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    SubjectRe: [patch 1/1] schedule removal of FUTEX_FD
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    On Tue, 2006-10-31 at 15:09 -0800, akpm@osdl.org wrote:
    > From: Andrew Morton <akpm@osdl.org>
    >
    > Apparently FUTEX_FD is unfixably racy and nothing uses it (or if it does, it
    > shouldn't).
    >
    > Add a warning printk, give any remaining users six months to migrate off it.

    This makes sense. FUTEX_FD was for the NGPT project which did userspace
    threading, and hence couldn't block. It was always kind of a hack
    (although unfixably racy isn't quite right, it depends on usage).

    However, the existence of FUTEX_FD is what made Ingo complain that we
    couldn't simply pin the futex page in memory, because now a process
    could pin one page per fd. Removing it would seem to indicate that we
    can return to a much simpler scheme of (1) pinning a page when someone
    does futex_wait, and (2) simply comparing futexes by physical address.

    Now, I realize with some dismay that simplicity is no longer a futex
    feature, but it might be worth considering?

    Cheers,
    Rusty.
    PS. I used to have a patch for "ratelim_printk()" which hashed on the
    format string to reduce the chance that one message limit would clobber
    other messages. I'll dig it out...

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