linux-kernel - Re: [GIT PATCH] TTY patches for 2.6.33-git

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Message-ID: <20091212214235.31429790@lxorguk.ukuu.org.uk>
Date:	Sat, 12 Dec 2009 21:42:35 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Greg KH <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PATCH] TTY patches for 2.6.33-git

> I think we could possibly add a "__might_sleep()" to _lock_kernel(). It 
> doesn't really sleep, but it's invalid to take the kernel lock in an 
> atomic region, so __might_sleep() might be the right thing anyway.

It's only invalid if you don't already hold the lock. The old tty code
worked because every path into tty_fasync already held the lock ! That
specific case - taking it the first time should definitely
__might_sleep().

Mind you it's probably still rather dumb and would be a good debugging
aid for -next to be able to warn on all offences if only to catch this
stuff for the future BKL removal work.

Alan
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