Re: [PATCH] cpuhotplug: introduce try_get_online_cpus() take 2

Paul E. McKenney
2009-06-08T14:25:46Z

On Mon, Jun 08, 2009 at 09:49:34AM +0530, Gautham R Shenoy wrote:
> Hi Paul,
>
> On Fri, Jun 05, 2009 at 08:37:14AM -0700, Paul E. McKenney wrote:
> >
> > One question for Gautham Shenoy -- are non-atomic CPU-hotplug notifiers
> > always invoked from the task that did the cpu_hotplug_begin()?
>
> Except for the notifiers handling two events, rest of the notifiers
> are always invoked from the task that did the cpu_hotplug_begin().
>
> The two events are CPU_DYING which is called from the context of the
> stop_machine_thread and CPU_STARTING which is called from the context of
> the idle thread on the CPU that has just come up. The notifiers handling
> these two events are expected to be atomic.
>
> > If so, well and good. If not, then it would not be possible to
> > expedite RCU grace periods from within CPU-hotplug notifiers.
>
> I hope this would be good enough :-)

Works for me!! ;-)

Thanx, Paul