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621934ee PM |
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 | |
4e87b2d7 | 19 | * Copyright (C) Fujitsu, 2012 |
621934ee PM |
20 | * |
21 | * Author: Paul McKenney <paulmck@us.ibm.com> | |
4e87b2d7 | 22 | * Lai Jiangshan <laijs@cn.fujitsu.com> |
621934ee PM |
23 | * |
24 | * For detailed explanation of Read-Copy Update mechanism see - | |
25 | * Documentation/RCU/ *.txt | |
26 | * | |
27 | */ | |
28 | ||
eabc0694 AS |
29 | #ifndef _LINUX_SRCU_H |
30 | #define _LINUX_SRCU_H | |
31 | ||
d14aada8 | 32 | #include <linux/mutex.h> |
ff195cb6 | 33 | #include <linux/rcupdate.h> |
931ea9d1 | 34 | #include <linux/workqueue.h> |
d14aada8 | 35 | |
621934ee | 36 | struct srcu_struct_array { |
cef50120 | 37 | unsigned long c[2]; |
b52ce066 | 38 | unsigned long seq[2]; |
621934ee PM |
39 | }; |
40 | ||
931ea9d1 LJ |
41 | struct rcu_batch { |
42 | struct rcu_head *head, **tail; | |
43 | }; | |
44 | ||
55c6659a LJ |
45 | #define RCU_BATCH_INIT(name) { NULL, &(name.head) } |
46 | ||
621934ee | 47 | struct srcu_struct { |
cef50120 | 48 | unsigned completed; |
43cf38eb | 49 | struct srcu_struct_array __percpu *per_cpu_ref; |
931ea9d1 LJ |
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; | |
632ee200 PM |
60 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
61 | struct lockdep_map dep_map; | |
62 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
621934ee PM |
63 | }; |
64 | ||
632ee200 PM |
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 | ||
55c6659a | 77 | #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, |
632ee200 PM |
78 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
79 | ||
e6a92013 | 80 | int init_srcu_struct(struct srcu_struct *sp); |
632ee200 | 81 | |
55c6659a | 82 | #define __SRCU_DEP_MAP_INIT(srcu_name) |
632ee200 PM |
83 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
84 | ||
f2ebfbc9 LJ |
85 | void process_srcu(struct work_struct *work); |
86 | ||
55c6659a LJ |
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 | ||
931ea9d1 LJ |
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 | ||
621934ee | 133 | void cleanup_srcu_struct(struct srcu_struct *sp); |
632ee200 PM |
134 | int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); |
135 | void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); | |
621934ee | 136 | void synchronize_srcu(struct srcu_struct *sp); |
0cd397d3 | 137 | void synchronize_srcu_expedited(struct srcu_struct *sp); |
621934ee | 138 | long srcu_batches_completed(struct srcu_struct *sp); |
931ea9d1 | 139 | void srcu_barrier(struct srcu_struct *sp); |
eabc0694 | 140 | |
632ee200 PM |
141 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
142 | ||
143 | /** | |
144 | * srcu_read_lock_held - might we be in SRCU read-side critical section? | |
145 | * | |
d20200b5 PM |
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, | |
632ee200 PM |
148 | * this assumes we are in an SRCU read-side critical section unless it can |
149 | * prove otherwise. | |
ff195cb6 | 150 | * |
867f236b PM |
151 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
152 | * and while lockdep is disabled. | |
153 | * | |
ff195cb6 PM |
154 | * Note that if the CPU is in the idle loop from an RCU point of view |
155 | * (ie: that we are in the section between rcu_idle_enter() and | |
156 | * rcu_idle_exit()) then srcu_read_lock_held() returns false even if | |
157 | * the CPU did an srcu_read_lock(). The reason for this is that RCU | |
158 | * ignores CPUs that are in such a section, considering these as in | |
159 | * extended quiescent state, so such a CPU is effectively never in an | |
160 | * RCU read-side critical section regardless of what RCU primitives it | |
161 | * invokes. This state of affairs is required --- we need to keep an | |
162 | * RCU-free window in idle where the CPU may possibly enter into low | |
163 | * power mode. This way we can notice an extended quiescent state to | |
164 | * other CPUs that started a grace period. Otherwise we would delay any | |
165 | * grace period as long as we run in the idle task. | |
c0d6d01b PM |
166 | * |
167 | * Similarly, we avoid claiming an SRCU read lock held if the current | |
168 | * CPU is offline. | |
632ee200 PM |
169 | */ |
170 | static inline int srcu_read_lock_held(struct srcu_struct *sp) | |
171 | { | |
867f236b | 172 | if (!debug_lockdep_rcu_enabled()) |
ff195cb6 | 173 | return 1; |
c0d6d01b PM |
174 | if (rcu_is_cpu_idle()) |
175 | return 0; | |
176 | if (!rcu_lockdep_current_cpu_online()) | |
177 | return 0; | |
ff195cb6 | 178 | return lock_is_held(&sp->dep_map); |
632ee200 PM |
179 | } |
180 | ||
181 | #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
182 | ||
183 | static inline int srcu_read_lock_held(struct srcu_struct *sp) | |
184 | { | |
185 | return 1; | |
186 | } | |
187 | ||
188 | #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
189 | ||
c26d34a5 | 190 | /** |
ca5ecddf PM |
191 | * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing |
192 | * @p: the pointer to fetch and protect for later dereferencing | |
193 | * @sp: pointer to the srcu_struct, which is used to check that we | |
