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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 | 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 | __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 |
255 |
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