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    SubjectRe: [PATCH v2 -tip 0/6] locking: Introduce range reader/writer lock
    On Thu, Apr 20, 2017 at 10:13:26AM -0700, Davidlohr Bueso wrote:

    > I have thought of some heuristics for avoiding sleeping under certain
    > constraints, which could mitigate the spinning step we loose, but I fear it
    > will never be exactly as fast as rwsems -- just consider
    > we always take the tree->lock.

    But tree->lock is a spinlock, so while this gets us out of rwsem-xadd
    territory for the fast paths, the whole lock-stealing and optimistic
    spinning stuff is on a different scale.

    Those are about avoiding actually going to sleep and having to be woken
    up (and waiting to become running) again, which is a long time.

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