[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/appletalk/ddp.c b/net/appletalk/ddp.c
index 7982656b9c83..296f186802ff 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -63,7 +63,7 @@
 #include <linux/atalk.h>
 
 struct datalink_proto *ddp_dl, *aarp_dl;
-static struct proto_ops atalk_dgram_ops;
+static const struct proto_ops atalk_dgram_ops;
 
 /**************************************************************************\
 *                                                                          *
@@ -1841,7 +1841,7 @@ static struct net_proto_family atalk_family_ops = {
         .owner          = THIS_MODULE,
 };
 
-static struct proto_ops SOCKOPS_WRAPPED(atalk_dgram_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(atalk_dgram_ops) = {
         .family         = PF_APPLETALK,
         .owner          = THIS_MODULE,
         .release        = atalk_release,