On Sat, 2 Aug 2014 15:58:57 -0700
"Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote:
> On Sat, Aug 02, 2014 at 04:47:19PM +0200, Oleg Nesterov wrote:
> > On 08/01, Paul E. McKenney wrote:
> > >
> > > 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. ;-)
> >
> > Sure, but the full blown synchronize_rcu_tasks() can't handle the idle
> > threads
> > anyway. An idle thread can not be deactivated and for_each_process() can't
> > see
> > it anyway.
>
> Indeed, if idle threads need to be tracked, their tracking will need to
> be at least partially special-cased.
>
Yeah, idle threads can be affected by the trampolines. That is, we can
still hook a trampoline to some function in the idle loop.
But we should be able to make the hardware call that puts the CPU to
sleep a quiescent state too. May need to be arch dependent. :-/
-- Steve
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