x86: replace LOCK_PREFIX in futex.h (9d55b992) · Commits · 戴 / test

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>

include/asm-x86/futex.h

+3 −3

Original line number	Diff line number	Diff line
		@@ -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_op_inuser(int encoded_op, int __user *uaddr)
		__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 @@ futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
		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"

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