linux-kernel - Re: [PATCH v4] mm: per-thread vma caching

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Message-ID: <CA+55aFxEGj9poWNLAncvrrOTzjDtrwMnOM_d3ACqRkcvY86qHA@mail.gmail.com>
Date:	Sun, 9 Mar 2014 10:16:32 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Davidlohr Bueso <davidlohr@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Michel Lespinasse <walken@...gle.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Davidlohr Bueso <davi@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] mm: per-thread vma caching

On Sun, Mar 9, 2014 at 10:09 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>
> But it's not the "while we're setting up a new thread", it is "since
> vmacache_valid() was called list time". And the cloning task can just
> sleep(A_LOT) and then do CLONE_VM.
>
> Of course, of course, this race is pute theoretical anyway. But imho
> makes sense to fix anyway, and the natural/trivial approach is just to
> move vmacache_flush(tsk) from dup_mm() to copy_mm(), right after the
> "if (!oldmm)" check.

Fair enough, you've convinced me it's subtle enough that we do not
want to play games..

          Linus
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