Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0+ */
2 : /*
3 : * Sleepable Read-Copy Update mechanism for mutual exclusion
4 : *
5 : * Copyright (C) IBM Corporation, 2006
6 : * Copyright (C) Fujitsu, 2012
7 : *
8 : * Author: Paul McKenney <paulmck@linux.ibm.com>
9 : * Lai Jiangshan <laijs@cn.fujitsu.com>
10 : *
11 : * For detailed explanation of Read-Copy Update mechanism see -
12 : * Documentation/RCU/ *.txt
13 : *
14 : */
15 :
16 : #ifndef _LINUX_SRCU_H
17 : #define _LINUX_SRCU_H
18 :
19 : #include <linux/mutex.h>
20 : #include <linux/rcupdate.h>
21 : #include <linux/workqueue.h>
22 : #include <linux/rcu_segcblist.h>
23 :
24 : struct srcu_struct;
25 :
26 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
27 :
28 : int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
29 : struct lock_class_key *key);
30 :
31 : #define init_srcu_struct(ssp) \
32 : ({ \
33 : static struct lock_class_key __srcu_key; \
34 : \
35 : __init_srcu_struct((ssp), #ssp, &__srcu_key); \
36 : })
37 :
38 : #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
39 : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
40 :
41 : int init_srcu_struct(struct srcu_struct *ssp);
42 :
43 : #define __SRCU_DEP_MAP_INIT(srcu_name)
44 : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
45 :
46 : #ifdef CONFIG_TINY_SRCU
47 : #include <linux/srcutiny.h>
48 : #elif defined(CONFIG_TREE_SRCU)
49 : #include <linux/srcutree.h>
50 : #else
51 : #error "Unknown SRCU implementation specified to kernel configuration"
52 : #endif
53 :
54 : void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
55 : void (*func)(struct rcu_head *head));
56 : void cleanup_srcu_struct(struct srcu_struct *ssp);
57 : int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
58 : void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
59 : void synchronize_srcu(struct srcu_struct *ssp);
60 : unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp);
61 : unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
62 : bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
63 :
64 : #ifdef CONFIG_NEED_SRCU_NMI_SAFE
65 : int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp);
66 : void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp);
67 : #else
68 : static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
69 : {
70 1865 : return __srcu_read_lock(ssp);
71 : }
72 : static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
73 : {
74 1865 : __srcu_read_unlock(ssp, idx);
75 : }
76 : #endif /* CONFIG_NEED_SRCU_NMI_SAFE */
77 :
78 : void srcu_init(void);
79 :
80 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
81 :
82 : /**
83 : * srcu_read_lock_held - might we be in SRCU read-side critical section?
84 : * @ssp: The srcu_struct structure to check
85 : *
86 : * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
87 : * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
88 : * this assumes we are in an SRCU read-side critical section unless it can
89 : * prove otherwise.
90 : *
91 : * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
92 : * and while lockdep is disabled.
93 : *
94 : * Note that SRCU is based on its own statemachine and it doesn't
95 : * relies on normal RCU, it can be called from the CPU which
96 : * is in the idle loop from an RCU point of view or offline.
97 : */
98 : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
99 : {
100 : if (!debug_lockdep_rcu_enabled())
101 : return 1;
102 : return lock_is_held(&ssp->dep_map);
103 : }
104 :
105 : /*
106 : * Annotations provide deadlock detection for SRCU.
107 : *
108 : * Similar to other lockdep annotations, except there is an additional
109 : * srcu_lock_sync(), which is basically an empty *write*-side critical section,
110 : * see lock_sync() for more information.
