summaryrefslogtreecommitdiffstats
path: root/kernel/rcutiny_plugin.h
blob: c5bea1137dcb87ecd9411b3d7eb308d8488540cf (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
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
/*
 * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition
 * Internal non-public definitions that provide either classic
 * or preemptible semantics.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (c) 2010 Linaro
 *
 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */

#ifdef CONFIG_TINY_PREEMPT_RCU

#include <linux/delay.h>

/* Global control variables for preemptible RCU. */
struct rcu_preempt_ctrlblk {
	struct rcu_ctrlblk rcb;	/* curtail: ->next ptr of last CB for GP. */
	struct rcu_head **nexttail;
				/* Tasks blocked in a preemptible RCU */
				/*  read-side critical section while an */
				/*  preemptible-RCU grace period is in */
				/*  progress must wait for a later grace */
				/*  period.  This pointer points to the */
				/*  ->next pointer of the last task that */
				/*  must wait for a later grace period, or */
				/*  to &->rcb.rcucblist if there is no */
				/*  such task. */
	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 not such task. */
	struct list_head *exp_tasks;
				/* Pointer to 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 cannot be any such task. */
	u8 gpnum;		/* Current grace period. */
	u8 gpcpu;		/* Last grace period blocked by the CPU. */
	u8 completed;		/* Last grace period completed. */
				/*  If all three are equal, RCU is idle. */
};

static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
	.rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist,
	.rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist,
	.nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist,
	.blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks),
};

static int rcu_preempted_readers_exp(void);
static void rcu_report_exp_done(void);

/*
 * Return true if the CPU has not yet responded to the current grace period.
 */
static int rcu_cpu_cur_gp(void)
{
	return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum;
}

/*
 * Check for a running RCU reader.  Because there is only one CPU,
 * there can be but one running RCU reader at a time.  ;-)
 */
static int rcu_preempt_running_reader(void)
{
	return current->rcu_read_lock_nesting;
}

/*
 * Check for preempted RCU readers blocking any grace period.
 * If the caller needs a reliable answer, it must disable hard irqs.
 */
static int rcu_preempt_blocked_readers_any(void)
{
	return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks);
}

/*
 * Check for preempted RCU readers blocking the current grace period.
 * If the caller needs a reliable answer, it must disable hard irqs.
 */
static int rcu_preempt_blocked_readers_cgp(void)
{
	return rcu_preempt_ctrlblk.gp_tasks != NULL;
}

/*
 * Return true if another preemptible-RCU grace period is needed.
 */
static int rcu_preempt_needs_another_gp(void)
{
	return *rcu_preempt_ctrlblk.rcb.curtail != NULL;
}

/*
 * Return true if a preemptible-RCU grace period is in progress.
 * The caller must disable hardirqs.
 */
static int rcu_preempt_gp_in_progress(void)
{
	return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum;
}

/*
 * Record a preemptible-RCU quiescent state for the specified CPU.  Note
 * that this just means that the task currently running on the CPU is
 * in a quiescent state.  There might be any number of tasks blocked
 * while in an RCU read-side critical section.
 *
 * Unlike the other rcu_*_qs() functions, callers to this function
 * must disable irqs in order to protect the assignment to
 * ->rcu_read_unlock_special.
 *
 * Because this is a single-CPU implementation, the only way a grace
 * period can end is if the CPU is in a quiescent state.  The reason is
 * that a blocked preemptible-RCU reader can exit its critical section
 * only if the CPU is running it at the time.  Therefore, when the
 * last task blocking the current grace period exits its RCU read-side
 * critical section, neither the CPU nor blocked tasks will be stopping
 * the current grace period.  (In contrast, SMP implementations
 * might have CPUs running in RCU read-side critical sections that
 * block later grace periods -- but this is not possible given only
 * one CPU.)
 */
static void rcu_preempt_cpu_qs(void)
{
	/* Record both CPU and task as having responded to current GP. */
	rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum;
	current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;

	/*
	 * If there is no GP, or if blocked readers are still blocking GP,
	 * then there is nothing more to do.
	 */
	if (!rcu_preempt_gp_in_progress() || rcu_preempt_blocked_readers_cgp())
		return;

	/* Advance callbacks. */
	rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum;
	rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail;
	rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail;

	/* If there are no blocked readers, next GP is done instantly. */
	if (!rcu_preempt_blocked_readers_any())
		rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail;

	/* If there are done callbacks, make RCU_SOFTIRQ process them. */
	if (*rcu_preempt_ctrlblk.rcb.donetail != NULL)
		raise_softirq(RCU_SOFTIRQ);
}

