linux-kernel - [PATCH 3/4] sbitmap: fix improper use of smp_mb__before

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Date:   Mon, 20 May 2019 19:23:57 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     Andrea Parri <andrea.parri@...rulasolutions.com>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Omar Sandoval <osandov@...com>, Ming Lei <ming.lei@...hat.com>,
        linux-block@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 3/4] sbitmap: fix improper use of smp_mb__before_atomic()

This barrier only applies to the read-modify-write operations; in
particular, it does not apply to the atomic_set() primitive.

Replace the barrier with an smp_mb().

Fixes: 6c0ca7ae292ad ("sbitmap: fix wakeup hang after sbq resize")
Cc: stable@...r.kernel.org
Reported-by: "Paul E. McKenney" <paulmck@...ux.ibm.com>
Reported-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
Reviewed-by: Ming Lei <ming.lei@...hat.com>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Omar Sandoval <osandov@...com>
Cc: Ming Lei <ming.lei@...hat.com>
Cc: linux-block@...r.kernel.org
Cc: "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 lib/sbitmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 155fe38756ecf..4a7fc4915dfc6 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -435,7 +435,7 @@ static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq,
 		 * to ensure that the batch size is updated before the wait
 		 * counts.
 		 */
-		smp_mb__before_atomic();
+		smp_mb();
 		for (i = 0; i < SBQ_WAIT_QUEUES; i++)
 			atomic_set(&sbq->ws[i].wait_cnt, 1);
 	}
-- 
2.7.4