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Date: Tue, 1 Nov 2011 16:04:20 -0400
From: Don Zickus <dzickus@redhat.com>
Subject: Re: [PATCH v2] kdump: Fix crash_kexec - smp_send_stop race in panic
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To: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: linux-arch@vger.kernel.org, heiko.carstens@de.ibm.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, "Eric W. Biederman" <ebiederm@xmission.com>, schwidefsky@de.ibm.com, Andrew Morton <akpm@linux-foundation.org>, Vivek Goyal <vgoyal@redhat.com>

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

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