Subject: x86: replace LOCK_PREFIX in futex.h
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 07 Feb 2008 13:05:19 +0100

The exception fixup for the futex macros __futex_atomic_op1/2 and
futex_atomic_cmpxchg_inatomic() is missing an entry when the lock
prefix is replaced by a NOP via SMP alternatives.

Chuck Ebert tracked this down from the information provided in:
https://bugzilla.redhat.com/show_bug.cgi?id=429412

A possible solution would be to add another fixup after the
LOCK_PREFIX, so both the LOCK and NOP case have their own entry in the
exception table, but it's not really worth the trouble.

Simply replace LOCK_PREFIX with lock and keep those untouched by SMP
alternatives.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
                                                                
Index: linux-2.6.23/include/asm-i386/futex.h
===================================================================
--- linux-2.6.23.orig/include/asm-i386/futex.h	2008-02-07 13:08:03.000000000 +0100
+++ linux-2.6.23/include/asm-i386/futex.h	2008-02-07 13:09:39.000000000 +0100
@@ -28,7 +28,7 @@
 "1:	movl	%2, %0\n\
 	movl	%0, %3\n"					\
 	insn "\n"						\
-"2:	" LOCK_PREFIX "cmpxchgl %3, %2\n\
+"2:	lock cmpxchgl %3, %2\n\
 	jnz	1b\n\
 3:	.section .fixup,\"ax\"\n\
 4:	mov	%5, %1\n\
@@ -68,7 +68,7 @@ futex_atomic_op_inuser (int encoded_op, 
 #endif
 		switch (op) {
 		case FUTEX_OP_ADD:
-			__futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret,
+			__futex_atomic_op1("lock xaddl %0, %2", ret,
 					   oldval, uaddr, oparg);
 			break;
 		case FUTEX_OP_OR:
@@ -111,7 +111,7 @@ futex_atomic_cmpxchg_inatomic(int __user
 		return -EFAULT;
 
 	__asm__ __volatile__(
-		"1:	" LOCK_PREFIX "cmpxchgl %3, %1		\n"
+		"1:	lock cmpxchgl %3, %1			\n"
 
 		"2:	.section .fixup, \"ax\"			\n"
 		"3:	mov     %2, %0				\n"
Index: linux-2.6.23/include/asm-x86_64/futex.h
===================================================================
--- linux-2.6.23.orig/include/asm-x86_64/futex.h	2008-02-07 13:08:03.000000000 +0100
+++ linux-2.6.23/include/asm-x86_64/futex.h	2008-02-07 13:09:39.000000000 +0100
@@ -27,7 +27,7 @@
 "1:	movl	%2, %0\n\
 	movl	%0, %3\n"					\
 	insn "\n"						\
-"2:	" LOCK_PREFIX "cmpxchgl %3, %2\n\
+"2:	"lock cmpxchgl %3, %2\n\
 	jnz	1b\n\
 3:	.section .fixup,\"ax\"\n\
 4:	mov	%5, %1\n\
@@ -62,7 +62,7 @@ futex_atomic_op_inuser (int encoded_op, 
 		__futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
 		break;
 	case FUTEX_OP_ADD:
-		__futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
+		__futex_atomic_op1("lock xaddl %0, %2", ret, oldval,
 				   uaddr, oparg);
 		break;
 	case FUTEX_OP_OR:
@@ -101,7 +101,7 @@ futex_atomic_cmpxchg_inatomic(int __user
 		return -EFAULT;
 
 	__asm__ __volatile__(
-		"1:	" LOCK_PREFIX "cmpxchgl %3, %1		\n"
+		"1:	lock cmpxchgl %3, %1			\n"
 
 		"2:	.section .fixup, \"ax\"			\n"
 		"3:	mov     %2, %0				\n"