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

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Message-ID: <20160126164120.GA3047@lst.de>
Date:	Tue, 26 Jan 2016 17:41:20 +0100
From:	Christoph Hellwig <hch@....de>
To:	Tejun Heo <tj@...nel.org>
Cc:	Christoph Hellwig <hch@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	"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>
Subject: Re: regression 4.4: deadlock in with cgroup percpu_rwsem

On Tue, Jan 26, 2016 at 10:28:46AM -0500, Tejun Heo wrote:
> Hmmm... why do you need to call percpu_ref_exit() from process
> context?  All it does is freeing the percpu counter and resetting the
> state, both of which can be done from any context.

I checked and that's true indeed.  You cought me doing cargo cult
programming as the callers I looked at already do this.