linux-kernel - Re: [PATCH RFC] PPC-BRIQ_PANEL: Remove BKL and replace with atomic variable.

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Date:	Mon, 19 Oct 2009 07:04:02 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	John Kacur <jkacur@...hat.com>
cc:	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arnd Bergmann <arndbergmann@...glemail.com>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH RFC] PPC-BRIQ_PANEL: Remove BKL and replace with atomic
 variable.

B1;2005;0cOn Sun, 18 Oct 2009, John Kacur wrote:

> >From b64c7d0f11eab96cb253b23c7264c999746116c0 Mon Sep 17 00:00:00 2001
> From: John Kacur <jkacur@...hat.com>
> Date: Sun, 18 Oct 2009 21:29:21 +0200
> Subject: [PATCH] PPC-BRIQ_PANEL: Remove BKL and replace with atomic variable.
> 
> There are no locks here except the bkl in briq_panel_open. It's only
> purpose is to ensure single access. Remove the bkl and ensure single access
> by making vfd_is_open an atomic_variable.

And again, can you please look more carefully at the init
vs. read/write functions ?

The BKL is not only protecting the single user variable it's also
serializing write against the access to the display in init.

Thanks,

	tglx
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