From c25eb3bfb97294d0543a81230fbc237046b4b84c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 23 Nov 2008 17:22:55 -0800 Subject: net: Convert TCP/DCCP listening hash tables to use RCU This is the last step to be able to perform full RCU lookups in __inet_lookup() : After established/timewait tables, we add RCU lookups to listening hash table. The only trick here is that a socket of a given type (TCP ipv4, TCP ipv6, ...) can now flight between two different tables (established and listening) during a RCU grace period, so we must use different 'nulls' end-of-chain values for two tables. We define a large value : #define LISTENING_NULLS_BASE (1U << 29) So that slots in listening table are guaranteed to have different end-of-chain values than slots in established table. A reader can still detect it finished its lookup in the right chain. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/inet_hashtables.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'include/net/inet_hashtables.h') diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h index ec7ee2e46d8c..f44bb5c77a70 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -99,9 +99,16 @@ struct inet_bind_hashbucket { struct hlist_head chain; }; +/* + * Sockets can be hashed in established or listening table + * We must use different 'nulls' end-of-chain value for listening + * hash table, or we might find a socket that was closed and + * reallocated/inserted into established hash table + */ +#define LISTENING_NULLS_BASE (1U << 29) struct inet_listen_hashbucket { spinlock_t lock; - struct hlist_head head; + struct hlist_nulls_head head; }; /* This is for listening sockets, thus all sockets which possess wildcards. */ -- cgit