summaryrefslogtreecommitdiff
path: root/kernel/rcu/rcu.h
blob: 00ddc92c577428bf5b803aa9a09cbb7d4d5def1c (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
/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * Read-Copy Update definitions shared among RCU implementations.
 *
 * Copyright IBM Corporation, 2011
 *
 * Author: Paul E. McKenney <paulmck@linux.ibm.com>
 */

#ifndef __LINUX_RCU_H
#define __LINUX_RCU_H

#include <trace/events/rcu.h>

/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
#define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)


/*
 * Grace-period counter management.
 */

#define RCU_SEQ_CTR_SHIFT	2
#define RCU_SEQ_STATE_MASK	((1 << RCU_SEQ_CTR_SHIFT) - 1)

/*
 * Return the counter portion of a sequence number previously returned
 * by rcu_seq_snap() or rcu_seq_current().
 */
static inline unsigned long rcu_seq_ctr(unsigned long s)
{
	return s >> RCU_SEQ_CTR_SHIFT;
}

/*
 * Return the state portion of a sequence number previously returned
 * by rcu_seq_snap() or rcu_seq_current().
 */
static inline int rcu_seq_state(unsigned long s)
{
	return s & RCU_SEQ_STATE_MASK;
}

/*
 * Set the state portion of the pointed-to sequence number.
 * The caller is responsible for preventing conflicting updates.
 */
static inline void rcu_seq_set_state(unsigned long *sp, int newstate)
{
	WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK);
	WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate);
}

/* Adjust sequence number for start of update-side operation. */
static inline void rcu_seq_start(unsigned long *sp)
{
	WRITE_ONCE(*sp, *sp + 1);
	smp_mb(); /* Ensure update-side operation after counter increment. */
	WARN_ON_ONCE(rcu_seq_state(*sp) != 1);
}

/* Compute the end-of-grace-period value for the specified sequence number. */
static inline unsigned long rcu_seq_endval(unsigned long *sp)
{
	return (*sp | RCU_SEQ_STATE_MASK) + 1;
}

/* Adjust sequence number for end of update-side operation. */
static inline void rcu_seq_end(unsigned long *sp)
{
	smp_mb(); /* Ensure update-side operation before counter increment. */
	WARN_ON_ONCE(!rcu_seq_state(*sp));
	WRITE_ONCE(*sp, rcu_seq_endval(sp));
}

/*
 * rcu_seq_snap - Take a snapshot of the update side's sequence number.
 *
 * This function returns the earliest value of the grace-period sequence number
 * that will indicate that a full grace period has elapsed since the current
 * time.  Once the grace-period sequence number has reached this value, it will
 * be safe to invoke all callbacks that have been registered prior to the
 * current time. This value is the current grace-period number plus two to the
 * power of the number of low-order bits reserved for state, then rounded up to
 * the next value in which the state bits are all zero.
 */
static inline unsigned long rcu_seq_snap(unsigned long *sp)
{
	unsigned long s;

	s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK;
	smp_mb(); /* Above access must not bleed into critical section. */
	return s;
}

/* Return the current value the update side's sequence number, no ordering. */
static inline unsigned long rcu_seq_current(unsigned long *sp)
{
	return READ_ONCE(*sp);
}

/*
 * Given a snapshot from rcu_seq_snap(), determine whether or not the
 * corresponding update-side operation has started.
 */
static inline bool rcu_seq_started(unsigned long *sp, unsigned long s)
{
	return ULONG_CMP_LT((s - 1) & ~RCU_SEQ_STATE_MASK, READ_ONCE(*sp));
}

/*
 * Given a snapshot from rcu_seq_snap(), determine whether or not a
 * full update-side operation has occurred.
 */
static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
{
	return ULONG_CMP_GE(READ_ONCE(*sp), s);
}

/*
 * Has a grace period completed since the time the old gp_seq was collected?
 */
static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new)
{
	return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK);
}

/*
 * Has a grace period started since the time the old gp_seq was collected?
 */
static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new)
{
	return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK,
			    new);
}

