[PKT_SCHED]: Qdisc drop operation is optional

The drop operation is optional and qdiscs must check if childs support it.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index 1641db33a994..3395ca7bcadf 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -165,7 +165,7 @@ static unsigned int prio_drop(struct Qdisc* sch)
 
         for (prio = q->bands-1; prio >= 0; prio--) {
                 qdisc = q->queues[prio];
-                if ((len = qdisc->ops->drop(qdisc)) != 0) {
+                if (qdisc->ops->drop && (len = qdisc->ops->drop(qdisc)) != 0) {
                         sch->q.qlen--;
                         return len;
                 }