Re: [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call

[Thomas Gleixner]

On Wed, 2 Mar 2016, Paul E. McKenney wrote:
> > --- a/kernel/cpu.c
> > +++ b/kernel/cpu.c
> > @@ -762,6 +762,7 @@ void cpuhp_report_idle_dead(void)
> >  	BUG_ON(st->state != CPUHP_AP_OFFLINE);
> >  	st->state = CPUHP_AP_IDLE_DEAD;
> >  	complete(&st->done);
> 
> Not to be repetitive or anything, but if we delay here, it can break
> RCU on a number of architectures.  Either the CPU can be killed holding
> one of RCU's locks or RCU can wrongly see the CPU as still being alive.
> Either can prevent future RCU grace periods from ever completing, thus
> OOMing the system.

Thanks for the reminder. I wanted to fix that, but then forgot again. Fix is
on the way.

Thanks,

	tglx