datapath: Call rcu_barrier() before unloading module.

According to article "RCU and Unloadable Modules" available at lwn.net,
a module that uses RCU callbacks should call rcu_barrier() before
unloading, because synchronize_rcu() does not ensure that all RCU callbacks
have actually completed, only that a grace period has elapsed.

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 252e3e0067ab8a047a0c115b4f9b9bb46188d674..d3dd6909ba9a4dec955a09680939a986dfa1189d 100644 (file)
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -1648,6 +1648,7 @@ error:
 
 static void dp_cleanup(void)
 {
+       rcu_barrier();
        unregister_chrdev(major, "openvswitch");
        unregister_netdevice_notifier(&dp_device_notifier);
        flow_exit();