Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756093Ab0HXVkF (ORCPT ); Tue, 24 Aug 2010 17:40:05 -0400 Received: from router-fw.net-space.pl ([89.174.63.77]:48926 "EHLO router-fw.net-space.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755993Ab0HXVkC (ORCPT ); Tue, 24 Aug 2010 17:40:02 -0400 Date: Tue, 24 Aug 2010 23:39:31 +0200 From: Daniel Kiper To: Yinghai Lu Cc: "H. Peter Anvin" , Daniel Kiper , mingo@redhat.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@elte.hu, linux-tip-commits@vger.kernel.org Subject: Re: [tip:x86/urgent] x86, apic: Fix apic=debug boot crash Message-ID: <20100824213931.GA1192@router-fw-old.local.net-space.pl> References: <20100819224616.GB9967@router-fw-old.local.net-space.pl> <20100823081212.GA13297@router-fw-old.local.net-space.pl> <9cca0990-1b78-40e7-a71d-f550b4f504aa@email.android.com> <4C72B6F7.8010706@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C72B6F7.8010706@kernel.org> User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1846 Lines: 70 Hello, On 08/23/2010 07:54 AM, H. Peter Anvin wrote: > It's already applied. Thx. On Mon, Aug 23, 2010 at 10:59:19AM -0700, Yinghai Lu wrote: [...] > >>>> x86, apic: Fix apic=debug boot crash > >>>> > >>>> Fix a boot crash when apic=debug is used and the APIC is > >>>> not properly initialized. > >>>> > >>>> This issue appears during Xen Dom0 kernel boot but the > >>>> fix is generic and the crash could occur on real hardware > >>>> as well. > >>> > >>> Do you have any report on real hardware? > >>> that could not happen on real hardware. > >> > >> Till now no, however I think it is good idea > >> to apply this patch now. It is not worth to wait > >> for another null pointer dereference. > > no, we should add BUG_ON() etc debug info there to see why that null cfg could happen. > because according to code, we should have null there. I think that BUG_ON() is too strong here because it is "debug" function and it should work also with let's say "invalid" data (in Xen case it is normal because APIC state is managed directly by hypervisor). Additionally, with this patch it is easy to differentiate between cfg != NULL and cfg == NULL. Please look below: cfg != NULL: IRQ to pin mappings: IRQ0 -> 0:2 IRQ1 -> 0:1 IRQ3 -> 0:3 IRQ4 -> 0:4 IRQ5 -> 0:5 IRQ6 -> 0:6 IRQ7 -> 0:7 IRQ8 -> 0:8 IRQ9 -> 0:9 IRQ10 -> 0:10 IRQ11 -> 0:11 IRQ12 -> 0:12 IRQ13 -> 0:13 IRQ14 -> 0:14 IRQ15 -> 0:15 .................................... done. cfg == NULL: IRQ to pin mappings: .................................... done. If I missed something or if you have any questions please drop me a line. Daniel -- 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/