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Date: Fri, 10 Aug 2012 16:46:06 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>, Tom Herbert <therbert@...gle.com>,
Mahesh Bandewar <maheshb@...gle.com>
Subject: [PATCH] net: remove delay at device dismantle
From: Eric Dumazet <edumazet@...gle.com>
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
in rollback_registered_many() after a rcu_barrier().
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.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Tom Herbert <therbert@...gle.com>
Cc: Mahesh Bandewar <maheshb@...gle.com>
---
include/linux/netdevice.h | 2 +-
net/core/dev.c | 23 +++++++----------------
net/core/dst.c | 2 +-
net/core/rtnetlink.c | 2 +-
net/ipv4/fib_frontend.c | 2 --
5 files changed, 10 insertions(+), 21 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a9db4f3..e3a43fd 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1550,7 +1550,7 @@ 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
diff --git a/net/core/dev.c b/net/core/dev.c
index a39354e..be3a5af 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1394,7 +1394,6 @@ rollback:
nb->notifier_call(nb, NETDEV_DOWN, dev);
}
nb->notifier_call(nb, NETDEV_UNREGISTER, dev);
- nb->notifier_call(nb, NETDEV_UNREGISTER_BATCH, dev);
}
}
@@ -1436,7 +1435,6 @@ 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:
@@ -5307,14 +5305,14 @@ 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();
+ /* Wait for rcu callbacks to finish before next phase */
+ rcu_barrier();
- list_for_each_entry(dev, head, unreg_list)
+ list_for_each_entry(dev, head, unreg_list) {
+ call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
dev_put(dev);
+ }
}
static void rollback_registered(struct net_device *dev)
@@ -5757,9 +5755,8 @@ 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
@@ -5821,11 +5818,6 @@ 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.
- */
- if (!list_empty(&list))
- rcu_barrier();
while (!list_empty(&list)) {
struct net_device *dev
@@ -6226,7 +6218,6 @@ 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);
/*
diff --git a/net/core/dst.c b/net/core/dst.c
index 56d6361..f6593d2 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -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) {
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 2c5a0a0..30f5a06 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2356,7 +2356,7 @@ 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;
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index c43ae3f..4fe50184 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1071,8 +1071,6 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
case NETDEV_CHANGE:
rt_cache_flush(dev_net(dev), 0);
break;
- case NETDEV_UNREGISTER_BATCH:
- break;
}
return NOTIFY_DONE;
}
--
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