On Wed, 2009-06-17 at 16:24 -0700, Eric W. Biederman wrote:
> > So it looks like I can also use rcu_read_lock(), but there's no
> > for_each_net_rcu(), should there be?
>
> I'm not using rcu safe list manipulation. What makes it look like
> rcu_read_lock() is safe?
Indeed. I was looking at rcu_barrier() only. How about the patch below?
johannes
Subject: net: make namespace iteration possible under RCU
We already call rcu_barrier(), so all we need to take
care of is using proper RCU list add/del primitives.
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
---
include/net/net_namespace.h | 3 +++
net/core/net_namespace.c | 7 ++++---
2 files changed, 7 insertions(+), 3 deletions(-)
--- wireless-testing.orig/include/net/net_namespace.h 2009-06-18 01:36:26.000000000 +0200
+++ wireless-testing/include/net/net_namespace.h 2009-06-18 01:39:35.000000000 +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 2009-06-18 01:36:39.000000000 +0200
+++ wireless-testing/net/core/net_namespace.c 2009-06-18 01:38:36.000000000 +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>
@@ -134,7 +135,7 @@ struct net *copy_net_ns(unsigned long fl
err = setup_net(new_net);
if (!err) {
rtnl_lock();
- list_add_tail(&new_net->list, &net_namespace_list);
+ list_add_tail_rcu(&new_net->list, &net_namespace_list);
rtnl_unlock();
}
mutex_unlock(&net_mutex);
@@ -163,7 +164,7 @@ 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();
/* Run all of the network namespace exit methods */
@@ -227,7 +228,7 @@ static int __init net_ns_init(void)
err = setup_net(&init_net);
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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