pkt_sched: Fix gen_estimator locks

While passing a qdisc root lock to gen_new_estimator() and
gen_replace_estimator() dev could be deactivated or even before
grafting proper root qdisc as qdisc_sleeping (e.g. qdisc_create), so
using qdisc_root_lock() is not enough. This patch adds
qdisc_root_sleeping_lock() for this, plus additional checks, where
necessary.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index 8fa90d6..9b720ad 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1839,7 +1839,7 @@
 
 		if (tca[TCA_RATE])
 			gen_replace_estimator(&cl->bstats, &cl->rate_est,
-					      qdisc_root_lock(sch),
+					      qdisc_root_sleeping_lock(sch),
 					      tca[TCA_RATE]);
 		return 0;
 	}
@@ -1930,7 +1930,7 @@
 
 	if (tca[TCA_RATE])
 		gen_new_estimator(&cl->bstats, &cl->rate_est,
-				  qdisc_root_lock(sch), tca[TCA_RATE]);
+				  qdisc_root_sleeping_lock(sch), tca[TCA_RATE]);
 
 	*arg = (unsigned long)cl;
 	return 0;