111 : */
112 :
113 : /* Annotates a srcu_read_lock() */
114 : static inline void srcu_lock_acquire(struct lockdep_map *map)
115 : {
116 : lock_map_acquire_read(map);
117 : }
118 :
119 : /* Annotates a srcu_read_lock() */
120 : static inline void srcu_lock_release(struct lockdep_map *map)
121 : {
122 : lock_map_release(map);
123 : }
124 :
125 : /* Annotates a synchronize_srcu() */
126 : static inline void srcu_lock_sync(struct lockdep_map *map)
127 : {
128 : lock_map_sync(map);
129 : }
130 :
131 : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
132 :
133 : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
134 : {
135 : return 1;
136 : }
137 :
138 : #define srcu_lock_acquire(m) do { } while (0)
139 : #define srcu_lock_release(m) do { } while (0)
140 : #define srcu_lock_sync(m) do { } while (0)
141 :
142 : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
143 :
144 : #define SRCU_NMI_UNKNOWN 0x0
145 : #define SRCU_NMI_UNSAFE 0x1
146 : #define SRCU_NMI_SAFE 0x2
147 :
148 : #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU)
149 : void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
150 : #else
151 : static inline void srcu_check_nmi_safety(struct srcu_struct *ssp,
152 : bool nmi_safe) { }
153 : #endif
154 :
155 :
156 : /**
157 : * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
158 : * @p: the pointer to fetch and protect for later dereferencing
159 : * @ssp: pointer to the srcu_struct, which is used to check that we
160 : * really are in an SRCU read-side critical section.
161 : * @c: condition to check for update-side use
162 : *
163 : * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
164 : * critical section will result in an RCU-lockdep splat, unless @c evaluates
165 : * to 1. The @c argument will normally be a logical expression containing
166 : * lockdep_is_held() calls.
167 : */
168 : #define srcu_dereference_check(p, ssp, c) \
169 : __rcu_dereference_check((p), __UNIQUE_ID(rcu), \
170 : (c) || srcu_read_lock_held(ssp), __rcu)
171 :
172 : /**
173 : * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
174 : * @p: the pointer to fetch and protect for later dereferencing
175 : * @ssp: pointer to the srcu_struct, which is used to check that we
176 : * really are in an SRCU read-side critical section.
177 : *
178 : * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
179 : * is enabled, invoking this outside of an RCU read-side critical
180 : * section will result in an RCU-lockdep splat.
181 : */
182 : #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
183 :
184 : /**
185 : * srcu_dereference_notrace - no tracing and no lockdep calls from here
186 : * @p: the pointer to fetch and protect for later dereferencing
187 : * @ssp: pointer to the srcu_struct, which is used to check that we
188 : * really are in an SRCU read-side critical section.
189 : */
190 : #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
191 :
192 : /**
193 : * srcu_read_lock - register a new reader for an SRCU-protected structure.
194 : * @ssp: srcu_struct in which to register the new reader.
195 : *
196 : * Enter an SRCU read-side critical section. Note that SRCU read-side
197 : * critical sections may be nested. However, it is illegal to
198 : * call anything that waits on an SRCU grace period for the same
199 : * srcu_struct, whether directly or indirectly. Please note that
200 : * one way to indirectly wait on an SRCU grace period is to acquire
201 : * a mutex that is held elsewhere while calling synchronize_srcu() or
202 : * synchronize_srcu_expedited().
203 : *
204 : * Note that srcu_read_lock() and the matching srcu_read_unlock() must
205 : * occur in the same context, for example, it is illegal to invoke
206 : * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
207 : * was invoked in process context.
208 : */
209 : static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
210 : {
211 : int retval;
212 :
213 132 : srcu_check_nmi_safety(ssp, false);
214 132 : retval = __srcu_read_lock(ssp);
215 : srcu_lock_acquire(&(ssp)->dep_map);
216 : return retval;
217 : }
218 :
219 : /**
220 : * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure.
221 : * @ssp: srcu_struct in which to register the new reader.
222 : *
223 : * Enter an SRCU read-side critical section, but in an NMI-safe manner.
224 : * See srcu_read_lock() for more information.
225 : */
226 : static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp)
227 : {
228 : int retval;
229 :
230 1865 : srcu_check_nmi_safety(ssp, true);
231 1865 : retval = __srcu_read_lock_nmisafe(ssp);
232 : rcu_lock_acquire(&(ssp)->dep_map);
233 : return retval;
234 : }
235 :
236 : /* Used by tracing, cannot be traced and cannot invoke lockdep. */
237 : static inline notrace int
238 : srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
239 : {
240 : int retval;
241 :
242 : srcu_check_nmi_safety(ssp, false);
243 : retval = __srcu_read_lock(ssp);
244 : return retval;
245 : }
246 :
247 : /**
248 : * srcu_down_read - register a new reader for an SRCU-protected structure.
