On (Wed) 07 Dec 2011 [12:34:48], Michael S. Tsirkin wrote:
> On Wed, Dec 07, 2011 at 01:18:50AM +0530, Amit Shah wrote:
> > Now to not race with a host issuing ballooning requests while we are in
> > the process of freezing, we just exit from the vballoon kthread when the
> > processes are asked to freeze. Upon thaw and restore, we re-start the
> > thread.
>
> ...
>
> > ---
> > drivers/virtio/virtio_balloon.c | 79 ++++++++++++++++++++++++++++++++++++++-
> > 1 files changed, 78 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> > index 8bf99be..10ec638 100644
> > --- a/drivers/virtio/virtio_balloon.c
> > +++ b/drivers/virtio/virtio_balloon.c
> > @@ -258,7 +258,13 @@ static int balloon(void *_vballoon)
> > while (!kthread_should_stop()) {
> > s64 diff;
> >
> > - try_to_freeze();
> > + /*
> > + * On suspend, we want to exit this thread. We will
> > + * start a new thread on resume.
> > + */
> > + if (freezing(current))
> > + break;
> > +
> > wait_event_interruptible(vb->config_change,
> > (diff = towards_target(vb)) != 0
> > || vb->need_stats_update
>
> ...
>
> Note: this relies on kthreads being frozen before devices.
> Looking at kernel/power/hibernate.c this is the case,
> but I think we should add a comment to note this.
Yes, it does. And for that reason, I mentioned that stopping the
thread doesn't buy us anything; I'll revert this change in the next
submission.
> Also Cc linux-pm crowd in case I got it wrong.
Amit
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