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    SubjectRe: spinlock which can morph into a mutex
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    On Fri, 2009-12-18 at 18:14 +0100, Thomas Gleixner wrote:
    > On Fri, 18 Dec 2009, Miquel van Smoorenburg wrote:
    > I think I need a spinlock that can morph into a mutex ..
    >
    > Is the writer frequency and the possible contention so high that you
    > need a spinlock at all ?

    Possibly - I don't want to degrade the performance of existing code
    (which uses a spinlock).

    > Test it :)

    Good point.

    > If the mutex is still to heavy weight for you, then you can solve it
    > without implementing another weird concurrency control:
    >
    > wait_event_(un)interruptible(&hash_wq, !hash_update_active);
    >
    > hash_update_active = 1;
    > ....
    > hash_update_active = 0;
    > wake_up(&hash_wq);

    Ah, ofcourse. Thanks for pointing that out!

    Thanks everybody for your input. I gained quite a bit of insight.

    Mike.



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