Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  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
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
// SPDX-License-Identifier: GPL-2.0+
/*
 * Read-Copy Update mechanism for mutual exclusion
 *
 * Copyright IBM Corporation, 2001
 *
 * Authors: Dipankar Sarma <dipankar@in.ibm.com>
 *	    Manfred Spraul <manfred@colorfullife.com>
 *
 * Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
 * Papers:
 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
 *
 * For detailed explanation of Read-Copy Update mechanism see -
 *		http://lse.sourceforge.net/locking/rcupdate.html
 *
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
#include <linux/torture.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/export.h>
#include <linux/hardirq.h>
#include <linux/delay.h>
#include <linux/moduleparam.h>
#include <linux/kthread.h>
#include <linux/tick.h>
#include <linux/rcupdate_wait.h>
#include <linux/sched/isolation.h>
#include <linux/kprobes.h>
#include <linux/slab.h>
#include <linux/irq_work.h>
#include <linux/rcupdate_trace.h>

#define CREATE_TRACE_POINTS

#include "rcu.h"

#ifdef MODULE_PARAM_PREFIX
#undef MODULE_PARAM_PREFIX
#endif
#define MODULE_PARAM_PREFIX "rcupdate."

#ifndef CONFIG_TINY_RCU
module_param(rcu_expedited, int, 0444);
module_param(rcu_normal, int, 0444);
static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT);
#if !defined(CONFIG_PREEMPT_RT) || defined(CONFIG_NO_HZ_FULL)
module_param(rcu_normal_after_boot, int, 0444);
#endif
#endif /* #ifndef CONFIG_TINY_RCU */

#ifdef CONFIG_DEBUG_LOCK_ALLOC
/**
 * rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
 * @ret:	Best guess answer if lockdep cannot be relied on
 *
 * Returns true if lockdep must be ignored, in which case ``*ret`` contains
 * the best guess described below.  Otherwise returns false, in which
 * case ``*ret`` tells the caller nothing and the caller should instead
 * consult lockdep.
 *
 * If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to nonzero iff in an
 * RCU-sched read-side critical section.  In absence of
 * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
 * critical section unless it can prove otherwise.  Note that disabling
 * of preemption (including disabling irqs) counts as an RCU-sched
 * read-side critical section.  This is useful for debug checks in functions
 * that required that they be called within an RCU-sched read-side
 * critical section.
 *
 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
 * and while lockdep is disabled.
 *
 * Note that if the CPU is in the idle loop from an RCU point of view (ie:
 * that we are in the section between ct_idle_enter() and ct_idle_exit())
 * then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an
 * rcu_read_lock().  The reason for this is that RCU ignores CPUs that are
 * in such a section, considering these as in extended quiescent state,
 * so such a CPU is effectively never in an RCU read-side critical section
 * regardless of what RCU primitives it invokes.  This state of affairs is
 * required --- we need to keep an RCU-free window in idle where the CPU may
 * possibly enter into low power mode. This way we can notice an extended
 * quiescent state to other CPUs that started a grace period. Otherwise
 * we would delay any grace period as long as we run in the idle task.
 *
 * Similarly, we avoid claiming an RCU read lock held if the current
 * CPU is offline.
 */
static bool rcu_read_lock_held_common(bool *ret)
{
	if (!debug_lockdep_rcu_enabled()) {
		*ret = true;
		return true;
	}
	if (!rcu_is_watching()) {
		*ret = false;
		return true;
	}
	if (!rcu_lockdep_current_cpu_online()) {
		*ret = false;
		return true;
	}
	return false;
}

int rcu_read_lock_sched_held(void)
{
	bool ret;

	if (rcu_read_lock_held_common(&ret))
		return ret;
	return lock_is_held(&rcu_sched_lock_map) || !preemptible();
}
EXPORT_SYMBOL(rcu_read_lock_sched_held);
#endif

