On Fri, Aug 01, 2014 at 05:53:10PM +0200, Oleg Nesterov wrote:
> On 07/30, Paul E. McKenney wrote:
> >
> > + rcu_read_lock();
> > + for_each_process_thread(g, t) {
> > + if (t != current && ACCESS_ONCE(t->on_rq) &&
> > + !is_idle_task(t)) {
> > + t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw);
> > + t->rcu_tasks_holdout = 1;
> > + list_add(&t->rcu_tasks_holdout_list,
> > + &rcu_tasks_holdouts);
> > + }
> > + }
> > + rcu_read_unlock();
>
> Wait, unless I missed something this can't work...
>
> The problem is, once the exiting task passes exit_notify() it can
> be removed from rcu lists.
>
> Now suppose that (say) proc_exit_connector() has a probe, and this
> task has jumped into trampoline and it was preempted there.
>
> No?
OK, this sounds to me like another vote for get_task_struct() as used
in the v3 series. Or am I missing something?
Thanx, Paul
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