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>
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@ -509,6 +509,11 @@ do { \
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* it in software. The address used in the cmpxchg16 instruction must be
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* aligned to a 16 byte boundary.
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*/
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#ifdef CONFIG_SMP
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#define CMPXCHG16B_EMU_CALL "call this_cpu_cmpxchg16b_emu\n\t" P6_NOP3
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#else
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#define CMPXCHG16B_EMU_CALL "call this_cpu_cmpxchg16b_emu\n\t" P6_NOP2
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#endif
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#define percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2) \
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({ \
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char __ret; \
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@ -517,7 +522,7 @@ do { \
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typeof(o2) __o2 = o2; \
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typeof(o2) __n2 = n2; \
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typeof(o2) __dummy; \
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alternative_io("call this_cpu_cmpxchg16b_emu\n\t" P6_NOP4, \
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alternative_io(CMPXCHG16B_EMU_CALL, \
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"cmpxchg16b " __percpu_prefix "(%%rsi)\n\tsetz %0\n\t", \
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X86_FEATURE_CX16, \
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ASM_OUTPUT2("=a"(__ret), "=d"(__dummy)), \
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