diff options
| author | Will Deacon <will.deacon@arm.com> | 2012-08-16 18:43:04 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-08-25 09:22:31 +0100 |
| commit | 08928e7aea930e6822ce8f1b20068bf857ecf20d (patch) | |
| tree | 89cba4f9789841cd2fbf129c945fbd25575be98a /arch/arm | |
| parent | e780c452cfea10cbfae1c96dc16e506758138b6f (diff) | |
| download | blackbird-obmc-linux-08928e7aea930e6822ce8f1b20068bf857ecf20d.tar.gz blackbird-obmc-linux-08928e7aea930e6822ce8f1b20068bf857ecf20d.zip | |
ARM: 7495/1: 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.
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
| -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..87c044910fe0 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 /* _ASM_MUTEX_H */ |
