Date: Thu, 4 Sep 2003 22:00:07 +0100
From: Jamie Lokier <jamie@shareable.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Hugh Dickins <hugh@veritas.com>, Andrew Morton <akpm@osdl.org>,
       Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
       Linus Torvalds <torvalds@osdl.org>
Subject: Re: [PATCH] Alternate futex non-page-pinning and COW fix
Message-ID: <20030904210007.GE31590@mail.jlokier.co.uk>
References: <Pine.LNX.4.44.0309031141310.1273-100000@localhost.localdomain> <20030904014229.2EFBF2C097@lists.samba.org>
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Rusty Russell wrote:
> I don't have a problem with the omission.  mremap is logically
> equivalent to munmap + mmap, so it's a subset of the "I unmapped
> underneath my futex!".  It's not like it's going to happen without the
> caller knowing: if the address doesn't change, then the futexes won't
> break.  If they do, the caller needs to reset them anyway.

I think mremap() on block of memory containing futexes is reasonable.
Imagine a big data structure with a table futex locks at the start of
it.  I'm not sure how useful it is, but it's not worthless.

Anyway, I have a patch, tested, which moves remapped futexes _and_
returns EFAULT to waiters when pages are unmapped.  It's kept separate
from the main futex patch so you can accept it or not.

-- Jamie

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