linux-kernel - Re: [PATCH, RFC] char dev BKL pushdown

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Date:	Sun, 18 May 2008 14:26:51 -0600
From:	corbet@....net (Jonathan Corbet)
To:	Arnd Bergmann <arnd@...db.de>
Cc:	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
Subject: Re: [PATCH, RFC] char dev BKL pushdown 

Arnd Bergmann <arnd@...db.de> wrote:

> Note that the majority of drivers use (grep suggests up to 165
> of them) uses misc_register instead of register_chrdev/cdev_add.
> Your patches are still correct, because you pushed the BKL into the
> misc_open function, but there is an obvious next step in pushing
> it further into the misc drivers.

There's a few intermediate dispatcher levels like this, actually.
Lots of video drivers get called behind video_open(), usb drivers from
usb_open(), etc.  Not much to be done but to push things down one level
at a time.

> In your current git tree, this change is no longer the final one, so
> bisecting the series may cause other bugs. You should probably reorder
> the patches at some point to avoid this.

Bisection is going to be problem regardless - if a problem turns up,
it's going to be the chrdev_open() change which gets fingered.  I bet,
though, that it will be a rare BKL-related problem which is reproducible
enough to be easily bisectable.

But, yes, I do need to reorganize the patch series once I'm done adding
on changes.

jon
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