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