Messages in this thread Patch in this message | | | Date | Fri, 23 Dec 2005 00:04:51 +0100 | From | Ingo Molnar <> | Subject | [patch 2/8] mutex subsystem, add asm-generic/mutex-[dec|xchg].h implementations |
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add the two generic mutex fastpath implementations.
Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
----
include/asm-generic/mutex-dec.h | 66 ++++++++++++++++++++++++++++++++++++ include/asm-generic/mutex-xchg.h | 71 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 137 insertions(+)
Index: linux/include/asm-generic/mutex-dec.h =================================================================== --- /dev/null +++ linux/include/asm-generic/mutex-dec.h @@ -0,0 +1,66 @@ +/* + * asm-generic/mutex-dec.h + * + * Generic wrappers for the mutex fastpath based on an xchg() implementation + * + */ +#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 + * @fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call <fn> if it + * wasn't 1 originally. This function MUST leave the value lower than 1 + * even when the "1" assertion wasn't true. + */ +#define __mutex_fastpath_lock(count, fn_name) \ +do { \ + if (unlikely(atomic_dec_return(count) < 0)) \ + fn_name(count); \ +} while (0) + +/** + * __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 + * @fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call <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 (*fn_name)(atomic_t *)) +{ + if (unlikely(atomic_dec_return(count) < 0)) + return fn_name(count); + else + return 0; +} + +/** + * __mutex_fastpath_unlock - try to promote the mutex from 0 to 1 + * @count: pointer of type atomic_t + * @fn: function to call if the original value was not 1 + * + * 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. + */ +#define __mutex_fastpath_unlock(count, fn_name) \ +do { \ + if (unlikely(atomic_inc_return(count) <= 0)) \ + fn_name(count); \ +} while (0) + +#define __mutex_slowpath_needs_to_unlock() 1 + +#endif Index: linux/include/asm-generic/mutex-xchg.h =================================================================== --- /dev/null +++ linux/include/asm-generic/mutex-xchg.h @@ -0,0 +1,71 @@ +/* + * asm-generic/mutex-xchg.h + * + * Generic wrappers for the mutex fastpath based on an xchg() implementation + * + * NOTE: An xchg based implementation is less optimal than a + * decrement/increment based implementation. If your architecture + * has a reasonable atomic dec/inc then don't use this file, use + * mutex-dec.h instead! + */ +#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 + * @fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call <fn> if it + * wasn't 1 originally. This function MUST leave the value lower than 1 + * even when the "1" assertion wasn't true. + */ +#define __mutex_fastpath_lock(count, fn_name) \ +do { \ + if (unlikely(atomic_xchg(count, 0) != 1)) \ + fn_name(count); \ +} while (0) + + +/** + * __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 + * @fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call <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 (*fn_name)(atomic_t *)) +{ + if (unlikely(atomic_xchg(count, 0) != 1)) + return fn_name(count); + else + return 0; +} + +/** + * __mutex_fastpath_unlock - try to promote the mutex from 0 to 1 + * @count: pointer of type atomic_t + * @fn: function to call if the original value was not 1 + * + * 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. + */ +#define __mutex_fastpath_unlock(count, fn_name) \ +do { \ + if (unlikely(atomic_xchg(count, 1) != 0)) \ + fn_name(count); \ +} while (0) + +#define __mutex_slowpath_needs_to_unlock() 0 + +#endif - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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