[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/wanrouter/af_wanpipe.c b/net/wanrouter/af_wanpipe.c
index 59fec59b2132..67948bf22dc4 100644
--- a/net/wanrouter/af_wanpipe.c
+++ b/net/wanrouter/af_wanpipe.c
@@ -181,7 +181,7 @@ struct wanpipe_opt
 #endif
 
 static int sk_count;
-extern struct proto_ops wanpipe_ops;
+extern const struct proto_ops wanpipe_ops;
 static unsigned long find_free_critical;
 
 static void wanpipe_unlink_driver(struct sock *sk);
@@ -2546,7 +2546,7 @@ static int wanpipe_connect(struct socket *sock, struct sockaddr *uaddr, int addr
         return 0;
 }
 
-struct proto_ops wanpipe_ops = {
+const struct proto_ops wanpipe_ops = {
         .family =       PF_WANPIPE,
         .owner =        THIS_MODULE,
         .release =      wanpipe_release,