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Paul E. McKenney621934e2006-10-04 02:17:02 -07001/*
2 * Sleepable Read-Copy Update mechanism for mutual exclusion
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2006
Lai Jiangshan4e87b2d2012-10-13 01:14:14 +080019 * Copyright (C) Fujitsu, 2012
Paul E. McKenney621934e2006-10-04 02:17:02 -070020 *
21 * Author: Paul McKenney <paulmck@us.ibm.com>
Lai Jiangshan4e87b2d2012-10-13 01:14:14 +080022 * Lai Jiangshan <laijs@cn.fujitsu.com>
Paul E. McKenney621934e2006-10-04 02:17:02 -070023 *
24 * For detailed explanation of Read-Copy Update mechanism see -
25 * Documentation/RCU/ *.txt
26 *
27 */
28
Alan Sterneabc0692006-10-04 02:17:04 -070029#ifndef _LINUX_SRCU_H
30#define _LINUX_SRCU_H
31
Paul E. McKenneyd14aada2010-04-19 22:24:22 -070032#include <linux/mutex.h>
Paul E. McKenneyff195cb2011-10-07 18:22:04 +020033#include <linux/rcupdate.h>
Lai Jiangshan931ea9d2012-03-19 16:12:13 +080034#include <linux/workqueue.h>
Paul E. McKenneyd14aada2010-04-19 22:24:22 -070035
Paul E. McKenney621934e2006-10-04 02:17:02 -070036struct srcu_struct_array {
Paul E. McKenneycef50122012-02-05 07:42:44 -080037 unsigned long c[2];
Lai Jiangshanb52ce062012-02-27 09:29:09 -080038 unsigned long seq[2];
Paul E. McKenney621934e2006-10-04 02:17:02 -070039};
40
Lai Jiangshan931ea9d2012-03-19 16:12:13 +080041struct rcu_batch {
42 struct rcu_head *head, **tail;
43};
44
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080045#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
46
Paul E. McKenney621934e2006-10-04 02:17:02 -070047struct srcu_struct {
Paul E. McKenneycef50122012-02-05 07:42:44 -080048 unsigned completed;
Tejun Heo43cf38e2010-02-02 14:38:57 +090049 struct srcu_struct_array __percpu *per_cpu_ref;
Lai Jiangshan931ea9d2012-03-19 16:12:13 +080050 spinlock_t queue_lock; /* protect ->batch_queue, ->running */
51 bool running;
52 /* callbacks just queued */
53 struct rcu_batch batch_queue;
54 /* callbacks try to do the first check_zero */
55 struct rcu_batch batch_check0;
56 /* callbacks done with the first check_zero and the flip */
57 struct rcu_batch batch_check1;
58 struct rcu_batch batch_done;
59 struct delayed_work work;
Paul E. McKenney632ee202010-02-22 17:04:45 -080060#ifdef CONFIG_DEBUG_LOCK_ALLOC
61 struct lockdep_map dep_map;
62#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
Paul E. McKenney621934e2006-10-04 02:17:02 -070063};
64
Paul E. McKenney632ee202010-02-22 17:04:45 -080065#ifdef CONFIG_DEBUG_LOCK_ALLOC
66
67int __init_srcu_struct(struct srcu_struct *sp, const char *name,
68 struct lock_class_key *key);
69
70#define init_srcu_struct(sp) \
71({ \
72 static struct lock_class_key __srcu_key; \
73 \
74 __init_srcu_struct((sp), #sp, &__srcu_key); \
75})
76
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080077#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
Paul E. McKenney632ee202010-02-22 17:04:45 -080078#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
79
Alan Sterne6a92012006-10-04 02:17:05 -070080int init_srcu_struct(struct srcu_struct *sp);
Paul E. McKenney632ee202010-02-22 17:04:45 -080081
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080082#define __SRCU_DEP_MAP_INIT(srcu_name)
Paul E. McKenney632ee202010-02-22 17:04:45 -080083#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
84
Lai Jiangshanf2ebfbc2012-10-13 01:14:15 +080085void process_srcu(struct work_struct *work);
86
Lai Jiangshan55c6659a2012-10-13 01:14:16 +080087#define __SRCU_STRUCT_INIT(name) \
88 { \
89 .completed = -300, \
90 .per_cpu_ref = &name##_srcu_array, \
91 .queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
92 .running = false, \
93 .batch_queue = RCU_BATCH_INIT(name.batch_queue), \
94 .batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
95 .batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
96 .batch_done = RCU_BATCH_INIT(name.batch_done), \
97 .work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
98 __SRCU_DEP_MAP_INIT(name) \
99 }
100
101/*
102 * define and init a srcu struct at build time.
