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 1585 : return __srcu_read_lock(ssp);
71 : }
72 : static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
73 : {
74 1585 : __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 : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
106 :
107 : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
108 : {
109 : return 1;
110 : }
111 :
112 : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
113 :
114 : #define SRCU_NMI_UNKNOWN 0x0
115 : #define SRCU_NMI_UNSAFE 0x1
116 : #define SRCU_NMI_SAFE 0x2
117 :
118 : #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU)
119 : void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
120 : #else
121 : static inline void srcu_check_nmi_safety(struct srcu_struct *ssp,
122 : bool nmi_safe) { }
123 : #endif
124 :
125 :
126 : /**
127 : * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
128 : * @p: the pointer to fetch and protect for later dereferencing
129 : * @ssp: pointer to the srcu_struct, which is used to check that we
130 : * really are in an SRCU read-side critical section.
131 : * @c: condition to check for update-side use
132 : *
133 : * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
134 : * critical section will result in an RCU-lockdep splat, unless @c evaluates
135 : * to 1. The @c argument will normally be a logical expression containing
136 : * lockdep_is_held() calls.
137 : */
138 : #define srcu_dereference_check(p, ssp, c) \
139 : __rcu_dereference_check((p), __UNIQUE_ID(rcu), \
140 : (c) || srcu_read_lock_held(ssp), __rcu)
141 :
142 : /**
143 : * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
144 : * @p: the pointer to fetch and protect for later dereferencing
145 : * @ssp: pointer to the srcu_struct, which is used to check that we
146 : * really are in an SRCU read-side critical section.
147 : *
148 : * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
149 : * is enabled, invoking this outside of an RCU read-side critical
150 : * section will result in an RCU-lockdep splat.
151 : */
152 : #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
153 :
154 : /**
155 : * srcu_dereference_notrace - no tracing and no lockdep calls from here
156 : * @p: the pointer to fetch and protect for later dereferencing
157 : * @ssp: pointer to the srcu_struct, which is used to check that we
158 : * really are in an SRCU read-side critical section.
159 : */
160 : #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
161 :
162 : /**
163 : * srcu_read_lock - register a new reader for an SRCU-protected structure.
164 : * @ssp: srcu_struct in which to register the new reader.
165 : *
166 : * Enter an SRCU read-side critical section. Note that SRCU read-side
167 : * critical sections may be nested. However, it is illegal to
168 : * call anything that waits on an SRCU grace period for the same
169 : * srcu_struct, whether directly or indirectly. Please note that
170 : * one way to indirectly wait on an SRCU grace period is to acquire
171 : * a mutex that is held elsewhere while calling synchronize_srcu() or
172 : * synchronize_srcu_expedited().
173 : *
174 : * Note that srcu_read_lock() and the matching srcu_read_unlock() must
175 : * occur in the same context, for example, it is illegal to invoke
176 : * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
177 : * was invoked in process context.
178 : */
179 : static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
180 : {
181 : int retval;
182 :
183 102 : srcu_check_nmi_safety(ssp, false);
184 102 : retval = __srcu_read_lock(ssp);
185 : rcu_lock_acquire(&(ssp)->dep_map);
186 : return retval;
187 : }
188 :
189 : /**
190 : * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure.
191 : * @ssp: srcu_struct in which to register the new reader.
192 : *
193 : * Enter an SRCU read-side critical section, but in an NMI-safe manner.
194 : * See srcu_read_lock() for more information.
195 : */
196 : static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp)
197 : {
198 : int retval;
199 :
200 1585 : srcu_check_nmi_safety(ssp, true);
201 1585 : retval = __srcu_read_lock_nmisafe(ssp);
202 : rcu_lock_acquire(&(ssp)->dep_map);
203 : return retval;
204 : }
205 :
206 : /* Used by tracing, cannot be traced and cannot invoke lockdep. */
207 : static inline notrace int
208 : srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
209 : {
210 : int retval;
211 :
212 : srcu_check_nmi_safety(ssp, false);
213 : retval = __srcu_read_lock(ssp);
214 : return retval;
215 : }
216 :
217 : /**
218 : * srcu_down_read - register a new reader for an SRCU-protected structure.
