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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
62ac665f MP |
2 | #ifndef _LINUX_PERCPU_RWSEM_H |
3 | #define _LINUX_PERCPU_RWSEM_H | |
4 | ||
9390ef0c | 5 | #include <linux/atomic.h> |
62ac665f | 6 | #include <linux/percpu.h> |
52b94129 | 7 | #include <linux/rcuwait.h> |
7f26482a | 8 | #include <linux/wait.h> |
001dac62 | 9 | #include <linux/rcu_sync.h> |
8ebe3473 | 10 | #include <linux/lockdep.h> |
62ac665f MP |
11 | |
12 | struct percpu_rw_semaphore { | |
001dac62 | 13 | struct rcu_sync rss; |
80127a39 | 14 | unsigned int __percpu *read_count; |
7f26482a PZ |
15 | struct rcuwait writer; |
16 | wait_queue_head_t waiters; | |
17 | atomic_t block; | |
1751060e PZ |
18 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
19 | struct lockdep_map dep_map; | |
20 | #endif | |
62ac665f MP |
21 | }; |
22 | ||
1751060e PZ |
23 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
24 | #define __PERCPU_RWSEM_DEP_MAP_INIT(lockname) .dep_map = { .name = #lockname }, | |
25 | #else | |
26 | #define __PERCPU_RWSEM_DEP_MAP_INIT(lockname) | |
27 | #endif | |
28 | ||
3f2947b7 | 29 | #define __DEFINE_PERCPU_RWSEM(name, is_static) \ |
11d9684c | 30 | static DEFINE_PER_CPU(unsigned int, __percpu_rwsem_rc_##name); \ |
3f2947b7 | 31 | is_static struct percpu_rw_semaphore name = { \ |
95bf33b5 | 32 | .rss = __RCU_SYNC_INITIALIZER(name.rss), \ |
11d9684c | 33 | .read_count = &__percpu_rwsem_rc_##name, \ |
52b94129 | 34 | .writer = __RCUWAIT_INITIALIZER(name.writer), \ |
7f26482a PZ |
35 | .waiters = __WAIT_QUEUE_HEAD_INITIALIZER(name.waiters), \ |
36 | .block = ATOMIC_INIT(0), \ | |
1751060e | 37 | __PERCPU_RWSEM_DEP_MAP_INIT(name) \ |
11d9684c | 38 | } |
1751060e | 39 | |
3f2947b7 ON |
40 | #define DEFINE_PERCPU_RWSEM(name) \ |
41 | __DEFINE_PERCPU_RWSEM(name, /* not static */) | |
42 | #define DEFINE_STATIC_PERCPU_RWSEM(name) \ | |
43 | __DEFINE_PERCPU_RWSEM(name, static) | |
11d9684c | 44 | |
206c98ff | 45 | extern bool __percpu_down_read(struct percpu_rw_semaphore *, bool); |
80127a39 | 46 | |
02e525b2 | 47 | static inline void percpu_down_read(struct percpu_rw_semaphore *sem) |
80127a39 PZ |
48 | { |
49 | might_sleep(); | |
50 | ||
1751060e | 51 | rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_); |
80127a39 PZ |
52 | |
53 | preempt_disable(); | |
54 | /* | |
55 | * We are in an RCU-sched read-side critical section, so the writer | |
56 | * cannot both change sem->state from readers_fast and start checking | |
57 | * counters while we are here. So if we see !sem->state, we know that | |
58 | * the writer won't be checking until we're past the preempt_enable() | |
e3e74054 | 59 | * and that once the synchronize_rcu() is done, the writer will see |
80127a39 PZ |
60 | * anything we did within this RCU-sched read-size critical section. |
61 | */ | |
71365d40 | 62 | if (likely(rcu_sync_is_idle(&sem->rss))) |
e6b1a44e | 63 | this_cpu_inc(*sem->read_count); |
71365d40 | 64 | else |
80127a39 | 65 | __percpu_down_read(sem, false); /* Unconditional memory barrier */ |
80127a39 | 66 | /* |
02e525b2 | 67 | * The preempt_enable() prevents the compiler from |
80127a39 PZ |
68 | * bleeding the critical section out. |
69 | */ | |
259d69b7 PZ |
70 | preempt_enable(); |
71 | } | |
72 | ||
206c98ff | 73 | static inline bool percpu_down_read_trylock(struct percpu_rw_semaphore *sem) |
