Re: [Qemu-devel] [Qemu-block] [PATCH 4/4] virtio-blk: Clean up start/stop with mutex and BH

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Thu, 24 Mar 2016 16:19:41 +0800
tu bo <tubo@linux.vnet.ibm.com> wrote:

> Hi Christian:
> 
> On 03/23/2016 05:12 PM, Christian Borntraeger wrote:
> > On 03/23/2016 10:08 AM, Paolo Bonzini wrote:
> >>
> >>
> >> On 23/03/2016 09:10, Cornelia Huck wrote:
> >>>> -    /* Kick right away to begin processing requests already in vring */
> >>>> -    event_notifier_set(virtio_queue_get_host_notifier(s->vq));
> >>>> +    vblk->dataplane_started = true;
> >>>>
> >>>> -    /* Get this show started by hooking up our callbacks */
> >>>> +    /* Get this show started by hooking up our callbacks.  */
> >>>>       aio_context_acquire(s->ctx);
> >>>>       virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, true, true);
> >>>>       aio_context_release(s->ctx);
> >>>> +    atomic_dec(&s->starting);
> >>>> +
> >>>> +    /* Kick right away to begin processing requests already in vring */
> >>>> +    event_notifier_set(virtio_queue_get_host_notifier(s->vq));
> >>>
> >>> I'm wondering whether moving this event_notifier_set() masks something?
> >>> IOW, may we run into trouble if the event notifier is set from some
> >>> other path before the callbacks are set up properly?
> >>
> >> The reentrancy check should catch that...  But:
> >>
> >> 1) the patch really makes no difference, your fix is enough for me
> >
> >
> > Tu Bo, can you test with master + Cornelias 6 refactoring patches and nothing on top?
> 
> With qemu master + Cornelia's 6 refactoring patches and nothing on top, 
> I did NOT see crash so far.

Cool, thanks for testing!

I'll re-send my patches with some added interface doc in patch 1. Stay
tuned.