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net: remove delay at device dismantle

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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: Eric 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: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2012-08-22 17:19:46 +00:00
committed by David S. Miller
parent bf277b0cce
commit 0115e8e30d
8 changed files with 27 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
net/core/dev.c
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@@ -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:
@@ -1468,7 +1466,8 @@ EXPORT_SYMBOL(unregister_netdevice_notifier);
int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
{
ASSERT_RTNL();
if (val != NETDEV_UNREGISTER_FINAL)
ASSERT_RTNL();
return raw_notifier_call_chain(&netdev_chain, val, dev);
}
EXPORT_SYMBOL(call_netdevice_notifiers);
@@ -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);
/*