* Peter Maydell (peter.mayd...@linaro.org) wrote:
> On Tue, 29 Oct 2019 at 23:00, Michael S. Tsirkin <m...@redhat.com> wrote:
> >
> > From: Jens Freimann <jfreim...@redhat.com>
> >
> > This patch adds a new migration state called wait-unplug. It is entered
> > after the SETUP state if failover devices are present. It will transition
> > into ACTIVE once all devices were succesfully unplugged from the guest.
> >
> > So if a guest doesn't respond or takes long to honor the unplug request
> > the user will see the migration state 'wait-unplug'.
> >
> > In the migration thread we query failover devices if they're are still
> > pending the guest unplug. When all are unplugged the migration
> > continues. If one device won't unplug migration will stay in wait_unplug
> > state.
> >
> > Signed-off-by: Jens Freimann <jfreim...@redhat.com>
> > Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> > Message-Id: <20191029114905.6856-9-jfreim...@redhat.com>
> > Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
> > Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> > ---
>
> Hi; Coverity has just (rather belatedly) noticed a possible
> issue in this code (CID 1429995):
>
> > @@ -3264,6 +3270,19 @@ static void *migration_thread(void *opaque)
> >
> > qemu_savevm_state_setup(s->to_dst_file);
> >
> > + if (qemu_savevm_nr_failover_devices()) {
> > + migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
> > + MIGRATION_STATUS_WAIT_UNPLUG);
> > +
> > + while (s->state == MIGRATION_STATUS_WAIT_UNPLUG &&
> > + qemu_savevm_state_guest_unplug_pending()) {
> > + qemu_sem_timedwait(&s->wait_unplug_sem, 250);
>
> Here we call qemu_sem_timedwait() but ignore the return value,
> whereas all the other callsites for that function do something
> with the return value. Is the code correct? (This is just a
> heuristic Coverity has, and it's wrong a fair amount of the
> time, so if it's wrong here too I can just mark it as a
> false-positive in the Coverity UI.)
Hmm it's OK; that semaphore isn't really used at the moment,
so it's pretty much just a sleep. And the loop always
calls the qemu_savevm_state_guest_unplug_pending() before
it goes around again; so it doesn't care if the return
value indicates timeout or not.
Dave
> thanks
> -- PMM
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
