Hi Sebastian,
On Tue, 2020-06-09 at 18:34 +0200, Sebastian Andrzej Siewior wrote:
> On 2020-06-09 11:17:53 [-0500], Tom Zanussi wrote:
> > Hi Sebastian,
>
> Hi Tom,
>
> > I did find a problem with the patch when configured as !SMP since
> > in
> > that case the RUN flag is never set (will send a patch for that
> > shortly), but that wouldn't be the case here.
>
> How?
>
My test machine with !SMP and !RT doesn't boot, and in that case we
have:
#define tasklet_trylock(t) 1
#define tasklet_tryunlock(t) 1
instead of setting/clearing the RUN flag.
So the cmpxchg with RUN+CHAIN can never work and we hit the loop.
> > #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
> > static inline int tasklet_trylock(struct tasklet_struct *t)
> > {
> > return !test_and_set_bit(TASKLET_STATE_RUN, &(t)->state);
> > }
>
> I can't tell from the backtrace if he runs with RT or without but I
> assumed RT. But yes, for !SMP && !RT it would explain it.
>
Yeah, for me !SMP and RT works, but !SMP and !RT doesn't.
I had assumed he was talking about the samely configured kernel, but
apparently it's not.
Tom
> > It would help to be able to reproduce it, but I haven't been able
> > to
> > yet.
> >
> > Tom
> >
>
> Sebastian