/*
 * Roughly how many full grace periods have elapsed between the collection
 * of the two specified grace periods?
 */
static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
{
	unsigned long rnd_diff;

	if (old == new)
		return 0;
	/*
	 * Compute the number of grace periods (still shifted up), plus
	 * one if either of new and old is not an exact grace period.
	 */
	rnd_diff = (new & ~RCU_SEQ_STATE_MASK) -
		   ((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK) +
		   ((new & RCU_SEQ_STATE_MASK) || (old & RCU_SEQ_STATE_MASK));
	if (ULONG_CMP_GE(RCU_SEQ_STATE_MASK, rnd_diff))
		return 1; /* Definitely no grace period has elapsed. */
	return ((rnd_diff - RCU_SEQ_STATE_MASK - 1) >> RCU_SEQ_CTR_SHIFT) + 2;
}

/*
 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
 * by call_rcu() and rcu callback execution, and are therefore not part
 * of the RCU API. These are in rcupdate.h because they are used by all
 * RCU implementations.
 */

#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
# define STATE_RCU_HEAD_READY	0
# define STATE_RCU_HEAD_QUEUED	1

extern struct debug_obj_descr rcuhead_debug_descr;

static inline int debug_rcu_head_queue(struct rcu_head *head)
{
	int r1;

	r1 = debug_object_activate(head, &rcuhead_debug_descr);
	debug_object_active_state(head, &rcuhead_debug_descr,
				  STATE_RCU_HEAD_READY,
				  STATE_RCU_HEAD_QUEUED);
	return r1;
}

static inline void debug_rcu_head_unqueue(struct rcu_head *head)
{
	debug_object_active_state(head, &rcuhead_debug_descr,
				  STATE_RCU_HEAD_QUEUED,
				  STATE_RCU_HEAD_READY);
	debug_object_deactivate(head, &rcuhead_debug_descr);
}
#else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
static inline int debug_rcu_head_queue(struct rcu_head *head)
{
	return 0;
}

static inline void debug_rcu_head_unqueue(struct rcu_head *head)
{
}
#endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */

extern int rcu_cpu_stall_suppress_at_boot;

static inline bool rcu_stall_is_suppressed_at_boot(void)
{
	return rcu_cpu_stall_suppress_at_boot && !rcu_inkernel_boot_has_ended();
}

#ifdef CONFIG_RCU_STALL_COMMON

extern int rcu_cpu_stall_ftrace_dump;
extern int rcu_cpu_stall_suppress;
extern int rcu_cpu_stall_timeout;
int rcu_jiffies_till_stall_check(void);

static inline bool rcu_stall_is_suppressed(void)
{
	return rcu_stall_is_suppressed_at_boot() || rcu_cpu_stall_suppress;
}

#define rcu_ftrace_dump_stall_suppress() \
do { \
	if (!rcu_cpu_stall_suppress) \
		rcu_cpu_stall_suppress = 3; \
} while (0)

#define rcu_ftrace_dump_stall_unsuppress() \
do { \
	if (rcu_cpu_stall_suppress == 3) \
		rcu_cpu_stall_suppress = 0; \
} while (0)

#else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */

static inline bool rcu_stall_is_suppressed(void)
{
	return rcu_stall_is_suppressed_at_boot();
}
#define rcu_ftrace_dump_stall_suppress()
#define rcu_ftrace_dump_stall_unsuppress()
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */

/*
 * Strings used in tracepoints need to be exported via the
 * tracing system such that tools like perf and trace-cmd can
 * translate the string address pointers to actual text.
 */
#define TPS(x)  tracepoint_string(x)

/*
 * Dump the ftrace buffer, but only one time per callsite per boot.
 */
#define rcu_ftrace_dump(oops_dump_mode) \
do { \
	static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
	\
	if (!atomic_read(&___rfd_beenhere) && \
	    !atomic_xchg(&___rfd_beenhere, 1)) { \
		tracing_off(); \
		rcu_ftrace_dump_stall_suppress(); \
		ftrace_dump(oops_dump_mode); \
		rcu_ftrace_dump_stall_unsuppress(); \
	} \
} while (0)

void rcu_early_boot_tests(void);
void rcu_test_sync_prims(void);

