Re: [PATCH v3 tip/core/rcu 3/9] rcu: Add synchronous grace-period waiting for RCU-tasks

Paul E. McKenney
2014-08-02T06:50:06Z

On Fri, Aug 01, 2014 at 11:32:51AM -0700, Paul E. McKenney wrote:
> On Fri, Aug 01, 2014 at 05:09:26PM +0200, Oleg Nesterov wrote:
> > On 07/31, Paul E. McKenney wrote:
> > >
> > > +void synchronize_rcu_tasks(void)
> > > +{
> > > + /* Complain if the scheduler has not started. */
> > > + rcu_lockdep_assert(!rcu_scheduler_active,
> > > + "synchronize_rcu_tasks called too soon");
> > > +
> > > + /* Wait for the grace period. */
> > > + wait_rcu_gp(call_rcu_tasks);
> > > +}
> >
> > Btw, what about CONFIG_PREEMPT=n ?
> >
> > I mean, can't synchronize_rcu_tasks() be synchronize_sched() in this
> > case?
>
> Excellent point, indeed it can!
>
> And if I do it right, it will make CONFIG_TASKS_RCU=y safe for kernel
> tinification. ;-)

Unless, that is, we need to wait for trampolines in the idle loop...

Sounds like a question for Steven. ;-)

Thanx, Paul