diff options
author | Will Deacon <will.deacon@arm.com> | 2012-08-16 13:43:04 -0400 |
---|---|---|
committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-08-25 04:22:31 -0400 |
commit | 08928e7aea930e6822ce8f1b20068bf857ecf20d (patch) | |
tree | 89cba4f9789841cd2fbf129c945fbd25575be98a | |
parent | e780c452cfea10cbfae1c96dc16e506758138b6f (diff) |
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>
-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 @@ | |||
9 | #define _ASM_MUTEX_H | 9 | #define _ASM_MUTEX_H |
10 | /* | 10 | /* |
11 | * On pre-ARMv6 hardware this results in a swp-based implementation, | 11 | * On pre-ARMv6 hardware this results in a swp-based implementation, |
12 | * which is the most efficient. For ARMv6+, we emit a pair of exclusive | 12 | * which is the most efficient. For ARMv6+, we have exclusive memory |
13 | * accesses instead. | 13 | * accessors and use atomic_dec to avoid the extra xchg operations |
14 | * on the locking slowpaths. | ||
14 | */ | 15 | */ |
16 | #if __LINUX_ARM_ARCH__ < 6 | ||
15 | #include <asm-generic/mutex-xchg.h> | 17 | #include <asm-generic/mutex-xchg.h> |
18 | #else | ||
19 | #include <asm-generic/mutex-dec.h> | ||
16 | #endif | 20 | #endif |
21 | #endif /* _ASM_MUTEX_H */ | ||