From mboxrd@z Thu Jan 1 00:00:00 1970 From: Don Zickus Subject: Re: [PATCH v2] kdump: Fix crash_kexec - smp_send_stop race in panic Date: Tue, 1 Nov 2011 16:04:20 -0400 Message-ID: <20111101200420.GN17705@redhat.com> References: <1319639649.3321.11.camel@br98xy6r> <20111028161143.e5ebf617.akpm@linux-foundation.org> <1320055036.2796.8.camel@br98xy6r> <20111031033948.a0edb7f3.akpm@linux-foundation.org> <1320064459.2796.26.camel@br98xy6r> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx1.redhat.com ([209.132.183.28]:11975 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750939Ab1KAUEc (ORCPT ); Tue, 1 Nov 2011 16:04:32 -0400 Content-Disposition: inline In-Reply-To: <1320064459.2796.26.camel@br98xy6r> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Michael Holzheu Cc: Andrew Morton , linux-arch@vger.kernel.org, heiko.carstens@de.ibm.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, "Eric W. Biederman" , schwidefsky@de.ibm.com, Vivek Goyal On Mon, Oct 31, 2011 at 01:34:19PM +0100, Michael Holzheu wrote: > Hello Andrew, hello linux-arch, > > > Well OK. Maybe some architectures do have this problem - who would > > notice? If that is the case, we just made the failure cases much more > > common. Could you check, please? > > @linux-arch: > > This patch introduces a spinlock to prevent parallel execution of the > panic code. Andrew pointed out that this might be a problem for > architectures that can't do smp_send_stop() on remote CPUs that have > interrupts disabled. When irq-disabled CPUs execute panic() in parallel, > we then would have looping CPUs. x86 has such problem and I posted a patch recently to fix it https://lkml.org/lkml/2011/10/13/426 Cheers, Don