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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, 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
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 : 5616246 : 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 : 5637291 : __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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