linux-kernel - Re: use of preempt_count instead of in

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Date:	Thu, 27 Mar 2008 11:51:33 -0700
From:	David Brownell <david-b@...bell.net>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Alan Stern <stern@...land.harvard.edu>, rpurdie@...ys.net
Cc:	gitster@...ox.com, corbet@....net, mingo@...e.hu, mb@...sch.de,
	linux-kernel@...r.kernel.org, khali@...ux-fr.org,
	geert@...ux-m68k.org, akpm@...ux-foundation.org
Subject: Re: use of preempt_count instead of in_atomic() at leds-gpio.c

On Wednesday 26 March 2008, Henrique de Moraes Holschuh wrote:
> On Wed, 26 Mar 2008, Alan Stern wrote:
> > On Tue, 25 Mar 2008, David Brownell wrote:
> > > I _almost_ hate bringing this lovely flamage back onto $SUBJECT ... but
> > > what's the resolution for the leds-gpio.c issue?  I've not seen a merge
> > > notice for the patch I submitted a week ago now:
> > > 
> > > 	http://marc.info/?l=linux-kernel&m=120597839009399&w=2
> > > 
> > > Just a "leaning..." comment:
> > > 
> > > 	http://marc.info/?l=linux-kernel&m=120606104619198&w=2
> > > 
> > > Seems to me that by now there ought to be resolution on at least
> > > one of the issues brought up on this thread.  :)
> > 
> > Is it reasonable to have two version of that subroutine: one meant to 
> > be called in a sleepable context and the other to be called when 
> > sleeping isn't allowed?

Not before 2.6.25 ships it isn't.  :)


> I have changed the thinkpad-acpi leds code to always assume an atomic
> context, but I too would appreciate a proper flag (or secondary hook)
> from the LED class to know when I am in an atomic context or not.
> 
> LED Triggers also need to be modified, they are mostly called from an
> atomic context so we have to assume that by default, but we'd do well to
> add a way to call them from non-atomic contexts.
> 
> Richard?  AFAIK, the ball *is* in your court as the LED maintainer.  You
> have to decide which way to go and tell us.

Presumably, both near-term and long-term solutions are needed.

I'd suggest merging the leds-gpio and thinkpad-acpi fixes
before 2.6.25 ships, and then *maybe* adopting something
more invasive.

- Dave
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