On Wed, Jul 30, 2014 at 02:52:41PM +0800, Lai Jiangshan wrote:
> On 07/29/2014 06:56 AM, Paul E. McKenney wrote:
>
> > + /*
> > + * Each pass through the following loop scans the list
> > + * of holdout tasks, removing any that are no longer
> > + * holdouts. When the list is empty, we are done.
> > + */
> > + while (!list_empty(&rcu_tasks_holdouts)) {
> > + schedule_timeout_interruptible(HZ / 10);
> > + flush_signals(current);
> > + rcu_read_lock();
> > + list_for_each_entry_rcu(t, &rcu_tasks_holdouts,
> > + rcu_tasks_holdout_list) {
> > + if (smp_load_acquire(&t->rcu_tasks_holdout))
> > + continue;
> > + list_del_init(&t->rcu_tasks_holdout_list);
> > + /* @@@ need to check for usermode on CPU. */
> > + }
> > + rcu_read_unlock();
>
> Maybe I missed something. The task @t may already exited and we access to
> the stale memory here if without patch 8/9.
Yep, patch 8/9 is not optional.
Thanx, Paul
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