/*
 * This function really isn't for public consumption, but RCU is special in
 * that context switches can allow the state machine to make progress.
 */
extern void resched_cpu(int cpu);

#if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU)

#include <linux/rcu_node_tree.h>

extern int rcu_num_lvls;
extern int num_rcu_lvl[];
extern int rcu_num_nodes;
static bool rcu_fanout_exact;
static int rcu_fanout_leaf;

/*
 * Compute the per-level fanout, either using the exact fanout specified
 * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
 */
static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
{
	int i;

	for (i = 0; i < RCU_NUM_LVLS; i++)
		levelspread[i] = INT_MIN;
	if (rcu_fanout_exact) {
		levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
		for (i = rcu_num_lvls - 2; i >= 0; i--)
			levelspread[i] = RCU_FANOUT;
	} else {
		int ccur;
		int cprv;

		cprv = nr_cpu_ids;
		for (i = rcu_num_lvls - 1; i >= 0; i--) {
			ccur = levelcnt[i];
			levelspread[i] = (cprv + ccur - 1) / ccur;
			cprv = ccur;
		}
	}
}

/* Returns a pointer to the first leaf rcu_node structure. */
#define rcu_first_leaf_node() (rcu_state.level[rcu_num_lvls - 1])

/* Is this rcu_node a leaf? */
#define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1)

/* Is this rcu_node the last leaf? */
#define rcu_is_last_leaf_node(rnp) ((rnp) == &rcu_state.node[rcu_num_nodes - 1])

/*
 * Do a full breadth-first scan of the {s,}rcu_node structures for the
 * specified state structure (for SRCU) or the only rcu_state structure
 * (for RCU).
 */
#define srcu_for_each_node_breadth_first(sp, rnp) \
	for ((rnp) = &(sp)->node[0]; \
	     (rnp) < &(sp)->node[rcu_num_nodes]; (rnp)++)
#define rcu_for_each_node_breadth_first(rnp) \
	srcu_for_each_node_breadth_first(&rcu_state, rnp)

/*
 * Scan the leaves of the rcu_node hierarchy for the rcu_state structure.
 * Note that if there is a singleton rcu_node tree with but one rcu_node
 * structure, this loop -will- visit the rcu_node structure.  It is still
 * a leaf node, even if it is also the root node.
 */
#define rcu_for_each_leaf_node(rnp) \
	for ((rnp) = rcu_first_leaf_node(); \
	     (rnp) < &rcu_state.node[rcu_num_nodes]; (rnp)++)

/*
 * Iterate over all possible CPUs in a leaf RCU node.
 */
#define for_each_leaf_node_possible_cpu(rnp, cpu) \
	for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
	     (cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
	     (cpu) <= rnp->grphi; \
	     (cpu) = cpumask_next((cpu), cpu_possible_mask))

/*
 * Iterate over all CPUs in a leaf RCU node's specified mask.
 */
#define rcu_find_next_bit(rnp, cpu, mask) \
	((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
#define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
	for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
	     (cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
	     (cpu) <= rnp->grphi; \
	     (cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))

/*
 * Wrappers for the rcu_node::lock acquire and release.
 *
 * Because the rcu_nodes form a tree, the tree traversal locking will observe
 * different lock values, this in turn means that an UNLOCK of one level
 * followed by a LOCK of another level does not imply a full memory barrier;
 * and most importantly transitivity is lost.
 *
 * In order to restore full ordering between tree levels, augment the regular
 * lock acquire functions with smp_mb__after_unlock_lock().
 *
 * As ->lock of struct rcu_node is a __private field, therefore one should use
 * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
 */
#define raw_spin_lock_rcu_node(p)					\
do {									\
	raw_spin_lock(&ACCESS_PRIVATE(p, lock));			\
	smp_mb__after_unlock_lock();					\
} while (0)

#define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock))

#define raw_spin_lock_irq_rcu_node(p)					\
do {									\
	raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock));			\
	smp_mb__after_unlock_lock();					\
} while (0)

#define raw_spin_unlock_irq_rcu_node(p)					\
	raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock))

