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authorKirill Tkhai <ktkhai@virtuozzo.com>2018-03-13 13:55:55 +0300
committerDavid S. Miller <davem@davemloft.net>2018-03-13 11:31:42 -0400
commit6056415d3a513846f774e7bbee0de0460b1c15df (patch)
tree1cc220ad263658e62a9da40a46c292926ee898f8 /include/net/net_namespace.h
parent8b4e6b3ca2ed63917e18303005fdd34a586e86db (diff)
net: Add comment about pernet_operations methods and synchronization
Make locking scheme be visible for users, and provide a comment what for we are need exit_batch() methods, and when it should be used. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/net_namespace.h')
-rw-r--r--include/net/net_namespace.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index d4417495773a..71abc8d79178 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -312,6 +312,20 @@ struct net *get_net_ns_by_id(struct net *net, int id);
struct pernet_operations {
struct list_head list;
+ /*
+ * Below methods are called without any exclusive locks.
+ * More than one net may be constructed and destructed
+ * in parallel on several cpus. Every pernet_operations
+ * have to keep in mind all other pernet_operations and
+ * to introduce a locking, if they share common resources.
+ *
+ * Exit methods using blocking RCU primitives, such as
+ * synchronize_rcu(), should be implemented via exit_batch.
+ * Then, destruction of a group of net requires single
+ * synchronize_rcu() related to these pernet_operations,
+ * instead of separate synchronize_rcu() for every net.
+ * Please, avoid synchronize_rcu() at all, where it's possible.
+ */
int (*init)(struct net *net);
void (*exit)(struct net *net);
void (*exit_batch)(struct list_head *net_exit_list);