Line data Source code
1 : /*
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, you can access it online at
16 : * http://www.gnu.org/licenses/gpl-2.0.html.
17 : *
18 : * Copyright (C) IBM Corporation, 2006
19 : * Copyright (C) Fujitsu, 2012
20 : *
21 : * Author: Paul McKenney <paulmck@us.ibm.com>
22 : * Lai Jiangshan <laijs@cn.fujitsu.com>
23 : *
24 : * For detailed explanation of Read-Copy Update mechanism see -
25 : * Documentation/RCU/ *.txt
26 : *
27 : */
28 :
29 : #ifndef _LINUX_SRCU_H
30 : #define _LINUX_SRCU_H
31 :
32 : #include <linux/mutex.h>
33 : #include <linux/rcupdate.h>
34 : #include <linux/workqueue.h>
35 :
36 : struct srcu_struct_array {
37 : unsigned long c[2];
38 : unsigned long seq[2];
39 : };
40 :
41 : struct rcu_batch {
42 : struct rcu_head *head, **tail;
43 : };
44 :
45 : #define RCU_BATCH_INIT(name) { NULL, &(name.head) }
46 :
47 : struct srcu_struct {
48 : unsigned completed;
49 : struct srcu_struct_array __percpu *per_cpu_ref;
50 : 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;
60 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
61 : struct lockdep_map dep_map;
62 : #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
63 : };
64 :
65 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
66 :
67 : int __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 :
77 : #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
78 : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
79 :
80 : int init_srcu_struct(struct srcu_struct *sp);
81 :
82 : #define __SRCU_DEP_MAP_INIT(srcu_name)
83 : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
84 :
85 : void process_srcu(struct work_struct *work);
86 :
87 : #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 :
113 : /**
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 : */
130 : void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
131 : void (*func)(struct rcu_head *head));
132 :
133 : void cleanup_srcu_struct(struct srcu_struct *sp);
134 : int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
135 : void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
136 : void synchronize_srcu(struct srcu_struct *sp);
137 : void synchronize_srcu_expedited(struct srcu_struct *sp);
138 : long srcu_batches_completed(struct srcu_struct *sp);
139 : void srcu_barrier(struct srcu_struct *sp);
140 :
141 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
142 :
143 : /**
144 : * srcu_read_lock_held - might we be in SRCU read-side critical section?
145 : *
146 : * 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,
148 : * this assumes we are in an SRCU read-side critical section unless it can
149 : * prove otherwise.
150 : *
151 : * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
152 : * and while lockdep is disabled.
153 : *
154 : * 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.
157 : */
158 : static inline int srcu_read_lock_held(struct srcu_struct *sp)
159 : {
160 : if (!debug_lockdep_rcu_enabled())
161 : return 1;
162 : return lock_is_held(&sp->dep_map);
163 : }
164 :
165 : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
166 :
167 : static 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 : /**
175 : * 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
180 : *
181 : * 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.
185 : */
186 : #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)
200 :
201 : /**
202 : * 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
206 : * 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().
212 : *
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.
217 : */
218 : static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
219 : {
220 1189060 : int retval = __srcu_read_lock(sp);
221 :
222 : rcu_lock_acquire(&(sp)->dep_map);
223 : 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 : */
233 : static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
234 : __releases(sp)
235 : {
236 : rcu_lock_release(&(sp)->dep_map);
237 1189060 : __srcu_read_unlock(sp, idx);
238 : }
239 :
240 : /**
241 : * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
242 : *
243 : * Converts the preceding srcu_read_unlock into a two-way memory barrier.
244 : *
245 : * Call this after srcu_read_unlock, to guarantee that all memory operations
246 : * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
247 : * the preceding srcu_read_unlock.
248 : */
249 : static inline void smp_mb__after_srcu_read_unlock(void)
250 : {
251 : /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
252 : }
253 :
254 : #endif
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