Date: Fri, 5 Sep 2003 18:55:52 +0100
From: Jamie Lokier <jamie@shareable.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Linus Torvalds <torvalds@osdl.org>, Hugh Dickins <hugh@veritas.com>,
       Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@redhat.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Alternate futex non-page-pinning and COW fix
Message-ID: <20030905175552.GB4588@mail.jlokier.co.uk>
References: <20030904171609.GA30394@mail.jlokier.co.uk> <20030905052006.72B952C135@lists.samba.org>
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Rusty Russell wrote:
> In message <20030904171609.GA30394@mail.jlokier.co.uk> you write:
> > What does PROT_SEM mean for Linux, btw?
> 
> It's a relic: some archs might need a special flag to ensure
> inter-process atomic ops worked as expected.  It was never fully
                                                       ~~~~~~~~~~~
> implemented, with the assumption that such archs just won't be able to
  ~~~~~~~~~~~
> use futexes, and if someone really wants to fix it, they will.

Looking at the kernel I can confidently say it was never implemented
at all.  sys_mprotect mentioned PROT_SEM but it was a misleading logic
error that did nothing useful :)

-- Jamie

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