[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/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 1b683f302657..8b5d10aaba05 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -54,7 +54,7 @@
 HLIST_HEAD(ax25_list);
 DEFINE_SPINLOCK(ax25_list_lock);
 
-static struct proto_ops ax25_proto_ops;
+static const struct proto_ops ax25_proto_ops;
 
 static void ax25_free_sock(struct sock *sk)
 {
@@ -1944,7 +1944,7 @@ static struct net_proto_family ax25_family_ops = {
         .owner  =       THIS_MODULE,
 };
 
-static struct proto_ops ax25_proto_ops = {
+static const struct proto_ops ax25_proto_ops = {
         .family         = PF_AX25,
         .owner          = THIS_MODULE,
         .release        = ax25_release,