From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755238AbZFEWU0 (ORCPT ); Fri, 5 Jun 2009 18:20:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751468AbZFEWUQ (ORCPT ); Fri, 5 Jun 2009 18:20:16 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:55430 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751247AbZFEWUO (ORCPT ); Fri, 5 Jun 2009 18:20:14 -0400 Date: Fri, 5 Jun 2009 15:20:04 -0700 From: Gary Hade To: Suresh Siddha Cc: "Eric W. Biederman" , "mingo@elte.hu" , "hpa@zytor.com" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "ak@linux.intel.com" , "travis@sgi.com" , "steiner@sgi.com" , Gary Hade , lcm@us.ibm.com Subject: Re: [patch] x64: Avoid irq_chip mask/unmask in fixup_irqs for interrupt-remapping Message-ID: <20090605222004.GE7514@us.ibm.com> References: <1244141989.27006.10369.camel@localhost.localdomain> <1244164694.27006.10374.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1244164694.27006.10374.camel@localhost.localdomain> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 04, 2009 at 06:18:14PM -0700, Suresh Siddha wrote: > On Thu, 2009-06-04 at 16:13 -0700, Eric W. Biederman wrote: > > Suresh Siddha writes: > > > > > From: Suresh Siddha > > > Subject: x64: Avoid irq_chip mask/unmask in fixup_irqs for interrupt-remapping > > > > > > In the presence of interrupt-remapping, irqs will be migrated in the > > > process context and we don't do (and there is no need to) irq_chip mask/unmask > > > while migrating the interrupt. > > > > > > Similarly fix the fixup_irqs() that get called during cpu offline and avoid > > > calling irq_chip mask/unmask for irqs that are ok to be migrated in the > > > process context. > > > > > > While we didn't observe any race condition with the existing code, > > > this change takes complete advantage of interrupt-remapping in > > > the newer generation platforms and avoids any potential HW lockup's > > > (that often worry Eric :) > > > > You now apparently fail to migrate the irq threads in tandem with > > the rest of the irqs. > > Eric, Are you referring to Gary's issues? As far as I understand, they > don't happen in the presence of interrupt-remapping. Suresh, We do not currently have the h/w on which to test this assertion but it seems like there is a good chance that at least the race that http://lkml.org/lkml/2009/6/2/377 fixes could reproduce there. The other problem that is repaired by http://lkml.org/lkml/2009/6/2/378 depends on the i/o redirection table write with remote IRR bit set lockup anomaly that the interrupt-remapping code may avoid or perhaps is not even present with that h/w. My proposed fix for the problem is based on previous interrupt-remapping code that you recently removed with http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=0280f7c416c652a2fd95d166f52b199ae61122c0 If I correctly understand your justification for the change it sounds like the interrupt-remapping code now "avoids" the problem. Thanks, Gary -- Gary Hade System x Enablement IBM Linux Technology Center 503-578-4503 IBM T/L: 775-4503 garyhade@us.ibm.com http://www.ibm.com/linux/ltc