/*
 * Start a new RCU grace period if warranted.  Hard irqs must be disabled.
 */
static void rcu_preempt_start_gp(void)
{
	if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) {

		/* Official start of GP. */
		rcu_preempt_ctrlblk.gpnum++;

		/* Any blocked RCU readers block new GP. */
		if (rcu_preempt_blocked_readers_any())
			rcu_preempt_ctrlblk.gp_tasks =
				rcu_preempt_ctrlblk.blkd_tasks.next;

		/* If there is no running reader, CPU is done with GP. */
		if (!rcu_preempt_running_reader())
			rcu_preempt_cpu_qs();
	}
}

/*
 * We have entered the scheduler, and the current task might soon be
 * context-switched away from.  If this task is in an RCU read-side
 * critical section, we will no longer be able to rely on the CPU to
 * record that fact, so we enqueue the task on the blkd_tasks list.
 * If the task started after the current grace period began, as recorded
 * by ->gpcpu, we enqueue at the beginning of the list.  Otherwise
 * before the element referenced by ->gp_tasks (or at the tail if
 * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element.
 * The task will dequeue itself when it exits the outermost enclosing
 * RCU read-side critical section.  Therefore, the current grace period
 * cannot be permitted to complete until the ->gp_tasks pointer becomes
 * NULL.
 *
 * Caller must disable preemption.
 */
void rcu_preempt_note_context_switch(void)
{
	struct task_struct *t = current;
	unsigned long flags;

	local_irq_save(flags); /* must exclude scheduler_tick(). */
	if (rcu_preempt_running_reader() &&
	    (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {

		/* Possibly blocking in an RCU read-side critical section. */
		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;

		/*
		 * If this CPU has already checked in, then this task
		 * will hold up the next grace period rather than the
		 * current grace period.  Queue the task accordingly.
		 * If the task is queued for the current grace period
		 * (i.e., this CPU has not yet passed through a quiescent
		 * state for the current grace period), then as long
		 * as that task remains queued, the current grace period
		 * cannot end.
		 */
		list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks);
		if (rcu_cpu_cur_gp())
			rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry;
	}

	/*
	 * Either we were not in an RCU read-side critical section to
	 * begin with, or we have now recorded that critical section
	 * globally.  Either way, we can now note a quiescent state
	 * for this CPU.  Again, if we were in an RCU read-side critical
	 * section, and if that critical section was blocking the current
	 * grace period, then the fact that the task has been enqueued
	 * means that current grace period continues to be blocked.
	 */
	rcu_preempt_cpu_qs();
	local_irq_restore(flags);
}

/*
 * Tiny-preemptible RCU implementation for rcu_read_lock().
 * Just increment ->rcu_read_lock_nesting, shared state will be updated
 * if we block.
 */
void __rcu_read_lock(void)
{
	current->rcu_read_lock_nesting++;
	barrier();  /* needed if we ever invoke rcu_read_lock in rcutiny.c */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);

/*
 * Handle special cases during rcu_read_unlock(), such as needing to
 * notify RCU core processing or task having blocked during the RCU
 * read-side critical section.
 */
static void rcu_read_unlock_special(struct task_struct *t)
{
	int empty;
	int empty_exp;
	unsigned long flags;
	struct list_head *np;
	int special;

	/*
	 * NMI handlers cannot block and cannot safely manipulate state.
	 * They therefore cannot possibly be special, so just leave.
	 */
	if (in_nmi())
		return;

	local_irq_save(flags);

	/*
	 * If RCU core is waiting for this CPU to exit critical section,
	 * let it know that we have done so.
	 */
	special = t->rcu_read_unlock_special;
	if (special & RCU_READ_UNLOCK_NEED_QS)
		rcu_preempt_cpu_qs();

	/* Hardware IRQ handlers cannot block. */
	if (in_irq()) {
		local_irq_restore(flags);
		return;
	}

	/* Clean up if blocked during RCU read-side critical section. */
	if (special & RCU_READ_UNLOCK_BLOCKED) {
		t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED;

		/*
		 * Remove this task from the ->blkd_tasks list and adjust
		 * any pointers that might have been referencing it.
		 */
		empty = !rcu_preempt_blocked_readers_cgp();
		empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL;
		np = t->rcu_node_entry.next;
		if (np == &rcu_preempt_ctrlblk.blkd_tasks)
			np = NULL;
		list_del(&t->rcu_node_entry);
		if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks)
			rcu_preempt_ctrlblk.gp_tasks = np;
		if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks)
			rcu_preempt_ctrlblk.exp_tasks = np;
		INIT_LIST_HEAD(&t->rcu_node_entry);

