[PATCH net V5 0/2] net/sched: taprio: fix picos_per_byte miscalculation

[PATCH net V5 0/2] net/sched: taprio: fix picos_per_byte miscalculation

[Leandro Dorileo]

This set fixes miscalculations based on invalid link speed values.

Changes in v5:
 + Don't iterate over all the net_device maintained list (suggested by: Florian Fainelli);

Changes in v4:
 + converted pr_info calls to netdev_dbg (suggested by: Florian Fainelli);

Changes in v3:
 + yet pr_info() format warnings;

Changes in v2:
 + fixed pr_info() format both on cbs and taprio patches;


Leandro Dorileo (2):
  net/sched: taprio: fix picos_per_byte miscalculation
  net/sched: cbs: fix port_rate miscalculation

 net/sched/sch_cbs.c    | 94 +++++++++++++++++++++++++++++++++++-------
 net/sched/sch_taprio.c | 93 ++++++++++++++++++++++++++++++++++-------
 2 files changed, 157 insertions(+), 30 deletions(-)

-- 
2.21.0

[PATCH net V5 1/2] net/sched: taprio: fix picos_per_byte miscalculation

[Leandro Dorileo]

The Time Aware Priority Scheduler is heavily dependent to link speed,
it relies on it to calculate transmission bytes per cycle, we can't
properly calculate the so called budget if the device has failed
to report the link speed.

In that case we can't dequeue packets assuming a wrong budget.
This patch makes sure we fail to dequeue case:

1) __ethtool_get_link_ksettings() reports error or 2) the ethernet
driver failed to set the ksettings' speed value (setting link speed
to SPEED_UNKNOWN).

Additionally we re calculate the budget whenever the link speed is
changed.

Fixes: 5a781ccbd19e4 ("tc: Add support for configuring the taprio scheduler")
Signed-off-by: Leandro Dorileo <leandro.maciel.dorileo@intel.com>
Reviewed-by: Vedang Patel <vedang.patel@intel.com>
---
 net/sched/sch_taprio.c | 93 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 77 insertions(+), 16 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 206e4dbed12f..cd089c4f9b0d 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -20,6 +20,9 @@
 #include <net/pkt_cls.h>
 #include <net/sch_generic.h>
 
+static LIST_HEAD(taprio_list);
+static DEFINE_SPINLOCK(taprio_list_lock);
+
 #define TAPRIO_ALL_GATES_OPEN -1
 
 struct sched_entry {
@@ -42,9 +45,9 @@ struct taprio_sched {
 	struct Qdisc *root;
 	s64 base_time;
 	int clockid;
-	int picos_per_byte; /* Using picoseconds because for 10Gbps+
-			     * speeds it's sub-nanoseconds per byte
-			     */
+	atomic64_t picos_per_byte; /* Using picoseconds because for 10Gbps+
+				    * speeds it's sub-nanoseconds per byte
+				    */
 	size_t num_entries;
 
 	/* Protects the update side of the RCU protected current_entry */
@@ -53,6 +56,7 @@ struct taprio_sched {
 	struct list_head entries;
 	ktime_t (*get_time)(void);
 	struct hrtimer advance_timer;
+	struct list_head taprio_list;
 };
 
 static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
@@ -117,7 +121,7 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch)
 
 static inline int length_to_duration(struct taprio_sched *q, int len)
 {
-	return (len * q->picos_per_byte) / 1000;
+	return (len * atomic64_read(&q->picos_per_byte)) / 1000;
 }
 
 static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
@@ -129,6 +133,11 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
 	u32 gate_mask;
 	int i;
 
+	if (atomic64_read(&q->picos_per_byte) == -1) {
+		WARN_ONCE(1, "taprio: dequeue() called with unknown picos per byte.");
+		return NULL;
+	}
+
 	rcu_read_lock();
 	entry = rcu_dereference(q->current_entry);
 	/* if there's no entry, it means that the schedule didn't
@@ -233,7 +242,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 
 	next->close_time = close_time;
 	atomic_set(&next->budget,
-		   (next->interval * 1000) / q->picos_per_byte);
+		   (next->interval * 1000) / atomic64_read(&q->picos_per_byte));
 
 first_run:
 	rcu_assign_pointer(q->current_entry, next);
@@ -567,7 +576,8 @@ static void taprio_start_sched(struct Qdisc *sch, ktime_t start)
 
 	first->close_time = ktime_add_ns(start, first->interval);
 	atomic_set(&first->budget,
-		   (first->interval * 1000) / q->picos_per_byte);
+		   (first->interval * 1000) /
+		   atomic64_read(&q->picos_per_byte));
 	rcu_assign_pointer(q->current_entry, NULL);
 
 	spin_unlock_irqrestore(&q->current_entry_lock, flags);
@@ -575,6 +585,48 @@ static void taprio_start_sched(struct Qdisc *sch, ktime_t start)
 	hrtimer_start(&q->advance_timer, start, HRTIMER_MODE_ABS);
 }
 
