ARM: mutex: use generic atomic_dec-based implementation for ARMv6+
authorWill Deacon <will.deacon@arm.com>
Mon, 13 Aug 2012 17:38:48 +0000 (17:38 +0000)
committerVarun Colbert <vcolbert@nvidia.com>
Mon, 10 Sep 2012 21:29:19 +0000 (14:29 -0700)
commit75bdd482816eba85414a71b86535fa87db336aa3
tree24d3861dd16b6a3440f655c359aef08db10f576e
parentc56d1413ee5fb5ae24f36e9e7b8e578f3d91db15
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>
arch/arm/include/asm/mutex.h