[libvirt] [PATCH] qemu: never send SIGKILL to qemu process unless specifically requested

[Daniel P. Berrange]

On Fri, Jan 27, 2012 at 01:35:35PM -0500, Laine Stump wrote:
> When libvirt is shutting down the qemu process, it first sends
> SIGTERM, then waits for 1.6 seconds and, if it sees the process still
> there, sends a SIGKILL.
> 
> There have been reports that this behavior can lead to data loss
> because the guest running in qemu doesn't have time to flush it's disk
> cache buffers before it's unceremoniously whacked.
> 
> One suggestion on how to solve that problem was to remove SIGKILL from
> the normal virDomainDestroyFlags, but still provide the ability to
> kill qemu with SIGKILL by using a new flag to virDomainDestroyFlags.
> This patch is a quick attempt at that in order to start a
> conversation on the topic.
> 
> So what are your opinions? Is this the right way to solve the problem?

No, we can't change the default semantics of virDomainDestroy in
this case. Applications expect that we do absolutely everything
possible to kill of the guest. This is particularly important for
cluster fencing usage. If we only use SIGTERM, then we're introducing
unacceptable risk to apps relying on this.

We could do the opposite though - have a flag to do a gracefully
destroy, leaving the default as un-graceful.

Daniel
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