On Fri, Feb 14, 2014 at 07:15:18PM +0800, Li Zefan wrote:

quoted

 		/*
+		 * A root's lifetime is governed by its top cgroup.  Zero
+		 * ref indicate that the root is being destroyed.  Wait for
+		 * destruction to complete so that the subsystems are free.
+		 * We can use wait_queue for the wait but this path is
+		 * super cold.  Let's just sleep for a bit and retry.
+		 */
+		if (!atomic_read(&root->top_cgroup.refcnt)) {

oops, this fix is wrong. We call kernfs_mount() without cgroup locks and it
drops cgroup refcnt if failed.

I guess we need to bump the refcnt and then drop it after kernfs_mount().

Alright, will wait for the updated fix.

Thanks!

-- 
tejun