#ifndef CONFIG_TINY_RCU

/*
 * Should expedited grace-period primitives always fall back to their
 * non-expedited counterparts?  Intended for use within RCU.  Note
 * that if the user specifies both rcu_expedited and rcu_normal, then
 * rcu_normal wins.  (Except during the time period during boot from
 * when the first task is spawned until the rcu_set_runtime_mode()
 * core_initcall() is invoked, at which point everything is expedited.)
 */
bool rcu_gp_is_normal(void)
{
	return READ_ONCE(rcu_normal) &&
	       rcu_scheduler_active != RCU_SCHEDULER_INIT;
}
EXPORT_SYMBOL_GPL(rcu_gp_is_normal);

static atomic_t rcu_async_hurry_nesting = ATOMIC_INIT(1);
/*
 * Should call_rcu() callbacks be processed with urgency or are
 * they OK being executed with arbitrary delays?
 */
bool rcu_async_should_hurry(void)
{
	return !IS_ENABLED(CONFIG_RCU_LAZY) ||
	       atomic_read(&rcu_async_hurry_nesting);
}
EXPORT_SYMBOL_GPL(rcu_async_should_hurry);

/**
 * rcu_async_hurry - Make future async RCU callbacks not lazy.
 *
 * After a call to this function, future calls to call_rcu()
 * will be processed in a timely fashion.
 */
void rcu_async_hurry(void)
{
	if (IS_ENABLED(CONFIG_RCU_LAZY))
		atomic_inc(&rcu_async_hurry_nesting);
}
EXPORT_SYMBOL_GPL(rcu_async_hurry);

/**
 * rcu_async_relax - Make future async RCU callbacks lazy.
 *
 * After a call to this function, future calls to call_rcu()
 * will be processed in a lazy fashion.
 */
void rcu_async_relax(void)
{
	if (IS_ENABLED(CONFIG_RCU_LAZY))
		atomic_dec(&rcu_async_hurry_nesting);
}
EXPORT_SYMBOL_GPL(rcu_async_relax);

static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
/*
 * Should normal grace-period primitives be expedited?  Intended for
 * use within RCU.  Note that this function takes the rcu_expedited
 * sysfs/boot variable and rcu_scheduler_active into account as well
 * as the rcu_expedite_gp() nesting.  So looping on rcu_unexpedite_gp()
 * until rcu_gp_is_expedited() returns false is a -really- bad idea.
 */
bool rcu_gp_is_expedited(void)
{
	return rcu_expedited || atomic_read(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);

/**
 * rcu_expedite_gp - Expedite future RCU grace periods
 *
 * After a call to this function, future calls to synchronize_rcu() and
 * friends act as the corresponding synchronize_rcu_expedited() function
 * had instead been called.
 */
void rcu_expedite_gp(void)
{
	atomic_inc(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_expedite_gp);

/**
 * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
 *
 * Undo a prior call to rcu_expedite_gp().  If all prior calls to
 * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
 * and if the rcu_expedited sysfs/boot parameter is not set, then all
 * subsequent calls to synchronize_rcu() and friends will return to
 * their normal non-expedited behavior.
 */
void rcu_unexpedite_gp(void)
{
	atomic_dec(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);

static bool rcu_boot_ended __read_mostly;

/*
 * Inform RCU of the end of the in-kernel boot sequence.
 */
void rcu_end_inkernel_boot(void)
{
	rcu_unexpedite_gp();
	rcu_async_relax();
	if (rcu_normal_after_boot)
		WRITE_ONCE(rcu_normal, 1);
	rcu_boot_ended = true;
}

/*
 * Let rcutorture know when it is OK to turn it up to eleven.
 */
bool rcu_inkernel_boot_has_ended(void)
{
	return rcu_boot_ended;
}
EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);

#endif /* #ifndef CONFIG_TINY_RCU */

/*
 * Test each non-SRCU synchronous grace-period wait API.  This is
 * useful just after a change in mode for these primitives, and
 * during early boot.
 */
void rcu_test_sync_prims(void)
{
	if (!IS_ENABLED(CONFIG_PROVE_RCU))
		return;
	pr_info("Running RCU synchronous self tests\n");
	synchronize_rcu();
	synchronize_rcu_expedited();
}

