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Commit 6056415d authored by Kirill Tkhai's avatar Kirill Tkhai Committed by David S. Miller
Browse files

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: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8b4e6b3c

include/net/net_namespace.h

+14 −0
Original line number Diff line number Diff line
@@ -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);