Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754653Ab1EDP2J (ORCPT ); Wed, 4 May 2011 11:28:09 -0400 Received: from smtp103.prem.mail.ac4.yahoo.com ([76.13.13.42]:46089 "HELO smtp103.prem.mail.ac4.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754282Ab1EDP2H (ORCPT ); Wed, 4 May 2011 11:28:07 -0400 X-Yahoo-SMTP: _Dag8S.swBC1p4FJKLCXbs8NQzyse1SYSgnAbY0- X-YMail-OSG: LjZKmWUVM1nidKSwtrXCJhLiS4aEtMBjB2PI5ImgWAnJkn_ w9nZw7WLsL1gcC.ovuOK9i8rbqippOzCuT2UAaaj.9Dl7WfpqMz3A6QNL6ue tXDvqdX5VFQM445iucr4cYt..asONfQ6GDdGOlBpMFBMX.b9xbWppYNtqBgd o0G0gYBPE6fNZyZIlnPmvTMxqTnJDj0X0hNPbXEJkkUrJmk8sBsxNsfbanGI vyZhVqmRhcnnuMVBfSnwntyoKpfWiTqanE2KbxTH8m3p3CnLAvZ3OkjexYzn RLSPrnkX90pAsdEXuU6EcmbzPmPejAa.ZS7lYkA.fe74pJrB_ X-Yahoo-Newman-Property: ymail-3 Date: Wed, 4 May 2011 10:28:02 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@router.home To: Linus Torvalds cc: Thomas Gleixner , Tejun Heo , Pekka Enberg , Ingo Molnar , Jens Axboe , Andrew Morton , werner , "H. Peter Anvin" , Linux Kernel Mailing List Subject: Re: [block IO crash] Re: 2.6.39-rc5-git2 boot crashs In-Reply-To: Message-ID: References: <20110504083559.GB25724@elte.hu> <20110504101932.GA3392@elte.hu> <20110504112746.GE8007@htj.dyndns.org> <20110504132022.GA17294@htj.dyndns.org> <20110504142532.GC17294@htj.dyndns.org> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) 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: 1944 Lines: 45 On Wed, 4 May 2011, Linus Torvalds wrote: > On Wed, May 4, 2011 at 8:00 AM, Christoph Lameter wrote: > > > > Right there is only the tid management that is added. Hope I am fast > > enough to at least get one patch in (not very well tested): > > So the thing that worries me about this is non-x86 architectures. > > Have we verified that the generic routines are ok for all > architectures? Has somebody checked the memory barriers in particular? There are no memory barriers used. The barrier() here is a compiler hint to not keep data across it. This is dealing with concurrency issues on the *same* cpu due to preemption and irqs. It avoids the interrupt disable. There no memory barrier issues for code running on a single cpu. The cpu is always guaranteed to have a consistent view of the data. There is an additional patchset that also uses a cmpxchg_double for the slowpath. There barrier issues may arise because concurrent access is possible but that is likely to be merged only in 2.6.41. The cmpxchg_double in that case is a locked operation. > Things that work on x86 may not work on non-x86. Everything should be > per-cpu _except_ for the initialization, I think, but that should be > double-checked. The fallback path is using interrupt disable / enable. This must be working on all arches AFAICT. > My gut reaction would be: let's do the minimal patch that just fixes > things to do irqsafe_cpu_cmpxchg_double() for 2.6.39, and then let's > remove the #ifdef'fery in -rc1. Or make _really_ sure that things are > ok for platforms that never even triggered the CMPXCHG_LOCAL case > before. > > Hmm? Ok. Pekka can put that patch in for the next round of merges? -- 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/