pkt_sched: Fix qdisc_watchdog() vs. dev_deactivate() race

dev_deactivate() can skip rescheduling of a qdisc by qdisc_watchdog()
or other timer calling netif_schedule() after dev_queue_deactivate().
We prevent this checking aliveness before scheduling the timer. Since
during deactivation the root qdisc is available only as qdisc_sleeping
additional accessor qdisc_root_sleeping() is created.

With feedback from Herbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index 47ef492c4ff4..8fa90d68ec6d 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -521,6 +521,10 @@ static void cbq_ovl_delay(struct cbq_class *cl)
         struct cbq_sched_data *q = qdisc_priv(cl->qdisc);
         psched_tdiff_t delay = cl->undertime - q->now;
 
+        if (test_bit(__QDISC_STATE_DEACTIVATED,
+                     &qdisc_root_sleeping(cl->qdisc)->state))
+                return;
+
         if (!cl->delayed) {
                 psched_time_t sched = q->now;
                 ktime_t expires;