#if !defined(CONFIG_TINY_RCU)

/*
 * Switch to run-time mode once RCU has fully initialized.
 */
static int __init rcu_set_runtime_mode(void)
{
	rcu_test_sync_prims();
	rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
	kfree_rcu_scheduler_running();
	rcu_test_sync_prims();
	return 0;
}
core_initcall(rcu_set_runtime_mode);

#endif /* #if !defined(CONFIG_TINY_RCU) */

#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
struct lockdep_map rcu_lock_map = {
	.name = "rcu_read_lock",
	.key = &rcu_lock_key,
	.wait_type_outer = LD_WAIT_FREE,
	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT implies PREEMPT_RCU */
};
EXPORT_SYMBOL_GPL(rcu_lock_map);

static struct lock_class_key rcu_bh_lock_key;
struct lockdep_map rcu_bh_lock_map = {
	.name = "rcu_read_lock_bh",
	.key = &rcu_bh_lock_key,
	.wait_type_outer = LD_WAIT_FREE,
	.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
};
EXPORT_SYMBOL_GPL(rcu_bh_lock_map);

static struct lock_class_key rcu_sched_lock_key;
struct lockdep_map rcu_sched_lock_map = {
	.name = "rcu_read_lock_sched",
	.key = &rcu_sched_lock_key,
	.wait_type_outer = LD_WAIT_FREE,
	.wait_type_inner = LD_WAIT_SPIN,
};
EXPORT_SYMBOL_GPL(rcu_sched_lock_map);

// Tell lockdep when RCU callbacks are being invoked.
static struct lock_class_key rcu_callback_key;
struct lockdep_map rcu_callback_map =
	STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
EXPORT_SYMBOL_GPL(rcu_callback_map);

noinstr int notrace debug_lockdep_rcu_enabled(void)
{
	return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) &&
	       current->lockdep_recursion == 0;
}
EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);

/**
 * rcu_read_lock_held() - might we be in RCU read-side critical section?
 *
 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
 * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
 * this assumes we are in an RCU read-side critical section unless it can
 * prove otherwise.  This is useful for debug checks in functions that
 * require that they be called within an RCU read-side critical section.
 *
 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
 * and while lockdep is disabled.
 *
 * Note that rcu_read_lock() and the matching rcu_read_unlock() must
 * occur in the same context, for example, it is illegal to invoke
 * rcu_read_unlock() in process context if the matching rcu_read_lock()
 * was invoked from within an irq handler.
 *
 * Note that rcu_read_lock() is disallowed if the CPU is either idle or
 * offline from an RCU perspective, so check for those as well.
 */
int rcu_read_lock_held(void)
{
	bool ret;

	if (rcu_read_lock_held_common(&ret))
		return ret;
	return lock_is_held(&rcu_lock_map);
}
EXPORT_SYMBOL_GPL(rcu_read_lock_held);

/**
 * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
 *
 * Check for bottom half being disabled, which covers both the
 * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
 * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
 * will show the situation.  This is useful for debug checks in functions
 * that require that they be called within an RCU read-side critical
 * section.
 *
 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
 *
 * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
 * offline from an RCU perspective, so check for those as well.
 */
int rcu_read_lock_bh_held(void)
{
	bool ret;

	if (rcu_read_lock_held_common(&ret))
		return ret;
	return in_softirq() || irqs_disabled();
}
EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);

int rcu_read_lock_any_held(void)
{
	bool ret;

	if (rcu_read_lock_held_common(&ret))
		return ret;
	if (lock_is_held(&rcu_lock_map) ||
	    lock_is_held(&rcu_bh_lock_map) ||
	    lock_is_held(&rcu_sched_lock_map))
		return 1;
	return !preemptible();
}
EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);

