linux-kernel - Re: [announce] "kill the Big Kernel Lock (BKL)" tree

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Message-ID: <7207.1210802867@vena.lwn.net>
Date:	Wed, 14 May 2008 16:07:47 -0600
From:	corbet@....net (Jonathan Corbet)
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	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: [announce] "kill the Big Kernel Lock (BKL)" tree 

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> I don't think there are *that* many. I found only 83 instances of 
> "register_chrdev()" in the kernel, so the open methods should be pretty 
> limited.

There's the drivers calling cdev_add() directly as well - another
40ish.  Still not a huge list, I guess.

> So it literally should be:
>  - remove one lock_kernel/unlock_kernel pair in fs/char_dev.c
>  - add max 83 pairs in the places that register those things
>  - external modules will need to add it themselves some day.

This is all certainly doable, but it leaves me with one concern: there
will be no signal to external module maintainers that the change needs
to be made.  So, beyond doubt, quite a few of them will just continue to
be shipped unfixed - and they will still run.  If any of them actually
*need* the BKL, something awful may happen to somebody someday.

jon
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