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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
24struct srcu_struct;
25
26#ifdef CONFIG_DEBUG_LOCK_ALLOC
27
28int __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
41int 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#elif defined(CONFIG_SRCU)
51#error "Unknown SRCU implementation specified to kernel configuration"
52#else
53/* Dummy definition for things like notifiers. Actual use gets link error. */
54struct srcu_struct { };
55#endif
56
57void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
58 void (*func)(struct rcu_head *head));
59void cleanup_srcu_struct(struct srcu_struct *ssp);
60int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
61void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
62void synchronize_srcu(struct srcu_struct *ssp);
63
64#ifdef CONFIG_DEBUG_LOCK_ALLOC
65
66/**
67 * srcu_read_lock_held - might we be in SRCU read-side critical section?
68 * @ssp: The srcu_struct structure to check
69 *
70 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
71 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
72 * this assumes we are in an SRCU read-side critical section unless it can
73 * prove otherwise.
74 *
75 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
76 * and while lockdep is disabled.
77 *
78 * Note that SRCU is based on its own statemachine and it doesn't
79 * relies on normal RCU, it can be called from the CPU which
80 * is in the idle loop from an RCU point of view or offline.
81 */
82static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
83{
84 if (!debug_lockdep_rcu_enabled())
85 return 1;
86 return lock_is_held(&ssp->dep_map);
87}
88
89#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
90
91static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
92{
93 return 1;
94}
95
96#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
97
98/**
99 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
100 * @p: the pointer to fetch and protect for later dereferencing
101 * @ssp: pointer to the srcu_struct, which is used to check that we
102 * really are in an SRCU read-side critical section.
103 * @c: condition to check for update-side use
104 *
105 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
106 * critical section will result in an RCU-lockdep splat, unless @c evaluates
107 * to 1. The @c argument will normally be a logical expression containing
108 * lockdep_is_held() calls.
109 */
110#define srcu_dereference_check(p, ssp, c) \
111 __rcu_dereference_check((p), (c) || srcu_read_lock_held(ssp), __rcu)
112
113/**
114 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
115 * @p: the pointer to fetch and protect for later dereferencing
116 * @ssp: pointer to the srcu_struct, which is used to check that we
117 * really are in an SRCU read-side critical section.
118 *
119 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
120 * is enabled, invoking this outside of an RCU read-side critical
121 * section will result in an RCU-lockdep splat.
122 */
123#define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
124
125/**
126 * srcu_dereference_notrace - no tracing and no lockdep calls from here
127 * @p: the pointer to fetch and protect for later dereferencing
128 * @ssp: pointer to the srcu_struct, which is used to check that we
129 * really are in an SRCU read-side critical section.
130 */
131#define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
132
133/**
134 * srcu_read_lock - register a new reader for an SRCU-protected structure.
135 * @ssp: srcu_struct in which to register the new reader.
136 *
137 * Enter an SRCU read-side critical section. Note that SRCU read-side
138 * critical sections may be nested. However, it is illegal to
139 * call anything that waits on an SRCU grace period for the same
140 * srcu_struct, whether directly or indirectly. Please note that
141 * one way to indirectly wait on an SRCU grace period is to acquire
142 * a mutex that is held elsewhere while calling synchronize_srcu() or
143 * synchronize_srcu_expedited().
144 *
145 * Note that srcu_read_lock() and the matching srcu_read_unlock() must
146 * occur in the same context, for example, it is illegal to invoke
147 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
148 * was invoked in process context.
149 */
150static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
151{
152 int retval;
153
154 retval = __srcu_read_lock(ssp);
155 rcu_lock_acquire(&(ssp)->dep_map);
156 return retval;
157}
158
159/* Used by tracing, cannot be traced and cannot invoke lockdep. */
160static inline notrace int
161srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
162{
163 int retval;
164
165 retval = __srcu_read_lock(ssp);
166 return retval;
167}
168
169/**
170 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
171 * @ssp: srcu_struct in which to unregister the old reader.
172 * @idx: return value from corresponding srcu_read_lock().
173 *
174 * Exit an SRCU read-side critical section.
175 */
176static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
177 __releases(ssp)
178{
179 WARN_ON_ONCE(idx & ~0x1);
180 rcu_lock_release(&(ssp)->dep_map);
181 __srcu_read_unlock(ssp, idx);
182}
183
184/* Used by tracing, cannot be traced and cannot call lockdep. */
185static inline notrace void
186srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
187{
188 __srcu_read_unlock(ssp, idx);
189}
190
191/**
192 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
193 *
194 * Converts the preceding srcu_read_unlock into a two-way memory barrier.
195 *
196 * Call this after srcu_read_unlock, to guarantee that all memory operations
197 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
198 * the preceding srcu_read_unlock.
199 */
200static inline void smp_mb__after_srcu_read_unlock(void)
201{
202 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
203}
204
205#endif
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
24struct srcu_struct;
25
26#ifdef CONFIG_DEBUG_LOCK_ALLOC
27
28int __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
41int 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
54void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
55 void (*func)(struct rcu_head *head));
56void cleanup_srcu_struct(struct srcu_struct *ssp);
57int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
58void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
59void synchronize_srcu(struct srcu_struct *ssp);
60unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp);
61unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
62bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
63
64#ifdef CONFIG_NEED_SRCU_NMI_SAFE
65int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp);
66void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp);
67#else
68static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
69{
70 return __srcu_read_lock(ssp);
71}
72static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
73{
74 __srcu_read_unlock(ssp, idx);
75}
76#endif /* CONFIG_NEED_SRCU_NMI_SAFE */
77
78void 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 */
98static 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() */
114static inline void srcu_lock_acquire(struct lockdep_map *map)
115{
116 lock_map_acquire_read(map);
117}
118
119/* Annotates a srcu_read_lock() */
120static inline void srcu_lock_release(struct lockdep_map *map)
121{
122 lock_map_release(map);
123}
124
125/* Annotates a synchronize_srcu() */
126static 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
133static 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)
149void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
150#else
151static 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 */
209static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
210{
211 int retval;
212
213 srcu_check_nmi_safety(ssp, false);
214 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 */
226static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp)
227{
228 int retval;
229
230 srcu_check_nmi_safety(ssp, true);
231 retval = __srcu_read_lock_nmisafe(ssp);
232 rcu_try_lock_acquire(&ssp->dep_map);
233 return retval;
234}
235
236/* Used by tracing, cannot be traced and cannot invoke lockdep. */
237static inline notrace int
238srcu_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 */
268static 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 */
282static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
283 __releases(ssp)
284{
285 WARN_ON_ONCE(idx & ~0x1);
286 srcu_check_nmi_safety(ssp, false);
287 srcu_lock_release(&ssp->dep_map);
288 __srcu_read_unlock(ssp, idx);
289}
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 */
298static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
299 __releases(ssp)
300{
301 WARN_ON_ONCE(idx & ~0x1);
302 srcu_check_nmi_safety(ssp, true);
303 rcu_lock_release(&ssp->dep_map);
304 __srcu_read_unlock_nmisafe(ssp, idx);
305}
306
307/* Used by tracing, cannot be traced and cannot call lockdep. */
308static inline notrace void
309srcu_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 */
323static 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 */
341static 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
346DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct,
347 _T->idx = srcu_read_lock(_T->lock),
348 srcu_read_unlock(_T->lock, _T->idx),
349 int idx)
350
351#endif