Re: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM

Peter Zijlstra
2011-05-26T17:15:23Z

On Thu, 2011-05-26 at 19:04 +0200, Oleg Nesterov wrote:
> On 05/26, Peter Zijlstra wrote:
> >
> > @@ -2636,7 +2636,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
> > * to spin on ->on_cpu if p is current, since that would
> > * deadlock.
> > */
> > - if (p == current) {
> > + if (cpu == smp_processor_id()) {
> > + p->sched_contributes_to_load = 0;
> > ttwu_queue(p, cpu);
>
> Btw. I do not pretend I really understand se->vruntime, but in this
> case we are doing enqueue_task() without ->task_waking(), however we
> pass ENQUEUE_WAKING. Is it correct?

No its not, that's the thing that I got wrong the first time and caused
these pauses.