linux-kernel - Re: [PATCH 0/4] futex: get_user_pages

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Date:	Tue, 30 Sep 2008 20:13:44 -0700
From:	"Ulrich Drepper" <drepper@...il.com>
To:	"Eric Dumazet" <dada1@...mosbay.com>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Nick Piggin" <nickpiggin@...oo.com.au>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 0/4] futex: get_user_pages_fast() for shared futexes

On Tue, Sep 30, 2008 at 3:55 AM, Eric Dumazet <dada1@...mosbay.com> wrote:
> I am not sure how it could be converted to private futexes, since
> old binaries (static glibc) will use FUTEX_WAKE like calls.

We considered this back when but any effort seems too much.  We'd
either need a clone flag (a scarce resource) or replace the set_tid
_address syscall.  Given that the futex is woken once per thread
lifetime it shouldn't be an issue.  If the semaphore shows up even
after this patch feel free to introduce a new set_tid_address syscall.
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