net: Convert TCP & DCCP hash tables to use RCU / hlist_nulls

RCU was added to UDP lookups, using a fast infrastructure :
- sockets kmem_cache use SLAB_DESTROY_BY_RCU and dont pay the
  price of call_rcu() at freeing time.
- hlist_nulls permits to use few memory barriers.

This patch uses same infrastructure for TCP/DCCP established
and timewait sockets.

Thanks to SLAB_DESTROY_BY_RCU, no slowdown for applications
using short lived TCP connections. A followup patch, converting
rwlocks to spinlocks will even speedup this case.

__inet_lookup_established() is pretty fast now we dont have to
dirty a contended cache line (read_lock/read_unlock)

Only established and timewait hashtable are converted to RCU
(bind table and listen table are still using traditional locking)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 46cb3490d48e..1117d4d8c8f1 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1090,8 +1090,8 @@ static int __init dccp_init(void)
         }
 
         for (i = 0; i < dccp_hashinfo.ehash_size; i++) {
-                INIT_HLIST_HEAD(&dccp_hashinfo.ehash[i].chain);
-                INIT_HLIST_HEAD(&dccp_hashinfo.ehash[i].twchain);
+                INIT_HLIST_NULLS_HEAD(&dccp_hashinfo.ehash[i].chain, i);
+                INIT_HLIST_NULLS_HEAD(&dccp_hashinfo.ehash[i].twchain, i);
         }
 
         if (inet_ehash_locks_alloc(&dccp_hashinfo))