/* * include/asm-generic/mutex-dec.h * * Generic implementation of the mutex fastpath, based on atomic * decrement/increment. */#ifndef _ASM_GENERIC_MUTEX_DEC_H#define _ASM_GENERIC_MUTEX_DEC_H /** *  __mutex_fastpath_lock - try to take the lock by moving the count *                          from 1 to a 0 value *  @count: pointer of type atomic_t *  @fail_fn: function to call if the original value was not 1 * * Change the count from 1 to a value lower than 1, and call <fail_fn> if * it wasn't 1 originally. This function MUST leave the value lower than * 1 even when the "1" assertion wasn't true. */static inline void__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *)){	if (unlikely(atomic_dec_return(count) < 0))		fail_fn(count);} /** *  __mutex_fastpath_lock_retval - try to take the lock by moving the count *                                 from 1 to a 0 value *  @count: pointer of type atomic_t *  @fail_fn: function to call if the original value was not 1 * * Change the count from 1 to a value lower than 1, and call <fail_fn> if * it wasn't 1 originally. This function returns 0 if the fastpath succeeds, * or anything the slow path function returns. */static inline int__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *)){	if (unlikely(atomic_dec_return(count) < 0))		return fail_fn(count);	return 0;} /** *  __mutex_fastpath_unlock - try to promote the count from 0 to 1 *  @count: pointer of type atomic_t *  @fail_fn: function to call if the original value was not 0 * * Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>. * In the failure case, this function is allowed to either set the value to * 1, or to set it to a value lower than 1. * * If the implementation sets it to a value of lower than 1, then the * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs * to return 0 otherwise. */static inline void__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *)){	if (unlikely(atomic_inc_return(count) <= 0))		fail_fn(count);} #define __mutex_slowpath_needs_to_unlock()		1 /** * __mutex_fastpath_trylock - try to acquire the mutex, without waiting * *  @count: pointer of type atomic_t *  @fail_fn: fallback function * * Change the count from 1 to a value lower than 1, and return 0 (failure) * if it wasn't 1 originally, or return 1 (success) otherwise. This function * MUST leave the value lower than 1 even when the "1" assertion wasn't true. * Additionally, if the value was < 0 originally, this function must not leave * it to 0 on failure. * * If the architecture has no effective trylock variant, it should call the * <fail_fn> spinlock-based trylock variant unconditionally. */static inline int__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)){	if (likely(atomic_cmpxchg(count, 1, 0) == 1))		return 1;	return 0;} #endif