linux-kernel - Re: [PATCH 5/6] procfs: Push down the bkl from ioctl

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Message-Id: <201003302054.11962.arnd@arndb.de>
Date:	Tue, 30 Mar 2010 20:54:11 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Kacur <jkacur@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 5/6] procfs: Push down the bkl from ioctl

On Tuesday 30 March 2010 20:27:12 Frederic Weisbecker wrote:
> On Tue, Mar 30, 2010 at 11:37:27AM +0100, Arnd Bergmann wrote:
> > On Tuesday 30 March 2010, Frederic Weisbecker wrote:
> > > Push down the bkl from procfs's ioctl main handler to its users.
> > > Only three procfs users implement an ioctl (non unlocked) handler.
> > > Turn them into unlocked_ioctl and push down the Devil inside.
> > 
> > Looks good to me. I would have used a single unlock and return statement
> > in i8k_ioctl and isdn_divert_ioctl, with goto instead of adding an
> > unlock to each return, but it doesn't matter much.
> 
> 
> I did that first, but actually that didn't make much difference:
> 
> ret = foo;            unlock_kernel()
> goto end;      VS     return foo;

Yes, the amount of code needed is comparable, but it is much easier
to validate that you did not miss an unlock when you know that there
is a single return statement in the function. It also helps the next
person that may want to replace the BKL with a different lock.

	Arnd
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