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: 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>
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index adf273f..6a5e6e4 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1147,8 +1147,12 @@
void *ptr)
{
struct net_device *dev = ptr;
- struct in_device *in_dev = __in_dev_get_rtnl(dev);
+ struct in_device *in_dev;
+ if (event == NETDEV_UNREGISTER_FINAL)
+ goto out;
+
+ in_dev = __in_dev_get_rtnl(dev);
ASSERT_RTNL();
if (!in_dev) {
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 7f073a3..fd7d9ae 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1041,7 +1041,7 @@
static int fib_netdev_event(struct notifier_block *this, unsigned long event, void *ptr)
{
struct net_device *dev = ptr;
- struct in_device *in_dev = __in_dev_get_rtnl(dev);
+ struct in_device *in_dev;
struct net *net = dev_net(dev);
if (event == NETDEV_UNREGISTER) {
@@ -1050,9 +1050,11 @@
return NOTIFY_DONE;
}
- if (!in_dev)
+ if (event == NETDEV_UNREGISTER_FINAL)
return NOTIFY_DONE;
+ in_dev = __in_dev_get_rtnl(dev);
+
switch (event) {
case NETDEV_UP:
for_ifa(in_dev) {
@@ -1071,8 +1073,6 @@
case NETDEV_CHANGE:
rt_cache_flush(dev_net(dev), 0);
break;
- case NETDEV_UNREGISTER_BATCH:
- break;
}
return NOTIFY_DONE;
}