Re: [BUG almost bisected] Splat in dequeue_rt_stack() and build error

[Valentin Schneider]

On 28/08/24 09:35, Paul E. McKenney wrote:
> On Wed, Aug 28, 2024 at 04:32:41PM +0200, Valentin Schneider wrote:
>> On 28/08/24 21:44, Chen Yu wrote:
>> >
>> > One question, although there is no DEQUEUE_DELAYED flag, it is possible
>> > the delayed task could be dequeued from CFS tree. Because the dequeue in
>> > set_schedule() does not have DEQUEUE_SLEEP. And in dequeue_entity():
>> >
>> >       bool sleep = flags & DEQUEUE_SLEEP;
>> >
>> >       if (flags & DEQUEUE_DELAYED) {
>> >
>> >       } else {
>> >               bool delay = sleep;
>> >               if (sched_feat(DELAY_DEQUEUE) && delay &&  //false
>> >                  !entity_eligible(cfs_rq, se) {
>> >               //do not dequeue
>> >               }
>> >       }
>> >
>> >       //dequeue the task    <---- we should reach here?
>> >
>>
>> You're quite right, so really here the main missing bit would be the final
>> __block_task() that a DEQUEUE_DELAYED dequeue_entities() would get us.
>
> 50*TREE03 passed, yay!  Thank you both!!!
>

Fantastic, I'll hammer this into a "proper" patch then. Thanks again for
all the testing!

> I started a 500*TREE03.
>
> Yes, the odds all 50 passing given the baseline 52% failure rate is
> something like 10^-16, but software bugs are not necessarily constrained
> by elementary statistics...
>

:-)

>                                                       Thanx, Paul