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, 5 insertions, 0 deletions

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 84d25f2e618..b1d2cfea89c 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -193,6 +193,11 @@ static inline struct Qdisc *qdisc_root(struct Qdisc *qdisc)
         return qdisc->dev_queue->qdisc;
 }
 
+static inline struct Qdisc *qdisc_root_sleeping(struct Qdisc *qdisc)
+{
+        return qdisc->dev_queue->qdisc_sleeping;
+}
+
 /* The qdisc root lock is a mechanism by which to top level
  * of a qdisc tree can be locked from any qdisc node in the
  * forest.  This allows changing the configuration of some