Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265234AbUJLOla (ORCPT ); Tue, 12 Oct 2004 10:41:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264980AbUJLOjz (ORCPT ); Tue, 12 Oct 2004 10:39:55 -0400 Received: from ipx20189.ipxserver.de ([80.190.249.56]:63109 "EHLO ipx20189.ipxserver.de") by vger.kernel.org with ESMTP id S265773AbUJLOiC (ORCPT ); Tue, 12 Oct 2004 10:38:02 -0400 Date: Tue, 12 Oct 2004 17:38:10 +0300 (EAT) From: Zwane Mwaikambo To: Nathan Lynch Cc: Ingo Molnar , Andrew Morton , Linux Kernel , Rusty Russell Subject: Re: [PATCH] i386 CPU hotplug updated for -mm In-Reply-To: <1097590569.6557.107.camel@biclops> Message-ID: References: <20041001204533.GA18684@elte.hu> <20041001204642.GA18750@elte.hu> <20041001143332.7e3a5aba.akpm@osdl.org> <1097560787.6557.99.camel@biclops> <20041012060410.GE1479@elte.hu> <1097590569.6557.107.camel@biclops> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1755 Lines: 43 On Tue, 12 Oct 2004, Nathan Lynch wrote: > On Tue, 2004-10-12 at 01:04, Ingo Molnar wrote: > > * Nathan Lynch wrote: > > > > > I fixed up the warning in cpu_down with the following patch and now am > > > running with that + 2.6.9-rc4-mm1 + your patch while doing continuous > > > online/offline and make -j8. It's been running for about 45 minutes > > > and I haven't seen the panic yet, although I'm at a loss to explain > > > why the change would fix it. Will let it run overnight and report > > > back... > > > > > /* Move it here so it can run. */ > > > - kthread_bind(p, smp_processor_id()); > > > + kthread_bind(p, get_cpu()); > > > + put_cpu(); > > > > > /* CPU is completely dead: tell everyone. Too late to complain. */ > > > if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu) > > > > hm, is there any assurance that smp_processor_id() == cpu? > > Actually, cpu != smp_processor_id(). cpu is the processor we have just > taken down at that point; we want the kthread to run on some other cpu. Nathan, thanks for doing that testing, the warning does indeed look to be a false positive. Looking at the code again, i realised that there might also be cases where someone does the following; preempt_disable(); cpu = smp_processor_id(); ... preempt_enable(); ... mod_local_cpu_variable[cpu]; So cached values of smp_processor_id() might also be a problem, although i haven't found any cases, but maybe that's just being overly paranoid =) - 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/