Re: [PATCH tip/core/rcu 02/20] x86: Use common outgoing-CPU-notification code

Paul E. McKenney
2015-03-03T19:42:30Z

On Tue, Mar 03, 2015 at 02:17:24PM -0500, Boris Ostrovsky wrote:
> On 03/03/2015 12:42 PM, Paul E. McKenney wrote:
> > }
> >@@ -511,7 +508,8 @@ static void xen_cpu_die(unsigned int cpu)
> > schedule_timeout(HZ/10);
> > }
> >- cpu_die_common(cpu);
> >+ (void)cpu_wait_death(cpu, 5);
> >+ /* FIXME: Are the below calls really safe in case of timeout? */
>
>
> Not for HVM guests (PV guests will only reach this point after
> target cpu has been marked as down by the hypervisor).
>
> We need at least to have a message similar to what native_cpu_die()
> prints on cpu_wait_death() failure. And I think we should not call
> the two routines below (three, actually --- there is also
> xen_teardown_timer() below, which is not part of the diff).
>
> -boris
>
>
> > xen_smp_intr_free(cpu);
> > xen_uninit_lock_cpu(cpu);

So something like this, then?

if (cpu_wait_death(cpu, 5)) {
xen_smp_intr_free(cpu);
xen_uninit_lock_cpu(cpu);
xen_teardown_timer(cpu);
}

Easy change for me to make if so!

Or do I need some other check for HVM-vs.-PV guests, and, if so, what
would that check be? And also if so, is it OK to online a PV guest's
CPU that timed out during its previous offline?

Thanx, Paul