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Date: Fri, 27 Sep 2002 13:11:47 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Andrew Morton <akpm@digeo.com>, Rusty Russell <rusty@rustcorp.com.au>,
       <linux-kernel@vger.kernel.org>
Subject: Re: [patch] 'sticky pages' support in the VM, futex-2.5.38-C5
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On Thu, 26 Sep 2002, Linus Torvalds wrote:

> and then the "callback" function just updates the page information in
> the futex block directly - as if it was looked up anew.

yes. And it would also have to rehash the futex queue (which is hashed
along (page,offset), because a FUTEX_WAKE has to find the proper queue -
but it's still very cheap.

this also means that FUTEX_WAIT does not have to make the futex page
writable - just making it present and hashing it along the physical page.  
Ie. more robust and less intrusive futexes.

	Ingo

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