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Subject: Re: [RFC][PATCH] create workqueue threads only when needed
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Oliver Neukum <oliver@neukum.org>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>,
       Frederic Weisbecker <fweisbec@gmail.com>,
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Date: Mon, 02 Feb 2009 20:46:33 +1100
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On Mon, 2009-02-02 at 10:14 +0100, Oliver Neukum wrote:
> Am Monday 02 February 2009 10:05:28 schrieb Benjamin Herrenschmidt:
> > > Work which /may/ sleep longer, for example performs SCSI transactions,
> > > needs to go into a private workqueue or other kind of context.
> > 
> > Well, it's a bit silly to allocate a private workqueue with all it's
> > associated per CPU kernel threads for something as rare as resetting
> > your eth NIC ... or even SCSI error handling in fact.
> 
> How do you avoid a deadlock if SCSI error handling doesn't use
> a dedicated workqueue?

Something such as slow-work or async funcs (not sure about the later, I
have to look at the implementation) but the basic idea is to have a pool
of threads for "generic" delayed work, when its busy, pick another one,
and the pool itself should resize if there's too much pressure.

Ben.