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    SubjectRe: [PATCH v2 3/4] mutex: Try to acquire mutex only if it is unlocked
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    On Wed, 2014-06-11 at 11:37 -0700, Jason Low wrote:
    > Upon entering the slowpath in __mutex_lock_common(), we try once more to
    > acquire the mutex. We only try to acquire if (lock->count >= 0). However,
    > what we actually want here is to try to acquire if the mutex is unlocked
    > (lock->count == 1).
    >
    > This patch changes it so that we only try-acquire the mutex upon entering
    > the slowpath if it is unlocked, rather than if the lock count is non-negative.
    > This helps further reduce unnecessary atomic xchg() operations.
    >
    > Furthermore, this patch uses !mutex_is_locked(lock) to do the initial
    > checks for if the lock is free rather than directly calling atomic_read()
    > on the lock->count, in order to improve readability.

    I think this patch can be merged in 2/4, like you had in v1. Otherwise
    looks good.



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