Re: [PATCH RT 1/2] tasklet: Address a race resulting in double-enqueue

[Sebastian Andrzej Siewior]

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?

| #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.

> It would help to be able to reproduce it, but I haven't been able to
> yet.
> 
> Tom
> 
Sebastian