+static void taprio_set_picos_per_byte(struct net_device *dev,
+				      struct taprio_sched *q)
+{
+	struct ethtool_link_ksettings ecmd;
+	int picos_per_byte = -1;
+
+	if (!__ethtool_get_link_ksettings(dev, &ecmd) &&
+	    ecmd.base.speed != SPEED_UNKNOWN)
+		picos_per_byte = div64_s64(NSEC_PER_SEC * 1000LL * 8,
+					   ecmd.base.speed * 1000 * 1000);
+
+	atomic64_set(&q->picos_per_byte, picos_per_byte);
+	netdev_dbg(dev, "taprio: set %s's picos_per_byte to: %lld, linkspeed: %d\n",
+		   dev->name, (long long)atomic64_read(&q->picos_per_byte),
+		   ecmd.base.speed);
+}
+
+static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
+			       void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct taprio_sched *q;
+	struct net_device *qdev;
+
+	ASSERT_RTNL();
+
+	if (event != NETDEV_UP && event != NETDEV_CHANGE)
+		return NOTIFY_DONE;
+
+	spin_lock(&taprio_list_lock);
+	list_for_each_entry(q, &taprio_list, taprio_list) {
+		qdev = qdisc_dev(q->root);
+		if (qdev == dev) {
+			taprio_set_picos_per_byte(dev, q);
+			break;
+		}
+	}
+	spin_unlock(&taprio_list_lock);
+
+	return NOTIFY_DONE;
+}
+
 static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 			 struct netlink_ext_ack *extack)
 {
@@ -582,9 +634,7 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 	struct taprio_sched *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
 	struct tc_mqprio_qopt *mqprio = NULL;
-	struct ethtool_link_ksettings ecmd;
 	int i, err, size;
-	s64 link_speed;
 	ktime_t start;
 
 	err = nla_parse_nested(tb, TCA_TAPRIO_ATTR_MAX, opt,
@@ -657,14 +707,7 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 					       mqprio->prio_tc_map[i]);
 	}
 
-	if (!__ethtool_get_link_ksettings(dev, &ecmd))
-		link_speed = ecmd.base.speed;
-	else
-		link_speed = SPEED_1000;
-
-	q->picos_per_byte = div64_s64(NSEC_PER_SEC * 1000LL * 8,
-				      link_speed * 1000 * 1000);
-
+	taprio_set_picos_per_byte(dev, q);
 	start = taprio_get_start_time(sch);
 	if (!start)
 		return 0;
@@ -681,6 +724,10 @@ static void taprio_destroy(struct Qdisc *sch)
 	struct sched_entry *entry, *n;
 	unsigned int i;
 
+	spin_lock(&taprio_list_lock);
+	list_del(&q->taprio_list);
+	spin_unlock(&taprio_list_lock);
+
 	hrtimer_cancel(&q->advance_timer);
 
 	if (q->qdiscs) {
@@ -735,6 +782,10 @@ static int taprio_init(struct Qdisc *sch, struct nlattr *opt,
 	if (!opt)
 		return -EINVAL;
 
+	spin_lock(&taprio_list_lock);
+	list_add(&q->taprio_list, &taprio_list);
+	spin_unlock(&taprio_list_lock);
+
 	return taprio_change(sch, opt, extack);
 }
 
@@ -947,14 +998,24 @@ static struct Qdisc_ops taprio_qdisc_ops __read_mostly = {
 	.owner		= THIS_MODULE,
 };
 
+static struct notifier_block taprio_device_notifier = {
+	.notifier_call = taprio_dev_notifier,
+};
+
 static int __init taprio_module_init(void)
 {
+	int err = register_netdevice_notifier(&taprio_device_notifier);
+
+	if (err)
+		return err;
+
 	return register_qdisc(&taprio_qdisc_ops);
 }
 
 static void __exit taprio_module_exit(void)
 {
 	unregister_qdisc(&taprio_qdisc_ops);
+	unregister_netdevice_notifier(&taprio_device_notifier);
 }
 
 module_init(taprio_module_init);
-- 
2.21.0

Re: [PATCH net V5 1/2] net/sched: taprio: fix picos_per_byte miscalculation

[Cong Wang]

