On Fri, Oct 19, 2012 at 05:33:18PM +0800, Li Zefan wrote:

On 2012/10/17 21:30, Michal Hocko wrote:

quoted

Now that mem_cgroup_pre_destroy callback doesn't fail finally we can
safely move on and forbit all the callbacks to fail. The last missing
piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so
that css_tryget fails so no new charges for the memcg can happen.

quoted

The callbacks are also called from within cgroup_lock to guarantee that
no new tasks show up. 

I'm afraid this won't work. See commit 3fa59dfbc3b223f02c26593be69ce6fc9a940405
("cgroup: fix potential deadlock in pre_destroy")

Yeah, you're right.  Argh... we really should unexport cgroup_lock
soon.

Thanks.

-- 
tejun