219 : * @ssp: srcu_struct in which to register the new reader.
220 : *
221 : * Enter a semaphore-like SRCU read-side critical section. Note that
222 : * SRCU read-side critical sections may be nested. However, it is
223 : * illegal to call anything that waits on an SRCU grace period for the
224 : * same 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(). But if you want lockdep to help you
228 : * keep this stuff straight, you should instead use srcu_read_lock().
229 : *
230 : * The semaphore-like nature of srcu_down_read() means that the matching
231 : * srcu_up_read() can be invoked from some other context, for example,
232 : * from some other task or from an irq handler. However, neither
233 : * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler.
234 : *
235 : * Calls to srcu_down_read() may be nested, similar to the manner in
236 : * which calls to down_read() may be nested.
237 : */
238 : static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)
239 : {
240 : WARN_ON_ONCE(in_nmi());
241 : srcu_check_nmi_safety(ssp, false);
242 : return __srcu_read_lock(ssp);
243 : }
244 :
245 : /**
246 : * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
247 : * @ssp: srcu_struct in which to unregister the old reader.
248 : * @idx: return value from corresponding srcu_read_lock().
249 : *
250 : * Exit an SRCU read-side critical section.
251 : */
252 102 : static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
253 : __releases(ssp)
254 : {
255 102 : WARN_ON_ONCE(idx & ~0x1);
256 102 : srcu_check_nmi_safety(ssp, false);
257 : rcu_lock_release(&(ssp)->dep_map);
258 102 : __srcu_read_unlock(ssp, idx);
259 102 : }
260 :
261 : /**
262 : * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure.
263 : * @ssp: srcu_struct in which to unregister the old reader.
264 : * @idx: return value from corresponding srcu_read_lock().
265 : *
266 : * Exit an SRCU read-side critical section, but in an NMI-safe manner.
267 : */
268 1585 : static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
269 : __releases(ssp)
270 : {
271 1585 : WARN_ON_ONCE(idx & ~0x1);
272 1585 : srcu_check_nmi_safety(ssp, true);
273 : rcu_lock_release(&(ssp)->dep_map);
274 1585 : __srcu_read_unlock_nmisafe(ssp, idx);
275 1585 : }
276 :
277 : /* Used by tracing, cannot be traced and cannot call lockdep. */
278 : static inline notrace void
279 : srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
280 : {
281 : srcu_check_nmi_safety(ssp, false);
282 : __srcu_read_unlock(ssp, idx);
283 : }
284 :
285 : /**
286 : * srcu_up_read - unregister a old reader from an SRCU-protected structure.
287 : * @ssp: srcu_struct in which to unregister the old reader.
288 : * @idx: return value from corresponding srcu_read_lock().
289 : *
290 : * Exit an SRCU read-side critical section, but not necessarily from
291 : * the same context as the maching srcu_down_read().
292 : */
293 : static inline void srcu_up_read(struct srcu_struct *ssp, int idx)
294 : __releases(ssp)
295 : {
296 : WARN_ON_ONCE(idx & ~0x1);
297 : WARN_ON_ONCE(in_nmi());
298 : srcu_check_nmi_safety(ssp, false);
299 : __srcu_read_unlock(ssp, idx);
300 : }
301 :
302 : /**
303 : * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
304 : *
305 : * Converts the preceding srcu_read_unlock into a two-way memory barrier.
306 : *
307 : * Call this after srcu_read_unlock, to guarantee that all memory operations
308 : * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
309 : * the preceding srcu_read_unlock.
310 : */
311 : static inline void smp_mb__after_srcu_read_unlock(void)
312 : {
313 : /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
314 : }
315 :
316 : #endif
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