On Thu, Mar 28, 2019 at 5:20 PM Leandro Dorileo
<leandro.maciel.dorileo@intel.com> wrote:
> +static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
> +                              void *ptr)
> +{
> +       struct net_device *dev = netdev_notifier_info_to_dev(ptr);
> +       struct taprio_sched *q;
> +       struct net_device *qdev;
> +
> +       ASSERT_RTNL();
> +
> +       if (event != NETDEV_UP && event != NETDEV_CHANGE)
> +               return NOTIFY_DONE;
> +
> +       spin_lock(&taprio_list_lock);
> +       list_for_each_entry(q, &taprio_list, taprio_list) {
> +               qdev = qdisc_dev(q->root);
> +               if (qdev == dev) {
> +                       taprio_set_picos_per_byte(dev, q);
> +                       break;

Is it safe to call __ethtool_get_link_ksettings() with spinlock held?
I mean is it blocking?

Please audit all the dev->ethtool_ops->get_link_ksettings(),
I just look at a few of them, it seems good.

Thanks.

Re: [PATCH net V5 1/2] net/sched: taprio: fix picos_per_byte miscalculation

[Leandro Dorileo]

Hi,


Cong Wang <xiyou.wangcong@gmail.com> writes:

> On Thu, Mar 28, 2019 at 5:20 PM Leandro Dorileo
> <leandro.maciel.dorileo@intel.com> wrote:
>> +static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
>> +                              void *ptr)
>> +{
>> +       struct net_device *dev = netdev_notifier_info_to_dev(ptr);
>> +       struct taprio_sched *q;
>> +       struct net_device *qdev;
>> +
>> +       ASSERT_RTNL();
>> +
>> +       if (event != NETDEV_UP && event != NETDEV_CHANGE)
>> +               return NOTIFY_DONE;
>> +
>> +       spin_lock(&taprio_list_lock);
>> +       list_for_each_entry(q, &taprio_list, taprio_list) {
>> +               qdev = qdisc_dev(q->root);
>> +               if (qdev == dev) {
>> +                       taprio_set_picos_per_byte(dev, q);
>> +                       break;
>
> Is it safe to call __ethtool_get_link_ksettings() with spinlock held?
> I mean is it blocking?
>
> Please audit all the dev->ethtool_ops->get_link_ksettings(),
> I just look at a few of them, it seems good.

Yep, you're right. There are some get_link_ksettings implementations that will lock
a mutex. I'm changing the implementation to avoid that.

Thanks for catching this up.

--
Dorileo

Re: [PATCH net V5 1/2] net/sched: taprio: fix picos_per_byte miscalculation

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2437 bytes --]

Hi Leandro,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net/master]

url:    https://github.com/0day-ci/linux/commits/Leandro-Dorileo/net-sched-taprio-fix-picos_per_byte-miscalculation/20190329-185809
config: i386-randconfig-l0-03292131 (attached as .config)
compiler: gcc-5 (Debian 5.5.0-3) 5.4.1 20171010
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   net/sched/sch_taprio.o: In function `ktime_compare':
>> include/linux/ktime.h:116: undefined reference to `__divdi3'
   net/sched/sch_taprio.o: In function `__write_once_size':
>> include/linux/compiler.h:219: undefined reference to `__divdi3'
>> include/linux/compiler.h:219: undefined reference to `__divdi3'

vim +116 include/linux/ktime.h

97fc79f9 Thomas Gleixner 2006-01-09  101  
398f382c Daniel Borkmann 2012-10-28  102  /**
398f382c Daniel Borkmann 2012-10-28  103   * ktime_compare - Compares two ktime_t variables for less, greater or equal
398f382c Daniel Borkmann 2012-10-28  104   * @cmp1:	comparable1
398f382c Daniel Borkmann 2012-10-28  105   * @cmp2:	comparable2
398f382c Daniel Borkmann 2012-10-28  106   *
36019265 Yacine Belkadi  2013-07-24  107   * Return: ...
398f382c Daniel Borkmann 2012-10-28  108   *   cmp1  < cmp2: return <0
398f382c Daniel Borkmann 2012-10-28  109   *   cmp1 == cmp2: return 0
398f382c Daniel Borkmann 2012-10-28  110   *   cmp1  > cmp2: return >0
398f382c Daniel Borkmann 2012-10-28  111   */
398f382c Daniel Borkmann 2012-10-28  112  static inline int ktime_compare(const ktime_t cmp1, const ktime_t cmp2)
398f382c Daniel Borkmann 2012-10-28  113  {
2456e855 Thomas Gleixner 2016-12-25  114  	if (cmp1 < cmp2)
398f382c Daniel Borkmann 2012-10-28  115  		return -1;
2456e855 Thomas Gleixner 2016-12-25 @116  	if (cmp1 > cmp2)
398f382c Daniel Borkmann 2012-10-28  117  		return 1;
398f382c Daniel Borkmann 2012-10-28  118  	return 0;
398f382c Daniel Borkmann 2012-10-28  119  }
398f382c Daniel Borkmann 2012-10-28  120  

