[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, 4 insertions, 4 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 3e2462760413..deda6fdb1e53 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -251,10 +251,10 @@ static void packet_sock_destruct(struct sock *sk)
 }
 
 
-static struct proto_ops packet_ops;
+static const struct proto_ops packet_ops;
 
 #ifdef CONFIG_SOCK_PACKET
-static struct proto_ops packet_ops_spkt;
+static const struct proto_ops packet_ops_spkt;
 
 static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,  struct packet_type *pt, struct net_device *orig_dev)
 {
@@ -1784,7 +1784,7 @@ out:
 
 
 #ifdef CONFIG_SOCK_PACKET
-static struct proto_ops packet_ops_spkt = {
+static const struct proto_ops packet_ops_spkt = {
         .family =       PF_PACKET,
         .owner =        THIS_MODULE,
         .release =      packet_release,
@@ -1806,7 +1806,7 @@ static struct proto_ops packet_ops_spkt = {
 };
 #endif
 
-static struct proto_ops packet_ops = {
+static const struct proto_ops packet_ops = {
         .family =       PF_PACKET,
         .owner =        THIS_MODULE,
         .release =      packet_release,