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 #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. */
54 struct srcu_struct { };
55 #endif
56
57 void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
58 void (*func)(struct rcu_head *head));
59 void cleanup_srcu_struct(struct srcu_struct *ssp);
60 int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
61 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
62 void synchronize_srcu(struct srcu_struct *ssp);
63 unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp);
64 unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
65 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
66
67 #ifdef CONFIG_SRCU
68 void srcu_init(void);
69 #else /* #ifdef CONFIG_SRCU */
srcu_init(void)70 static inline void srcu_init(void) { }
71 #endif /* #else #ifdef CONFIG_SRCU */
72
73 #ifdef CONFIG_DEBUG_LOCK_ALLOC
74
75 /**
76 * srcu_read_lock_held - might we be in SRCU read-side critical section?
77 * @ssp: The srcu_struct structure to check
78 *
79 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
80 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
81 * this assumes we are in an SRCU read-side critical section unless it can
82 * prove otherwise.
83 *
84 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
85 * and while lockdep is disabled.
86 *
87 * Note that SRCU is based on its own statemachine and it doesn't
88 * relies on normal RCU, it can be called from the CPU which
89 * is in the idle loop from an RCU point of view or offline.
90 */
srcu_read_lock_held(const struct srcu_struct * ssp)91 static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
92 {
93 if (!debug_lockdep_rcu_enabled())
94 return 1;
95 return lock_is_held(&ssp->dep_map);
96 }
97
98 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
99
srcu_read_lock_held(const struct srcu_struct * ssp)100 static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
101 {
102 return 1;
103 }
104
105 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
106
107 /**
108 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
109 * @p: the pointer to fetch and protect for later dereferencing
110 * @ssp: pointer to the srcu_struct, which is used to check that we
111 * really are in an SRCU read-side critical section.
112 * @c: condition to check for update-side use
113 *
114 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
115 * critical section will result in an RCU-lockdep splat, unless @c evaluates
116 * to 1. The @c argument will normally be a logical expression containing
117 * lockdep_is_held() calls.
118 */
119 #define srcu_dereference_check(p, ssp, c) \
120 __rcu_dereference_check((p), (c) || srcu_read_lock_held(ssp), __rcu)
121
122 /**
123 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
124 * @p: the pointer to fetch and protect for later dereferencing
125 * @ssp: pointer to the srcu_struct, which is used to check that we
126 * really are in an SRCU read-side critical section.
127 *
128 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
129 * is enabled, invoking this outside of an RCU read-side critical
130 * section will result in an RCU-lockdep splat.
131 */
132 #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
133
134 /**
135 * srcu_dereference_notrace - no tracing and no lockdep calls from here
136 * @p: the pointer to fetch and protect for later dereferencing
137 * @ssp: pointer to the srcu_struct, which is used to check that we
138 * really are in an SRCU read-side critical section.
139 */
140 #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
141
142 /**
143 * srcu_read_lock - register a new reader for an SRCU-protected structure.
144 * @ssp: srcu_struct in which to register the new reader.
145 *
146 * Enter an SRCU read-side critical section. Note that SRCU read-side
147 * critical sections may be nested. However, it is illegal to
148 * call anything that waits on an SRCU grace period for the same
149 * srcu_struct, whether directly or indirectly. Please note that
150 * one way to indirectly wait on an SRCU grace period is to acquire
151 * a mutex that is held elsewhere while calling synchronize_srcu() or
152 * synchronize_srcu_expedited().
153 *
154 * Note that srcu_read_lock() and the matching srcu_read_unlock() must
155 * occur in the same context, for example, it is illegal to invoke
156 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
157 * was invoked in process context.
158 */
srcu_read_lock(struct srcu_struct * ssp)159 static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
160 {
161 int retval;
162
163 retval = __srcu_read_lock(ssp);
164 rcu_lock_acquire(&(ssp)->dep_map);
165 return retval;
166 }
167
168 /* Used by tracing, cannot be traced and cannot invoke lockdep. */
169 static inline notrace int
srcu_read_lock_notrace(struct srcu_struct * ssp)170 srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
171 {
172 int retval;
173
174 retval = __srcu_read_lock(ssp);
175 return retval;
176 }
177
178 /**
179 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
180 * @ssp: srcu_struct in which to unregister the old reader.
181 * @idx: return value from corresponding srcu_read_lock().
182 *
183 * Exit an SRCU read-side critical section.
184 */
srcu_read_unlock(struct srcu_struct * ssp,int idx)185 static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
186 __releases(ssp)
187 {
188 WARN_ON_ONCE(idx & ~0x1);
189 rcu_lock_release(&(ssp)->dep_map);
190 __srcu_read_unlock(ssp, idx);
191 }
192
193 /* Used by tracing, cannot be traced and cannot call lockdep. */
194 static inline notrace void
srcu_read_unlock_notrace(struct srcu_struct * ssp,int idx)195 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
196 {
197 __srcu_read_unlock(ssp, idx);
198 }
199
200 /**
201 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
202 *
203 * Converts the preceding srcu_read_unlock into a two-way memory barrier.
204 *
205 * Call this after srcu_read_unlock, to guarantee that all memory operations
206 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
207 * the preceding srcu_read_unlock.
208 */
smp_mb__after_srcu_read_unlock(void)209 static inline void smp_mb__after_srcu_read_unlock(void)
210 {
211 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
212 }
213
214 #endif
215