summaryrefslogtreecommitdiffstats
path: root/include/linux/srcu.h
blob: 6eb691b083581ff88ffd9e7c3da73bc5aa2170fd (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
/*
 * Sleepable Read-Copy Update mechanism for mutual exclusion
 *
 * 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) IBM Corporation, 2006
 * Copyright (C) Fujitsu, 2012
 *
 * Author: Paul McKenney <paulmck@us.ibm.com>
 *	   Lai Jiangshan <laijs@cn.fujitsu.com>
 *
 * For detailed explanation of Read-Copy Update mechanism see -
 * 		Documentation/RCU/ *.txt
 *
 */

#ifndef _LINUX_SRCU_H
#define _LINUX_SRCU_H

#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>

struct srcu_struct_array {
	unsigned long c[2];
	unsigned long seq[2];
};

struct rcu_batch {
	struct rcu_head *head, **tail;
};

#define RCU_BATCH_INIT(name) { NULL, &(name.head) }

struct srcu_struct {
	unsigned completed;
	struct srcu_struct_array __percpu *per_cpu_ref;
	spinlock_t queue_lock; /* protect ->batch_queue, ->running */
	bool running;
	/* callbacks just queued */
	struct rcu_batch batch_queue;
	/* callbacks try to do the first check_zero */
	struct rcu_batch batch_check0;
	/* callbacks done with the first check_zero and the flip */
	struct rcu_batch batch_check1;
	struct rcu_batch batch_done;
	struct delayed_work work;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC

int __init_srcu_struct(struct srcu_struct *sp, const char *name,
		       struct lock_class_key *key);

#define init_srcu_struct(sp) \
({ \
	static struct lock_class_key __srcu_key; \
	\
	__init_srcu_struct((sp), #sp, &__srcu_key); \
})

#define __SRCU_DEP_MAP_INIT(srcu_name)	.dep_map = { .name = #srcu_name },
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

int init_srcu_struct(struct srcu_struct *sp);

#define __SRCU_DEP_MAP_INIT(srcu_name)
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

void process_srcu(struct work_struct *work);

#define __SRCU_STRUCT_INIT(name)					\
	{								\
		.completed = -300,					\
		.per_cpu_ref = &name##_srcu_array,			\
		.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock),	\
		.running = false,					\
		.batch_queue = RCU_BATCH_INIT(name.batch_queue),	\
		.batch_check0 = RCU_BATCH_INIT(name.batch_check0),	\
		.batch_check1 = RCU_BATCH_INIT(name.batch_check1),	\
		.batch_done = RCU_BATCH_INIT(name.batch_done),		\
		.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
		__SRCU_DEP_MAP_INIT(name)				\
	}

/*
 * define and init a srcu struct at build time.
 * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
 */
#define DEFINE_SRCU(name)						\
	static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
	struct srcu_struct name = __SRCU_STRUCT_INIT(name);

#define DEFINE_STATIC_SRCU(name)					\
	static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
	static struct srcu_struct name = __SRCU_STRUCT_INIT(name);

/**
 * call_srcu() - Queue a callback for invocation after an SRCU grace period
 * @sp: srcu_struct in queue the callback
 * @head: structure to be used for queueing the SRCU callback.
 * @func: function to be invoked after the SRCU grace period
 *
 * The callback function will be invoked some time after a full SRCU
 * grace period elapses, in other words after all pre-existing SRCU
 * read-side critical sections have completed.  However, the callback
 * function might well execute concurrently with other SRCU read-side
 * critical sections that started after call_srcu() was invoked.  SRCU
 * read-side critical sections are delimited by srcu_read_lock() and
 * srcu_read_unlock(), and may be nested.
 *
 * The callback will be invoked from process context, but must nevertheless
 * be fast and must not block.
 */
void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
		void (*func)(struct rcu_head *head));

void cleanup_srcu_struct(struct srcu_struct *sp);
int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
void synchronize_srcu(struct srcu_struct *sp);
void synchronize_srcu_expedited(struct srcu_struct *sp);
long srcu_batches_completed(struct srcu_struct *sp);
void srcu_barrier(struct srcu_struct *sp);

