Re: [Qemu-devel] [Qemu-block] Clean Block Driver Shutdown

[Stefan Hajnoczi <stefanha@gmail.com>]

On Tue, Oct 17, 2017 at 01:46:25PM +0200, Kevin Wolf wrote:
> Am 17.10.2017 um 12:33 hat Peter Lieven geschrieben:
> > I noticed that Qemu quits at several points with an exit() if the
> > supplied parameters in the commandline are incorrect. This at some
> > stages happens after there have already been connections to storage
> > backends established.
> 
> Maybe we need to come to the conclusion that exit() is always wrong,
> even during the initialisation.
> 
> > These connections are not cleanly shut down in this case. For posix
> > file backends that doesn't matter, but for other backends this leads
> > to errors. E.g. iSCSI Targets log an aborted iSCSI connection due to
> > tcp reset.
> > 
> > I wonder what is the best way to fix this. A simply call to
> > bdrv_close_all() in an atexit handler seems to work.  But is this a
> > good solution? Maybe register this handler only until the VM starts.
> > Or do we need an atexit handler in each block driver that requires a
> > clean shutdown?
> 
> No, definitely not code in every single block driver. We need to make
> sure to properly clean up what has been started.
> 
> An atexit handler is probably relatively easy. I think it would be
> cleaner to have proper error paths even in main(), like in every other
> function. I'm not sure if this would be reasonably easy to achieve,
> though.

I agree that converting from exit(3) to real error handling is cleanest.
Doing so would also be a good opportunity to consolidate ad-hoc
fprintf(stderr) and error_report() calls.

Stefan