[PATCH 1/3] seq_file: add RCU versions of new hlist/list iterators (v3)

[PATCH 1/3] seq_file: add RCU versions of new hlist/list iterators (v3)

[Stephen Hemminger]

[-- Attachment #1: seq_hlist_rcu.patch --]
[-- Type: text/plain, Size: 4142 bytes --]

Many usages of seq_file use RCU protected lists, so non RCU
iterators will not work safely.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

---
Add comment (same as other RCU functions)

 fs/seq_file.c            |   56 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/rculist.h  |    5 ++++
 include/linux/seq_file.h |   12 +++++++---
 3 files changed, 70 insertions(+), 3 deletions(-)

--- a/fs/seq_file.c	2010-02-22 09:17:18.362742798 -0800
+++ b/fs/seq_file.c	2010-02-22 09:20:54.481180584 -0800
@@ -750,3 +750,74 @@ struct hlist_node *seq_hlist_next(void *
 		return node->next;
 }
 EXPORT_SYMBOL(seq_hlist_next);
+
+/**
+ * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
+ * @head: the head of the hlist
+ * @pos:  the start position of the sequence
+ *
+ * Called at seq_file->op->start().
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
+				       loff_t pos)
+{
+	struct hlist_node *node;
+
+	__hlist_for_each_rcu(node, head)
+		if (pos-- == 0)
+			return node;
+	return NULL;
+}
+EXPORT_SYMBOL(seq_hlist_start_rcu);
+
+/**
+ * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
+ * @head: the head of the hlist
+ * @pos:  the start position of the sequence
+ *
+ * Called at seq_file->op->start(). Call this function if you want to
+ * print a header at the top of the output.
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
+					    loff_t pos)
+{
+	if (!pos)
+		return SEQ_START_TOKEN;
+
+	return seq_hlist_start_rcu(head, pos - 1);
+}
+EXPORT_SYMBOL(seq_hlist_start_head_rcu);
+
+/**
+ * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
+ * @v:    the current iterator
+ * @head: the head of the hlist
+ * @pos:  the current posision
+ *
+ * Called at seq_file->op->next().
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+struct hlist_node *seq_hlist_next_rcu(void *v,
+				      struct hlist_head *head,
+				      loff_t *ppos)
+{
+	struct hlist_node *node = v;
+
+	++*ppos;
+	if (v == SEQ_START_TOKEN)
+		return rcu_dereference(head->first);
+	else
+		return rcu_dereference(node->next);
+}
+EXPORT_SYMBOL(seq_hlist_next_rcu);
--- a/include/linux/seq_file.h	2010-02-22 09:17:18.382742869 -0800
+++ b/include/linux/seq_file.h	2010-02-22 09:21:10.841180579 -0800
@@ -140,10 +140,17 @@ extern struct list_head *seq_list_next(v
  */
 
 extern struct hlist_node *seq_hlist_start(struct hlist_head *head,
-		loff_t pos);
+					  loff_t pos);
 extern struct hlist_node *seq_hlist_start_head(struct hlist_head *head,
-		loff_t pos);
+					       loff_t pos);
 extern struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
-		loff_t *ppos);
+					 loff_t *ppos);
 
+extern struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
+					      loff_t pos);
+extern struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
+						   loff_t pos);
+extern struct hlist_node *seq_hlist_next_rcu(void *v,
+						   struct hlist_head *head,
+						   loff_t *ppos);
 #endif
--- a/include/linux/rculist.h	2010-02-22 09:17:18.372742980 -0800
+++ b/include/linux/rculist.h	2010-02-22 09:17:26.771810143 -0800
@@ -406,6 +406,11 @@ static inline void hlist_add_after_rcu(s
 		n->next->pprev = &n->next;
 }
 
+#define __hlist_for_each_rcu(pos, head)			\
+	for (pos = rcu_dereference((head)->first);	\
+	     pos && ({ prefetch(pos->next); 1; });	\
+	     pos = rcu_dereference(pos->next))
+
 /**
  * hlist_for_each_entry_rcu - iterate over rcu list of given type
  * @tpos:	the type * to use as a loop cursor.