		/*
		 * If this was the last task on the current list, and if
		 * we aren't waiting on the CPU, report the quiescent state
		 * and start a new grace period if needed.
		 */
		if (!empty && !rcu_preempt_blocked_readers_cgp()) {
			rcu_preempt_cpu_qs();
			rcu_preempt_start_gp();
		}

		/*
		 * If this was the last task on the expedited lists,
		 * then we need wake up the waiting task.
		 */
		if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL)
			rcu_report_exp_done();
	}
	local_irq_restore(flags);
}

/*
 * Tiny-preemptible RCU implementation for rcu_read_unlock().
 * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
 * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
 * invoke rcu_read_unlock_special() to clean up after a context switch
 * in an RCU read-side critical section and other special cases.
 */
void __rcu_read_unlock(void)
{
	struct task_struct *t = current;

	barrier();  /* needed if we ever invoke rcu_read_unlock in rcutiny.c */
	--t->rcu_read_lock_nesting;
	barrier();  /* decrement before load of ->rcu_read_unlock_special */
	if (t->rcu_read_lock_nesting == 0 &&
	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
		rcu_read_unlock_special(t);
#ifdef CONFIG_PROVE_LOCKING
	WARN_ON_ONCE(t->rcu_read_lock_nesting < 0);
#endif /* #ifdef CONFIG_PROVE_LOCKING */
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);

/*
 * Check for a quiescent state from the current CPU.  When a task blocks,
 * the task is recorded in the rcu_preempt_ctrlblk structure, which is
 * checked elsewhere.  This is called from the scheduling-clock interrupt.
 *
 * Caller must disable hard irqs.
 */
static void rcu_preempt_check_callbacks(void)
{
	struct task_struct *t = current;

	if (!rcu_preempt_running_reader() && rcu_preempt_gp_in_progress())
		rcu_preempt_cpu_qs();
	if (&rcu_preempt_ctrlblk.rcb.rcucblist !=
	    rcu_preempt_ctrlblk.rcb.donetail)
		raise_softirq(RCU_SOFTIRQ);
	if (rcu_preempt_gp_in_progress() && rcu_preempt_running_reader())
		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
}

/*
 * TINY_PREEMPT_RCU has an extra callback-list tail pointer to
 * update, so this is invoked from __rcu_process_callbacks() to
 * handle that case.  Of course, it is invoked for all flavors of
 * RCU, but RCU callbacks can appear only on one of the lists, and
 * neither ->nexttail nor ->donetail can possibly be NULL, so there
 * is no need for an explicit check.
 */
static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
{
	if (rcu_preempt_ctrlblk.nexttail == rcp->donetail)
		rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist;
}

/*
 * Process callbacks for preemptible RCU.
 */
static void rcu_preempt_process_callbacks(void)
{
	__rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb);
}

/*
 * Queue a preemptible -RCU callback for invocation after a grace period.
 */
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
	unsigned long flags;

	debug_rcu_head_queue(head);
	head->func = func;
	head->next = NULL;

	local_irq_save(flags);
	*rcu_preempt_ctrlblk.nexttail = head;
	rcu_preempt_ctrlblk.nexttail = &head->next;
	rcu_preempt_start_gp();  /* checks to see if GP needed. */
	local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(call_rcu);

void rcu_barrier(void)
{
	struct rcu_synchronize rcu;

	init_rcu_head_on_stack(&rcu.head);
	init_completion(&rcu.completion);
	/* Will wake me after RCU finished. */
	call_rcu(&rcu.head, wakeme_after_rcu);
	/* Wait for it. */
	wait_for_completion(&rcu.completion);
	destroy_rcu_head_on_stack(&rcu.head);
}
EXPORT_SYMBOL_GPL(rcu_barrier);

/*
 * synchronize_rcu - wait until a grace period has elapsed.
 *
 * Control will return to the caller some time after a full grace
 * period has elapsed, in other words after all currently executing RCU
 * read-side critical sections have completed.  RCU read-side critical
 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
 * and may be nested.
 */
void synchronize_rcu(void)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	if (!rcu_scheduler_active)
		return;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

	WARN_ON_ONCE(rcu_preempt_running_reader());
	if (!rcu_preempt_blocked_readers_any())
		return;

	/* Once we get past the fastpath checks, same code as rcu_barrier(). */
	rcu_barrier();
}
EXPORT_SYMBOL_GPL(synchronize_rcu);

static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
static unsigned long sync_rcu_preempt_exp_count;
static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);

