This Linux kernel change "sbitmap: fix improper use of smp_mb__before_atomic()" is included in the Linux 5.2 release. This change is authored by Andrea Parri <andrea.parri [at] amarulasolutions.com> on Mon May 20 19:23:57 2019 +0200. The commit for this change in Linux stable tree is a0934fd (patch).
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]> Signed-off-by: Jens Axboe <[email protected]>
There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.
lib/sbitmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 155fe38..4a7fc49 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); }