-- 

[PATCH 2/3] packet: convert socket list to RCU (v3)

[Stephen Hemminger]

[-- Attachment #1: packet-list-rcu.patch --]
[-- Type: text/plain, Size: 6199 bytes --]

Convert AF_PACKET to use RCU, eliminating one more reader/writer lock.

There is no need for a real sk_del_node_init_rcu(), because sk_del_node_init
is doing the equivalent thing to hlst_del_init_rcu already; but added
some comments to try and make that obvious.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

---

 include/net/netns/packet.h |    4 ++--
 include/net/sock.h         |   10 ++++++++++
 net/packet/af_packet.c     |   42 ++++++++++++++++++++----------------------
 3 files changed, 32 insertions(+), 24 deletions(-)

--- a/include/net/netns/packet.h	2010-02-22 09:07:28.562430023 -0800
+++ b/include/net/netns/packet.h	2010-02-22 09:11:00.042269423 -0800
@@ -4,11 +4,11 @@
 #ifndef __NETNS_PACKET_H__
 #define __NETNS_PACKET_H__
 
-#include <linux/list.h>
+#include <linux/rculist.h>
 #include <linux/spinlock.h>
 
 struct netns_packet {
-	rwlock_t		sklist_lock;
+	spinlock_t		sklist_lock;
 	struct hlist_head	sklist;
 };
 
--- a/net/packet/af_packet.c	2010-02-22 09:07:28.551185873 -0800
+++ b/net/packet/af_packet.c	2010-02-22 09:11:00.063367114 -0800
@@ -1262,24 +1262,22 @@ static int packet_release(struct socket 
 	net = sock_net(sk);
 	po = pkt_sk(sk);
 
-	write_lock_bh(&net->packet.sklist_lock);
-	sk_del_node_init(sk);
+	spin_lock_bh(&net->packet.sklist_lock);
+	sk_del_node_init_rcu(sk);
 	sock_prot_inuse_add(net, sk->sk_prot, -1);
-	write_unlock_bh(&net->packet.sklist_lock);
-
-	/*
-	 *	Unhook packet receive handler.
-	 */
+	spin_unlock_bh(&net->packet.sklist_lock);
 
+	spin_lock(&po->bind_lock);
 	if (po->running) {
 		/*
-		 *	Remove the protocol hook
+		 * Remove from protocol table
 		 */
-		dev_remove_pack(&po->prot_hook);
 		po->running = 0;
 		po->num = 0;
+		__dev_remove_pack(&po->prot_hook);
 		__sock_put(sk);
 	}
+	spin_unlock(&po->bind_lock);
 
 	packet_flush_mclist(sk);
 
@@ -1291,10 +1289,10 @@ static int packet_release(struct socket 
 	if (po->tx_ring.pg_vec)
 		packet_set_ring(sk, &req, 1, 1);
 
+	synchronize_net();
 	/*
 	 *	Now the socket is dead. No more input will appear.
 	 */
-
 	sock_orphan(sk);
 	sock->sk = NULL;
 
@@ -1478,10 +1476,11 @@ static int packet_create(struct net *net
 		po->running = 1;
 	}
 
-	write_lock_bh(&net->packet.sklist_lock);
-	sk_add_node(sk, &net->packet.sklist);
+	spin_lock_bh(&net->packet.sklist_lock);
+	sk_add_node_rcu(sk, &net->packet.sklist);
 	sock_prot_inuse_add(net, &packet_proto, 1);
-	write_unlock_bh(&net->packet.sklist_lock);
+	spin_unlock_bh(&net->packet.sklist_lock);
+
 	return 0;
 out:
 	return err;
@@ -2075,8 +2074,8 @@ static int packet_notifier(struct notifi
 	struct net_device *dev = data;
 	struct net *net = dev_net(dev);
 
