU_TREE_NONCORE */