pkt_sched: Add lockdep annotation for qdisc locks

Qdisc locks are initialized in the same function, qdisc_alloc(), so
lockdep can't distinguish tx qdisc lock from rx and reports "possible
recursive locking detected" when both these locks are taken eg. while
using act_mirred with ifb. This looks like a false positive. Anyway,
after this patch these locks will be reported more exactly.

Reported-by: Denys Fedoryshchenko <denys@visp.net.lb>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 98c00847a3d22d69f97abff267b1c1b43610affa..7d7070b1eebd3dd5290776fe3cdf230ee8232b70 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -27,6 +27,7 @@
 #include <linux/kmod.h>
 #include <linux/list.h>
 #include <linux/hrtimer.h>
+#include <linux/lockdep.h>
 
 #include <net/net_namespace.h>
 #include <net/sock.h>
@@ -707,6 +708,10 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
        return err;
 }
 
+/* lockdep annotation is needed for ingress; egress gets it only for name */
+static struct lock_class_key qdisc_tx_lock;
+static struct lock_class_key qdisc_rx_lock;
+
 /*
    Allocate and initialize new qdisc.
 
@@ -767,6 +772,7 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue,
        if (handle == TC_H_INGRESS) {
                sch->flags |= TCQ_F_INGRESS;
                handle = TC_H_MAKE(TC_H_INGRESS, 0);
+               lockdep_set_class(qdisc_lock(sch), &qdisc_rx_lock);
        } else {
                if (handle == 0) {
                        handle = qdisc_alloc_handle(dev);
@@ -774,6 +780,7 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue,
                        if (handle == 0)
                                goto err_out3;
                }
+               lockdep_set_class(qdisc_lock(sch), &qdisc_tx_lock);
        }
 
        sch->handle = handle;