-	read_lock(&net->packet.sklist_lock);
-	sk_for_each(sk, node, &net->packet.sklist) {
+	rcu_read_lock();
+	sk_for_each_rcu(sk, node, &net->packet.sklist) {
 		struct packet_sock *po = pkt_sk(sk);
 
 		switch (msg) {
@@ -2104,18 +2103,19 @@ static int packet_notifier(struct notifi
 			}
 			break;
 		case NETDEV_UP:
-			spin_lock(&po->bind_lock);
-			if (dev->ifindex == po->ifindex && po->num &&
-			    !po->running) {
-				dev_add_pack(&po->prot_hook);
-				sock_hold(sk);
-				po->running = 1;
+			if (dev->ifindex == po->ifindex) {
+				spin_lock(&po->bind_lock);
+				if (po->num && !po->running) {
+					dev_add_pack(&po->prot_hook);
+					sock_hold(sk);
+					po->running = 1;
+				}
+				spin_unlock(&po->bind_lock);
 			}
-			spin_unlock(&po->bind_lock);
 			break;
 		}
 	}
-	read_unlock(&net->packet.sklist_lock);
+	rcu_read_unlock();
 	return NOTIFY_DONE;
 }
 
@@ -2512,24 +2512,24 @@ static struct notifier_block packet_netd
 #ifdef CONFIG_PROC_FS
 
 static void *packet_seq_start(struct seq_file *seq, loff_t *pos)
-	__acquires(seq_file_net(seq)->packet.sklist_lock)
+	__acquires(RCU)
 {
 	struct net *net = seq_file_net(seq);
-	read_lock(&net->packet.sklist_lock);
-	return seq_hlist_start_head(&net->packet.sklist, *pos);
+
+	rcu_read_lock();
+	return seq_hlist_start_head_rcu(&net->packet.sklist, *pos);
 }
 
 static void *packet_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
 	struct net *net = seq_file_net(seq);
-	return seq_hlist_next(v, &net->packet.sklist, pos);
+	return seq_hlist_next_rcu(v, &net->packet.sklist, pos);
 }
 
 static void packet_seq_stop(struct seq_file *seq, void *v)
-	__releases(seq_file_net(seq)->packet.sklist_lock)
+	__releases(RCU)
 {
-	struct net *net = seq_file_net(seq);
-	read_unlock(&net->packet.sklist_lock);
+	rcu_read_unlock();
 }
 
 static int packet_seq_show(struct seq_file *seq, void *v)
@@ -2581,7 +2581,7 @@ static const struct file_operations pack
 
 static int __net_init packet_net_init(struct net *net)
 {
-	rwlock_init(&net->packet.sklist_lock);
+	spin_lock_init(&net->packet.sklist_lock);
 	INIT_HLIST_HEAD(&net->packet.sklist);
 
 	if (!proc_net_fops_create(net, "packet", 0, &packet_seq_fops))
--- a/include/net/sock.h	2010-02-22 09:07:28.572429848 -0800
+++ b/include/net/sock.h	2010-02-22 09:11:00.063367114 -0800
@@ -381,6 +381,7 @@ static __inline__ void __sk_del_node(str
 	__hlist_del(&sk->sk_node);
 }
 
+/* NB: equivalent to hlist_del_init_rcu */
 static __inline__ int __sk_del_node_init(struct sock *sk)
 {
 	if (sk_hashed(sk)) {
@@ -421,6 +422,7 @@ static __inline__ int sk_del_node_init(s
 	}
 	return rc;
 }
+#define sk_del_node_init_rcu(sk)	sk_del_node_init(sk)
 
 static __inline__ int __sk_nulls_del_node_init_rcu(struct sock *sk)
 {
@@ -454,6 +456,12 @@ static __inline__ void sk_add_node(struc
 	__sk_add_node(sk, list);
 }
 
