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authorEric Dumazet <eric.dumazet@gmail.com>2011-03-28 18:06:58 +0200
committerTejun Heo <tj@kernel.org>2011-03-28 18:06:58 +0200
commit5f55924deaa62d6df687c131fb92aebe071ec787 (patch)
tree2888f5163793d9b37ff6726e470853d5d727abe3 /arch/x86
parent787e5b06a80e7fc9dc02d9b53a9d8d2ac63b7ace (diff)
percpu: Avoid extra NOP in percpu_cmpxchg16b_double
percpu_cmpxchg16b_double() uses alternative_io() and looks like : e8 .. .. .. .. call this_cpu_cmpxchg16b_emu X bytes NOPX or, once patched (if cpu supports native instruction) on SMP build : 65 48 0f c7 0e cmpxchg16b %gs:(%rsi) 0f 94 c0 sete %al on !SMP build : 48 0f c7 0e cmpxchg16b (%rsi) 0f 94 c0 sete %al Therefore, NOPX should be : P6_NOP3 on SMP P6_NOP2 on !SMP Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/percpu.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index d475b4398d8b..d68fca61ad91 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -509,6 +509,11 @@ do { \
* it in software. The address used in the cmpxchg16 instruction must be
* aligned to a 16 byte boundary.
*/
+#ifdef CONFIG_SMP
+#define CMPXCHG16B_EMU_CALL "call this_cpu_cmpxchg16b_emu\n\t" P6_NOP3
+#else
+#define CMPXCHG16B_EMU_CALL "call this_cpu_cmpxchg16b_emu\n\t" P6_NOP2
+#endif
#define percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2) \
({ \
char __ret; \
@@ -517,7 +522,7 @@ do { \
typeof(o2) __o2 = o2; \
typeof(o2) __n2 = n2; \
typeof(o2) __dummy; \
- alternative_io("call this_cpu_cmpxchg16b_emu\n\t" P6_NOP4, \
+ alternative_io(CMPXCHG16B_EMU_CALL, \
"cmpxchg16b " __percpu_prefix "(%%rsi)\n\tsetz %0\n\t", \
X86_FEATURE_CX16, \
ASM_OUTPUT2("=a"(__ret), "=d"(__dummy)), \