Re: [Qemu-devel] [PATCH 0/1] add exit-script option to qemu

[Dominik Csapak]

On 10/4/18 3:51 PM, Daniel P. Berrangé wrote:
> On Wed, Oct 03, 2018 at 11:13:43AM +0200, Dominik Csapak wrote:
> > this patch aims to execute a script when qemu exits
> > so that one can do cleanups when using --daemonize without
> > having to use the qmp monitor
>
> IMHO the idea of cleanup scripts run by QEMU itself is flawed.
> QEMU will inevitably crash before cleanup scripts can be run,
> so whatever mgmt app is using QEMU needs to be able to do
> cleanup without QEMU's help.
>
> I think this can be done more reliably with a wrapper script,
> that spawns QEMU, waits for it to exit and then calls the
> cleanup script. On Linux at least you can use prctl() with
> PR_SET_CHILD_SUBREAPER so you can detect exit'ing of QEMU
> even after it has daemonized.
>
> Perhaps we could have such a wrapper script put in the
> contrib directory
>
> Regards,
> Daniel
Hi,

for cleaning up after qemu crashes, you are completely right,
(ignoring that the downscript for tap devices also never gets executed
then), but this series has another use.

With it, a user can determine the reason of a graceful shutdown
(e.g., if it was by a signal, qmp or from inside) of qemu,
especially when using -no-reboot without using qmp

and using qmp for that is not very practical for everyone,
or is there another way for that which i am missing?

Regards,
Dominik