103 * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
104 */
105#define DEFINE_SRCU(name) \
106 static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
107 struct srcu_struct name = __SRCU_STRUCT_INIT(name);
108
109#define DEFINE_STATIC_SRCU(name) \
110 static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
111 static struct srcu_struct name = __SRCU_STRUCT_INIT(name);
112
Lai Jiangshan931ea9d2012-03-19 16:12:13 +0800113/**
114 * call_srcu() - Queue a callback for invocation after an SRCU grace period
115 * @sp: srcu_struct in queue the callback
116 * @head: structure to be used for queueing the SRCU callback.
117 * @func: function to be invoked after the SRCU grace period
118 *
119 * The callback function will be invoked some time after a full SRCU
120 * grace period elapses, in other words after all pre-existing SRCU
121 * read-side critical sections have completed. However, the callback
122 * function might well execute concurrently with other SRCU read-side
123 * critical sections that started after call_srcu() was invoked. SRCU
124 * read-side critical sections are delimited by srcu_read_lock() and
125 * srcu_read_unlock(), and may be nested.
126 *
127 * The callback will be invoked from process context, but must nevertheless
128 * be fast and must not block.
129 */
130void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
131 void (*func)(struct rcu_head *head));
132
Paul E. McKenney621934e2006-10-04 02:17:02 -0700133void cleanup_srcu_struct(struct srcu_struct *sp);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800134int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
135void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
Paul E. McKenney621934e2006-10-04 02:17:02 -0700136void synchronize_srcu(struct srcu_struct *sp);
Paul E. McKenney0cd397d2009-10-25 19:03:51 -0700137void synchronize_srcu_expedited(struct srcu_struct *sp);
Paul E. McKenney621934e2006-10-04 02:17:02 -0700138long srcu_batches_completed(struct srcu_struct *sp);
Lai Jiangshan931ea9d2012-03-19 16:12:13 +0800139void srcu_barrier(struct srcu_struct *sp);
Alan Sterneabc0692006-10-04 02:17:04 -0700140
Paul E. McKenney632ee202010-02-22 17:04:45 -0800141#ifdef CONFIG_DEBUG_LOCK_ALLOC
142
143/**
144 * srcu_read_lock_held - might we be in SRCU read-side critical section?
145 *
Paul E. McKenneyd20200b2010-03-30 10:52:21 -0700146 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
147 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
Paul E. McKenney632ee202010-02-22 17:04:45 -0800148 * this assumes we are in an SRCU read-side critical section unless it can
149 * prove otherwise.
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200150 *
Paul E. McKenney867f2362011-10-07 18:22:05 +0200151 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
152 * and while lockdep is disabled.
153 *
Lai Jiangshan511a0862012-11-29 16:46:06 +0800154 * Note that SRCU is based on its own statemachine and it doesn't
155 * relies on normal RCU, it can be called from the CPU which
156 * is in the idle loop from an RCU point of view or offline.
Paul E. McKenney632ee202010-02-22 17:04:45 -0800157 */
158static inline int srcu_read_lock_held(struct srcu_struct *sp)
159{
Paul E. McKenney867f2362011-10-07 18:22:05 +0200160 if (!debug_lockdep_rcu_enabled())
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200161 return 1;
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200162 return lock_is_held(&sp->dep_map);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800163}
164
165#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
166
167static inline int srcu_read_lock_held(struct srcu_struct *sp)
168{
169 return 1;
170}
171
172#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
173
174/**
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700175 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
176 * @p: the pointer to fetch and protect for later dereferencing
177 * @sp: pointer to the srcu_struct, which is used to check that we
178 * really are in an SRCU read-side critical section.
