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x86: Add support for cmpxchg_double

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A simple implementation that only supports the word size and does not
have a fallback mode (would require a spinlock).

Add 32 and 64 bit support for cmpxchg_double. cmpxchg double uses
the cmpxchg8b or cmpxchg16b instruction on x86 processors to compare
and swap 2 machine words. This allows lockless algorithms to move more
context information through critical sections.

Set a flag CONFIG_CMPXCHG_DOUBLE to signal that support for double word
cmpxchg detection has been build into the kernel. Note that each subsystem
using cmpxchg_double has to implement a fall back mechanism as long as
we offer support for processors that do not implement cmpxchg_double.

Reviewed-by: H. Peter Anvin <hpa@zytor.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Christoph Lameter <cl@linux.com>
Link: http://lkml.kernel.org/r/20110601172614.173427964@linux.com
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Christoph Lameter
2011-06-01 12:25:47 -05:00
committed by H. Peter Anvin
parent 5629937872
commit 3824abd127
4 changed files with 98 additions and 0 deletions
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2
arch/x86/include/asm/cpufeature.h
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@@ -288,6 +288,8 @@ extern const char * const x86_power_flags[32];
#define cpu_has_hypervisor boot_cpu_has(X86_FEATURE_HYPERVISOR)
#define cpu_has_pclmulqdq boot_cpu_has(X86_FEATURE_PCLMULQDQ)
#define cpu_has_perfctr_core boot_cpu_has(X86_FEATURE_PERFCTR_CORE)
#define cpu_has_cx8 boot_cpu_has(X86_FEATURE_CX8)
#define cpu_has_cx16 boot_cpu_has(X86_FEATURE_CX16)
#if defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_64)
# define cpu_has_invlpg 1