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

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Message-ID: <20080520195157.50384ac9@core>
Date:	Tue, 20 May 2008 19:51:57 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Arnd Bergmann <arnd@...db.de>
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>,
	Alexander Viro <viro@....linux.org.uk>,
	linux-kernel@...r.kernel.org, Wim Van Sebroeck <wim@...ana.be>
Subject: Re: [PATCH, RFC] char dev BKL pushdown

> Right, unless Alan or Wim are confident enough that removing the
> BKL won't break the drivers (more than they are today).
> Almost all of the open functions go along the lines of
> 
> int open(struct file *f, struct inode *i)
> {
> 	if (wd_is_open)
> 		return -EBUSY;
> 	wd_is_open = 1;
> 	
> 	start_wd();
> 
> 	return nonseekable_open(f, i);
> }
> 
> nonseekable_open doesn't need the BKL by itself, and the wd_is_open
> variable is protected by the misc_mtx mutex.
> I can't see any scenario in which start_wd() would need the BKL, or

You need to review the use of misc_register(). Which is what I did
already and sorted out for each watchdog - the job is done and completed
and the various problem cases fixed. Watchdog has already been made BKL
removal safe in the patch series I sent.

Alan
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