179 * @c: condition to check for update-side use
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800180 *
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700181 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
182 * critical section will result in an RCU-lockdep splat, unless @c evaluates
183 * to 1. The @c argument will normally be a logical expression containing
184 * lockdep_is_held() calls.
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800185 */
Paul E. McKenneyca5ecdd2010-04-28 14:39:09 -0700186#define srcu_dereference_check(p, sp, c) \
187 __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu)
188
189/**
190 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
191 * @p: the pointer to fetch and protect for later dereferencing
192 * @sp: pointer to the srcu_struct, which is used to check that we
193 * really are in an SRCU read-side critical section.
194 *
195 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
196 * is enabled, invoking this outside of an RCU read-side critical
197 * section will result in an RCU-lockdep splat.
198 */
199#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
Paul E. McKenneyc26d34a2010-02-22 17:04:46 -0800200
201/**
Paul E. McKenney632ee202010-02-22 17:04:45 -0800202 * srcu_read_lock - register a new reader for an SRCU-protected structure.
203 * @sp: srcu_struct in which to register the new reader.
204 *
205 * Enter an SRCU read-side critical section. Note that SRCU read-side
Paul E. McKenney73d4da42010-08-16 10:50:54 -0700206 * critical sections may be nested. However, it is illegal to
207 * call anything that waits on an SRCU grace period for the same
208 * srcu_struct, whether directly or indirectly. Please note that
209 * one way to indirectly wait on an SRCU grace period is to acquire
210 * a mutex that is held elsewhere while calling synchronize_srcu() or
211 * synchronize_srcu_expedited().
Paul E. McKenney3842a082011-11-28 10:42:42 -0800212 *
213 * Note that srcu_read_lock() and the matching srcu_read_unlock() must
214 * occur in the same context, for example, it is illegal to invoke
215 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
216 * was invoked in process context.
Paul E. McKenney632ee202010-02-22 17:04:45 -0800217 */
218static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
219{
220 int retval = __srcu_read_lock(sp);
221
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200222 rcu_lock_acquire(&(sp)->dep_map);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800223 return retval;
224}
225
226/**
227 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
228 * @sp: srcu_struct in which to unregister the old reader.
229 * @idx: return value from corresponding srcu_read_lock().
230 *
231 * Exit an SRCU read-side critical section.
232 */
233static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
234 __releases(sp)
235{
Paul E. McKenneyff195cb2011-10-07 18:22:04 +0200236 rcu_lock_release(&(sp)->dep_map);
Paul E. McKenney632ee202010-02-22 17:04:45 -0800237 __srcu_read_unlock(sp, idx);
238}
239
Paul E. McKenney0c53dd82011-10-09 15:13:11 -0700240/**
241 * srcu_read_lock_raw - register a new reader for an SRCU-protected structure.
242 * @sp: srcu_struct in which to register the new reader.
243 *
244 * Enter an SRCU read-side critical section. Similar to srcu_read_lock(),
245 * but avoids the RCU-lockdep checking. This means that it is legal to
246 * use srcu_read_lock_raw() in one context, for example, in an exception
247 * handler, and then have the matching srcu_read_unlock_raw() in another
248 * context, for example in the task that took the exception.
249 *
250 * However, the entire SRCU read-side critical section must reside within a
251 * single task. For example, beware of using srcu_read_lock_raw() in
252 * a device interrupt handler and srcu_read_unlock() in the interrupted
253 * task: This will not work if interrupts are threaded.
254 */
255static inline int srcu_read_lock_raw(struct srcu_struct *sp)
256{
257 unsigned long flags;
258 int ret;
259
260 local_irq_save(flags);
261 ret = __srcu_read_lock(sp);
262 local_irq_restore(flags);
263 return ret;
264}
265
266/**
267 * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure.
268 * @sp: srcu_struct in which to unregister the old reader.
269 * @idx: return value from corresponding srcu_read_lock_raw().
270 *
271 * Exit an SRCU read-side critical section without lockdep-RCU checking.
272 * See srcu_read_lock_raw() for more details.
273 */
274static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx)
275{
276 unsigned long flags;
277
278 local_irq_save(flags);
279 __srcu_read_unlock(sp, idx);
280 local_irq_restore(flags);
281}
282
Alan Sterneabc0692006-10-04 02:17:04 -0700283#endif