Re: [PATCH RFC tip/core/rcu 1/9] rcu: Add call_rcu_tasks()

[Paul E. McKenney]

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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