On Fri, Jan 22, 2016 at 8:33 AM, Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> wrote:
On Fri, Jan 22, 2016 at 10:51:04AM -0500, Tejun Heo wrote:
> On Fri, Jan 22, 2016 at 09:48:54AM -0500, Johannes Weiner wrote:
> > On Fri, Jan 22, 2016 at 04:50:42PM +0300, Vladimir Davydov wrote:
> > > From first glance, it looks like the bug was triggered, because
> > > mem_cgroup_css_offline was run for a child cgroup earlier than for its
> > > parent. This couldn't happen for sure before the cgroup was switched to
> > > percpu_ref, because cgroup_destroy_wq has always had max_active == 1.
> > > Now, however, it looks like this is perfectly possible for
> > > css_killed_ref_fn is called from an rcu callback - see kill_css ->
> > > percpu_ref_kill_and_confirm. This breaks kmemcg assumptions.
> > >
> > > I'll take a look what can be done about that.
> >
> > It's an acknowledged problem in the cgroup core then, and not an issue
> > with kmemcg. Tejun sent a fix to correct the offlining order here:
> >
> > https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1056544.html
>
> Patche descriptions updated and applied to cgroup/for-4.5-fixes.
>
> http://lkml.kernel.org/g/20160122154503.GD32380@xxxxxxxxxxxxxxx
> http://lkml.kernel.org/g/20160122154552.GE32380@xxxxxxxxxxxxxxx
I couldn't reproduce the issue with the two patches applied. Looks like
they fix it.
Thanks,
Vladimir
Thanks for the quick turn around! I'll test it when it gets into the mainline. Do you know what versions the fixes will go into?
Thanks,
Brian
Brian