+static __inline__ void sk_add_node_rcu(struct sock *sk, struct hlist_head *list)
+{
+	sock_hold(sk);
+	hlist_add_head_rcu(&sk->sk_node, list);
+}
+
 static __inline__ void __sk_nulls_add_node_rcu(struct sock *sk, struct hlist_nulls_head *list)
 {
 	hlist_nulls_add_head_rcu(&sk->sk_nulls_node, list);
@@ -478,6 +486,8 @@ static __inline__ void sk_add_bind_node(
 
 #define sk_for_each(__sk, node, list) \
 	hlist_for_each_entry(__sk, node, list, sk_node)
+#define sk_for_each_rcu(__sk, node, list) \
+	hlist_for_each_entry_rcu(__sk, node, list, sk_node)
 #define sk_nulls_for_each(__sk, node, list) \
 	hlist_nulls_for_each_entry(__sk, node, list, sk_nulls_node)
 #define sk_nulls_for_each_rcu(__sk, node, list) \

-- 

[PATCH 3/3] af_key: locking change

[Stephen Hemminger]

[-- Attachment #1: pfkey-rcu.patch --]
[-- Type: text/plain, Size: 4076 bytes --]

Get rid of custom locking that was using wait queue, lock, and atomic
to basically build a queued mutex.  Use RCU for read side.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

--- a/net/key/af_key.c	2010-02-22 09:19:03.242742827 -0800
+++ b/net/key/af_key.c	2010-02-22 09:22:53.921492802 -0800
@@ -41,9 +41,7 @@ struct netns_pfkey {
 	struct hlist_head table;
 	atomic_t socks_nr;
 };
-static DECLARE_WAIT_QUEUE_HEAD(pfkey_table_wait);
-static DEFINE_RWLOCK(pfkey_table_lock);
-static atomic_t pfkey_table_users = ATOMIC_INIT(0);
+static DEFINE_MUTEX(pfkey_mutex);
 
 struct pfkey_sock {
 	/* struct sock must be the first member of struct pfkey_sock */
@@ -108,50 +106,6 @@ static void pfkey_sock_destruct(struct s
 	atomic_dec(&net_pfkey->socks_nr);
 }
 
-static void pfkey_table_grab(void)
-{
-	write_lock_bh(&pfkey_table_lock);
-
-	if (atomic_read(&pfkey_table_users)) {
-		DECLARE_WAITQUEUE(wait, current);
-
-		add_wait_queue_exclusive(&pfkey_table_wait, &wait);
-		for(;;) {
-			set_current_state(TASK_UNINTERRUPTIBLE);
-			if (atomic_read(&pfkey_table_users) == 0)
-				break;
-			write_unlock_bh(&pfkey_table_lock);
-			schedule();
-			write_lock_bh(&pfkey_table_lock);
-		}
-
-		__set_current_state(TASK_RUNNING);
-		remove_wait_queue(&pfkey_table_wait, &wait);
-	}
-}
-
-static __inline__ void pfkey_table_ungrab(void)
-{
-	write_unlock_bh(&pfkey_table_lock);
-	wake_up(&pfkey_table_wait);
-}
-
-static __inline__ void pfkey_lock_table(void)
-{
-	/* read_lock() synchronizes us to pfkey_table_grab */
-
-	read_lock(&pfkey_table_lock);
-	atomic_inc(&pfkey_table_users);
-	read_unlock(&pfkey_table_lock);
-}
-
-static __inline__ void pfkey_unlock_table(void)
-{
-	if (atomic_dec_and_test(&pfkey_table_users))
-		wake_up(&pfkey_table_wait);
-}
-
-
 static const struct proto_ops pfkey_ops;
 
 static void pfkey_insert(struct sock *sk)
@@ -159,16 +113,16 @@ static void pfkey_insert(struct sock *sk
 	struct net *net = sock_net(sk);
 	struct netns_pfkey *net_pfkey = net_generic(net, pfkey_net_id);
 
