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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Tejun Heo <tj@kernel.org>, Stephen Boyd <sboyd@codeaurora.org>
Subject: Re: [PATCH 2/2] firmware_class: Move request_firmware_nowait() to workqueues
Date: Wed, 28 Mar 2012 00:55:06 +0200
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On Wednesday, March 28, 2012, Tejun Heo wrote:
> On Wed, Mar 28, 2012 at 12:21:27AM +0200, Rafael J. Wysocki wrote:
> > On Wednesday, March 28, 2012, Tejun Heo wrote:
> > > On Tue, Mar 27, 2012 at 02:28:30PM -0700, Stephen Boyd wrote:
> > > > Oddly enough a work_struct was already part of the firmware_work
> > > > structure but nobody was using it. Instead of creating a new
> > > > kthread for each request_firmware_nowait() call just schedule the
> > > > work on the long system workqueue. This should avoid some overhead
> > > > in forking new threads when they're not strictly necessary.
> > > > 
> > > > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> > > > ---
> > > > 
> > > > Is it better to use alloc_workqueue() and not put these on the system
> > > > long workqueue?
> > > 
> > > No, just use schedule_work() unless there are specific requirements
> > > which can't be fulfilled that way (e.g. it's on memory allocation
> > > path, may consume large amount of cpu cycles, ...)
> > 
> > It may wait quite long.
> 
> That shouldn't matter.  system_long_wq's name is a bit misleading at
> this point.  The only reason it's used currently is to avoid cyclic
> dependency involving flush_workqueue(), which calls for clearer
> solution anyway.  So, yeap, using system_wq should be fine here.

Good, thanks for the explanation.

Stephen, care to respin?

Rafael