Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751926AbbBHBMq (ORCPT ); Sat, 7 Feb 2015 20:12:46 -0500 Received: from mail.orcon.net.nz ([219.88.242.52]:47657 "EHLO mail.orcon.net.nz" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750747AbbBHBMo (ORCPT ); Sat, 7 Feb 2015 20:12:44 -0500 Date: Sun, 8 Feb 2015 14:12:04 +1300 From: Michael Cree To: Greg KH Cc: Mathieu Desnoyers , linux-alpha@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , Huang Ying , linux-kernel@vger.kernel.org, Paul McKenney , David Howells , Pranith Kumar , stable@vger.kernel.org Subject: Re: [PATCH] llist: Fix missing lockless_dereference() Message-ID: <20150208011204.GB10472@omega> Mail-Followup-To: Michael Cree , Greg KH , Mathieu Desnoyers , linux-alpha@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , Huang Ying , linux-kernel@vger.kernel.org, Paul McKenney , David Howells , Pranith Kumar , stable@vger.kernel.org References: <1423274934-10625-1-git-send-email-mathieu.desnoyers@efficios.com> <20150207221625.GB31119@kroah.com> <1117480383.90061.1423348244225.JavaMail.zimbra@efficios.com> <20150208004729.GA10472@omega> <20150208005941.GA3524@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150208005941.GA3524@kroah.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Bayes-Prob: 0.0001 (Score 0: No Bayes scoring rules defined, tokens from: outbound) X-Spam-Score: -2.33 () [Hold at 3.00] FREEMAIL_FROM:0.001,FSL_HELO_NON_FQDN_1:0.001,HELO_NO_DOMAIN:0.001,PORN_RP_NASTY:0.3,RDNS_DYNAMIC:0.363,CC(NZ:-3) X-CanIt-Geo: ip=60.234.221.162; country=NZ; latitude=-41.0000; longitude=174.0000; http://maps.google.com/maps?q=-41.0000,174.0000&z=6 X-CanItPRO-Stream: base:outbound X-Canit-Stats-ID: 01NNBc5Hs - ba3a089f2366 - 20150208 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1968 Lines: 43 On Sun, Feb 08, 2015 at 08:59:41AM +0800, Greg KH wrote: > On Sun, Feb 08, 2015 at 01:47:29PM +1300, Michael Cree wrote: > > On Sat, Feb 07, 2015 at 10:30:44PM +0000, Mathieu Desnoyers wrote: > > > > On Fri, Feb 06, 2015 at 09:08:21PM -0500, Mathieu Desnoyers wrote: > > > > > A lockless_dereference() appears to be missing in llist_del_first(). > > > > > It should only matter for Alpha in practice. > > > > What could one anticipate to be the symptoms of such a missing > > lockless_dereference()? > > > > The Alpha kernel is behaving pretty well provided one builds a machine > > specific kernel and UP. When running an SMP kernel some packages > > (most notably the java runtime, but there are a few others) occasionally > > lock up in a pthread call --- could be a problem in libc rather then the > > kernel. > > Hm, if only UP alpha needs to be supported, odds are we could rip a lot > of odd stuff out of the kernel that deals with memory barriers and other > nasty locking things that the Alpha requires. > > Would that be ok? Or is someone somewhere going to want to be running a > SMP kernel on Alpha in the future? I am running an SMP kernel on a 3-cpu Alpha system; it mostly works just fine. I was just noting that there is something up with java---it locks up occassionally in a pthread call, and there are a few other packages that occasionally fail in test suites when being built under an SMP kernel but always pass when built under an UP kernel which suggests there is a little buglet somewhere in the SMP code, either in the kernel or in libc. Running an SMP system for the Debian Alpha build daemon at debian-ports is really useful for keeping up with the other architectures. Cheers Michael. -- 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/