net: factorize sync-rcu call in unregister_netdevice_many
Add dev_close_many and dev_deactivate_many to factorize another
sync-rcu operation on the netdevice unregister path.
$ modprobe dummy numdummies=10000
$ ip link set dev dummy* up
$ time rmmod dummy
Without the patch With the patch
real 0m 24.63s real 0m 5.15s
user 0m 0.00s user 0m 0.00s
sys 0m 6.05s sys 0m 5.14s
Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 7ac26d2..794b20d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1222,52 +1222,90 @@
}
EXPORT_SYMBOL(dev_open);
-static int __dev_close(struct net_device *dev)
+static int __dev_close_many(struct list_head *head)
{
- const struct net_device_ops *ops = dev->netdev_ops;
+ struct net_device *dev;
ASSERT_RTNL();
might_sleep();
- /*
- * Tell people we are going down, so that they can
- * prepare to death, when device is still operating.
- */
- call_netdevice_notifiers(NETDEV_GOING_DOWN, dev);
+ list_for_each_entry(dev, head, unreg_list) {
+ /*
+ * Tell people we are going down, so that they can
+ * prepare to death, when device is still operating.
+ */
+ call_netdevice_notifiers(NETDEV_GOING_DOWN, dev);
- clear_bit(__LINK_STATE_START, &dev->state);
+ clear_bit(__LINK_STATE_START, &dev->state);
- /* Synchronize to scheduled poll. We cannot touch poll list,
- * it can be even on different cpu. So just clear netif_running().
- *
- * dev->stop() will invoke napi_disable() on all of it's
- * napi_struct instances on this device.
- */
- smp_mb__after_clear_bit(); /* Commit netif_running(). */
+ /* Synchronize to scheduled poll. We cannot touch poll list, it
+ * can be even on different cpu. So just clear netif_running().
+ *
+ * dev->stop() will invoke napi_disable() on all of it's
+ * napi_struct instances on this device.
+ */
+ smp_mb__after_clear_bit(); /* Commit netif_running(). */
+ }
- dev_deactivate(dev);
+ dev_deactivate_many(head);
+
+ list_for_each_entry(dev, head, unreg_list) {
+ const struct net_device_ops *ops = dev->netdev_ops;
+
+ /*
+ * Call the device specific close. This cannot fail.
+ * Only if device is UP
+ *
+ * We allow it to be called even after a DETACH hot-plug
+ * event.
+ */
+ if (ops->ndo_stop)
+ ops->ndo_stop(dev);
+
+ /*
+ * Device is now down.
+ */
+
+ dev->flags &= ~IFF_UP;
+
+ /*
+ * Shutdown NET_DMA
+ */
+ net_dmaengine_put();
+ }
+
+ return 0;
+}
+
+static int __dev_close(struct net_device *dev)
+{
+ LIST_HEAD(single);
+
+ list_add(&dev->unreg_list, &single);
+ return __dev_close_many(&single);
+}
+
+int dev_close_many(struct list_head *head)
+{
+ struct net_device *dev, *tmp;
+ LIST_HEAD(tmp_list);
+
+ list_for_each_entry_safe(dev, tmp, head, unreg_list)
+ if (!(dev->flags & IFF_UP))
+ list_move(&dev->unreg_list, &tmp_list);
+
+ __dev_close_many(head);
/*
- * Call the device specific close. This cannot fail.
- * Only if device is UP
- *
- * We allow it to be called even after a DETACH hot-plug
- * event.
+ * Tell people we are down
*/
- if (ops->ndo_stop)
- ops->ndo_stop(dev);
+ list_for_each_entry(dev, head, unreg_list) {
+ rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
+ call_netdevice_notifiers(NETDEV_DOWN, dev);
+ }
- /*
- * Device is now down.
- */
-
- dev->flags &= ~IFF_UP;
-
- /*
- * Shutdown NET_DMA
- */
- net_dmaengine_put();
-
+ /* rollback_registered_many needs the complete original list */
+ list_splice(&tmp_list, head);
return 0;
}
@@ -1282,16 +1320,10 @@
*/
int dev_close(struct net_device *dev)
{
- if (!(dev->flags & IFF_UP))
- return 0;
+ LIST_HEAD(single);
- __dev_close(dev);
-
- /*
- * Tell people we are down
- */
- rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
- call_netdevice_notifiers(NETDEV_DOWN, dev);
+ list_add(&dev->unreg_list, &single);
+ dev_close_many(&single);
return 0;
}
@@ -4963,10 +4995,12 @@
}
BUG_ON(dev->reg_state != NETREG_REGISTERED);
+ }
- /* If device is running, close it first. */
- dev_close(dev);
+ /* If device is running, close it first. */
+ dev_close_many(head);
+ list_for_each_entry(dev, head, unreg_list) {
/* And unlink it from device chain. */
unlist_netdevice(dev);