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sbitmap: use smp_mb__after_atomic() in sbq_wake_up()
We always do an atomic clear_bit() right before we call sbq_wake_up(), so we can use smp_mb__after_atomic(). While we're here, comment the memory barriers in here a little more. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -299,8 +299,14 @@ static void sbq_wake_up(struct sbitmap_queue *sbq)
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struct sbq_wait_state *ws;
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int wait_cnt;
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/* Ensure that the wait list checks occur after clear_bit(). */
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smp_mb();
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/*
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* Pairs with the memory barrier in set_current_state() to ensure the
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* proper ordering of clear_bit()/waitqueue_active() in the waker and
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* test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See
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* the comment on waitqueue_active(). This is __after_atomic because we
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* just did clear_bit() in the caller.
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*/
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smp_mb__after_atomic();
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ws = sbq_wake_ptr(sbq);
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if (!ws)
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@ -331,7 +337,8 @@ void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
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int i, wake_index;
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/*
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* Make sure all changes prior to this are visible from other CPUs.
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* Pairs with the memory barrier in set_current_state() like in
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* sbq_wake_up().
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*/
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smp_mb();
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wake_index = atomic_read(&sbq->wake_index);
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