[PATCH 1/1] net: Add rtnl_lock for netif_device_attach/detach

["Li, Zhen-Hua" <zhen-hual@hp.com>]

From: "Li, Zhen-Hua" <zhen-hual@hp.com>

As netif_running is called in netif_device_attach/detach. There should be
rtnl_lock/unlock called, to avoid dev stat change during netif_device_attach
and detach being called.
I checked NIC some drivers,  some of them have netif_device_attach/detach
called between rtnl_lock/unlock, while some drivers do not.

This patch is tring to find a generic way to fix this for all NIC drivers.

Signed-off-by: Li, Zhen-Hua <zhen-hual@hp.com>
---
 net/core/dev.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 5b3042e..795bbc5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2190,10 +2190,19 @@ EXPORT_SYMBOL(__dev_kfree_skb_any);
  */
 void netif_device_detach(struct net_device *dev)
 {
+	/**
+	 * As netif_running is called , rtnl_lock and unlock are needed to
+	 * avoid __LINK_STATE_START bit changes during this function call.
+	 */
+	int need_unlock;
+
+	need_unlock = rtnl_trylock();
 	if (test_and_clear_bit(__LINK_STATE_PRESENT, &dev->state) &&
 	    netif_running(dev)) {
 		netif_tx_stop_all_queues(dev);
 	}
+	if (need_unlock)
+		rtnl_unlock();
 }
 EXPORT_SYMBOL(netif_device_detach);
 
@@ -2205,11 +2214,20 @@ EXPORT_SYMBOL(netif_device_detach);
  */
 void netif_device_attach(struct net_device *dev)
 {
+	/**
+	 * As netif_running is called , rtnl_lock and unlock are needed to
+	 * avoid __LINK_STATE_START bit changes during this function call.
+	 */
+	int need_unlock;
+
+	need_unlock = rtnl_trylock();
 	if (!test_and_set_bit(__LINK_STATE_PRESENT, &dev->state) &&
 	    netif_running(dev)) {
 		netif_tx_wake_all_queues(dev);
 		__netdev_watchdog_up(dev);
 	}
+	if (need_unlock)
+		rtnl_unlock();
 }
 EXPORT_SYMBOL(netif_device_attach);
 
-- 
1.7.10.4