Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755321AbXFLWwR (ORCPT ); Tue, 12 Jun 2007 18:52:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753273AbXFLWwK (ORCPT ); Tue, 12 Jun 2007 18:52:10 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:44700 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752691AbXFLWwI (ORCPT ); Tue, 12 Jun 2007 18:52:08 -0400 From: "Rafael J. Wysocki" To: "Siddha, Suresh B" , "Eric W. Biederman" Subject: Re: [PATCH] x86: Document the hotplug code is incompatible with x86 irq handling Date: Wed, 13 Jun 2007 00:58:42 +0200 User-Agent: KMail/1.9.5 Cc: Pavel Machek , Andrew Morton , Andi Kleen , linux-kernel@vger.kernel.org, Neil Brown , Ingo Molnar , asit.k.mallick@intel.com References: <200706130016.09490.rjw@sisk.pl> <20070612222432.GC17143@linux-os.sc.intel.com> In-Reply-To: <20070612222432.GC17143@linux-os.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200706130058.43227.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2864 Lines: 67 On Wednesday, 13 June 2007 00:24, Siddha, Suresh B wrote: > On Wed, Jun 13, 2007 at 12:16:08AM +0200, Rafael J. Wysocki wrote: > > On Tuesday, 12 June 2007 23:56, Siddha, Suresh B wrote: > > > On Tue, Jun 12, 2007 at 10:52:09PM +0200, Rafael J. Wysocki wrote: > > > > On Tuesday, 12 June 2007 20:19, Eric W. Biederman wrote: > > > > > Because you are calling unfixably broken code. That should be a decent > > > > > incentive to do something else won't it? > > > > > > > > Can you please tell me _what_ else can be done? > > > > > > > > > IOAPICs do not support what the code is doing here. There is lots of > > > > > practical evidence including bad experiences and practical tests that > > > > > support this. > > > > > > > > Well, AFAICS, Suresh has tried to debug one failing case recently without > > > > any consistent conclusions. I don't know of any other test cases (links, > > > > please?). > > > > > > Rafael, Darrick Wong's issue looks different and hence I was motivated to > > > look and fix if it was a SW issue. For now, I am not able to comprehend > > > what is happening on Darrick Wong's system. Need more help from Darrick > > > as he has the golden failing system. > > > > > > Meanwhile I talked to our hardware folks about the irq migration in general. > > > > > > One good news is that future versions of chipsets will have an Interrupt > > > Remapping feature(for more details please refer to > > > http://download.intel.com/technology/computing/vptech/Intel(r)_VT_for_Direct_IO.pdf) > > > where in we can reliably migrate the irq to someother cpu in the process > > > context. > > > > > > And for the existing platforms, chipset folks don't see a reason why the > > > Eric's algorithm(specified below) should fail. > > > > > > Eric's algorithm for level triggered(edge triggered should be easier than > > > level triggered): > > > - Mask the irq in process context. > > > - Poll RIRR until an ack of for the irq was not pending. > > > - Migrate the irq. > > > > > > Eric had a problem of stuck remote IRR on E75xx chipset with this algorithm > > > and my next step is to reproduce this issue on this platform and understand > > > the behavior. > > > > OK > > > > In that case, do I understand correctly that we are going to implement the > > Eric's algorithm above for the CPU hotunplugging on x86 once you've figured > > out what's the E75xx issue? > > That is the idea. Thanks. OK, thanks. Eric, would you agree to follow this plan without making the entire CPU hotplug (on x86) depend on BROKEN? Rafael -- "Premature optimization is the root of all evil." - Donald Knuth - 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/