From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760249AbYBFXnk (ORCPT ); Wed, 6 Feb 2008 18:43:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757343AbYBFXnc (ORCPT ); Wed, 6 Feb 2008 18:43:32 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:60547 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755679AbYBFXna (ORCPT ); Wed, 6 Feb 2008 18:43:30 -0500 Date: Thu, 7 Feb 2008 00:43:09 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Greg KH , Chuck Ebbert , Thomas Gleixner , linux-kernel , Andi Kleen , Gerd Hoffmann , Andrew Morton , Stable Team Subject: Re: [stable] The SMP alternatives code breaks exception fixup? Message-ID: <20080206234309.GA13758@elte.hu> References: <479504F6.4080005@redhat.com> <47964FD5.6020801@redhat.com> <20080206231020.GB12395@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Linus Torvalds wrote: > > I don't see this in Linus's tree, am I just missing it? Do you have > > a git commit id? > > Isn't this 9d55b9923a1b7ea8193b8875c57ec940dc2ff027 (possibly with > 2532ec6d178abc55681d049097d3dc577eaa266c on top)? yeah. Greg: note that this is against post-unification asm-x86/futex.h so it wont apply to .24. I've backported the fix to .24 - find it below. (untested but obvious) Ingo -----------------------> Subject: x86: replace LOCK_PREFIX in futex.h From: Thomas Gleixner 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 Signed-off-by: Ingo Molnar --- include/asm-x86/futex_32.h | 6 +++--- include/asm-x86/futex_64.h | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) Index: linux-2.6.24/include/asm-x86/futex_32.h =================================================================== --- linux-2.6.24.orig/include/asm-x86/futex_32.h +++ linux-2.6.24/include/asm-x86/futex_32.h @@ -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, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -111,8 +111,8 @@ 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" " jmp 2b \n" Index: linux-2.6.24/include/asm-x86/futex_64.h =================================================================== --- linux-2.6.24.orig/include/asm-x86/futex_64.h +++ linux-2.6.24/include/asm-x86/futex_64.h @@ -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: @@ -101,8 +101,8 @@ 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" " jmp 2b \n"