Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752512AbZA1Sw6 (ORCPT ); Wed, 28 Jan 2009 13:52:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751375AbZA1Swt (ORCPT ); Wed, 28 Jan 2009 13:52:49 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:54386 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751155AbZA1Swt (ORCPT ); Wed, 28 Jan 2009 13:52:49 -0500 Date: Wed, 28 Jan 2009 13:52:47 -0500 (EST) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Peter Zijlstra cc: LKML , Linus Torvalds , Ingo Molnar , Thomas Gleixner , Andrew Morton , Arjan van de Ven , Rusty Russell , jens.axboe@oracle.com Subject: Re: Buggy IPI and MTRR code on low memory In-Reply-To: <1233166834.10992.61.camel@laptop> Message-ID: References: <1233161182.10992.52.camel@laptop> <1233166834.10992.61.camel@laptop> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1550 Lines: 38 On Wed, 28 Jan 2009, Peter Zijlstra wrote: > On Wed, 2009-01-28 at 12:24 -0500, Steven Rostedt wrote: > > On Wed, 28 Jan 2009, Peter Zijlstra wrote: > > > --- > > > Subject: x86: fix potential deadlock in set_mtrr() > > > From: Peter Zijlstra > > > Date: Wed Jan 28 17:17:32 CET 2009 > > > > > > smp_call_function() can fall-back to waiting on completion in case of > > > low memory (GFP_ATOMIC). set_mtrr() relies on the async behaviour of !wait. > > > > > > This would deadlock. > > > > > > Fix this by providing per-cpu csd's and using __smp_call_function_single(). > > > > I applied the patch but it still locked up in the testing NMI > > watchdog code. Not saying your patch is at fault, because we never made it > > to your code. This is probably not an issue, since if we have low memory > > at bootup, we have much bigger problems to deal with. > > > > I'll have skip the NMI test and see if it locks up any place else. > > Right, the NMI code does exactly the same, in that case your patch might > well be the best way forward. Is there any reason to force the user to have to deal with a wait? We can add this code to handle the failed alloc case, and I can even make it a bit better to only do the copy *d = data; when the RELEASE flag is set. -- Steve -- 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/