Re: [PATCH 2/6] xen/hvm kexec: unregister shutdown+sysrq watches during reboot

[Olaf Hering <olaf@aepfle.de>]

On Thu, Jul 28, Ian Campbell wrote:

> Getting into the kdump kernel is a kexec like operation though and
> shares many of the code paths, doesn't it?

The big difference is that kdump is entered in an unreliable state,
while kexec is a controlled reboot.

> > > If this requires changes outside the kernel (e.g. state reset helpers
> > > in hypervisor or tools) - so be it.
> > 
> > Are you suggesting that there have to be ways for a domU to query the
> > state of its registered watches and shut them all down during very early
> > boot?
> 
> Perhaps the xenstore protocol could be enhanced with a mechanism to
> clear all existing watches? A kernel could call that at start of day.

I wonder why xenstore knows that sysrq and shutdown nodes are busy,
while the device, backend and state files can be watched twice.

Olaf