[PATCH net-next 1/2] Phonet: put protocols array under RCU

[PATCH net-next 1/2] Phonet: put protocols array under RCU

[Rémi Denis-Courmont]

From: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>

Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
---
 net/phonet/af_phonet.c |   20 +++++++++++---------
 1 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
index 8d3a55b..ed65da2 100644
--- a/net/phonet/af_phonet.c
+++ b/net/phonet/af_phonet.c
@@ -35,7 +35,6 @@
 
 /* Transport protocol registration */
 static struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;
-static DEFINE_SPINLOCK(proto_tab_lock);
 
 static struct phonet_protocol *phonet_proto_get(int protocol)
 {
@@ -44,11 +43,11 @@ static struct phonet_protocol *phonet_proto_get(int protocol)
 	if (protocol >= PHONET_NPROTO)
 		return NULL;
 
-	spin_lock(&proto_tab_lock);
+	rcu_read_lock();
 	pp = proto_tab[protocol];
 	if (pp && !try_module_get(pp->prot->owner))
 		pp = NULL;
-	spin_unlock(&proto_tab_lock);
+	rcu_read_unlock();
 
 	return pp;
 }
@@ -439,6 +438,8 @@ static struct packet_type phonet_packet_type __read_mostly = {
 	.func = phonet_rcv,
 };
 
+static DEFINE_MUTEX(proto_tab_lock);
+
 int __init_or_module phonet_proto_register(int protocol,
 						struct phonet_protocol *pp)
 {
@@ -451,12 +452,12 @@ int __init_or_module phonet_proto_register(int protocol,
 	if (err)
 		return err;
 
-	spin_lock(&proto_tab_lock);
+	mutex_lock(&proto_tab_lock);
 	if (proto_tab[protocol])
 		err = -EBUSY;
 	else
-		proto_tab[protocol] = pp;
-	spin_unlock(&proto_tab_lock);
+		rcu_assign_pointer(proto_tab[protocol], pp);
+	mutex_unlock(&proto_tab_lock);
 
 	return err;
 }
@@ -464,10 +465,11 @@ EXPORT_SYMBOL(phonet_proto_register);
 
 void phonet_proto_unregister(int protocol, struct phonet_protocol *pp)
 {
-	spin_lock(&proto_tab_lock);
+	mutex_lock(&proto_tab_lock);
 	BUG_ON(proto_tab[protocol] != pp);
-	proto_tab[protocol] = NULL;
-	spin_unlock(&proto_tab_lock);
+	rcu_assign_pointer(proto_tab[protocol], NULL);
+	mutex_unlock(&proto_tab_lock);
+	synchronize_rcu();
 	proto_unregister(pp->prot);
 }
 EXPORT_SYMBOL(phonet_proto_unregister);
-- 
1.6.3.3

[PATCH net-next 2/2] Phonet: convert routing table to RCU

[Rémi Denis-Courmont]

From: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>

Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
---
 net/phonet/pn_dev.c |   59 +++++++++++++++++++++++++++++---------------------
 1 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 6d64fda..3287f8f 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -34,7 +34,7 @@
 #include <net/phonet/pn_dev.h>
 
 struct phonet_routes {
-	spinlock_t		lock;
+	struct mutex		lock;
 	struct net_device	*table[64];
 };
 
@@ -248,17 +248,22 @@ static void phonet_route_autodel(struct net_device *dev)
 
 	/* Remove left-over Phonet routes */
 	bitmap_zero(deleted, 64);
-	spin_lock_bh(&pnn->routes.lock);
+	mutex_lock(&pnn->routes.lock);
 	for (i = 0; i < 64; i++)
 		if (dev == pnn->routes.table[i]) {
+			rcu_assign_pointer(pnn->routes.table[i], NULL);
 			set_bit(i, deleted);
-			pnn->routes.table[i] = NULL;
-			dev_put(dev);
 		}
-	spin_unlock_bh(&pnn->routes.lock);
+	mutex_unlock(&pnn->routes.lock);
+
+	if (bitmap_empty(deleted, 64))
+		return; /* short-circuit RCU */
+	synchronize_rcu();
 	for (i = find_first_bit(deleted, 64); i < 64;
-			i = find_next_bit(deleted, 64, i + 1))
+			i = find_next_bit(deleted, 64, i + 1)) {
 		rtm_phonet_notify(RTM_DELROUTE, dev, i);
+		dev_put(dev);
+	}
 }
 
