On Thu, 12 Jul 2007 12:48:41 +1000 Rusty Russell <[EMAIL PROTECTED]> wrote:
> On Wed, 2007-07-11 at 19:28 -0700, David Miller wrote:
> > From: Rusty Russell <[EMAIL PROTECTED]>
> > Date: Thu, 12 Jul 2007 11:21:51 +1000
> >
> > > To do inter-guest (ie. inter-process) I/O you really have to make sure
> > > the other side doesn't go away.
> >
> > You should just let it exit and when it does you receive some kind of
> > exit notification that resets your virtual device channel.
> >
> > I think the reference counting approach is error and deadlock prone.
> > Be more loose and let the events reset the virtual devices when
> > guests go splat.
>
> There are two places where we grab task refcnt. One might be avoidable
> (will test and get back) but the deferred wakeup isn't really:
>
> /* We cache one process to wakeup: helps for batching & wakes outside
> locks. */
> void set_wakeup_process(struct lguest *lg, struct task_struct *p)
> {
> if (p == lg->wake)
> return;
>
> if (lg->wake) {
> wake_up_process(lg->wake);
> put_task_struct(lg->wake);
> }
> lg->wake = p;
> if (lg->wake)
> get_task_struct(lg->wake);
> }
<handwaving>
We seem to be taking the reference against the wrong thing here. It should
be against the mm, not against a task_struct?
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