linux-kernel - Re: regression 4.4: deadlock in with cgroup percpu

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Message-ID: <20160119193845.GT3520@mtj.duckdns.org>
Date:	Tue, 19 Jan 2016 14:38:45 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org >> Linux Kernel Mailing List" 
	<linux-kernel@...r.kernel.org>,
	linux-s390 <linux-s390@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: regression 4.4: deadlock in with cgroup percpu_rwsem

Hello,

On Tue, Jan 19, 2016 at 08:36:18PM +0100, Christian Borntraeger wrote:
> No, its not a task_struct. Activating some more debug information did indeed 
> revealed several other issues (overwritten redzones etc). Unfortunately I 
> only saw the broken things after the facts, so I do not know which code did that.
> When I disabled the cgroup controllers in libvirt I was no longer able to trigger
> the bugs. Still trying to narrow things down.

Hmmm... that's worrying.  CONFIG_DEBUG_PAGEALLOC sometimes can catch
these sort of bugs red-handed.  Might worth trying.

Thanks.

-- 
tejun