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

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Message-ID: <20100408213043.GB7990@nowhere>
Date:	Thu, 8 Apr 2010 23:30:46 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Jan Blunck <jblunck@...e.de>,
	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>,
	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 Thu, Apr 08, 2010 at 11:27:26PM +0200, Arnd Bergmann wrote:
> On Thursday 08 April 2010 22:45:45 Jan Blunck wrote:
> > On Sun, Mar 28, 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',
> > 
> > That is not that easy. generic_file_llseek() is testing against 'offset <
> > inode->i_sb->s_maxbytes'. This is not necessarily true when you think about
> > directories with random offset cookies. I know that seeking on directories is
> > stupid but don't blame me.
> 
> Oh, I see. Would it work if we extend generic_file_llseek to only check s_maxbytes
> if S_ISREG(inode->i_mode)))?
> 
> > > Yes, that also sounds like a good idea. I believe that Jan actually posted
> > > a patch to do that at some point.
> > 
> > Yes, it is in
> > 
> > http://git.infradead.org/users/jblunck/linux-2.6.git bkl/default-lseek
> > 
> > There are some other patches in that branch that are not upstream yet. Mind to
> > take them for your bkl-removal branch?
> 
> Frederic is now collecting the new patches. Your default-lseek series looks
> good to me, except for the obvious one that says 'FIXME' in the subject.
> 
> Maybe Frederic can add your series except for that one as another branch to
> get pulled into his kill-the-bkl master branch.


Ok, will have a look at this soon (I will also put a branch for the procfs
series).

Thanks.

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