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    SubjectRe: [PATCH 1/12]: MUTEX: Implement mutexes

    On Sat, 17 Dec 2005, Nick Piggin wrote:

    > Steven Rostedt wrote:
    > > On Fri, 2005-12-16 at 23:13 +0000, David Howells wrote:
    > >>This patch set does the following:
    > >>
    > >> DECLARE_SEM_MUTEX_LOCKED for counting semaphores.
    > >>
    > >
    > >
    > > Could we really get rid of that "MUTEX" part. A counting semaphore is
    > > _not_ a mutex, although a mutex _is_ a counting semaphore. As is a Jack
    > > Russell is a dog, but a dog is not a Jack Russell.
    > >
    > Really?
    > A Jack Russell is a dog because anything you say about a dog can
    > also be said about a Jack Russell.

    I said a Jack Russell _is_ a dog, but a dog is not a Jack Russell.
    Everything you can say about a dog you can't say about a Jack Russell.
    Since, a dog can have other characteristics than a Jack Russell has. A dog
    can be big and lazy, but I would not say that about a Jack Russell.

    > A counting semaphore is a mutex for the same reason (and observe
    > that 99% of users use the semaphore as a mutex). A mutex definitely
    > is not a counting semaphore. David's implementation of mutexes
    > don't count at all.

    But a counting semaphore of (one) _is_ a mutex! But a mutex can't have
    more than one. As for David's code, that's just arguing implementation,
    and not the semantics of it.

    -- Steve

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