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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _BCACHEFS_TWO_STATE_LOCK_H
#define _BCACHEFS_TWO_STATE_LOCK_H
#include <linux/atomic.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include "util.h"
/*
* Two-state lock - can be taken for add or block - both states are shared,
* like read side of rwsem, but conflict with other state:
*/
typedef struct {
atomic_long_t v;
wait_queue_head_t wait;
} two_state_lock_t;
static inline void two_state_lock_init(two_state_lock_t *lock)
{
atomic_long_set(&lock->v, 0);
init_waitqueue_head(&lock->wait);
}
static inline void bch2_two_state_unlock(two_state_lock_t *lock, int s)
{
long i = s ? 1 : -1;
EBUG_ON(atomic_long_read(&lock->v) == 0);
if (atomic_long_sub_return_release(i, &lock->v) == 0)
wake_up_all(&lock->wait);
}
static inline bool bch2_two_state_trylock(two_state_lock_t *lock, int s)
{
long i = s ? 1 : -1;
long v = atomic_long_read(&lock->v), old;
do {
old = v;
if (i > 0 ? v < 0 : v > 0)
return false;
} while ((v = atomic_long_cmpxchg_acquire(&lock->v,
old, old + i)) != old);
return true;
}
void __bch2_two_state_lock(two_state_lock_t *, int);
static inline void bch2_two_state_lock(two_state_lock_t *lock, int s)
{
if (!bch2_two_state_trylock(lock, s))
__bch2_two_state_lock(lock, s);
}
#endif /* _BCACHEFS_TWO_STATE_LOCK_H */
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