[PATCH 1/1] sched/core: Fix migrate_swap() vs. hotplug

[Peter Zijlstra]

On Fri, Jun 06, 2025 at 11:46:57AM +0800, Kuyo Chang wrote:

> Thank you for your patch.
> I believe this patch also effectively addresses this race condition.
> I will queue it in our test pool for testing.

Thank you; I shall await the results!


> > @@ -101,12 +98,12 @@ static bool cpu_stop_queue_work(unsigned int
> > cpu, struct cpu_stop_work *work)
> >         raw_spin_lock_irqsave(&stopper->lock, flags);
> >         enabled = stopper->enabled;
> >         if (enabled)
> > -               __cpu_stop_queue_work(stopper, work, &wakeq);
> > +               __cpu_stop_queue_work(stopper, work);
> >         else if (work->done)
> >                 cpu_stop_signal_done(work->done);
> >         raw_spin_unlock_irqrestore(&stopper->lock, flags);
> > 
> > -       wake_up_q(&wakeq);
> > +       wake_up_process(stopper->thread);
> 
> BTW, should we add enabled check here?
> 	if (enabled) 
> 		wake_up_process(stopper->thread);

Ah yes. Spuriously waking the stopper thread is harmless, but wasteful.

> >         preempt_enable();
> > 
> >         return enabled;