80127a39 | 74 | { |
206c98ff | 75 | bool ret = true; |
80127a39 PZ |
76 | |
77 | preempt_disable(); | |
78 | /* | |
79 | * Same as in percpu_down_read(). | |
80 | */ | |
71365d40 | 81 | if (likely(rcu_sync_is_idle(&sem->rss))) |
e6b1a44e | 82 | this_cpu_inc(*sem->read_count); |
71365d40 | 83 | else |
80127a39 PZ |
84 | ret = __percpu_down_read(sem, true); /* Unconditional memory barrier */ |
85 | preempt_enable(); | |
86 | /* | |
87 | * The barrier() from preempt_enable() prevents the compiler from | |
88 | * bleeding the critical section out. | |
89 | */ | |
90 | ||
91 | if (ret) | |
1751060e | 92 | rwsem_acquire_read(&sem->dep_map, 0, 1, _RET_IP_); |
80127a39 PZ |
93 | |
94 | return ret; | |
95 | } | |
96 | ||
02e525b2 | 97 | static inline void percpu_up_read(struct percpu_rw_semaphore *sem) |
80127a39 | 98 | { |
1751060e PZ |
99 | rwsem_release(&sem->dep_map, _RET_IP_); |
100 | ||
02e525b2 | 101 | preempt_disable(); |
80127a39 PZ |
102 | /* |
103 | * Same as in percpu_down_read(). | |
104 | */ | |
ac8dec42 | 105 | if (likely(rcu_sync_is_idle(&sem->rss))) { |
e6b1a44e | 106 | this_cpu_dec(*sem->read_count); |
ac8dec42 DB |
107 | } else { |
108 | /* | |
109 | * slowpath; reader will only ever wake a single blocked | |
110 | * writer. | |
111 | */ | |
112 | smp_mb(); /* B matches C */ | |
113 | /* | |
114 | * In other words, if they see our decrement (presumably to | |
115 | * aggregate zero, as that is the only time it matters) they | |
116 | * will also see our critical section. | |
117 | */ | |
e6b1a44e | 118 | this_cpu_dec(*sem->read_count); |
ac8dec42 DB |
119 | rcuwait_wake_up(&sem->writer); |
120 | } | |
80127a39 | 121 | preempt_enable(); |
80127a39 | 122 | } |
5c1eabe6 | 123 | |
01fe8a3f | 124 | extern bool percpu_is_read_locked(struct percpu_rw_semaphore *); |
a1fd3e24 ON |
125 | extern void percpu_down_write(struct percpu_rw_semaphore *); |
126 | extern void percpu_up_write(struct percpu_rw_semaphore *); | |
62ac665f | 127 | |
01fe8a3f ME |
128 | static inline bool percpu_is_write_locked(struct percpu_rw_semaphore *sem) |
129 | { | |
130 | return atomic_read(&sem->block); | |
131 | } | |
132 | ||
8ebe3473 ON |
133 | extern int __percpu_init_rwsem(struct percpu_rw_semaphore *, |
134 | const char *, struct lock_class_key *); | |
80127a39 | 135 | |
a1fd3e24 | 136 | extern void percpu_free_rwsem(struct percpu_rw_semaphore *); |
62ac665f | 137 | |
80127a39 | 138 | #define percpu_init_rwsem(sem) \ |
8ebe3473 ON |
139 | ({ \ |
140 | static struct lock_class_key rwsem_key; \ | |
80127a39 | 141 | __percpu_init_rwsem(sem, #sem, &rwsem_key); \ |
8ebe3473 ON |
142 | }) |
143 | ||
1751060e PZ |
144 | #define percpu_rwsem_is_held(sem) lockdep_is_held(sem) |
145 | #define percpu_rwsem_assert_held(sem) lockdep_assert_held(sem) | |
11d9684c | 146 | |
55cc1565 ON |
147 | static inline void percpu_rwsem_release(struct percpu_rw_semaphore *sem, |
148 | bool read, unsigned long ip) | |
149 | { | |
1751060e | 150 | lock_release(&sem->dep_map, ip); |
55cc1565 ON |
151 | } |
152 | ||
153 | static inline void percpu_rwsem_acquire(struct percpu_rw_semaphore *sem, | |
154 | bool read, unsigned long ip) | |
155 | { | |
1751060e | 156 | lock_acquire(&sem->dep_map, 0, 1, read, 1, NULL, ip); |
55cc1565 ON |
157 | } |
158 | ||
62ac665f | 159 | #endif |