linux-kernel - Re: [GIT, RFC] Killing the Big Kernel Lock

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Message-ID: <20100328201516.GE5116@nowhere>
Date:	Sun, 28 Mar 2010 22:15:17 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Stefan Richter <stefanr@...6.in-berlin.de>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	Matthew Wilcox <matthew@....cx>,
	Thomas Gleixner <tglx@...utronix.de>, jblunck@...e.de,
	Alan Cox <alan@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	John Kacur <jkacur@...hat.com>
Subject: Re: [GIT, RFC] Killing the Big Kernel Lock

On Sun, Mar 28, 2010 at 09:05:50PM +0100, Arnd Bergmann wrote:
> > General thoughts:
> > 
> > ".llseek = NULL," so far meant "do the Right Thing on lseek() and
> > friends, as far as the fs core can tell".  Shouldn't we keep it that
> > way?  It's as close to other ".method = NULL," as it can get, which
> > either mean "silently skip this method if it doesn't matter" (e.g.
> > .flush) or "fail attempts to use this method with a fitting errno" (e.g.
> > .write).
> 
> My series changes the default from 'default_llseek' to 'generic_file_llseek',
> which is almost identical, except for taking the inode mutex instead of the
> BKL. 


What if another file operation changes the file pointer while holding the bkl?
You're not protected anymore in this case.

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