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From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@zip.com.au>
Subject: Re: [patch] 'sticky pages' support in the VM, futex-2.5.38-C5
Date: Thu, 26 Sep 2002 17:27:59 +0200 (CEST)	[thread overview]
Message-ID: <Pine.LNX.4.44.0209261712420.20778-100000@localhost.localdomain> (raw)
In-Reply-To: <200209261501.g8QF1pc02251@penguin.transmeta.com>


On Thu, 26 Sep 2002, Linus Torvalds wrote:

> This patch seems trivially broken by having two futexes on the same
> page.  When the first futex removes itself, it will clear the sticky
> bit, even though the other futex is still pinning the same page.

sigh. And we cannot even properly detect which unpin_page() was the last
unpinning of the page - there can be so many other reasons a page's count
is elevated. And keeping a page sticky forever is no solution either, the
number of sticky pages would increase significantly, causing real fork()
problems.

> Trust me, you'll have to use the page list approach.

yeah, will try that now. I'm a bit worried about the mandatory cross-CPU
TLB flushes though.

	Ingo


       reply	other threads:[~2002-09-26 15:16 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <200209261501.g8QF1pc02251@penguin.transmeta.com>
2002-09-26 15:27 ` Ingo Molnar [this message]
2002-09-26 16:48   ` Alan Cox
2002-09-27  8:05 Martin Wirth
2002-09-27  9:27 ` Ingo Molnar
  -- strict thread matches above, loose matches on Subject: below --
2002-09-26 11:30 Ingo Molnar
2002-09-26 15:01 ` Linus Torvalds
2002-09-26 22:09 ` Andrew Morton
2002-09-26 22:32   ` Linus Torvalds
2002-09-27  7:53     ` Ingo Molnar
2002-09-26 22:45   ` Linus Torvalds
2002-09-26 22:56     ` Linus Torvalds
2002-09-27 11:11     ` Ingo Molnar
2002-10-04 22:47 ` Jamie Lokier
2002-10-04 23:20   ` Linus Torvalds

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