#ifdef CONFIG_DEBUG_LOCK_ALLOC

/**
 * srcu_read_lock_held - might we be in SRCU read-side critical section?
 *
 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
 * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
 * this assumes we are in an SRCU read-side critical section unless it can
 * prove otherwise.
 *
 * Checks 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 rcu_idle_enter() and
 * rcu_idle_exit()) then srcu_read_lock_held() returns false even if
 * the CPU did an srcu_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 SRCU read lock held if the current
 * CPU is offline.
 */
static inline int srcu_read_lock_held(struct srcu_struct *sp)
{
	if (!debug_lockdep_rcu_enabled())
		return 1;
	if (rcu_is_cpu_idle())
		return 0;
	if (!rcu_lockdep_current_cpu_online())
		return 0;
	return lock_is_held(&sp->dep_map);
}

#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

static inline int srcu_read_lock_held(struct srcu_struct *sp)
{
	return 1;
}

#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

/**
 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
 * @p: the pointer to fetch and protect for later dereferencing
 * @sp: pointer to the srcu_struct, which is used to check that we
 *	really are in an SRCU read-side critical section.
 * @c: condition to check for update-side use
 *
 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
 * critical section will result in an RCU-lockdep splat, unless @c evaluates
 * to 1.  The @c argument will normally be a logical expression containing
 * lockdep_is_held() calls.
 */
#define srcu_dereference_check(p, sp, c) \
	__rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu)

/**
 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
 * @p: the pointer to fetch and protect for later dereferencing
 * @sp: pointer to the srcu_struct, which is used to check that we
 *	really are in an SRCU read-side critical section.
 *
 * Makes rcu_dereference_check() do the dirty work.  If PROVE_RCU
 * is enabled, invoking this outside of an RCU read-side critical
 * section will result in an RCU-lockdep splat.
 */
#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)

/**
 * srcu_read_lock - register a new reader for an SRCU-protected structure.
 * @sp: srcu_struct in which to register the new reader.
 *
 * Enter an SRCU read-side critical section.  Note that SRCU read-side
 * critical sections may be nested.  However, it is illegal to
 * call anything that waits on an SRCU grace period for the same
 * srcu_struct, whether directly or indirectly.  Please note that
 * one way to indirectly wait on an SRCU grace period is to acquire
 * a mutex that is held elsewhere while calling synchronize_srcu() or
 * synchronize_srcu_expedited().
 *
 * Note that srcu_read_lock() and the matching srcu_read_unlock() must
 * occur in the same context, for example, it is illegal to invoke
 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
 * was invoked in process context.
 */
static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
{
	int retval = __srcu_read_lock(sp);

	rcu_lock_acquire(&(sp)->dep_map);
	rcu_lockdep_assert(!rcu_is_cpu_idle(),
			   "srcu_read_lock() used illegally while idle");
	return retval;
}

/**
 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
 * @sp: srcu_struct in which to unregister the old reader.
 * @idx: return value from corresponding srcu_read_lock().
 *
 * Exit an SRCU read-side critical section.
 */
static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
	__releases(sp)
{
	rcu_lockdep_assert(!rcu_is_cpu_idle(),
			   "srcu_read_unlock() used illegally while idle");
	rcu_lock_release(&(sp)->dep_map);
	__srcu_read_unlock(sp, idx);
}

/**
 * srcu_read_lock_raw - register a new reader for an SRCU-protected structure.
 * @sp: srcu_struct in which to register the new reader.
 *
 * Enter an SRCU read-side critical section.  Similar to srcu_read_lock(),
 * but avoids the RCU-lockdep checking.  This means that it is legal to
 * use srcu_read_lock_raw() in one context, for example, in an exception
 * handler, and then have the matching srcu_read_unlock_raw() in another
 * context, for example in the task that took the exception.
 *
 * However, the entire SRCU read-side critical section must reside within a
 * single task.  For example, beware of using srcu_read_lock_raw() in
 * a device interrupt handler and srcu_read_unlock() in the interrupted
 * task:  This will not work if interrupts are threaded.
 */
static inline int srcu_read_lock_raw(struct srcu_struct *sp)
{
	unsigned long flags;
	int ret;

	local_irq_save(flags);
	ret =  __srcu_read_lock(sp);
	local_irq_restore(flags);
	return ret;
}

/**
 * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure.
 * @sp: srcu_struct in which to unregister the old reader.
 * @idx: return value from corresponding srcu_read_lock_raw().
 *
 * Exit an SRCU read-side critical section without lockdep-RCU checking.
 * See srcu_read_lock_raw() for more details.
 */
static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx)
{
	unsigned long flags;

	local_irq_save(flags);
	__srcu_read_unlock(sp, idx);
	local_irq_restore(flags);
}

#endif
OpenPOWER on IntegriCloud