249 : * @ssp: srcu_struct in which to register the new reader.
250 : *
251 : * Enter a semaphore-like SRCU read-side critical section. Note that
252 : * SRCU read-side critical sections may be nested. However, it is
253 : * illegal to call anything that waits on an SRCU grace period for the
254 : * same srcu_struct, whether directly or indirectly. Please note that
255 : * one way to indirectly wait on an SRCU grace period is to acquire
256 : * a mutex that is held elsewhere while calling synchronize_srcu() or
257 : * synchronize_srcu_expedited(). But if you want lockdep to help you
258 : * keep this stuff straight, you should instead use srcu_read_lock().
259 : *
260 : * The semaphore-like nature of srcu_down_read() means that the matching
261 : * srcu_up_read() can be invoked from some other context, for example,
262 : * from some other task or from an irq handler. However, neither
263 : * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler.
264 : *
265 : * Calls to srcu_down_read() may be nested, similar to the manner in
266 : * which calls to down_read() may be nested.
267 : */
268 : static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)
269 : {
270 : WARN_ON_ONCE(in_nmi());
271 : srcu_check_nmi_safety(ssp, false);
272 : return __srcu_read_lock(ssp);
273 : }
274 :
275 : /**
276 : * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
277 : * @ssp: srcu_struct in which to unregister the old reader.
278 : * @idx: return value from corresponding srcu_read_lock().
279 : *
280 : * Exit an SRCU read-side critical section.
281 : */
282 132 : static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
283 : __releases(ssp)
284 : {
285 132 : WARN_ON_ONCE(idx & ~0x1);
286 132 : srcu_check_nmi_safety(ssp, false);
287 : srcu_lock_release(&(ssp)->dep_map);
288 132 : __srcu_read_unlock(ssp, idx);
289 132 : }
290 :
291 : /**
292 : * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure.
293 : * @ssp: srcu_struct in which to unregister the old reader.
294 : * @idx: return value from corresponding srcu_read_lock().
295 : *
296 : * Exit an SRCU read-side critical section, but in an NMI-safe manner.
297 : */
298 1865 : static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
299 : __releases(ssp)
300 : {
301 1865 : WARN_ON_ONCE(idx & ~0x1);
302 1865 : srcu_check_nmi_safety(ssp, true);
303 : rcu_lock_release(&(ssp)->dep_map);
304 1865 : __srcu_read_unlock_nmisafe(ssp, idx);
305 1865 : }
306 :
307 : /* Used by tracing, cannot be traced and cannot call lockdep. */
308 : static inline notrace void
309 : srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
310 : {
311 : srcu_check_nmi_safety(ssp, false);
312 : __srcu_read_unlock(ssp, idx);
313 : }
314 :
315 : /**
316 : * srcu_up_read - unregister a old reader from an SRCU-protected structure.
317 : * @ssp: srcu_struct in which to unregister the old reader.
318 : * @idx: return value from corresponding srcu_read_lock().
319 : *
320 : * Exit an SRCU read-side critical section, but not necessarily from
321 : * the same context as the maching srcu_down_read().
322 : */
323 : static inline void srcu_up_read(struct srcu_struct *ssp, int idx)
324 : __releases(ssp)
325 : {
326 : WARN_ON_ONCE(idx & ~0x1);
327 : WARN_ON_ONCE(in_nmi());
328 : srcu_check_nmi_safety(ssp, false);
329 : __srcu_read_unlock(ssp, idx);
330 : }
331 :
332 : /**
333 : * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
334 : *
335 : * Converts the preceding srcu_read_unlock into a two-way memory barrier.
336 : *
337 : * Call this after srcu_read_unlock, to guarantee that all memory operations
338 : * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
339 : * the preceding srcu_read_unlock.
340 : */
341 : static inline void smp_mb__after_srcu_read_unlock(void)
342 : {
343 : /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
344 : }
345 :
346 : #endif
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