:::::: The code at line 116 was first introduced by commit
:::::: 2456e855354415bfaeb7badaa14e11b3e02c8466 ktime: Get rid of the union

:::::: TO: Thomas Gleixner <tglx@linutronix.de>
:::::: CC: Thomas Gleixner <tglx@linutronix.de>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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Re: [PATCH net V5 1/2] net/sched: taprio: fix picos_per_byte miscalculation

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 851 bytes --]

Hi Leandro,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net/master]

url:    https://github.com/0day-ci/linux/commits/Leandro-Dorileo/net-sched-taprio-fix-picos_per_byte-miscalculation/20190329-185809
config: m68k-allmodconfig (attached as .config)
compiler: m68k-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=m68k 

All errors (new ones prefixed by >>):

>> ERROR: "__divdi3" [net/sched/sch_taprio.ko] undefined!

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 48977 bytes --]

[PATCH net V5 2/2] net/sched: cbs: fix port_rate miscalculation

[Leandro Dorileo]

The Credit Based Shaper heavily depends on link speed to calculate
the scheduling credits, we can't properly calculate the credits if the
device has failed to report the link speed.

In that case we can't dequeue packets assuming a wrong port rate that will
result into an inconsistent credit distribution.

This patch makes sure we fail to dequeue case:

1) __ethtool_get_link_ksettings() reports error or 2) the ethernet driver
failed to set the ksettings' speed value (setting link speed to
SPEED_UNKNOWN).

Additionally we properly re calculate the port rate whenever the link speed
is changed.

Fixes: 3d0bd028ffb4a ("net/sched: Add support for HW offloading for CBS")
Signed-off-by: Leandro Dorileo <leandro.maciel.dorileo@intel.com>
Reviewed-by: Vedang Patel <vedang.patel@intel.com>
---
 net/sched/sch_cbs.c | 94 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 80 insertions(+), 14 deletions(-)

diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
index c6a502933fe7..9d450af98965 100644
--- a/net/sched/sch_cbs.c
+++ b/net/sched/sch_cbs.c
@@ -61,16 +61,20 @@
 #include <linux/string.h>
 #include <linux/errno.h>
 #include <linux/skbuff.h>
+#include <net/netevent.h>
 #include <net/netlink.h>
 #include <net/sch_generic.h>
 #include <net/pkt_sched.h>
 
+static LIST_HEAD(cbs_list);
+static DEFINE_SPINLOCK(cbs_list_lock);
+
 #define BYTES_PER_KBIT (1000LL / 8)
 
 struct cbs_sched_data {
 	bool offload;
 	int queue;
-	s64 port_rate; /* in bytes/s */
+	atomic64_t port_rate; /* in bytes/s */
 	s64 last; /* timestamp in ns */
 	s64 credits; /* in bytes */
 	s32 locredit; /* in bytes */
@@ -82,6 +86,7 @@ struct cbs_sched_data {
 		       struct sk_buff **to_free);
 	struct sk_buff *(*dequeue)(struct Qdisc *sch);
 	struct Qdisc *qdisc;
+	struct list_head cbs_list;
 };
 
 static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch,
@@ -181,6 +186,11 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
 	s64 credits;
 	int len;
 
+	if (atomic64_read(&q->port_rate) == -1) {
+		WARN_ONCE(1, "cbs: dequeue() called with unknown port rate.");
+		return NULL;
+	}
+
 	if (q->credits < 0) {
 		credits = timediff_to_credits(now - q->last, q->idleslope);
 
@@ -207,7 +217,8 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
 	/* As sendslope is a negative number, this will decrease the
 	 * amount of q->credits.
 	 */
-	credits = credits_from_len(len, q->sendslope, q->port_rate);
+	credits = credits_from_len(len, q->sendslope,
+				   atomic64_read(&q->port_rate));
 	credits += q->credits;
 
 	q->credits = max_t(s64, credits, q->locredit);
@@ -294,6 +305,46 @@ static int cbs_enable_offload(struct net_device *dev, struct cbs_sched_data *q,
 	return 0;
 }
 
