From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (netops-testserver-4-out.sgi.com [192.48.171.29]) by ozlabs.org (Postfix) with ESMTP id 0CC1FDDE26 for ; Thu, 4 Oct 2007 05:33:09 +1000 (EST) Message-ID: <4703EBE0.7080106@sgi.com> Date: Wed, 03 Oct 2007 12:22:08 -0700 From: Mike Travis MIME-Version: 1.0 To: Paul Jackson Subject: Re: [PATCH 08/10] ia64: Convert cpu_sibling_map to a per_cpu data array (v3) References: <20070912015644.927677070@sgi.com> <20070912015647.214306428@sgi.com> <20070928024901.24ab6c99.pj@sgi.com> In-Reply-To: <20070928024901.24ab6c99.pj@sgi.com> Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-mm@kvack.org, ak@suse.de, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, sparclinux@vger.kernel.org, akpm@linux-foundation.org, clameter@sgi.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Paul, I just now found this. I'll take a look immediately. I tried it on a couple of systems but not margin. Thanks, Mike Paul Jackson wrote: > Mike, > > I think there is a bug either in this ia64 patch, or in the related > generic arch patch: Convert cpu_sibling_map to be a per cpu variable > (v3). > > It dies early in boot on me, on the SGI internal 8 processor IA64 > system that you and I know as 'margin'. The death is a hard hang, due > to a corrupt stack, due to a bogus cpu index. > > I haven't tracked it down all the way, but have gotten this far. If I add > the following patch, I get a panic on the BUG_ON if I have these two patches > in 2.6.23-rc8-mm1, but it boots just fine if I don't have these two patches. > > It seems that the "cpu_sibling_map[cpu]" cpumask_t is empty (all zero > bits) with your two patches applied, but has some non-zero bits > otherwise, which leads to 'group' being NR_CPUS instead of a useful CPU > number. Unfortunately, I have no idea why the "cpu_sibling_map[cpu]" > cpumask_t is empty -- good luck on that part. > > The patch that catches this bug earlier is this: > > --- 2.6.23-rc8-mm1.orig/kernel/sched.c 2007-09-28 01:42:20.144561024 -0700 > +++ 2.6.23-rc8-mm1/kernel/sched.c 2007-09-28 02:27:14.239075497 -0700 > @@ -5905,6 +5905,7 @@ static int cpu_to_phys_group(int cpu, co > #else > group = cpu; > #endif > + BUG_ON(group == NR_CPUS); > if (sg) > *sg = &per_cpu(sched_group_phys, group); > return group; > >