x86: replace LOCK_PREFIX in futex.h
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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/futex.h b/include/asm-x86/futex.h
index 62828d6..9d91926 100644
--- a/include/asm-x86/futex.h
+++ b/include/asm-x86/futex.h
@@ -30,7 +30,7 @@
"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 \
@@ -72,7 +72,7 @@
__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:
@@ -111,8 +111,8 @@
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"
" jmp 2b \n"