net: make namespace iteration possible under RCU
All we need to take care of is using proper RCU list
add/del primitives and inserting a synchronize_rcu()
at one place to make sure the exit notifiers are run
after everybody has stopped iterating the list.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index b7292a2..5cd0b22 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -6,6 +6,7 @@
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/idr.h>
+#include <linux/rculist.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
@@ -127,7 +128,7 @@
rv = setup_net(net);
if (rv == 0) {
rtnl_lock();
- list_add_tail(&net->list, &net_namespace_list);
+ list_add_tail_rcu(&net->list, &net_namespace_list);
rtnl_unlock();
}
mutex_unlock(&net_mutex);
@@ -156,9 +157,16 @@
/* Don't let anyone else find us. */
rtnl_lock();
- list_del(&net->list);
+ list_del_rcu(&net->list);
rtnl_unlock();
+ /*
+ * Another CPU might be rcu-iterating the list, wait for it.
+ * This needs to be before calling the exit() notifiers, so
+ * the rcu_barrier() below isn't sufficient alone.
+ */
+ synchronize_rcu();
+
/* Run all of the network namespace exit methods */
list_for_each_entry_reverse(ops, &pernet_list, list) {
if (ops->exit)
@@ -219,7 +227,7 @@
panic("Could not setup the initial network namespace");
rtnl_lock();
- list_add_tail(&init_net.list, &net_namespace_list);
+ list_add_tail_rcu(&init_net.list, &net_namespace_list);
rtnl_unlock();
mutex_unlock(&net_mutex);