linux-kernel - Re: [GIT PULL] futex fixlet

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Message-ID: <CA+55aFzPfysGq+ihMioGXASs3ixn9RBOuju2UhygKY_qtoo_Ag@mail.gmail.com>
Date:	Fri, 30 Dec 2011 12:06:18 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Darren Hart <dvhltc@...ibm.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [GIT PULL] futex fixlet

On Fri, Dec 30, 2011 at 9:07 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>
> So I _think_ you're completely right and we can simply kill the whole
> thing, but I've been trying very hard to forget everything kernel
> related for a week, and I really shouldn't kick-start my brain until
> somewhere next week.

Ok.

Ingo, I'd suggest you put a patch like that into -next, and mark it
for stable after it has gotten lots more testing.

Something like the appended *totally* untested code. It compiles, but
maybe there really is some "!page->mapping" case that could possibly
matter.

I can't see it, though - but we should definitely get some testing for
this before I'd put it in a release. Since we do that
"get_user_pages_fast()" and ask for a writable page, the result should
be as stable as it will ever get. There is still the race with
hugepage splitting, but at least that one has a comment.

                       Linus

View attachment "patch.diff" of type "text/x-patch" (1093 bytes)