linux-kernel - Re: [PATCH 2/3, RFC] watchdog dev BKL pushdown

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Date:	Tue, 20 May 2008 10:30:11 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jonathan Corbet <corbet@....net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Alexander Viro <viro@....linux.org.uk>,
	linux-kernel@...r.kernel.org, Wim Van Sebroeck <wim@...ana.be>
Subject: Re: [PATCH 2/3, RFC] watchdog dev BKL pushdown

On Tuesday 20 May 2008, Christoph Hellwig wrote:
> On Tue, May 20, 2008 at 01:14:23AM +0200, Arnd Bergmann wrote:
> > The Big Kernel Lock has been pushed down from chardev_open
> > to misc_open, this change moves it to the individual watchdog
> > driver open functions.
> > 
> > As before, the change was purely mechanical, most drivers
> > should actually not need the BKL.
> 
> Actually I'd prefer to fix this for real.  This single open stuff aswell
> as same set of ioctls are duplicated all over the watchdog drivers.  We'd
> be much better off introducing a simple watchdog layer that handles this
> plus proper locking and convert drivers over to it gradually.

I fully agree, I thought the same thing when I did the patches. I remember
that Wim had a git tree doing this, which is still active at
http://git.kernel.org/?p=linux/kernel/git/wim/linux-2.6-watchdog-experimental.git;a=commitdiff;h=732c54027e6c866f98857c4a6d1c6c466459dcd5

Unfortunately, it hasn't seen much activitity over the last two years, and
the number of watchdog drivers seems to have exploded: I count 67 of them,
including some outside of drivers/watchdog.

Wim, was there anything preventing you from integrating the generic
watchdog layer back then?

	Arnd <><
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