From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422912AbWJPWlA (ORCPT ); Mon, 16 Oct 2006 18:41:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422910AbWJPWlA (ORCPT ); Mon, 16 Oct 2006 18:41:00 -0400 Received: from ns2.suse.de ([195.135.220.15]:1215 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S1422912AbWJPWk7 (ORCPT ); Mon, 16 Oct 2006 18:40:59 -0400 From: Andi Kleen To: Zachary Amsden Subject: Re: [RFC] Avoid PIT SMP lockups Date: Tue, 17 Oct 2006 00:40:49 +0200 User-Agent: KMail/1.9.3 Cc: caglar@pardus.org.tr, Gerd Hoffmann , john stultz , lkml References: <1160170736.6140.31.camel@localhost.localdomain> <200610121045.32846.caglar@pardus.org.tr> <453404F6.5040202@vmware.com> In-Reply-To: <453404F6.5040202@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200610170040.49502.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > It might only happen with SMP because the difficulty of getting good > enough TSC / timer IRQ synchronization during boot increases > exponentially with SMP configurations. And it might pass 10% of the time > because you were lucky enough not to fire off another timer interrupt yet. We have the same problem with NMI watchdog events unfortunately. Need to call something in the nmi watchdog code to make sure it is not renewed and then reenabled. Or maybe it's better to figure out a way that yields atomic patches. I think the best way is to make sure all alternative() patches are always done before the code can be ever executed - this means doing it very early for the main kernel. The only exception would be the LOCK prefix patching, which should be atomic. iirc there was some more patching except lock prefixes going on for SMP<->UP transisitions, but last time I checked they didn't look particularly useful and could be probably eliminated. -Andi