#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

/**
 * wakeme_after_rcu() - Callback function to awaken a task after grace period
 * @head: Pointer to rcu_head member within rcu_synchronize structure
 *
 * Awaken the corresponding task now that a grace period has elapsed.
 */
void wakeme_after_rcu(struct rcu_head *head)
{
	struct rcu_synchronize *rcu;

	rcu = container_of(head, struct rcu_synchronize, head);
	complete(&rcu->completion);
}
EXPORT_SYMBOL_GPL(wakeme_after_rcu);

void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
		   struct rcu_synchronize *rs_array)
{
	int i;
	int j;

	/* Initialize and register callbacks for each crcu_array element. */
	for (i = 0; i < n; i++) {
		if (checktiny &&
		    (crcu_array[i] == call_rcu)) {
			might_sleep();
			continue;
		}
		for (j = 0; j < i; j++)
			if (crcu_array[j] == crcu_array[i])
				break;
		if (j == i) {
			init_rcu_head_on_stack(&rs_array[i].head);
			init_completion(&rs_array[i].completion);
			(crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
		}
	}

	/* Wait for all callbacks to be invoked. */
	for (i = 0; i < n; i++) {
		if (checktiny &&
		    (crcu_array[i] == call_rcu))
			continue;
		for (j = 0; j < i; j++)
			if (crcu_array[j] == crcu_array[i])
				break;
		if (j == i) {
			wait_for_completion(&rs_array[i].completion);
			destroy_rcu_head_on_stack(&rs_array[i].head);
		}
	}
}
EXPORT_SYMBOL_GPL(__wait_rcu_gp);

void finish_rcuwait(struct rcuwait *w)
{
	rcu_assign_pointer(w->task, NULL);
	__set_current_state(TASK_RUNNING);
}
EXPORT_SYMBOL_GPL(finish_rcuwait);

#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
void init_rcu_head(struct rcu_head *head)
{
	debug_object_init(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(init_rcu_head);

void destroy_rcu_head(struct rcu_head *head)
{
	debug_object_free(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_rcu_head);

static bool rcuhead_is_static_object(void *addr)
{
	return true;
}

/**
 * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
 * @head: pointer to rcu_head structure to be initialized
 *
 * This function informs debugobjects of a new rcu_head structure that
 * has been allocated as an auto variable on the stack.  This function
 * is not required for rcu_head structures that are statically defined or
 * that are dynamically allocated on the heap.  This function has no
 * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
 */
void init_rcu_head_on_stack(struct rcu_head *head)
{
	debug_object_init_on_stack(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);

/**
 * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
 * @head: pointer to rcu_head structure to be initialized
 *
 * This function informs debugobjects that an on-stack rcu_head structure
 * is about to go out of scope.  As with init_rcu_head_on_stack(), this
 * function is not required for rcu_head structures that are statically
 * defined or that are dynamically allocated on the heap.  Also as with
 * init_rcu_head_on_stack(), this function has no effect for
 * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
 */
void destroy_rcu_head_on_stack(struct rcu_head *head)
{
	debug_object_free(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);

const struct debug_obj_descr rcuhead_debug_descr = {
	.name = "rcu_head",
	.is_static_object = rcuhead_is_static_object,
};
EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */

#if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
			       unsigned long secs,
			       unsigned long c_old, unsigned long c)
{
	trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
}
EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
#else
#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
	do { } while (0)
#endif

#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST) || IS_ENABLED(CONFIG_LOCK_TORTURE_TEST) || IS_MODULE(CONFIG_LOCK_TORTURE_TEST)
/* Get rcutorture access to sched_setaffinity(). */
long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
	int ret;

	ret = sched_setaffinity(pid, in_mask);
	WARN_ONCE(ret, "%s: sched_setaffinity(%d) returned %d\n", __func__, pid, ret);
	return ret;
}
EXPORT_SYMBOL_GPL(torture_sched_setaffinity);
#endif

int rcu_cpu_stall_notifiers __read_mostly; // !0 = provide stall notifiers (rarely useful)
EXPORT_SYMBOL_GPL(rcu_cpu_stall_notifiers);

