linux-kernel - Re: [tip:bkl/drivers] drivers: Remove BKL from misc

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Message-ID: <20091014171249.57dcdcfc@lxorguk.ukuu.org.uk>
Date:	Wed, 14 Oct 2009 17:12:49 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	gregkh@...e.de, tglx@...utronix.de
Cc:	tglx@...utronix.de, linux-tip-commits@...r.kernel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	gregkh@...e.de
Subject: Re: [tip:bkl/drivers] drivers: Remove BKL from misc_open

On Wed, 14 Oct 2009 15:47:39 GMT
tip-bot for Thomas Gleixner <tglx@...utronix.de> wrote:

> Commit-ID:  40b798efe3460797a4ac928ee2e038774e2758eb
> Gitweb:     http://git.kernel.org/tip/40b798efe3460797a4ac928ee2e038774e2758eb
> Author:     Thomas Gleixner <tglx@...utronix.de>
> AuthorDate: Sat, 10 Oct 2009 15:35:43 +0000
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Wed, 14 Oct 2009 17:33:32 +0200
> 
> drivers: Remove BKL from misc_open
> 
> misc_open() is already serialized with misc_mtx. Remove the BKL
> locking which got there via the BKL pushdown.

NAK.

You can't simply assume the mutex is enough - you have to either push it
down or review *every* possible called point below the lock_kernel take.

In this case the open method of the misc devices below sometimes uses the
BKL.
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