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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#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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
106
107static 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)
119void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
120#else
121static 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 */
179static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
180{
181 int retval;
182
183 srcu_check_nmi_safety(ssp, false);
184 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 */
196static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp)
197{
198 int retval;
199
200 srcu_check_nmi_safety(ssp, true);
201 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. */
207static inline notrace int
208srcu_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 */
238static 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 */
252static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
253 __releases(ssp)
254{
255 WARN_ON_ONCE(idx & ~0x1);
256 srcu_check_nmi_safety(ssp, false);
257 rcu_lock_release(&(ssp)->dep_map);
258 __srcu_read_unlock(ssp, idx);
259}
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 */
268static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
269 __releases(ssp)
270{
271 WARN_ON_ONCE(idx & ~0x1);
272 srcu_check_nmi_safety(ssp, true);
273 rcu_lock_release(&(ssp)->dep_map);
274 __srcu_read_unlock_nmisafe(ssp, idx);
275}
276
277/* Used by tracing, cannot be traced and cannot call lockdep. */
278static inline notrace void
279srcu_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 */
293static 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 */
311static 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