net: build_ehash_secret() and rt_bind_peer() cleanups

Now cmpxchg() is available on all arches, we can use it in
build_ehash_secret() and rt_bind_peer() instead of using spinlocks.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
CC: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/af_inet.c

@@ -227,18 +227,16 @@ EXPORT_SYMBOL(inet_ehash_secret);
 
 /*
  * inet_ehash_secret must be set exactly once
- * Instead of using a dedicated spinlock, we (ab)use inetsw_lock
  */
 void build_ehash_secret(void)
 {
 	u32 rnd;
+
 	do {
 		get_random_bytes(&rnd, sizeof(rnd));
 	} while (rnd == 0);
-	spin_lock_bh(&inetsw_lock);
-	if (!inet_ehash_secret)
-		inet_ehash_secret = rnd;
-	spin_unlock_bh(&inetsw_lock);
+
+	cmpxchg(&inet_ehash_secret, 0, rnd);
 }
 EXPORT_SYMBOL(build_ehash_secret);
 

net/ipv4/route.c

@@ -1268,18 +1268,11 @@ static int rt_intern_hash(unsigned hash, struct rtable *rt,
 
 void rt_bind_peer(struct rtable *rt, int create)
 {
-	static DEFINE_SPINLOCK(rt_peer_lock);
 	struct inet_peer *peer;
 
 	peer = inet_getpeer(rt->rt_dst, create);
 
-	spin_lock_bh(&rt_peer_lock);
-	if (rt->peer == NULL) {
-		rt->peer = peer;
-		peer = NULL;
-	}
-	spin_unlock_bh(&rt_peer_lock);
-	if (peer)
+	if (peer && cmpxchg(&rt->peer, NULL, peer) != NULL)
 		inet_putpeer(peer);
 }