From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754516AbZILNpQ (ORCPT ); Sat, 12 Sep 2009 09:45:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754455AbZILNpP (ORCPT ); Sat, 12 Sep 2009 09:45:15 -0400 Received: from tomts13-srv.bellnexxia.net ([209.226.175.34]:41605 "EHLO tomts13-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754448AbZILNpN (ORCPT ); Sat, 12 Sep 2009 09:45:13 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AigFAOs/q0pMROOX/2dsb2JhbACBU9kShBgFgVY Date: Sat, 12 Sep 2009 09:45:15 -0400 From: Mathieu Desnoyers To: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de Cc: linux-tip-commits@vger.kernel.org Subject: Re: [tip:tracing/core] x86/tracing: comment need for atomic nop Message-ID: <20090912134515.GC22876@Krystal> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 09:44:33 up 25 days, 34 min, 3 users, load average: 0.09, 0.15, 0.12 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * tip-bot for Steven Rostedt (srostedt@redhat.com) wrote: > Commit-ID: fc06b8520b3bf9aaeb2e27debe6719c215bd4916 > Gitweb: http://git.kernel.org/tip/fc06b8520b3bf9aaeb2e27debe6719c215bd4916 > Author: Steven Rostedt > AuthorDate: Thu, 10 Sep 2009 17:22:44 -0400 > Committer: Steven Rostedt > CommitDate: Thu, 10 Sep 2009 17:22:44 -0400 > > x86/tracing: comment need for atomic nop > > The dynamic function tracer relys on the macro P6_NOP5 always being > an atomic NOP. If for some reason it is changed to be two operations > (like a nop2 nop3) it can faults within the kernel when the function > tracer modifies the code. > > This patch adds a comment to note that the P6_NOPs are expected to > be atomic. This will hopefully prevent anyone from changing that. > > Reported-by: Mathieu Desnoyer With an added "s" to my last name, that will be good. Thanks ! Acked-by: Mathieu Desnoyers > Signed-off-by: Steven Rostedt > > > --- > arch/x86/include/asm/nops.h | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/nops.h b/arch/x86/include/asm/nops.h > index ad2668e..6d8723a 100644 > --- a/arch/x86/include/asm/nops.h > +++ b/arch/x86/include/asm/nops.h > @@ -65,6 +65,8 @@ > 6: osp nopl 0x00(%eax,%eax,1) > 7: nopl 0x00000000(%eax) > 8: nopl 0x00000000(%eax,%eax,1) > + Note: All the above are assumed to be a single instruction. > + There is kernel code that depends on this. > */ > #define P6_NOP1 GENERIC_NOP1 > #define P6_NOP2 ".byte 0x66,0x90\n" -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68