[PATCH] RCU: use rcu_assign_pointer()

This patch uses the rcu_assign_pointer() API to eliminate a number of explicit
memory barriers from code using RCU.  This has been tested successfully on
i386 and ppc64.

Signed-off-by: <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 11 insertions, 18 deletions

diff --git a/net/core/netfilter.c b/net/core/netfilter.c
index 91b3bb238edc..9db8b4467f9d 100644
--- a/net/core/netfilter.c
+++ b/net/core/netfilter.c
@@ -751,10 +751,9 @@ int nf_log_register(int pf, nf_logfn *logfn)
 
 	/* Any setup of logging members must be done before
 	 * substituting pointer. */
-	smp_wmb();
 	spin_lock(&nf_log_lock);
 	if (!nf_logging[pf]) {
-		nf_logging[pf] = logfn;
+		rcu_assign_pointer(nf_logging[pf], logfn);
 		ret = 0;
 	}
 	spin_unlock(&nf_log_lock);
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index 34f0b81e1784..32e3cd4bc3b9 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -287,10 +287,9 @@ static int dn_insert_route(struct dn_route *rt, unsigned hash, struct dn_route *
 		if (compare_keys(&rth->fl, &rt->fl)) {
 			/* Put it first */
 			*rthp = rth->u.rt_next;
-			smp_wmb();
-			rth->u.rt_next = dn_rt_hash_table[hash].chain;
-			smp_wmb();
-			dn_rt_hash_table[hash].chain = rth;
+			rcu_assign_pointer(rth->u.rt_next,
+					   dn_rt_hash_table[hash].chain);
+			rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth);
 
 			rth->u.dst.__use++;
 			dst_hold(&rth->u.dst);
@@ -304,10 +303,8 @@ static int dn_insert_route(struct dn_route *rt, unsigned hash, struct dn_route *
 		rthp = &rth->u.rt_next;
 	}
 
-	smp_wmb();
-	rt->u.rt_next = dn_rt_hash_table[hash].chain;
-	smp_wmb();
-	dn_rt_hash_table[hash].chain = rt;
+	rcu_assign_pointer(rt->u.rt_next, dn_rt_hash_table[hash].chain);
+	rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt);
 	
 	dst_hold(&rt->u.dst);
 	rt->u.dst.__use++;
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index bda63766b6ab..cb697aba93a2 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -158,8 +158,7 @@ struct in_device *inetdev_init(struct net_device *dev)
 
 	/* Account for reference dev->ip_ptr */
 	in_dev_hold(in_dev);
-	smp_wmb();
-	dev->ip_ptr = in_dev;
+	rcu_assign_pointer(dev->ip_ptr, in_dev);
 
 #ifdef CONFIG_SYSCTL
 	devinet_sysctl_register(in_dev, &in_dev->cnf);
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 27ce169f63b9..2d8003194fdd 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -801,14 +801,13 @@ restart:
 			 * must be visible to another weakly ordered CPU before
 			 * the insertion at the start of the hash chain.
 			 */
-			smp_wmb();
-			rth->u.rt_next = rt_hash_table[hash].chain;
+			rcu_assign_pointer(rth->u.rt_next,
+					   rt_hash_table[hash].chain);
 			/*
 			 * Since lookup is lockfree, the update writes
 			 * must be ordered for consistency on SMP.
 			 */
-			smp_wmb();
-			rt_hash_table[hash].chain = rth;
+			rcu_assign_pointer(rt_hash_table[hash].chain, rth);
 
 			rth->u.dst.__use++;
 			dst_hold(&rth->u.dst);
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 127fb296bf92..fee8da1a1c77 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -453,10 +453,9 @@ qdisc_create(struct net_device *dev, u32 handle, struct rtattr **tca, int *errp)
 
 	/* enqueue is accessed locklessly - make sure it's visible
 	 * before we set a netdevice's qdisc pointer to sch */
-	smp_wmb();
 	if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS-1])) == 0) {
 		qdisc_lock_tree(dev);
-		list_add_tail(&sch->list, &dev->qdisc_list);
+		list_add_tail_rcu(&sch->list, &dev->qdisc_list);
 		qdisc_unlock_tree(dev);
 
 #ifdef CONFIG_NET_ESTIMATOR