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Commit f66227de authored by Omar Sandoval's avatar Omar Sandoval Committed by Jens Axboe
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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: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 4d199c6f

lib/sbitmap.c

+10 −3
Original line number Diff line number Diff line
@@ -299,8 +299,14 @@ static void sbq_wake_up(struct sbitmap_queue *sbq) 
	struct sbq_wait_state *ws;

	int wait_cnt;



	/* Ensure that the wait list checks occur after clear_bit(). */

	smp_mb();

	/*

	 * Pairs with the memory barrier in set_current_state() to ensure the

	 * proper ordering of clear_bit()/waitqueue_active() in the waker and

	 * test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See

	 * the comment on waitqueue_active(). This is __after_atomic because we

	 * just did clear_bit() in the caller.

	 */

	smp_mb__after_atomic();



	ws = sbq_wake_ptr(sbq);

	if (!ws)
@@ -331,7 +337,8 @@ void sbitmap_queue_wake_all(struct sbitmap_queue *sbq) 
	int i, wake_index;



	/*

	 * Make sure all changes prior to this are visible from other CPUs.

	 * Pairs with the memory barrier in set_current_state() like in

	 * sbq_wake_up().

	 */

	smp_mb();

	wake_index = atomic_read(&sbq->wake_index);