1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_TWO_STATE_LOCK_H
3 #define _BCACHEFS_TWO_STATE_LOCK_H
4
5 #include <linux/atomic.h>
6 #include <linux/sched.h>
7 #include <linux/wait.h>
8
9 #include "util.h"
10
11 /*
12 * Two-state lock - can be taken for add or block - both states are shared,
13 * like read side of rwsem, but conflict with other state:
14 */
15 typedef struct {
16 atomic_long_t v;
17 wait_queue_head_t wait;
18 } two_state_lock_t;
19
20 static inline void two_state_lock_init(two_state_lock_t *lock)
21 {
22 atomic_long_set(&lock->v, 0);
23 init_waitqueue_head(&lock->wait);
24 }
25
26 static inline void bch2_two_state_unlock(two_state_lock_t *lock, int s)
27 {
28 long i = s ? 1 : -1;
29
30 EBUG_ON(atomic_long_read(&lock->v) == 0);
31
32 if (atomic_long_sub_return_release(i, &lock->v) == 0)
33 wake_up_all(&lock->wait);
34 }
35
36 static inline bool bch2_two_state_trylock(two_state_lock_t *lock, int s)
37 {
38 long i = s ? 1 : -1;
39 long old;
40
41 old = atomic_long_read(&lock->v);
42 do {
43 if (i > 0 ? old < 0 : old > 0)
44 return false;
45 } while (!atomic_long_try_cmpxchg_acquire(&lock->v, &old, old + i));
46
47 return true;
48 }
49
50 void __bch2_two_state_lock(two_state_lock_t *, int);
51
52 static inline void bch2_two_state_lock(two_state_lock_t *lock, int s)
53 {
54 if (!bch2_two_state_trylock(lock, s))
55 __bch2_two_state_lock(lock, s);
56 }
57
58 #endif /* _BCACHEFS_TWO_STATE_LOCK_H */
59
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