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git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - include/asm-generic/mutex-dec.h
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
31 * @fail_fn: function to call if the original value was not 1
33 * Change the count from 1 to a value lower than 1, and call <fail_fn> if
34 * it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
35 * or anything the slow path function returns.
38 __mutex_fastpath_lock_retval(atomic_t
*count
, int (*fail_fn
)(atomic_t
*))
40 if (unlikely(atomic_dec_return(count
) < 0))
41 return fail_fn(count
);
46 * __mutex_fastpath_unlock - try to promote the count from 0 to 1
47 * @count: pointer of type atomic_t
48 * @fail_fn: function to call if the original value was not 0
50 * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
51 * In the failure case, this function is allowed to either set the value to
52 * 1, or to set it to a value lower than 1.
54 * If the implementation sets it to a value of lower than 1, then the
55 * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs
56 * to return 0 otherwise.
59 __mutex_fastpath_unlock(atomic_t
*count
, void (*fail_fn
)(atomic_t
*))
61 if (unlikely(atomic_inc_return(count
) <= 0))
65 #define __mutex_slowpath_needs_to_unlock() 1
68 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting
70 * @count: pointer of type atomic_t
71 * @fail_fn: fallback function
73 * Change the count from 1 to a value lower than 1, and return 0 (failure)
74 * if it wasn't 1 originally, or return 1 (success) otherwise. This function
75 * MUST leave the value lower than 1 even when the "1" assertion wasn't true.
76 * Additionally, if the value was < 0 originally, this function must not leave
79 * If the architecture has no effective trylock variant, it should call the
80 * <fail_fn> spinlock-based trylock variant unconditionally.
83 __mutex_fastpath_trylock(atomic_t
*count
, int (*fail_fn
)(atomic_t
*))
85 if (likely(atomic_cmpxchg(count
, 1, 0) == 1))