linux-kernel - Re: [GIT PULL] core kernel fixes

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Message-ID: <alpine.LFD.2.01.0905180840420.3301@localhost.localdomain>
Date:	Mon, 18 May 2009 08:48:50 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [GIT PULL] core kernel fixes

On Mon, 18 May 2009, Ingo Molnar wrote:
> 
> Thomas Gleixner (1):
>       futex: futex mapping needs to be writable

I do not believe this is right.

Just a few lines later, we have:

         * NOTE: When userspace waits on a MAP_SHARED mapping, even if
         * it's a read-only handle, it's expected that futexes attach to   
         * the object not the particular process.

note how we are _supposed_ to be able to wait for something that is 
read-only. As such, asking for a writable page is bogus.

I'm not going to pull this. I can well imagine that there was a real bug, 
but this is _not_ the real fix.

The commentary is also TOTAL CRAP as far as I can tell. It starts out 
with:

    commit 734b05b10e51d4ba38c8fc3ee02e846aab09eedf (futex: use
    fast_gup()) calls get_user_pages_fast() with the write argument set to
    0. This went unnoticed [...]

and that is pure and utter SHIT. The fact is, the write argument was 
ALWAYS zero, and commit 734b05b10e51d4ba38c8fc3ee02e846aab09eedf has 
nothing to do with anything what-so-ever, and nothing went unnoticed 
anywhere.

The real bug was apparently just commit e4dc5b7a3 ("clean up").

I also have to object to the "Impact" line of that commit. That line is 
nonsensical and stupid. I hate to bring up this discussion again, but 
dammit, if those Impact lines are crap, then they are crap and should not 
be there! 

The fact that they _look_ nicer and do not break up the story any more 
doesn't change that fact. If you cannot write sane and meaningful impact 
lines, then f*ck me with a spoon - JUST DON'T DO THEM!

I'm upset. Quite frankly, there are just _so_ many things wrong with that 
commit that I get angry when it is sent this late in the game. 

		Linus
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