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Subject[PATCH] x86 : revert replace LOCK_PREFIX in futex.h
Depends on :

x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug

On Thu, 14 Aug 2008, Mathieu Desnoyers wrote:
>
> Changing the 0x90 (single-byte nop) currently used into a 0x3E DS segment
> override prefix should fix this issue. Since the default of the atomic
> instructions is to use the DS segment anyway, it should not affect the
> behavior.

Ok, so I think this is an _excellent_ patch, but I'd like to also then use
LOCK_PREFIX in include/asm-x86/futex.h.

See commit 9d55b9923a1b7ea8193b8875c57ec940dc2ff027.

Linus

Applies to 2.6.27-rc2 (and -rc3 unless hell broke loose in futex.h between rc2
and rc3).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: H. Peter Anvin <hpa@zytor.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Roland McGrath <roland@redhat.com>
CC: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
CC: Steven Rostedt <srostedt@redhat.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: David Miller <davem@davemloft.net>
CC: Ulrich Drepper <drepper@redhat.com>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Gregory Haskins <ghaskins@novell.com>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
CC: "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
CC: Clark Williams <williams@redhat.com>
CC: Christoph Lameter <cl@linux-foundation.org>
CC: Andi Kleen <andi@firstfloor.org>
CC: Harvey Harrison <harvey.harrison@gmail.com>
---
include/asm-x86/futex.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6-lttng/include/asm-x86/futex.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-x86/futex.h 2008-08-15 12:32:38.000000000 -0400
+++ linux-2.6-lttng/include/asm-x86/futex.h 2008-08-15 12:41:33.000000000 -0400
@@ -25,7 +25,7 @@
asm volatile("1:\tmovl %2, %0\n" \
"\tmovl\t%0, %3\n" \
"\t" insn "\n" \
- "2:\tlock; cmpxchgl %3, %2\n" \
+ "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
"\tjnz\t1b\n" \
"3:\t.section .fixup,\"ax\"\n" \
"4:\tmov\t%5, %1\n" \
@@ -64,7 +64,7 @@ static inline int futex_atomic_op_inuser
__futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
break;
case FUTEX_OP_ADD:
- __futex_atomic_op1("lock; xaddl %0, %2", ret, oldval,
+ __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
uaddr, oparg);
break;
case FUTEX_OP_OR:
@@ -122,7 +122,7 @@ static inline int futex_atomic_cmpxchg_i
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;

- asm volatile("1:\tlock; cmpxchgl %3, %1\n"
+ asm volatile("1:\t" LOCK_PREFIX "cmpxchgl %3, %1\n"
"2:\t.section .fixup, \"ax\"\n"
"3:\tmov %2, %0\n"
"\tjmp 2b\n"
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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