#define raw_spin_lock_irqsave_rcu_node(p, flags)			\
do {									\
	raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags);	\
	smp_mb__after_unlock_lock();					\
} while (0)

#define raw_spin_unlock_irqrestore_rcu_node(p, flags)			\
	raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)

#define raw_spin_trylock_rcu_node(p)					\
({									\
	bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock));	\
									\
	if (___locked)							\
		smp_mb__after_unlock_lock();				\
	___locked;							\
})

#define raw_lockdep_assert_held_rcu_node(p)				\
	lockdep_assert_held(&ACCESS_PRIVATE(p, lock))

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

#ifdef CONFIG_SRCU
void srcu_init(void);
#else /* #ifdef CONFIG_SRCU */
static inline void srcu_init(void) { }
#endif /* #else #ifdef CONFIG_SRCU */

#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_normal(void) { return true; }
static inline bool rcu_gp_is_expedited(void) { return false; }
static inline void rcu_expedite_gp(void) { }
static inline void rcu_unexpedite_gp(void) { }
static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_gp_is_normal(void);     /* Internal RCU use. */
bool rcu_gp_is_expedited(void);  /* Internal RCU use. */
void rcu_expedite_gp(void);
void rcu_unexpedite_gp(void);
void rcupdate_announce_bootup_oddness(void);
void rcu_request_urgent_qs_task(struct task_struct *t);
#endif /* #else #ifdef CONFIG_TINY_RCU */

#define RCU_SCHEDULER_INACTIVE	0
#define RCU_SCHEDULER_INIT	1
#define RCU_SCHEDULER_RUNNING	2

enum rcutorture_type {
	RCU_FLAVOR,
	RCU_TASKS_FLAVOR,
	RCU_TRIVIAL_FLAVOR,
	SRCU_FLAVOR,
	INVALID_RCU_FLAVOR
};

#if defined(CONFIG_TREE_RCU)
void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
			    unsigned long *gp_seq);
void do_trace_rcu_torture_read(const char *rcutorturename,
			       struct rcu_head *rhp,
			       unsigned long secs,
			       unsigned long c_old,
			       unsigned long c);
#else
static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
					  int *flags, unsigned long *gp_seq)
{
	*flags = 0;
	*gp_seq = 0;
}
#ifdef 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);
#else
#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
	do { } while (0)
#endif
#endif

#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask);
#endif

#ifdef CONFIG_TINY_SRCU

static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
					   struct srcu_struct *sp, int *flags,
					   unsigned long *gp_seq)
{
	if (test_type != SRCU_FLAVOR)
		return;
	*flags = 0;
	*gp_seq = sp->srcu_idx;
}

#elif defined(CONFIG_TREE_SRCU)

void srcutorture_get_gp_data(enum rcutorture_type test_type,
			     struct srcu_struct *sp, int *flags,
			     unsigned long *gp_seq);

#endif

#ifdef CONFIG_TINY_RCU
static inline unsigned long rcu_get_gp_seq(void) { return 0; }
static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
static inline unsigned long
srcu_batches_completed(struct srcu_struct *sp) { return 0; }
static inline void rcu_force_quiescent_state(void) { }
static inline void show_rcu_gp_kthreads(void) { }
static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
static inline void rcu_fwd_progress_check(unsigned long j) { }
#else /* #ifdef CONFIG_TINY_RCU */
unsigned long rcu_get_gp_seq(void);
unsigned long rcu_exp_batches_completed(void);
unsigned long srcu_batches_completed(struct srcu_struct *sp);
void show_rcu_gp_kthreads(void);
int rcu_get_gp_kthreads_prio(void);
void rcu_fwd_progress_check(unsigned long j);
void rcu_force_quiescent_state(void);
extern struct workqueue_struct *rcu_gp_wq;
extern struct workqueue_struct *rcu_par_gp_wq;
#endif /* #else #ifdef CONFIG_TINY_RCU */

#ifdef CONFIG_RCU_NOCB_CPU
bool rcu_is_nocb_cpu(int cpu);
void rcu_bind_current_to_nocb(void);
#else
static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
static inline void rcu_bind_current_to_nocb(void) { }
#endif

#endif /* __LINUX_RCU_H */