Re: [PATCH 4/6] cgroups: forbid pre_destroy callback to fail

Tejun Heo
2012-10-19T20:17:43Z

On Fri, Oct 19, 2012 at 05:33:18PM +0800, Li Zefan wrote:
> On 2012/10/17 21:30, Michal Hocko wrote:
> > 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.
>
> > 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