pkt_sched: Fix qdisc list locking

Since some qdiscs call qdisc_tree_decrease_qlen() (so qdisc_lookup())
without rtnl_lock(), adding and deleting from a qdisc list needs
additional locking. This patch adds global spinlock qdisc_list_lock
and wrapper functions for modifying the list. It is considered as a
temporary solution until hfsc_dequeue(), netem_dequeue() and
tbf_dequeue() (or qdisc_tree_decrease_qlen()) are redone.

With feedback from Herbert Xu and David S. Miller.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 3 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index c3ed4d44fc14..5f0ade7806a7 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -526,10 +526,9 @@ void qdisc_destroy(struct Qdisc *qdisc)
             !atomic_dec_and_test(&qdisc->refcnt))
                 return;
 
-        if (qdisc->parent)
-                list_del(&qdisc->list);
-
 #ifdef CONFIG_NET_SCHED
+        qdisc_list_del(qdisc);
+
         qdisc_put_stab(qdisc->stab);
 #endif
         gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);