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net: make namespace iteration possible under RCU

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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>
This commit is contained in:
Johannes Berg 2009-07-10 09:51:33 +00:00 committed by David S. Miller
parent 6c04bb18dd
commit 11a28d373e
2 changed files with 14 additions and 3 deletions
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3
include/net/net_namespace.h
View file

@ -208,6 +208,9 @@ static inline struct net *read_pnet(struct net * const *pnet)
#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

14
net/core/net_namespace.c
View file

@ -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_struct *work)
/* 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);