+static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q)
+{
+	struct ethtool_link_ksettings ecmd;
+	int port_rate = -1;
+
+	if (!__ethtool_get_link_ksettings(dev, &ecmd) &&
+	    ecmd.base.speed != SPEED_UNKNOWN)
+		port_rate = ecmd.base.speed * 1000 * BYTES_PER_KBIT;
+
+	atomic64_set(&q->port_rate, port_rate);
+	netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n",
+		   dev->name, (long long)atomic64_read(&q->port_rate),
+		   ecmd.base.speed);
+}
+
+static int cbs_dev_notifier(struct notifier_block *nb, unsigned long event,
+			    void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct cbs_sched_data *q;
+	struct net_device *qdev;
+
+	ASSERT_RTNL();
+
+	if (event != NETDEV_UP && event != NETDEV_CHANGE)
+		return NOTIFY_DONE;
+
+	spin_lock(&cbs_list_lock);
+	list_for_each_entry(q, &cbs_list, cbs_list) {
+		qdev = qdisc_dev(q->qdisc);
+		if (qdev == dev) {
+			cbs_set_port_rate(dev, q);
+			break;
+		}
+	}
+	spin_unlock(&cbs_list_lock);
+
+	return NOTIFY_DONE;
+}
+
 static int cbs_change(struct Qdisc *sch, struct nlattr *opt,
 		      struct netlink_ext_ack *extack)
 {
@@ -315,16 +366,7 @@ static int cbs_change(struct Qdisc *sch, struct nlattr *opt,
 	qopt = nla_data(tb[TCA_CBS_PARMS]);
 
 	if (!qopt->offload) {
-		struct ethtool_link_ksettings ecmd;
-		s64 link_speed;
-
-		if (!__ethtool_get_link_ksettings(dev, &ecmd))
-			link_speed = ecmd.base.speed;
-		else
-			link_speed = SPEED_1000;
-
-		q->port_rate = link_speed * 1000 * BYTES_PER_KBIT;
-
+		cbs_set_port_rate(dev, q);
 		cbs_disable_offload(dev, q);
 	} else {
 		err = cbs_enable_offload(dev, q, qopt, extack);
@@ -347,6 +389,7 @@ static int cbs_init(struct Qdisc *sch, struct nlattr *opt,
 {
 	struct cbs_sched_data *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
+	int err;
 
 	if (!opt) {
 		NL_SET_ERR_MSG(extack, "Missing CBS qdisc options  which are mandatory");
@@ -367,7 +410,17 @@ static int cbs_init(struct Qdisc *sch, struct nlattr *opt,
 
 	qdisc_watchdog_init(&q->watchdog, sch);
 
-	return cbs_change(sch, opt, extack);
+	err = cbs_change(sch, opt, extack);
+	if (err)
+		return err;
+
+	if (!q->offload) {
+		spin_lock(&cbs_list_lock);
+		list_add(&q->cbs_list, &cbs_list);
+		spin_unlock(&cbs_list_lock);
+	}
+
+	return 0;
 }
 
 static void cbs_destroy(struct Qdisc *sch)
@@ -375,8 +428,11 @@ static void cbs_destroy(struct Qdisc *sch)
 	struct cbs_sched_data *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
 
-	qdisc_watchdog_cancel(&q->watchdog);
+	spin_lock(&cbs_list_lock);
+	list_del(&q->cbs_list);
+	spin_unlock(&cbs_list_lock);
 
+	qdisc_watchdog_cancel(&q->watchdog);
 	cbs_disable_offload(dev, q);
 
 	if (q->qdisc)
@@ -487,14 +543,24 @@ static struct Qdisc_ops cbs_qdisc_ops __read_mostly = {
 	.owner		=	THIS_MODULE,
 };
 
+static struct notifier_block cbs_device_notifier = {
+	.notifier_call = cbs_dev_notifier,
+};
+
 static int __init cbs_module_init(void)
 {
+	int err = register_netdevice_notifier(&cbs_device_notifier);
+
+	if (err)
+		return err;
+
 	return register_qdisc(&cbs_qdisc_ops);
 }
 
 static void __exit cbs_module_exit(void)
 {
 	unregister_qdisc(&cbs_qdisc_ops);
+	unregister_netdevice_notifier(&cbs_device_notifier);
 }
 module_init(cbs_module_init)
 module_exit(cbs_module_exit)
-- 
2.21.0