From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756532Ab0D1Sv2 (ORCPT ); Wed, 28 Apr 2010 14:51:28 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53053 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756394Ab0D1Sv0 (ORCPT ); Wed, 28 Apr 2010 14:51:26 -0400 Date: Wed, 28 Apr 2010 11:50:39 -0700 From: Andrew Morton To: Prarit Bhargava Cc: linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com, x86@kernel.org, clalance@redhat.com, drjones@redhat.com, stable@kernel.org Subject: Re: [PATCH] Fix NULL pointer for Xen guests Message-Id: <20100428115039.c276594a.akpm@linux-foundation.org> In-Reply-To: <4BD87E72.4050609@redhat.com> References: <20100427152434.16193.49104.sendpatchset@prarit.bos.redhat.com> <20100428112658.4cf11292.akpm@linux-foundation.org> <4BD87E72.4050609@redhat.com> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.9; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 28 Apr 2010 14:29:06 -0400 Prarit Bhargava wrote: > > > On 04/28/2010 02:26 PM, Andrew Morton wrote: > > On Tue, 27 Apr 2010 11:24:42 -0400 > > Prarit Bhargava wrote: > > > > > >> Upstream PV guests fail to boot because of a NULL pointer. It is possible that > >> xen guests have irq_desc->chip_data = NULL. > >> > >> Test for NULL chip_data pointer before attempting to complete an irq move. > >> > >> Signed-off-by: Prarit Bhargava > >> Acked-by: Suresh Siddha > >> > >> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c > >> index 127b871..eb2789c 100644 > >> --- a/arch/x86/kernel/apic/io_apic.c > >> +++ b/arch/x86/kernel/apic/io_apic.c > >> @@ -2545,6 +2545,9 @@ void irq_force_complete_move(int irq) > >> struct irq_desc *desc = irq_to_desc(irq); > >> struct irq_cfg *cfg = desc->chip_data; > >> > >> + if (!cfg) > >> + return; > >> + > >> __irq_complete_move(&desc, cfg->vector); > >> } > >> #else > >> > > I assume this is needed for 2.6.34? > > > > What about 2.6.33.x and earlier? > > > > Hey Andrew, > > I actually pinged Chris Wright to see about including this in the > -stable branches. I haven't heard anything back so I'll reping him. > Well. Pinging people offlist isn't very reliable. Put Cc: at the end of the changelog and cc stable@kernel.org on the original patch and then the patch will reliably receive consideration for backporting. I have added Cc: to my copy of the patch, so the -stable guys will at least see it when I drop it after it is merged. But if the x86 maintainers were to merge your patch as you sent it, it would have no Cc: when it goes into Linus's tree. I worry that if the -stable maintainer see me drop a patch, but the patch in Linus's tree doesn't have the stable tag, they might not merge the fix into -stable. I bugged them about this scenario recently and the reply was a bit waffly ;) By far the safest thing to do is to include the stable tag in your changelog right at the outset.