[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, 8 insertions, 8 deletions

diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index f121f7de2032..e57683d424f7 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -62,12 +62,12 @@
 
 static int irda_create(struct socket *sock, int protocol);
 
-static struct proto_ops irda_stream_ops;
-static struct proto_ops irda_seqpacket_ops;
-static struct proto_ops irda_dgram_ops;
+static const struct proto_ops irda_stream_ops;
+static const struct proto_ops irda_seqpacket_ops;
+static const struct proto_ops irda_dgram_ops;
 
 #ifdef CONFIG_IRDA_ULTRA
-static struct proto_ops irda_ultra_ops;
+static const struct proto_ops irda_ultra_ops;
 #define ULTRA_MAX_DATA 382
 #endif /* CONFIG_IRDA_ULTRA */
 
@@ -2464,7 +2464,7 @@ static struct net_proto_family irda_family_ops = {
         .owner  = THIS_MODULE,
 };
 
-static struct proto_ops SOCKOPS_WRAPPED(irda_stream_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(irda_stream_ops) = {
         .family =       PF_IRDA,
         .owner =        THIS_MODULE,
         .release =      irda_release,
@@ -2485,7 +2485,7 @@ static struct proto_ops SOCKOPS_WRAPPED(irda_stream_ops) = {
         .sendpage =     sock_no_sendpage,
 };
 
-static struct proto_ops SOCKOPS_WRAPPED(irda_seqpacket_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(irda_seqpacket_ops) = {
         .family =       PF_IRDA,
         .owner =        THIS_MODULE,
         .release =      irda_release,
@@ -2506,7 +2506,7 @@ static struct proto_ops SOCKOPS_WRAPPED(irda_seqpacket_ops) = {
         .sendpage =     sock_no_sendpage,
 };
 
-static struct proto_ops SOCKOPS_WRAPPED(irda_dgram_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(irda_dgram_ops) = {
         .family =       PF_IRDA,
         .owner =        THIS_MODULE,
         .release =      irda_release,
@@ -2528,7 +2528,7 @@ static struct proto_ops SOCKOPS_WRAPPED(irda_dgram_ops) = {
 };
 
 #ifdef CONFIG_IRDA_ULTRA
-static struct proto_ops SOCKOPS_WRAPPED(irda_ultra_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(irda_ultra_ops) = {
         .family =       PF_IRDA,
         .owner =        THIS_MODULE,
         .release =      irda_release,