From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 28 Mar 2011 16:06:58 +0000 (+0200)
Subject: percpu: Avoid extra NOP in percpu_cmpxchg16b_double
X-Git-Tag: v3.0-rc1~315^2^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5f55924deaa62d6df687c131fb92aebe071ec787;p=pandora-kernel.git

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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