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Re: [Xen-devel] [PATCH 2/6] xen/hvm kexec: unregister shutdown+sysrq wat

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 2/6] xen/hvm kexec: unregister shutdown+sysrq watches during reboot
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Date: Thu, 28 Jul 2011 12:37:32 +0100
Cc: Olaf Hering <olaf@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Thu, 28 Jul 2011, Jan Beulich wrote:
> >>> On 26.07.11 at 13:52, Olaf Hering <olaf@xxxxxxxxx> wrote:
> > Unregister the shutdown and sysrq watch during kexec.  The watches can
> > not be re-registered in the kexec kernel because they are still seen as
> > busy by xenstore.
> 
> This and subsequent patches don't look right to me from a conceptual
> pov: If the kexec attempt is due to a crash, the dying kernel should be
> doing as little as possible, and the new kernel should really do the
> cleanup. The more logic gets added to the shutdown path of the old
> kernel, the more likely it'll become that the kexec attempt will fail.
> 
> If this requires changes outside the kernel (e.g. state reset helpers
> in hypervisor or tools) - so be it.

I agree.
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