[NET]: move struct proto_ops to const

I noticed that some of 'struct proto_ops' used in the kernel may share
a cache line used by locks or other heavily modified data. (default
linker alignement is 32 bytes, and L1_CACHE_LINE is 64 or 128 at
least)

This patch makes sure a 'struct proto_ops' can be declared as const,
so that all cpus can share all parts of it without false sharing.

This is not mandatory : a driver can still use a read/write structure
if it needs to (and eventually a __read_mostly)

I made a global stubstitute to change all existing occurences to make
them const.

This should reduce the possibility of false sharing on SMP, and
speedup some socket system calls.

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/decnet/af_decnet.c b/net/decnet/af_decnet.c
index d402e9020c68..65e3baed0251 100644
--- a/net/decnet/af_decnet.c
+++ b/net/decnet/af_decnet.c
@@ -149,7 +149,7 @@ static void dn_keepalive(struct sock *sk);
 #define DN_SK_HASH_MASK (DN_SK_HASH_SIZE - 1)
 
 
-static struct proto_ops dn_proto_ops;
+static const struct proto_ops dn_proto_ops;
 static DEFINE_RWLOCK(dn_hash_lock);
 static struct hlist_head dn_sk_hash[DN_SK_HASH_SIZE];
 static struct hlist_head dn_wild_sk;
@@ -2342,7 +2342,7 @@ static struct net_proto_family	dn_family_ops = {
         .owner  =       THIS_MODULE,
 };
 
-static struct proto_ops dn_proto_ops = {
+static const struct proto_ops dn_proto_ops = {
         .family =       AF_DECnet,
         .owner =        THIS_MODULE,
         .release =      dn_release,