Tejun Heo (tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org) wrote:

Hello,

On Tue, Dec 20, 2011 at 03:14:30PM -0800, Mandeep Singh Baines wrote:

quoted

@@ -2287,14 +2280,12 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
 			cgroup_unlock();
 			return -EACCES;
 		}
-		get_task_struct(tsk);
 		rcu_read_unlock();

This is before threadgroup is locked.  What guarantees @tsk doesn't go
away once rcu is unlocked?

Nothing. D'oh. I'll remove the changes to attach_task_by_id and leave
the others.

Thanks.

-- 
tejun