Hello, Li.

On Wed, Nov 14, 2012 at 11:20:47AM +0800, Li Zefan wrote:

quoted

It also removes the need to check whether cgroup->dentry is %NULL in
cgroup_path.  If a cgroup is visible, its dentry is guaranteed to be
visible too.

I'm afraid this isn't safe.

The cgroup is visible to a controller soon after ss->create(), and then
the controller might call cgroup_path() while cgrp->dentry is still NULL.

Hmmm... I can't find any case where ss->create() is calling
cgroup_path().  Do you remember which one that was?

This can happen for cpu cgroup I think, and in fact the NULL check was
added for this reason IIRC.

Then, I think we better move the dentry assignment further up.  It's
really silly to be unable to answer "what's this new cgroup's name?"
for any callback really.  Will update accordingly.

Thanks.

-- 
tejun