/*
 * Return non-zero if there are any tasks in RCU read-side critical
 * sections blocking the current preemptible-RCU expedited grace period.
 * If there is no preemptible-RCU expedited grace period currently in
 * progress, returns zero unconditionally.
 */
static int rcu_preempted_readers_exp(void)
{
	return rcu_preempt_ctrlblk.exp_tasks != NULL;
}

/*
 * Report the exit from RCU read-side critical section for the last task
 * that queued itself during or before the current expedited preemptible-RCU
 * grace period.
 */
static void rcu_report_exp_done(void)
{
	wake_up(&sync_rcu_preempt_exp_wq);
}

/*
 * Wait for an rcu-preempt grace period, but expedite it.  The basic idea
 * is to rely in the fact that there is but one CPU, and that it is
 * illegal for a task to invoke synchronize_rcu_expedited() while in a
 * preemptible-RCU read-side critical section.  Therefore, any such
 * critical sections must correspond to blocked tasks, which must therefore
 * be on the ->blkd_tasks list.  So just record the current head of the
 * list in the ->exp_tasks pointer, and wait for all tasks including and
 * after the task pointed to by ->exp_tasks to drain.
 */
void synchronize_rcu_expedited(void)
{
	unsigned long flags;
	struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk;
	unsigned long snap;

	barrier(); /* ensure prior action seen before grace period. */

	WARN_ON_ONCE(rcu_preempt_running_reader());

	/*
	 * Acquire lock so that there is only one preemptible RCU grace
	 * period in flight.  Of course, if someone does the expedited
	 * grace period for us while we are acquiring the lock, just leave.
	 */
	snap = sync_rcu_preempt_exp_count + 1;
	mutex_lock(&sync_rcu_preempt_exp_mutex);
	if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count))
		goto unlock_mb_ret; /* Others did our work for us. */

	local_irq_save(flags);

	/*
	 * All RCU readers have to already be on blkd_tasks because
	 * we cannot legally be executing in an RCU read-side critical
	 * section.
	 */

	/* Snapshot current head of ->blkd_tasks list. */
	rpcp->exp_tasks = rpcp->blkd_tasks.next;
	if (rpcp->exp_tasks == &rpcp->blkd_tasks)
		rpcp->exp_tasks = NULL;
	local_irq_restore(flags);

	/* Wait for tail of ->blkd_tasks list to drain. */
	if (rcu_preempted_readers_exp())
		wait_event(sync_rcu_preempt_exp_wq,
			   !rcu_preempted_readers_exp());

	/* Clean up and exit. */
	barrier(); /* ensure expedited GP seen before counter increment. */
	sync_rcu_preempt_exp_count++;
unlock_mb_ret:
	mutex_unlock(&sync_rcu_preempt_exp_mutex);
	barrier(); /* ensure subsequent action seen after grace period. */
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);

/*
 * Does preemptible RCU need the CPU to stay out of dynticks mode?
 */
int rcu_preempt_needs_cpu(void)
{
	if (!rcu_preempt_running_reader())
		rcu_preempt_cpu_qs();
	return rcu_preempt_ctrlblk.rcb.rcucblist != NULL;
}

/*
 * Check for a task exiting while in a preemptible -RCU read-side
 * critical section, clean up if so.  No need to issue warnings,
 * as debug_check_no_locks_held() already does this if lockdep
 * is enabled.
 */
void exit_rcu(void)
{
	struct task_struct *t = current;

	if (t->rcu_read_lock_nesting == 0)
		return;
	t->rcu_read_lock_nesting = 1;
	rcu_read_unlock();
}

#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */

/*
 * Because preemptible RCU does not exist, it never has any callbacks
 * to check.
 */
static void rcu_preempt_check_callbacks(void)
{
}

/*
 * Because preemptible RCU does not exist, it never has any callbacks
 * to remove.
 */
static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
{
}

/*
 * Because preemptible RCU does not exist, it never has any callbacks
 * to process.
 */
static void rcu_preempt_process_callbacks(void)
{
}

#endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */

#ifdef CONFIG_DEBUG_LOCK_ALLOC

#include <linux/kernel_stat.h>

/*
 * During boot, we forgive RCU lockdep issues.  After this function is
 * invoked, we start taking RCU lockdep issues seriously.
 */
void rcu_scheduler_starting(void)
{
	WARN_ON(nr_context_switches() > 0);
	rcu_scheduler_active = 1;
}

#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */