Re: cpu stopper threads and setaffinity leads to deadlock

[Mike Galbraith]

On Thu, 2018-08-02 at 10:12 +0200, Peter Zijlstra wrote:
> On Wed, Aug 01, 2018 at 06:34:40PM -0700, Sodagudi Prasad wrote:
> > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
> > index e190d1e..f932e1e 100644
> > --- a/kernel/stop_machine.c
> > +++ b/kernel/stop_machine.c
> > @@ -87,9 +87,9 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct
> > cpu_stop_work *work)
> >                 __cpu_stop_queue_work(stopper, work, &wakeq);
> >         else if (work->done)
> >                 cpu_stop_signal_done(work->done);
> > -       raw_spin_unlock_irqrestore(&stopper->lock, flags);
> > 
> >         wake_up_q(&wakeq);
> > +       raw_spin_unlock_irqrestore(&stopper->lock, flags);
> > 
> 
> That puts the wakeup back under stopper lock, which causes another
> deadlock iirc.

Yup, one you fixed.

0b26351b910fb (Peter Zijlstra 2018-04-20 11:50:05 +0200 92)     wake_up_q(&wakeq);