linux-kernel - Re: Writeback threads and freezable

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Message-ID: <20131213185237.GD27070@htj.dyndns.org>
Date:	Fri, 13 Dec 2013 13:52:37 -0500
From:	Tejun Heo <tj@...nel.org>
To:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Jens Axboe <axboe@...nel.dk>
Cc:	tomaz.solc@...lix.org, aaron.lu@...el.com,
	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: Writeback threads and freezable

On Fri, Dec 13, 2013 at 12:49:32PM -0500, Tejun Heo wrote:
> I'm not completely sure what to do.  We can make an exception for
> bdi_wq and thaw it early but that breaks the guarantee that bdi is
> frozen between device suspend and resume invocations and we might as
> well just remove WQ_FREEZABLE from it.  I don't know.

Ugh, so I removed WQ_FREEZABLE on bdi and the same deadlock now
happens through jbd2 which is a freezable kthread.  This whole kthread
freezer thing is rotten and fundamentally broken. :(

-- 
tejun
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