Re: cpu stopper threads and setaffinity leads to deadlock

[Sodagudi Prasad]

On 2018-08-03 04:41, Thomas Gleixner wrote:
> Prasad.
>
> On Thu, 2 Aug 2018, Peter Zijlstra wrote:
> > So why didn't you do the 'obvious' parallel to what you did for
> > cpu_stop_queue_two_works(), namely:
>
> Is that patch fixing the issue for you?
<Prasad> Hi Thomas and Peter,

Yes. Tested both versions of patches and both variants are working on 
Qualcomm devices
with stress testing of set affinity and tasks cross-migration, which 
were previously leading to the deadlock.

-Thanks, Prasad
> > --- a/kernel/stop_machine.c
> > +++ b/kernel/stop_machine.c
> > @@ -81,6 +81,7 @@ static bool cpu_stop_queue_work(unsigned
> >  	unsigned long flags;
> >  	bool enabled;
> >
> > +	preempt_disable();
> >  	raw_spin_lock_irqsave(&stopper->lock, flags);
> >  	enabled = stopper->enabled;
> >  	if (enabled)
> > @@ -90,6 +91,7 @@ static bool cpu_stop_queue_work(unsigned
> >  	raw_spin_unlock_irqrestore(&stopper->lock, flags);
> >
> >  	wake_up_q(&wakeq);
> > +	preempt_enable();
> >
> >  	return enabled;
> >  }

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