1/* 2 * include/asm-generic/mutex-dec.h 3 * 4 * Generic implementation of the mutex fastpath, based on atomic 5 * decrement/increment. 6 */ 7#ifndef _ASM_GENERIC_MUTEX_DEC_H 8#define _ASM_GENERIC_MUTEX_DEC_H 9 10/** 11 * __mutex_fastpath_lock - try to take the lock by moving the count 12 * from 1 to a 0 value 13 * @count: pointer of type atomic_t 14 * @fail_fn: function to call if the original value was not 1 15 * 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. 19 */ 20static inline void 21__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *)) 22{ 23 if (unlikely(atomic_dec_return_acquire(count) < 0)) 24 fail_fn(count); 25} 26 27/** 28 * __mutex_fastpath_lock_retval - try to take the lock by moving the count 29 * from 1 to a 0 value 30 * @count: pointer of type atomic_t 31 * 32 * Change the count from 1 to a value lower than 1. This function returns 0 33 * if the fastpath succeeds, or -1 otherwise. 34 */ 35static inline int 36__mutex_fastpath_lock_retval(atomic_t *count) 37{ 38 if (unlikely(atomic_dec_return_acquire(count) < 0)) 39 return -1; 40 return 0; 41} 42 43/** 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 47 * 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. 51 * 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. 55 */ 56static inline void 57__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *)) 58{ 59 if (unlikely(atomic_inc_return_release(count) <= 0)) 60 fail_fn(count); 61} 62 63#define __mutex_slowpath_needs_to_unlock() 1 64 65/** 66 * __mutex_fastpath_trylock - try to acquire the mutex, without waiting 67 * 68 * @count: pointer of type atomic_t 69 * @fail_fn: fallback function 70 * 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 75 * it to 0 on failure. 76 * 77 * If the architecture has no effective trylock variant, it should call the 78 * <fail_fn> spinlock-based trylock variant unconditionally. 79 */ 80static inline int 81__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) 82{ 83 if (likely(atomic_cmpxchg_acquire(count, 1, 0) == 1)) 84 return 1; 85 return 0; 86} 87 88#endif 89