Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753108AbXJ1VWD (ORCPT ); Sun, 28 Oct 2007 17:22:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751198AbXJ1VVy (ORCPT ); Sun, 28 Oct 2007 17:21:54 -0400 Received: from one.firstfloor.org ([213.235.205.2]:35257 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751138AbXJ1VVy (ORCPT ); Sun, 28 Oct 2007 17:21:54 -0400 Date: Sun, 28 Oct 2007 22:21:50 +0100 From: Andi Kleen To: Mathieu Desnoyers Cc: Andi Kleen , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Fix x86_64 TIF_SYSCALL_TRACE race in entry.S Message-ID: <20071028212150.GA20321@one.firstfloor.org> References: <20071026193738.GA1591@Krystal> <20071027180837.GA18134@Krystal> <20071028211527.GA9129@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071028211527.GA9129@Krystal> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 883 Lines: 20 > Setting the thread flag being an atomic operation, I would expect > setting/clearing it asynchronously from another thread to be a valid It could be a very short stop. Also do you start kernel tracing that often? > Here is a modified version where I add my test only in the path where we > know that we have work to do, therefore removing the supplementary test > from the performance critical path. Would it be more acceptable ? It's better, but stopping would be even better. I wouldn't be surprised if there are other problems with async thread flags changing. Also I object to you calling this a bug. It's a new feature. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/