diff options
| author | Will Deacon <will.deacon@arm.com> | 2012-08-13 17:38:48 +0000 |
|---|---|---|
| committer | Varun Colbert <vcolbert@nvidia.com> | 2012-09-10 14:29:19 -0700 |
| commit | 75bdd482816eba85414a71b86535fa87db336aa3 (patch) | |
| tree | 24d3861dd16b6a3440f655c359aef08db10f576e /arch | |
| parent | c56d1413ee5fb5ae24f36e9e7b8e578f3d91db15 (diff) | |
ARM: mutex: use generic atomic_dec-based implementation for ARMv6+
Commit a76d7bd96d65 ("ARM: 7467/1: mutex: use generic xchg-based
implementation for ARMv6+") removed the barrier-less, ARM-specific
mutex implementation in favour of the generic xchg-based code.
Since then, a bug was uncovered in the xchg code when running on SMP
platforms, due to interactions between the locking paths and the
MUTEX_SPIN_ON_OWNER code. This was fixed in 0bce9c46bf3b ("mutex: place
lock in contended state after fastpath_lock failure"), however, the
atomic_dec-based mutex algorithm is now marginally more efficient for
ARM (~0.5% improvement in hackbench scores on dual A15).
This patch moves ARMv6+ platforms to the atomic_dec-based mutex code.
Change-Id: I8f64e98ccb61cc1cb9cb68ee15e55d8a792792f5
Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Reviewed-on: http://git-master/r/130941
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Tested-by: Bharat Nihalani <bnihalani@nvidia.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/include/asm/mutex.h | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/arm/include/asm/mutex.h b/arch/arm/include/asm/mutex.h index b1479fd04a95..6e813d93a736 100644 --- a/arch/arm/include/asm/mutex.h +++ b/arch/arm/include/asm/mutex.h @@ -9,8 +9,13 @@ #define _ASM_MUTEX_H /* * On pre-ARMv6 hardware this results in a swp-based implementation, - * which is the most efficient. For ARMv6+, we emit a pair of exclusive - * accesses instead. + * which is the most efficient. For ARMv6+, we have exclusive memory + * accessors and use atomic_dec to avoid the extra xchg operations + * on the locking slowpaths. */ +#if __LINUX_ARM_ARCH__ < 6 #include <asm-generic/mutex-xchg.h> +#else +#include <asm-generic/mutex-dec.h> +#endif #endif |