On Sat, 2012-09-08 at 14:13 +0530, Srikar Dronamraju wrote:
> >
> > signed-off-by: Andrew Theurer <habanero@xxxxxxxxxxxxxxxxxx>
> >
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index fbf1fd0..c767915 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -4844,6 +4844,9 @@ bool __sched yield_to(struct task_struct *p, bool
> > preempt)
> >
> > again:
> > p_rq = task_rq(p);
> > + if (task_running(p_rq, p) || p->state || !(p_rq->curr->flags &
> > PF_VCPU)) {
> > + goto out_no_unlock;
> > + }
> > double_rq_lock(rq, p_rq);
> > while (task_rq(p) != p_rq) {
> > double_rq_unlock(rq, p_rq);
> > @@ -4856,8 +4859,6 @@ again:
> > if (curr->sched_class != p->sched_class)
> > goto out;
> >
> > - if (task_running(p_rq, p) || p->state)
> > - goto out;
>
> Is it possible that by this time the current thread takes double rq
> lock, thread p could actually be running? i.e is there merit to keep
> this check around even with your similar check above?
I think that's a good idea. I'll add that back in.
>
> >
> > yielded = curr->sched_class->yield_to_task(rq, p, preempt);
> > if (yielded) {
> > @@ -4879,6 +4880,7 @@ again:
> >
> > out:
> > double_rq_unlock(rq, p_rq);
> > +out_no_unlock:
> > local_irq_restore(flags);
> >
> > if (yielded)
> >
> >
>
-Andrew Theurer
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