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Diffstat (limited to 'include/asm-generic/mutex-xchg.h')
-rw-r--r-- | include/asm-generic/mutex-xchg.h | 120 |
1 files changed, 0 insertions, 120 deletions
diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h deleted file mode 100644 index 3269ec4e195f..000000000000 --- a/include/asm-generic/mutex-xchg.h +++ /dev/null @@ -1,120 +0,0 @@ -/* - * include/asm-generic/mutex-xchg.h - * - * Generic implementation of the mutex fastpath, based on xchg(). - * - * NOTE: An xchg based implementation might be less optimal than an atomic - * decrement/increment based implementation. If your architecture - * has a reasonable atomic dec/inc then you should probably use - * asm-generic/mutex-dec.h instead, or you could open-code an - * optimized version in asm/mutex.h. - */ -#ifndef _ASM_GENERIC_MUTEX_XCHG_H -#define _ASM_GENERIC_MUTEX_XCHG_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_xchg(count, 0) != 1)) - /* - * We failed to acquire the lock, so mark it contended - * to ensure that any waiting tasks are woken up by the - * unlock slow path. - */ - if (likely(atomic_xchg_acquire(count, -1) != 1)) - 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 - * - * Change the count from 1 to a value lower than 1. This function returns 0 - * if the fastpath succeeds, or -1 otherwise. - */ -static inline int -__mutex_fastpath_lock_retval(atomic_t *count) -{ - if (unlikely(atomic_xchg_acquire(count, 0) != 1)) - if (likely(atomic_xchg(count, -1) != 1)) - return -1; - return 0; -} - -/** - * __mutex_fastpath_unlock - try to promote the mutex 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 mutex from 0 to 1. if it wasn't 0, call <function> - * In the failure case, this function is allowed to either set the value to - * 1, or to set it to a value lower than one. - * If the implementation sets it to a value of lower than one, 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_xchg_release(count, 1) != 0)) - fail_fn(count); -} - -#define __mutex_slowpath_needs_to_unlock() 0 - -/** - * __mutex_fastpath_trylock - try to acquire the mutex, without waiting - * - * @count: pointer of type atomic_t - * @fail_fn: spinlock based trylock implementation - * - * 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 *)) -{ - int prev; - - if (atomic_read(count) != 1) - return 0; - - prev = atomic_xchg_acquire(count, 0); - if (unlikely(prev < 0)) { - /* - * The lock was marked contended so we must restore that - * state. If while doing so we get back a prev value of 1 - * then we just own it. - * - * [ In the rare case of the mutex going to 1, to 0, to -1 - * and then back to 0 in this few-instructions window, - * this has the potential to trigger the slowpath for the - * owner's unlock path needlessly, but that's not a problem - * in practice. ] - */ - prev = atomic_xchg_acquire(count, prev); - if (prev < 0) - prev = 0; - } - - return prev; -} - -#endif |