2 * include/asm-generic/mutex-dec.h
4 * Generic implementation of the mutex fastpath, based on atomic
7 #ifndef _ASM_GENERIC_MUTEX_DEC_H
8 #define _ASM_GENERIC_MUTEX_DEC_H
11 * __mutex_fastpath_lock - try to take the lock by moving the count
13 * @count: pointer of type atomic_t
14 * @fail_fn: function to call if the original value was not 1
16 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
17 * it wasn't 1 originally. This function MUST leave the value lower than
18 * 1 even when the "1" assertion wasn't true.
21 __mutex_fastpath_lock(atomic_t
*count
, void (*fail_fn
)(atomic_t
*))
23 if (unlikely(atomic_dec_return(count
) < 0))
28 * __mutex_fastpath_lock_retval - try to take the lock by moving the count
30 * @count: pointer of type atomic_t
32 * Change the count from 1 to a value lower than 1. This function returns 0
33 * if the fastpath succeeds, or -1 otherwise.
36 __mutex_fastpath_lock_retval(atomic_t
*count
)
38 if (unlikely(atomic_dec_return(count
) < 0))
44 * __mutex_fastpath_unlock - try to promote the count from 0 to 1
45 * @count: pointer of type atomic_t
46 * @fail_fn: function to call if the original value was not 0
48 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
49 * In the failure case, this function is allowed to either set the value to
50 * 1, or to set it to a value lower than 1.
52 * If the implementation sets it to a value of lower than 1, then the
53 * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
54 * to return 0 otherwise.
57 __mutex_fastpath_unlock(atomic_t
*count
, void (*fail_fn
)(atomic_t
*))
59 if (unlikely(atomic_inc_return(count
) <= 0))
63 #define __mutex_slowpath_needs_to_unlock() 1
66 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
68 * @count: pointer of type atomic_t
69 * @fail_fn: fallback function
71 * Change the count from 1 to a value lower than 1, and return 0 (failure)
72 * if it wasn't 1 originally, or return 1 (success) otherwise. This function
73 * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
74 * Additionally, if the value was < 0 originally, this function must not leave
77 * If the architecture has no effective trylock variant, it should call the
78 * <fail_fn> spinlock-based trylock variant unconditionally.
81 __mutex_fastpath_trylock(atomic_t
*count
, int (*fail_fn
)(atomic_t
*))
83 if (likely(atomic_cmpxchg(count
, 1, 0) == 1))
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