Re: [PATCH tip/core/rcu 2/3] rcu: make hot-unplugged CPU relinquish its own RCU callbacks

Paul E. McKenney
2009-10-07T13:51:29Z

On Wed, Oct 07, 2009 at 09:16:12AM -0400, Steven Rostedt wrote:
> Paul,
>
> Still suffering jetlag? ;-)

As a matter of fact, yes. ;-)

> On Tue, 2009-10-06 at 21:48 -0700, Paul E. McKenney wrote:
> > From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> >
> > The current interaction between RCU and CPU hotplug requires that
> > RCU block in CPU notifiers waiting for callbacks to drain. This can
> > be greatly simplified by haing each CPU relinquish its own callbacks,
> having
>
> > and for both _rcu_barrier() and CPU_DEAD notifiers to adopt all callbacks
> > that were previously relinquished. This change also eliminates the
> > possibility of certain types of hangs due to the previous practice of
> > waiting for callbacks to be invoked from within CPU notifiers. If you
> > don't every wait, you cannot hang.
> ever
>
> ;-)

Courtesy of "git cherry-pick" and my being out of it. ;-)

Thanx, Paul

> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> -- Steve
>
>