[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/llc/af_llc.c b/net/llc/af_llc.c
index b6d3df5c911c..9cf65f9d8902 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -36,7 +36,7 @@
 static u16 llc_ui_sap_last_autoport = LLC_SAP_DYN_START;
 static u16 llc_ui_sap_link_no_max[256];
 static struct sockaddr_llc llc_ui_addrnull;
-static struct proto_ops llc_ui_ops;
+static const struct proto_ops llc_ui_ops;
 
 static int llc_ui_wait_for_conn(struct sock *sk, long timeout);
 static int llc_ui_wait_for_disc(struct sock *sk, long timeout);
@@ -1098,7 +1098,7 @@ static struct net_proto_family llc_ui_family_ops = {
         .owner  = THIS_MODULE,
 };
 
-static struct proto_ops llc_ui_ops = {
+static const struct proto_ops llc_ui_ops = {
         .family      = PF_LLC,
         .owner       = THIS_MODULE,
         .release     = llc_ui_release,