3.16.75-rc1 review patch. If anyone has any objections, please let me know.
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From: Andrea Parri andrea.parri@amarulasolutions.com
commit a0934fd2b1208458e55fc4b48f55889809fce666 upstream.
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") Reported-by: "Paul E. McKenney" paulmck@linux.ibm.com Reported-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Andrea Parri andrea.parri@amarulasolutions.com Reviewed-by: Ming Lei ming.lei@redhat.com Cc: Jens Axboe axboe@kernel.dk Cc: Omar Sandoval osandov@fb.com Cc: Ming Lei ming.lei@redhat.com Cc: linux-block@vger.kernel.org Cc: "Paul E. McKenney" paulmck@linux.ibm.com Cc: Peter Zijlstra peterz@infradead.org Signed-off-by: Jens Axboe axboe@kernel.dk [bwh: Backported to 3.16: adjust filename] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- block/blk-mq-tag.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -499,7 +499,7 @@ static void bt_update_count(struct blk_m * Pairs with the memory barrier in bt_clear_tag() to ensure * that the batch size is updated before the wait counts. */ - smp_mb__before_atomic(); + smp_mb(); for (i = 0; i < BT_WAIT_QUEUES; i++) atomic_set(&bt->bs[i].wait_cnt, 1); }