[PATCH] x86: percpu_to_op() misses memory and flags clobbers

From: Eric Dumazet
Date: Wed Apr 01 2009 - 04:13:49 EST


While playing with new percpu_{read|write|add|sub} stuff in network tree,
I found x86 asm was a litle bit optimistic.

We need to tell gcc that percpu_{write|add|sub|or|xor} are modyfing
memory and possibly eflags. We could add another parameter to percpu_to_op()
to separate the plain "mov" case (not changing eflags),
but let keep it simple for the moment.

Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index aee103b..fd4f8ec 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -82,22 +82,26 @@ do { \
case 1: \
asm(op "b %1,"__percpu_arg(0) \
: "+m" (var) \
- : "ri" ((T__)val)); \
+ : "ri" ((T__)val) \
+ : "memory", "cc"); \
break; \
case 2: \
asm(op "w %1,"__percpu_arg(0) \
: "+m" (var) \
- : "ri" ((T__)val)); \
+ : "ri" ((T__)val) \
+ : "memory", "cc"); \
break; \
case 4: \
asm(op "l %1,"__percpu_arg(0) \
: "+m" (var) \
- : "ri" ((T__)val)); \
+ : "ri" ((T__)val) \
+ : "memory", "cc"); \
break; \
case 8: \
asm(op "q %1,"__percpu_arg(0) \
: "+m" (var) \
- : "re" ((T__)val)); \
+ : "re" ((T__)val) \
+ : "memory", "cc"); \
break; \
default: __bad_percpu_size(); \
} \
--
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