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_api.c b/net/sched/sch_api.c
index ef0efeca6352..45f442d7de47 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -444,6 +444,10 @@ void qdisc_watchdog_schedule(struct qdisc_watchdog *wd, psched_time_t expires)
 {
         ktime_t time;
 
+        if (test_bit(__QDISC_STATE_DEACTIVATED,
+                     &qdisc_root_sleeping(wd->qdisc)->state))
+                return;
+
         wd->qdisc->flags |= TCQ_F_THROTTLED;
         time = ktime_set(0, 0);
         time = ktime_add_ns(time, PSCHED_US2NS(expires));