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

From: Eric Dumazet <[email-masked]>
Date: Wed, 01 Apr 2009 10:13:06 +0200

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 <[email-masked]>

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();			\
 	}						\