2019-05-20 18:20:53

by Andrea Parri

[permalink] [raw]
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: [email protected]
Reported-by: "Paul E. McKenney" <[email protected]>
Reported-by: Peter Zijlstra <[email protected]>
Signed-off-by: Andrea Parri <[email protected]>
Reviewed-by: Ming Lei <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Omar Sandoval <[email protected]>
Cc: Ming Lei <[email protected]>
Cc: [email protected]
Cc: "Paul E. McKenney" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
---
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