Re: [Qemu-devel] [PATCH] vl.c/exit: pause cpus before closing block devices

[Paolo Bonzini]

----- Original Message -----
> From: "Dr. David Alan Gilbert" <address@hidden>
> To: "Alberto Garcia" <address@hidden>
> Cc: address@hidden, address@hidden, address@hidden
> Sent: Thursday, August 3, 2017 6:45:17 PM
> Subject: Re: [Qemu-devel] [PATCH] vl.c/exit: pause cpus before closing block 
> devices
> 
> * Alberto Garcia (address@hidden) wrote:
> > On Thu, Jul 13, 2017 at 08:01:16PM +0100, Dr. David Alan Gilbert (git)
> > wrote:
> > > --- a/vl.c
> > > +++ b/vl.c
> > > @@ -4787,8 +4787,8 @@ int main(int argc, char **argv, char **envp)
> > >      replay_disable_events();
> > >      iothread_stop_all();
> > >  
> > > -    bdrv_close_all();
> > >      pause_all_vcpus();
> > > +    bdrv_close_all();
> > >      res_free();
> > 
> > I haven't debugged it yet, but in my computer iotest 093 stops working
> > (it never finishes) after this change.
> 
> Yes, I can reproduce that here (I've got to explicitly run 093 - it
> doesn't do it automatically for me):

The culprit so to speak is this:

        if (qtest_enabled()) {
            /* For testing block IO throttling only */
            tg->clock_type = QEMU_CLOCK_VIRTUAL;
        }

So after pause_all_vcpus(), the clock doesn't advance and bdrv_close_all
hangs.  Should throttling be disabled by the time bdrv_close drains the
BlockDriverState, and likewise for bdrv_close_all?

Paolo