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Date: Tue, 30 Sep 2008 20:13:44 -0700
From: "Ulrich Drepper" <drepper@gmail.com>
To: "Eric Dumazet" <dada1@cosmosbay.com>
Subject: Re: [PATCH 0/4] futex: get_user_pages_fast() for shared futexes
Cc: "Peter Zijlstra" <a.p.zijlstra@chello.nl>,
       "Nick Piggin" <nickpiggin@yahoo.com.au>, "Ingo Molnar" <mingo@elte.hu>,
       "Thomas Gleixner" <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
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On Tue, Sep 30, 2008 at 3:55 AM, Eric Dumazet <dada1@cosmosbay.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.