On Tue, 17 Dec 2013 13:42:48 +0100
Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> >> @@ -1068,8 +1082,10 @@ unsigned long wait_task_inactive(struct
> >> * is actually now running somewhere else!
> >> */
> >> while (task_running(rq, p)) {
> >> - if (match_state && unlikely(p->state != match_state))
> >> + if (match_state && unlikely(p->state != match_state)
> >> + && unlikely(p->saved_state != match_state))
> >> return 0;
> >> + }
> >
> >Yeah, it should just be:
> >
> > if (match_state && check_task_state(p, match_state))
> > return 0;
>
> Are you sure?
No :-)
> If the state matches we should continue as long as it runs
> therefore I would go for !check_task_state(). The problem here was that
Yeah yeah, hey, I typed it by hand, no cut and paste there. Thus, I
dropped the '!' by accident ;-)
Hey! Here's a case where cut and paste would have prevented the bug!
> I return 0 in both cases.
>
> >Also, looking at check_task_state():
> >
> >+static bool check_task_state(struct task_struct *p, long match_state)
> >+{
> >+ bool match = false;
> >+
> >+ raw_spin_lock_irq(&p->pi_lock);
> >+ if (p->state == match_state)
> >+ match = true;
> >+ else if (p->saved_state == match_state)
> >+ match = true;
> >
> >Why the if () else if()? and not just:
> >
> > if (p->state == match_state || p->save_state == match_state)
> > match = true;
> >?
> >
> >The else if makes me think there's something missing.
>
> Okay I can do this. But regarding the check_task_state part, I think I
> should go with:
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1076,9 +1076,7 @@ static bool check_task_state(struct task_struct *p, long match_state)
> bool match = false;
>
> raw_spin_lock_irq(&p->pi_lock);
> - if (p->state == match_state)
> - match = true;
> - else if (p->saved_state == match_state)
> + if (p->state == match_state || p->saved_state == match_state)
> match = true;
> raw_spin_unlock_irq(&p->pi_lock);
>
> @@ -1129,11 +1127,8 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state)
> * is actually now running somewhere else!
> */
> while (task_running(rq, p)) {
> - if (match_state) {
> - if (!unlikely(check_task_state(p, match_state)))
> - return 0;
> + if (match_state && !check_task_state(p, match_state))
Ah, it was that "!unlikely(" that caused me to miss the '!'. That
should have been: likely(!check_task_state()). But anyway, I rather
just keep what you wrote and drop the unlikely altogether.
> return 0;
> - }
> cpu_relax();
> }
>
>
> Any objections?
>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
