[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/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 95f33cc7a24e..7f0781e4326f 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -57,7 +57,7 @@
 
 #define VERSION "2.8"
 
-static struct proto_ops l2cap_sock_ops;
+static const struct proto_ops l2cap_sock_ops;
 
 static struct bt_sock_list l2cap_sk_list = {
         .lock = RW_LOCK_UNLOCKED
@@ -2161,7 +2161,7 @@ static ssize_t l2cap_sysfs_show(struct class *dev, char *buf)
 
 static CLASS_ATTR(l2cap, S_IRUGO, l2cap_sysfs_show, NULL);
 
-static struct proto_ops l2cap_sock_ops = {
+static const struct proto_ops l2cap_sock_ops = {
         .family         = PF_BLUETOOTH,
         .owner          = THIS_MODULE,
         .release        = l2cap_sock_release,