linux-kernel - Re: [PATCH] firewire: sbp2: parallelize login/inquiry, reconnect, and shutdown

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Message-ID: <4CB468C1.8000004@kernel.org>
Date:	Tue, 12 Oct 2010 15:55:13 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
CC:	linux1394-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firewire: sbp2: parallelize login/inquiry, reconnect,
 and shutdown

Hello,

On 10/11/2010 11:39 PM, Stefan Richter wrote:
> Stefan Richter wrote:
>> There are indeed situations where the last module reference was already
>> put down before the work is run for the last time.  Thanks for the hint.
>>
>> What is preferable, an own workqueue instance whose destroy_workqueue()
>> lets sbp2_cleanup wait for unfinished work, or module ref-counting like
>> below?
> 
> Anoher thing:  Somebody might have swap space on a FireWire disk.

It doesn't have to be swap.  Having a rw filesystem mounted is enough
to be in the memory reclaim path.

> Yet the system workqueues that firewire-core and (perhaps)
> firewire-sbp2 are using are created without WQ_RESCUER.
> 
> Does this --- fringe use case as it might be --- call for private
> workqueues in firewire-core (for fw_device.work) and firewire-sbp2 (for
> sbp2_logical_unit.work)?
> 
> Besides the less interesting cases of device discovery and shutdown,
> both of these works are also involved in SBP reconnect which needs to be
> performed at each FireWire bus reset (which can happen anytime for a
> variety of reasons).

Yes, it would definitely be better to put them in a workqueue with
WQ_RESCUER (or the new WQ_MEM_RECLAIM).

Thanks.

-- 
tejun
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