From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: Possible regression with cgroups in 3.11
Date: Wed, 13 Nov 2013 16:38:06 +0900
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To: Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>, Markus Blank-Burian <burian-iYtK5bfT9M8b1SvskN2V4Q@public.gmane.org>, Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Ying Han <yinghan-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Greg Thelen <gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Michel Lespinasse <walken-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, "Srivatsa S. Bhat" <srivatsa.bhat-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Lai Jiangshan <laijs-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>, Alexander Duyck <alexander.h.duyck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Yinghai Lu <yinghai-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>

Hey, guys.

cc'ing people from "workqueue, pci: INFO: possible recursive locking
detected" thread.

  http://thread.gmane.org/gmane.linux.kernel/1525779

So, to resolve that issue, we ripped out lockdep annotation from
work_on_cpu() and cgroup is now experiencing deadlock involving
work_on_cpu().  It *could* be that workqueue is actually broken or
memcg is looping but it doesn't seem like a very good idea to not have
lockdep annotation around work_on_cpu().

IIRC, there was one pci code path which called work_on_cpu()
recursively.  Would it be possible for that path to use something like
work_on_cpu_nested(XXX, depth) so that we can retain lockdep
annotation on work_on_cpu()?

Thanks.

-- 
tejun