[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/ipx/af_ipx.c b/net/ipx/af_ipx.c
index 34b3bb868409..6c464c11bb09 100644
--- a/net/ipx/af_ipx.c
+++ b/net/ipx/af_ipx.c
@@ -75,7 +75,7 @@ static struct datalink_proto *pEII_datalink;
 static struct datalink_proto *p8023_datalink;
 static struct datalink_proto *pSNAP_datalink;
 
-static struct proto_ops ipx_dgram_ops;
+static const struct proto_ops ipx_dgram_ops;
 
 LIST_HEAD(ipx_interfaces);
 DEFINE_SPINLOCK(ipx_interfaces_lock);
@@ -1901,7 +1901,7 @@ static struct net_proto_family ipx_family_ops = {
         .owner          = THIS_MODULE,
 };
 
-static struct proto_ops SOCKOPS_WRAPPED(ipx_dgram_ops) = {
+static const struct proto_ops SOCKOPS_WRAPPED(ipx_dgram_ops) = {
         .family         = PF_IPX,
         .owner          = THIS_MODULE,
         .release        = ipx_release,