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From: David Brownell <david-b@pacbell.net>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Subject: Re: [patch 2.6.24-rc2 1/3] generic gpio -- gpio_chip support
Date: Thu, 15 Nov 2007 00:17:29 -0800
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Cc: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel list <linux-kernel@vger.kernel.org>,
       Florian Fainelli <florian.fainelli@telecomint.eu>,
       Haavard Skinnemoen <hskinnemoen@atmel.com>
References: <200711091136.20051.david-b@pacbell.net> <200711142228.10934.david-b@pacbell.net> <200711150551.54230.nickpiggin@yahoo.com.au>
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On Wednesday 14 November 2007, Nick Piggin wrote:
> > > > All this does is prevent constant and needless checking for
> > > > "do you want to preempt me now?" "now?" "now?" in "now?" the
> > > > middle "now?" of "now?" i/o "now?" loops.
> > >
> > > Actually that's wrong.
> >
> > Certainly it's right for the mainstream kernel.  Dropping a
> > lock (other than a raw spinlock) does that checking; when a
> > loop needs to acquire then drop such a lock, that's exactly
> > what's going on.
> 
> Obviously a raw spinlock is no different from a regular
> spinlock upstream.

Erm, no.  The raw ones don't have the extra logic when
the lock gets dropped.