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

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From: Stefan Richter
Date: Sunday, March 28, 2010 - 5:27 am

Arnd Bergmann wrote:

Sounds like a plan, but (a) if my .llseek = no_llseek and your .llseek =
default_llseek are not within diff context range, you (or whoever else
merges mine and yours) only get a compiler warning (Initializer entry
defined twice) rather than a merge conflict which couldn't be missed,
(b) there won't be a merge conflict in "BKL removal: mark remaining
users as 'depends on BKL'".  (c) While I don't mind adding more visual
clutter to ieee1394/*, I prefer terse coding in firewire/*.

How about I put my nonseekable_open additions into a release branch and
send you a pull request after a few days exposure in linux-next?  If you
do not plan to respin your patch queue soon or at all, I could even let
you pull a for-arnd branch with a semantically correct merge of yours
and mine.

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).

Of course, as we have already seen with infiniband, firewire, ieee1394,
.llseek = NULL is ambiguous in practice.  Does the driver really want to
use default_llseek, or should it rather use no_llseek and/or
nonseekable_open, or should it even implement a dummy_llseek() { return
0; } which avoids the BKL but preserves ABI behaviour?  This needs to be
resolved for each and every case eventually, regardless of whether or
when your addition of .llseek = default_llseek enters mainline.
-- 
Stefan Richter
-=====-==-=- --== ===--
http://arcgraph.de/sr/
--
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Messages in current thread:
Re: [GIT, RFC] Killing the Big Kernel Lock, Andrew Morton, (Wed Mar 24, 2:07 pm)
[GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Wed Mar 24, 2:40 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Roland Dreier, (Wed Mar 24, 2:53 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Wed Mar 24, 2:59 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Alan Cox, (Wed Mar 24, 3:10 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Ingo Molnar, (Wed Mar 24, 3:23 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Wed Mar 24, 3:25 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Thu Mar 25, 3:26 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Jiri Kosina, (Thu Mar 25, 5:55 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Thu Mar 25, 6:06 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Thu Mar 25, 6:38 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Dan Carpenter, (Thu Mar 25, 6:40 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Thu Mar 25, 7:14 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Stefan Richter, (Fri Mar 26, 4:47 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Sat Mar 27, 7:37 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Stefan Richter, (Sun Mar 28, 5:27 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 1:04 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Sun Mar 28, 1:05 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 1:11 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 1:15 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 1:33 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Sun Mar 28, 2:34 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Andi Kleen, (Sun Mar 28, 2:58 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 4:18 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 4:24 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Sun Mar 28, 4:38 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock II, Andi Kleen, (Sun Mar 28, 6:07 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Mon Mar 29, 4:04 am)
Re: [GIT, RFC] Killing the Big Kernel Lock II, Arnd Bergmann, (Mon Mar 29, 4:48 am)
Re: [GIT, RFC] Killing the Big Kernel Lock II, Andi Kleen, (Mon Mar 29, 5:30 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, John Kacur, (Mon Mar 29, 5:45 am)
Re: [GIT, RFC] Killing the Big Kernel Lock II, Arnd Bergmann, (Mon Mar 29, 7:43 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Mon Mar 29, 10:59 am)
Re: [GIT, RFC] Killing the Big Kernel Lock II, Andi Kleen, (Mon Mar 29, 1:11 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Mon Mar 29, 2:18 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Roland Dreier, (Tue Mar 30, 10:22 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Roland Dreier, (Wed Mar 31, 3:11 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Wed Mar 31, 3:20 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Thu Apr 1, 1:50 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Jan Blunck, (Thu Apr 8, 1:45 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Arnd Bergmann, (Thu Apr 8, 2:27 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Frederic Weisbecker, (Thu Apr 8, 2:30 pm)
Re: [GIT, RFC] Killing the Big Kernel Lock, Jan Blunck, (Fri Apr 9, 4:02 am)
Re: [GIT, RFC] Killing the Big Kernel Lock, Stefan Richter, (Sat Apr 10, 8:13 am)