Possible race between cgroup_attach_proc and de_thread, and questionable code in de_thread.
Paul E. McKenney
paulmck at linux.vnet.ibm.com
Mon Aug 15 11:01:55 PDT 2011
On Sun, Aug 14, 2011 at 07:51:19PM +0200, Oleg Nesterov wrote:
> On 07/28, Paul E. McKenney wrote:
> > On Thu, Jul 28, 2011 at 11:08:13AM +1000, NeilBrown wrote:
> > >
> > > I disagree. It also requires - by virtue of the use of while_each_thread() -
> > > that 'g' remains on the list that 't' is walking along.
> > Doesn't the following code in the loop body deal with this possibilty?
> > /* Exit if t or g was unhashed during refresh. */
> > if (t->state == TASK_DEAD || g->state == TASK_DEAD)
> > goto unlock;
> This code is completely wrong even if while_each_thread() was fine.
> I sent the patch but it was ignored.
> [PATCH] fix the racy check_hung_uninterruptible_tasks()->rcu_lock_break()
If it helps...
Acked-by: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
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