194 | * really are in an SRCU read-side critical section. | |
195 | * @c: condition to check for update-side use | |
c26d34a5 | 196 | * |
ca5ecddf PM |
197 | * If PROVE_RCU is enabled, invoking this outside of an RCU read-side |
198 | * critical section will result in an RCU-lockdep splat, unless @c evaluates | |
199 | * to 1. The @c argument will normally be a logical expression containing | |
200 | * lockdep_is_held() calls. | |
c26d34a5 | 201 | */ |
ca5ecddf PM |
202 | #define srcu_dereference_check(p, sp, c) \ |
203 | __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) | |
204 | ||
205 | /** | |
206 | * srcu_dereference - fetch SRCU-protected pointer for later dereferencing | |
207 | * @p: the pointer to fetch and protect for later dereferencing | |
208 | * @sp: pointer to the srcu_struct, which is used to check that we | |
209 | * really are in an SRCU read-side critical section. | |
210 | * | |
211 | * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU | |
212 | * is enabled, invoking this outside of an RCU read-side critical | |
213 | * section will result in an RCU-lockdep splat. | |
214 | */ | |
215 | #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) | |
c26d34a5 | 216 | |
632ee200 PM |
217 | /** |
218 | * srcu_read_lock - register a new reader for an SRCU-protected structure. | |
219 | * @sp: srcu_struct in which to register the new reader. | |
220 | * | |
221 | * Enter an SRCU read-side critical section. Note that SRCU read-side | |
73d4da4d PM |
222 | * critical sections may be nested. However, it is illegal to |
223 | * call anything that waits on an SRCU grace period for the same | |
224 | * srcu_struct, whether directly or indirectly. Please note that | |
225 | * one way to indirectly wait on an SRCU grace period is to acquire | |
226 | * a mutex that is held elsewhere while calling synchronize_srcu() or | |
227 | * synchronize_srcu_expedited(). | |
3842a083 PM |
228 | * |
229 | * Note that srcu_read_lock() and the matching srcu_read_unlock() must | |
230 | * occur in the same context, for example, it is illegal to invoke | |
231 | * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() | |
232 | * was invoked in process context. | |
632ee200 PM |
233 | */ |
234 | static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) | |
235 | { | |
236 | int retval = __srcu_read_lock(sp); | |
237 | ||
ff195cb6 | 238 | rcu_lock_acquire(&(sp)->dep_map); |
bde23c68 HC |
239 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
240 | "srcu_read_lock() used illegally while idle"); | |
632ee200 PM |
241 | return retval; |
242 | } | |
243 | ||
244 | /** | |
245 | * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. | |
246 | * @sp: srcu_struct in which to unregister the old reader. | |
247 | * @idx: return value from corresponding srcu_read_lock(). | |
248 | * | |
249 | * Exit an SRCU read-side critical section. | |
250 | */ | |
251 | static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) | |
252 | __releases(sp) | |
253 | { | |
bde23c68 HC |
254 | rcu_lockdep_assert(!rcu_is_cpu_idle(), |
255 | "srcu_read_unlock() used illegally while idle"); | |
ff195cb6 | 256 | rcu_lock_release(&(sp)->dep_map); |
632ee200 PM |
257 | __srcu_read_unlock(sp, idx); |
258 | } | |
259 | ||
0c53dd8b PM |
260 | /** |
261 | * srcu_read_lock_raw - register a new reader for an SRCU-protected structure. | |
262 | * @sp: srcu_struct in which to register the new reader. | |
263 | * | |
264 | * Enter an SRCU read-side critical section. Similar to srcu_read_lock(), | |
265 | * but avoids the RCU-lockdep checking. This means that it is legal to | |
266 | * use srcu_read_lock_raw() in one context, for example, in an exception | |
267 | * handler, and then have the matching srcu_read_unlock_raw() in another | |
268 | * context, for example in the task that took the exception. | |
269 | * | |
270 | * However, the entire SRCU read-side critical section must reside within a | |
271 | * single task. For example, beware of using srcu_read_lock_raw() in | |
272 | * a device interrupt handler and srcu_read_unlock() in the interrupted | |
273 | * task: This will not work if interrupts are threaded. | |
274 | */ | |
275 | static inline int srcu_read_lock_raw(struct srcu_struct *sp) | |
276 | { | |
277 | unsigned long flags; | |
278 | int ret; | |
279 | ||
280 | local_irq_save(flags); | |
281 | ret = __srcu_read_lock(sp); | |
282 | local_irq_restore(flags); | |
283 | return ret; | |
284 | } | |
285 | ||
286 | /** | |
287 | * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure. | |
288 | * @sp: srcu_struct in which to unregister the old reader. | |
289 | * @idx: return value from corresponding srcu_read_lock_raw(). | |
290 | * | |
291 | * Exit an SRCU read-side critical section without lockdep-RCU checking. | |
292 | * See srcu_read_lock_raw() for more details. | |
293 | */ | |
294 | static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx) | |
295 | { | |
296 | unsigned long flags; | |
297 | ||
298 | local_irq_save(flags); | |
299 | __srcu_read_unlock(sp, idx); | |
300 | local_irq_restore(flags); | |
301 | } | |
302 | ||
eabc0694 | 303 | #endif |