[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/x25/af_x25.c b/net/x25/af_x25.c
index 020d73cc8414..ca8b3b0b920d 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -64,7 +64,7 @@ int sysctl_x25_ack_holdback_timeout    = X25_DEFAULT_T2;
 HLIST_HEAD(x25_list);
 DEFINE_RWLOCK(x25_list_lock);
 
-static struct proto_ops x25_proto_ops;
+static const struct proto_ops x25_proto_ops;
 
 static struct x25_address null_x25_address = {"               "};
 
@@ -1391,7 +1391,7 @@ static struct net_proto_family x25_family_ops = {
 	.owner	=	THIS_MODULE,
 };
 
-static struct proto_ops SOCKOPS_WRAPPED(x25_proto_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(x25_proto_ops) = {
 	.family =	AF_X25,
 	.owner =	THIS_MODULE,
 	.release =	x25_release,