IPV4: use rcu to walk list of devices in IGMP

This also needs to be optimized for large number of devices.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/igmp.c

@@ -2311,7 +2311,7 @@ static inline struct ip_mc_list *igmp_mc_get_first(struct seq_file *seq)
 	struct igmp_mc_iter_state *state = igmp_mc_seq_private(seq);
 
 	state->in_dev = NULL;
-	for_each_netdev(net, state->dev) {
+	for_each_netdev_rcu(net, state->dev) {
 		struct in_device *in_dev;
 		in_dev = in_dev_get(state->dev);
 		if (!in_dev)
@@ -2361,9 +2361,9 @@ static struct ip_mc_list *igmp_mc_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *igmp_mc_seq_start(struct seq_file *seq, loff_t *pos)
-	__acquires(dev_base_lock)
+	__acquires(rcu)
 {
-	read_lock(&dev_base_lock);
+	rcu_read_lock();
 	return *pos ? igmp_mc_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
 }
 
@@ -2379,7 +2379,7 @@ static void *igmp_mc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void igmp_mc_seq_stop(struct seq_file *seq, void *v)
-	__releases(dev_base_lock)
+	__releases(rcu)
 {
 	struct igmp_mc_iter_state *state = igmp_mc_seq_private(seq);
 	if (likely(state->in_dev != NULL)) {
@@ -2388,7 +2388,7 @@ static void igmp_mc_seq_stop(struct seq_file *seq, void *v)
 		state->in_dev = NULL;
 	}
 	state->dev = NULL;
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 }
 
 static int igmp_mc_seq_show(struct seq_file *seq, void *v)
@@ -2462,7 +2462,7 @@ static inline struct ip_sf_list *igmp_mcf_get_first(struct seq_file *seq)
 
 	state->idev = NULL;
 	state->im = NULL;
-	for_each_netdev(net, state->dev) {
+	for_each_netdev_rcu(net, state->dev) {
 		struct in_device *idev;
 		idev = in_dev_get(state->dev);
 		if (unlikely(idev == NULL))
@@ -2528,8 +2528,9 @@ static struct ip_sf_list *igmp_mcf_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *igmp_mcf_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(rcu)
 {
-	read_lock(&dev_base_lock);
+	rcu_read_lock();
 	return *pos ? igmp_mcf_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
 }
 
@@ -2545,6 +2546,7 @@ static void *igmp_mcf_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void igmp_mcf_seq_stop(struct seq_file *seq, void *v)
+	__releases(rcu)
 {
 	struct igmp_mcf_iter_state *state = igmp_mcf_seq_private(seq);
 	if (likely(state->im != NULL)) {
@@ -2557,7 +2559,7 @@ static void igmp_mcf_seq_stop(struct seq_file *seq, void *v)
 		state->idev = NULL;
 	}
 	state->dev = NULL;
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 }
 
 static int igmp_mcf_seq_show(struct seq_file *seq, void *v)