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@xxxxxxxxxxxxxxxx>
---
include/net/net_namespace.h | 3 +++
net/core/net_namespace.c | 14 +++++++++++---
2 files changed, 14 insertions(+), 3 deletions(-)
--- wireless-testing.orig/include/net/net_namespace.h 2009-07-07 04:14:39.000000000 +0200
+++ wireless-testing/include/net/net_namespace.h 2009-07-07 12:17:17.000000000 +0200
@@ -211,6 +211,9 @@ static inline struct net *read_pnet(stru
#define for_each_net(VAR) \
list_for_each_entry(VAR, &net_namespace_list, list)
+#define for_each_net_rcu(VAR) \
+ list_for_each_entry_rcu(VAR, &net_namespace_list, list)
+
#ifdef CONFIG_NET_NS
#define __net_init
#define __net_exit
--- wireless-testing.orig/net/core/net_namespace.c 2009-07-07 03:43:35.000000000 +0200
+++ wireless-testing/net/core/net_namespace.c 2009-07-07 12:18:19.000000000 +0200
@@ -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 @@ static struct net *net_create(void)
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 @@ static void cleanup_net(struct work_stru
/* 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 @@ static int __init net_ns_init(void)
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);
--
--
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