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 two_state_lock_init(two_state_lock_t * lock)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 bch2_two_state_unlock(two_state_lock_t * lock,int s)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 bch2_two_state_trylock(two_state_lock_t * lock,int s)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 bch2_two_state_lock(two_state_lock_t * lock,int s)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