[PATCH RT 23/36] ARM: cmpxchg: define __HAVE_ARCH_CMPXCHG for armv6 and later

Steven Rostedt
2015-03-12T19:27:55Z

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3.12.38-rt53-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

Both pi_stress and sigwaittest in rt-test show performance gain with
__HAVE_ARCH_CMPXCHG. Testing result on coretile_express_a9x4:

pi_stress -p 99 --duration=300 (on linux-3.4-rc5; bigger is better)
vanilla: Total inversion performed: 5493381
patched: Total inversion performed: 5621746

sigwaittest -p 99 -l 100000 (on linux-3.4-rc5-rt6; less is better)
3.4-rc5-rt6: Min 24, Cur 27, Avg 30, Max 98
patched: Min 19, Cur 21, Avg 23, Max 96

Signed-off-by: Yong Zhang <yong.zhang0 at gmail.com>
Cc: Russell King <rmk+kernel at arm.linux.org.uk>
Cc: Nicolas Pitre <nico at linaro.org>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: linux-arm-kernel at lists.infradead.org
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/arm/include/asm/cmpxchg.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
index 4f009c10540d..a86b680dd7cf 100644
--- a/arch/arm/include/asm/cmpxchg.h
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -127,6 +127,8 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size

#else /* min ARCH >= ARMv6 */

+#define __HAVE_ARCH_CMPXCHG 1
+
extern void __bad_cmpxchg(volatile void *ptr, int size);

/*
--
2.1.4