net: inet_add_protocol() can use cmpxchg()
Use cmpxchg() to get rid of spinlocks in inet_add_protocol() and
friends.
inet_protos[] & inet6_protos[] are moved to read_mostly section
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/protocol.c b/net/ipv6/protocol.c
index 1fa3468..9bb936a 100644
--- a/net/ipv6/protocol.c
+++ b/net/ipv6/protocol.c
@@ -25,28 +25,14 @@
#include <linux/spinlock.h>
#include <net/protocol.h>
-const struct inet6_protocol *inet6_protos[MAX_INET_PROTOS];
-static DEFINE_SPINLOCK(inet6_proto_lock);
-
+const struct inet6_protocol *inet6_protos[MAX_INET_PROTOS] __read_mostly;
int inet6_add_protocol(const struct inet6_protocol *prot, unsigned char protocol)
{
- int ret, hash = protocol & (MAX_INET_PROTOS - 1);
+ int hash = protocol & (MAX_INET_PROTOS - 1);
- spin_lock_bh(&inet6_proto_lock);
-
- if (inet6_protos[hash]) {
- ret = -1;
- } else {
- inet6_protos[hash] = prot;
- ret = 0;
- }
-
- spin_unlock_bh(&inet6_proto_lock);
-
- return ret;
+ return !cmpxchg(&inet6_protos[hash], NULL, prot) ? 0 : -1;
}
-
EXPORT_SYMBOL(inet6_add_protocol);
/*
@@ -57,20 +43,10 @@
{
int ret, hash = protocol & (MAX_INET_PROTOS - 1);
- spin_lock_bh(&inet6_proto_lock);
-
- if (inet6_protos[hash] != prot) {
- ret = -1;
- } else {
- inet6_protos[hash] = NULL;
- ret = 0;
- }
-
- spin_unlock_bh(&inet6_proto_lock);
+ ret = (cmpxchg(&inet6_protos[hash], prot, NULL) == prot) ? 0 : -1;
synchronize_net();
return ret;
}
-
EXPORT_SYMBOL(inet6_del_protocol);