Commit 0115e8e3 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: remove delay at device dismantle 



I noticed extra one second delay in device dismantle, tracked down to
a call to dst_dev_event() while some call_rcu() are still in RCU queues.

These call_rcu() were posted by rt_free(struct rtable *rt) calls.

We then wait a little (but one second) in netdev_wait_allrefs() before
kicking again NETDEV_UNREGISTER.

As the call_rcu() are now completed, dst_dev_event() can do the needed
device swap on busy dst.

To solve this problem, add a new NETDEV_UNREGISTER_FINAL, called
after a rcu_barrier(), but outside of RTNL lock.

Use NETDEV_UNREGISTER_FINAL with care !

Change dst_dev_event() handler to react to NETDEV_UNREGISTER_FINAL

Also remove NETDEV_UNREGISTER_BATCH, as its not used anymore after
IP cache removal.

With help from Gao feng

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Mahesh Bandewar <maheshb@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent bf277b0c

include/linux/netdevice.h

+1 −1
Original line number Diff line number Diff line
@@ -1553,7 +1553,7 @@ struct packet_type { 
#define NETDEV_PRE_TYPE_CHANGE	0x000E

#define NETDEV_POST_TYPE_CHANGE	0x000F

#define NETDEV_POST_INIT	0x0010

#define NETDEV_UNREGISTER_BATCH 0x0011

#define NETDEV_UNREGISTER_FINAL 0x0011

#define NETDEV_RELEASE		0x0012

#define NETDEV_NOTIFY_PEERS	0x0013

#define NETDEV_JOIN		0x0014

net/core/dev.c

+8 −14
Original line number Diff line number Diff line
@@ -1406,7 +1406,6 @@ rollback: 
				nb->notifier_call(nb, NETDEV_DOWN, dev);

			}

			nb->notifier_call(nb, NETDEV_UNREGISTER, dev);

			nb->notifier_call(nb, NETDEV_UNREGISTER_BATCH, dev);

		}

	}
@@ -1448,7 +1447,6 @@ int unregister_netdevice_notifier(struct notifier_block *nb) 
				nb->notifier_call(nb, NETDEV_DOWN, dev);

			}

			nb->notifier_call(nb, NETDEV_UNREGISTER, dev);

			nb->notifier_call(nb, NETDEV_UNREGISTER_BATCH, dev);

		}

	}

unlock:
@@ -1468,6 +1466,7 @@ EXPORT_SYMBOL(unregister_netdevice_notifier); 


int call_netdevice_notifiers(unsigned long val, struct net_device *dev)

{

	if (val != NETDEV_UNREGISTER_FINAL)

		ASSERT_RTNL();

	return raw_notifier_call_chain(&netdev_chain, val, dev);

}
@@ -5331,10 +5330,6 @@ static void rollback_registered_many(struct list_head *head) 
		netdev_unregister_kobject(dev);

	}



	/* Process any work delayed until the end of the batch */

	dev = list_first_entry(head, struct net_device, unreg_list);

	call_netdevice_notifiers(NETDEV_UNREGISTER_BATCH, dev);



	synchronize_net();



	list_for_each_entry(dev, head, unreg_list)
@@ -5787,9 +5782,8 @@ static void netdev_wait_allrefs(struct net_device *dev) 


			/* Rebroadcast unregister notification */

			call_netdevice_notifiers(NETDEV_UNREGISTER, dev);

			/* don't resend NETDEV_UNREGISTER_BATCH, _BATCH users

			 * should have already handle it the first time */



			rcu_barrier();

			call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);

			if (test_bit(__LINK_STATE_LINKWATCH_PENDING,

				     &dev->state)) {

				/* We must not have linkwatch events
@@ -5851,9 +5845,8 @@ void netdev_run_todo(void) 


	__rtnl_unlock();



	/* Wait for rcu callbacks to finish before attempting to drain

	 * the device list.  This usually avoids a 250ms wait.

	 */



	/* Wait for rcu callbacks to finish before next phase */

	if (!list_empty(&list))

		rcu_barrier();
@@ -5862,6 +5855,8 @@ void netdev_run_todo(void) 
			= list_first_entry(&list, struct net_device, todo_list);

		list_del(&dev->todo_list);



		call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);



		if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {

			pr_err("network todo '%s' but state %d\n",

			       dev->name, dev->reg_state);
@@ -6256,7 +6251,6 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char 
	   the device is just moving and can keep their slaves up.

	*/

	call_netdevice_notifiers(NETDEV_UNREGISTER, dev);

	call_netdevice_notifiers(NETDEV_UNREGISTER_BATCH, dev);

	rtmsg_ifinfo(RTM_DELLINK, dev, ~0U);



	/*

net/core/dst.c

+1 −1
Original line number Diff line number Diff line
@@ -374,7 +374,7 @@ static int dst_dev_event(struct notifier_block *this, unsigned long event, 
	struct dst_entry *dst, *last = NULL;



	switch (event) {

	case NETDEV_UNREGISTER:

	case NETDEV_UNREGISTER_FINAL:

	case NETDEV_DOWN:

		mutex_lock(&dst_gc_mutex);

		for (dst = dst_busy_list; dst; dst = dst->next) {

net/core/fib_rules.c

+2 −1
Original line number Diff line number Diff line
@@ -711,15 +711,16 @@ static int fib_rules_event(struct notifier_block *this, unsigned long event, 
	struct net *net = dev_net(dev);

	struct fib_rules_ops *ops;



	ASSERT_RTNL();



	switch (event) {

	case NETDEV_REGISTER:

		ASSERT_RTNL();

		list_for_each_entry(ops, &net->rules_ops, list)

			attach_rules(&ops->rules_list, dev);

		break;



	case NETDEV_UNREGISTER:

		ASSERT_RTNL();

		list_for_each_entry(ops, &net->rules_ops, list)

			detach_rules(&ops->rules_list, dev);

		break;

net/core/rtnetlink.c

+1 −1
Original line number Diff line number Diff line
@@ -2358,7 +2358,7 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi 
	case NETDEV_PRE_TYPE_CHANGE:

	case NETDEV_GOING_DOWN:

	case NETDEV_UNREGISTER:

	case NETDEV_UNREGISTER_BATCH:

	case NETDEV_UNREGISTER_FINAL:

	case NETDEV_RELEASE:

	case NETDEV_JOIN:

		break;

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