linux-kernel - Re: Possible regression with cgroups in 3.11

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Message-ID: <20131113073806.GA23244@mtj.dyndns.org>
Date:	Wed, 13 Nov 2013 16:38:06 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Li Zefan <lizefan@...wei.com>,
	Markus Blank-Burian <burian@...nster.de>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	David Rientjes <rientjes@...gle.com>,
	Ying Han <yinghan@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	Michel Lespinasse <walken@...gle.com>, cgroups@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: Possible regression with cgroups in 3.11

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
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