From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755098Ab1IBTeT (ORCPT ); Fri, 2 Sep 2011 15:34:19 -0400 Received: from claw.goop.org ([74.207.240.146]:45129 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754875Ab1IBTeR (ORCPT ); Fri, 2 Sep 2011 15:34:17 -0400 Message-ID: <4E612FB6.9030904@goop.org> Date: Fri, 02 Sep 2011 12:34:14 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0) Gecko/20110816 Thunderbird/6.0 MIME-Version: 1.0 To: Peter Zijlstra CC: "H. Peter Anvin" , Linus Torvalds , Ingo Molnar , the arch/x86 maintainers , Linux Kernel Mailing List , Nick Piggin , Avi Kivity , Marcelo Tosatti , KVM , Andi Kleen , Xen Devel , Srivatsa Vaddagiri , Jeremy Fitzhardinge Subject: Re: [PATCH 11/13] x86/ticketlock: only do kick after doing unlock References: <8cd2c77886e2d3fcad8258aa62509b3b2fae5545.1314922370.git.jeremy.fitzhardinge@citrix.com> <1314974968.1861.3.camel@twins> In-Reply-To: <1314974968.1861.3.camel@twins> X-Enigmail-Version: 1.3.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/02/2011 07:49 AM, Peter Zijlstra wrote: > On Thu, 2011-09-01 at 17:55 -0700, Jeremy Fitzhardinge wrote: >> From: Srivatsa Vaddagiri >> >> We must release the lock before checking to see if the lock is in >> slowpath or else there's a potential race where the lock enters the >> slow path after the unlocker has checked the slowpath flag, but before >> it has actually unlocked. >> >> Signed-off-by: Srivatsa Vaddagiri >> Signed-off-by: Jeremy Fitzhardinge > Wouldn't it be much better to fold it back so that this bug never > happens when you bisect? Yes indeed. J From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH 11/13] x86/ticketlock: only do kick after doing unlock Date: Fri, 02 Sep 2011 12:34:14 -0700 Message-ID: <4E612FB6.9030904@goop.org> References: <8cd2c77886e2d3fcad8258aa62509b3b2fae5545.1314922370.git.jeremy.fitzhardinge@citrix.com> <1314974968.1861.3.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , Nick Piggin , KVM , the arch/x86 maintainers , Linux Kernel Mailing List , Srivatsa Vaddagiri , Andi Kleen , Avi Kivity , Jeremy Fitzhardinge , "H. Peter Anvin" , Ingo Molnar , Linus Torvalds , Xen Devel To: Peter Zijlstra Return-path: In-Reply-To: <1314974968.1861.3.camel@twins> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com List-Id: kvm.vger.kernel.org On 09/02/2011 07:49 AM, Peter Zijlstra wrote: > On Thu, 2011-09-01 at 17:55 -0700, Jeremy Fitzhardinge wrote: >> From: Srivatsa Vaddagiri >> >> We must release the lock before checking to see if the lock is in >> slowpath or else there's a potential race where the lock enters the >> slow path after the unlocker has checked the slowpath flag, but before >> it has actually unlocked. >> >> Signed-off-by: Srivatsa Vaddagiri >> Signed-off-by: Jeremy Fitzhardinge > Wouldn't it be much better to fold it back so that this bug never > happens when you bisect? Yes indeed. J