-	pfkey_table_grab();
-	sk_add_node(sk, &net_pfkey->table);
-	pfkey_table_ungrab();
+	mutex_lock(&pfkey_mutex);
+	sk_add_node_rcu(sk, &net_pfkey->table);
+	mutex_unlock(&pfkey_mutex);
 }
 
 static void pfkey_remove(struct sock *sk)
 {
-	pfkey_table_grab();
-	sk_del_node_init(sk);
-	pfkey_table_ungrab();
+	mutex_lock(&pfkey_mutex);
+	sk_del_node_init_rcu(sk);
+	mutex_unlock(&pfkey_mutex);
 }
 
 static struct proto key_proto = {
@@ -223,6 +177,8 @@ static int pfkey_release(struct socket *
 	sock_orphan(sk);
 	sock->sk = NULL;
 	skb_queue_purge(&sk->sk_write_queue);
+
+	synchronize_rcu();
 	sock_put(sk);
 
 	return 0;
@@ -277,8 +233,8 @@ static int pfkey_broadcast(struct sk_buf
 	if (!skb)
 		return -ENOMEM;
 
-	pfkey_lock_table();
-	sk_for_each(sk, node, &net_pfkey->table) {
+	rcu_read_lock();
+	sk_for_each_rcu(sk, node, &net_pfkey->table) {
 		struct pfkey_sock *pfk = pfkey_sk(sk);
 		int err2;
 
@@ -309,7 +265,7 @@ static int pfkey_broadcast(struct sk_buf
 		if ((broadcast_flags & BROADCAST_REGISTERED) && err)
 			err = err2;
 	}
-	pfkey_unlock_table();
+	rcu_read_unlock();
 
 	if (one_sk != NULL)
 		err = pfkey_broadcast_one(skb, &skb2, allocation, one_sk);
@@ -3702,8 +3658,8 @@ static void *pfkey_seq_start(struct seq_
 	struct net *net = seq_file_net(f);
 	struct netns_pfkey *net_pfkey = net_generic(net, pfkey_net_id);
 
-	read_lock(&pfkey_table_lock);
-	return seq_hlist_start_head(&net_pfkey->table, *ppos);
+	rcu_read_lock();
+	return seq_hlist_start_head_rcu(&net_pfkey->table, *ppos);
 }
 
 static void *pfkey_seq_next(struct seq_file *f, void *v, loff_t *ppos)
@@ -3711,12 +3667,12 @@ static void *pfkey_seq_next(struct seq_f
 	struct net *net = seq_file_net(f);
 	struct netns_pfkey *net_pfkey = net_generic(net, pfkey_net_id);
 
-	return seq_hlist_next(v, &net_pfkey->table, ppos);
+	return seq_hlist_next_rcu(v, &net_pfkey->table, ppos);
 }
 
 static void pfkey_seq_stop(struct seq_file *f, void *v)
 {
-	read_unlock(&pfkey_table_lock);
+	rcu_read_unlock();
 }
 
 static const struct seq_operations pfkey_seq_ops = {

-- 

Re: [PATCH 1/3] seq_file: add RCU versions of new hlist/list iterators (v3)

[David Miller]

From: Stephen Hemminger <shemminger@vyatta.com>
Date: Mon, 22 Feb 2010 09:57:17 -0800

> Many usages of seq_file use RCU protected lists, so non RCU
> iterators will not work safely.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Applied.

Re: [PATCH 2/3] packet: convert socket list to RCU (v3)

[David Miller]

From: Stephen Hemminger <shemminger@vyatta.com>
Date: Mon, 22 Feb 2010 09:57:18 -0800

> Convert AF_PACKET to use RCU, eliminating one more reader/writer lock.
> 
> There is no need for a real sk_del_node_init_rcu(), because sk_del_node_init
> is doing the equivalent thing to hlst_del_init_rcu already; but added
> some comments to try and make that obvious.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Applied.

Re: [PATCH 3/3] af_key: locking change

[David Miller]

From: Stephen Hemminger <shemminger@vyatta.com>
Date: Mon, 22 Feb 2010 09:57:19 -0800

> Get rid of custom locking that was using wait queue, lock, and atomic
> to basically build a queued mutex.  Use RCU for read side.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

Applied.