#ifdef CONFIG_RCU_STALL_COMMON
int rcu_cpu_stall_ftrace_dump __read_mostly;
module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
#ifdef CONFIG_RCU_CPU_STALL_NOTIFIER
module_param(rcu_cpu_stall_notifiers, int, 0444);
#endif // #ifdef CONFIG_RCU_CPU_STALL_NOTIFIER
int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
module_param(rcu_cpu_stall_suppress, int, 0644);
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
module_param(rcu_cpu_stall_timeout, int, 0644);
int rcu_exp_cpu_stall_timeout __read_mostly = CONFIG_RCU_EXP_CPU_STALL_TIMEOUT;
module_param(rcu_exp_cpu_stall_timeout, int, 0644);
int rcu_cpu_stall_cputime __read_mostly = IS_ENABLED(CONFIG_RCU_CPU_STALL_CPUTIME);
module_param(rcu_cpu_stall_cputime, int, 0644);
bool rcu_exp_stall_task_details __read_mostly;
module_param(rcu_exp_stall_task_details, bool, 0644);
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */

// Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
// warnings.  Also used by rcutorture even if stall warnings are excluded.
int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);

/**
 * get_completed_synchronize_rcu - Return a pre-completed polled state cookie
 *
 * Returns a value that will always be treated by functions like
 * poll_state_synchronize_rcu() as a cookie whose grace period has already
 * completed.
 */
unsigned long get_completed_synchronize_rcu(void)
{
	return RCU_GET_STATE_COMPLETED;
}
EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu);

#ifdef CONFIG_PROVE_RCU

/*
 * Early boot self test parameters.
 */
static bool rcu_self_test;
module_param(rcu_self_test, bool, 0444);

static int rcu_self_test_counter;

static void test_callback(struct rcu_head *r)
{
	rcu_self_test_counter++;
	pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
}

DEFINE_STATIC_SRCU(early_srcu);
static unsigned long early_srcu_cookie;

struct early_boot_kfree_rcu {
	struct rcu_head rh;
};

static void early_boot_test_call_rcu(void)
{
	static struct rcu_head head;
	int idx;
	static struct rcu_head shead;
	struct early_boot_kfree_rcu *rhp;

	idx = srcu_down_read(&early_srcu);
	srcu_up_read(&early_srcu, idx);
	call_rcu(&head, test_callback);
	early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
	call_srcu(&early_srcu, &shead, test_callback);
	rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
	if (!WARN_ON_ONCE(!rhp))
		kfree_rcu(rhp, rh);
}

void rcu_early_boot_tests(void)
{
	pr_info("Running RCU self tests\n");

	if (rcu_self_test)
		early_boot_test_call_rcu();
	rcu_test_sync_prims();
}

static int rcu_verify_early_boot_tests(void)
{
	int ret = 0;
	int early_boot_test_counter = 0;

	if (rcu_self_test) {
		early_boot_test_counter++;
		rcu_barrier();
		early_boot_test_counter++;
		srcu_barrier(&early_srcu);
		WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
		cleanup_srcu_struct(&early_srcu);
	}
	if (rcu_self_test_counter != early_boot_test_counter) {
		WARN_ON(1);
		ret = -1;
	}

	return ret;
}
late_initcall(rcu_verify_early_boot_tests);
#else
void rcu_early_boot_tests(void) {}
#endif /* CONFIG_PROVE_RCU */

#include "tasks.h"

#ifndef CONFIG_TINY_RCU

/*
 * Print any significant non-default boot-time settings.
 */
void __init rcupdate_announce_bootup_oddness(void)
{
	if (rcu_normal)
		pr_info("\tNo expedited grace period (rcu_normal).\n");
	else if (rcu_normal_after_boot)
		pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
	else if (rcu_expedited)
		pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
	if (rcu_cpu_stall_suppress)
		pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
	if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
		pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
	rcu_tasks_bootup_oddness();
}

#endif /* #ifndef CONFIG_TINY_RCU */