linux-kernel - Re: [PATCH] input: remove BKL from uinput open function

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Message-Id: <201001302257.09354.arnd@arndb.de>
Date:	Sat, 30 Jan 2010 22:57:09 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Thadeu Lima de Souza Cascardo <cascardo@...oscopio.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: remove BKL from uinput open function

On Saturday 30 January 2010, Dmitry Torokhov wrote:
> On Sat, Jan 30, 2010 at 07:41:20AM +0100, Arnd Bergmann wrote:
> > The change looks good, but the same driver also uses the BKL in the
> > default_llseek function. It would be nice to get rid of that in the
> > same patch, e.g. by adding a ".llseek = generic_file_llseek," line
> > in the file_operations, or making it call nonseekable_open() if the
> > driver does not require seek to do anything.
> > 
> 
> I am afraid you mixed up the drivers, I don't see uinput implementing
> seek...

Sorry, I should have been clearer, but not implementing llseek
is the problem I was referring to: When a driver has no explicit
.llseek operation in its file operations and does not call
nonseekable_open from its open operation, the VFS layer will
implicitly use default_llseek, which takes the BKL. We're
in the process of changing drivers not to do this, one by one
so we can kill the BKL in the end.

	Arnd

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