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