 /* notify Phonet of device events */
@@ -300,7 +305,7 @@ static int phonet_init_net(struct net *net)
 
 	INIT_LIST_HEAD(&pnn->pndevs.list);
 	spin_lock_init(&pnn->pndevs.lock);
-	spin_lock_init(&pnn->routes.lock);
+	mutex_init(&pnn->routes.lock);
 	net_assign_generic(net, phonet_net_id, pnn);
 	return 0;
 }
@@ -361,13 +366,13 @@ int phonet_route_add(struct net_device *dev, u8 daddr)
 	int err = -EEXIST;
 
 	daddr = daddr >> 2;
-	spin_lock_bh(&routes->lock);
+	mutex_lock(&routes->lock);
 	if (routes->table[daddr] == NULL) {
-		routes->table[daddr] = dev;
+		rcu_assign_pointer(routes->table[daddr], dev);
 		dev_hold(dev);
 		err = 0;
 	}
-	spin_unlock_bh(&routes->lock);
+	mutex_unlock(&routes->lock);
 	return err;
 }
 
@@ -375,17 +380,20 @@ int phonet_route_del(struct net_device *dev, u8 daddr)
 {
 	struct phonet_net *pnn = net_generic(dev_net(dev), phonet_net_id);
 	struct phonet_routes *routes = &pnn->routes;
-	int err = -ENOENT;
 
 	daddr = daddr >> 2;
-	spin_lock_bh(&routes->lock);
-	if (dev == routes->table[daddr]) {
-		routes->table[daddr] = NULL;
-		dev_put(dev);
-		err = 0;
-	}
-	spin_unlock_bh(&routes->lock);
-	return err;
+	mutex_lock(&routes->lock);
+	if (dev == routes->table[daddr])
+		rcu_assign_pointer(routes->table[daddr], NULL);
+	else
+		dev = NULL;
+	mutex_unlock(&routes->lock);
+
+	if (!dev)
+		return -ENOENT;
+	synchronize_rcu();
+	dev_put(dev);
+	return 0;
 }
 
 struct net_device *phonet_route_get(struct net *net, u8 daddr)
@@ -397,9 +405,9 @@ struct net_device *phonet_route_get(struct net *net, u8 daddr)
 	ASSERT_RTNL(); /* no need to hold the device */
 
 	daddr >>= 2;
-	spin_lock_bh(&routes->lock);
-	dev = routes->table[daddr];
-	spin_unlock_bh(&routes->lock);
+	rcu_read_lock();
+	dev = rcu_dereference(routes->table[daddr]);
+	rcu_read_unlock();
 	return dev;
 }
 
@@ -409,11 +417,12 @@ struct net_device *phonet_route_output(struct net *net, u8 daddr)
 	struct phonet_routes *routes = &pnn->routes;
 	struct net_device *dev;
 
-	spin_lock_bh(&routes->lock);
-	dev = routes->table[daddr >> 2];
+	daddr >>= 2;
+	rcu_read_lock();
+	dev = rcu_dereference(routes->table[daddr]);
 	if (dev)
 		dev_hold(dev);
-	spin_unlock_bh(&routes->lock);
+	rcu_read_unlock();
 
 	if (!dev)
 		dev = phonet_device_get(net); /* Default route */
-- 
1.6.3.3

Re: [PATCH net-next 1/2] Phonet: put protocols array under RCU

[David Miller]

From: Rémi Denis-Courmont <remi@remlab.net>
Date: Fri, 13 Nov 2009 17:01:18 +0200

> From: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
> 
> Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>

Applied.

Re: [PATCH net-next 2/2] Phonet: convert routing table to RCU

[David Miller]

From: Rémi Denis-Courmont <remi@remlab.net>
Date: Fri, 13 Nov 2009 17:01:19 +0200

> From: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
> 
> Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>

Applied.

Re: [PATCH net-next 1/2] Phonet: put protocols array under RCU

[Paul E. McKenney]

On Fri, Nov 13, 2009 at 05:01:18PM +0200, Rémi Denis-Courmont wrote:
> From: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
> 
> Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
> ---
>  net/phonet/af_phonet.c |   20 +++++++++++---------
>  1 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
> index 8d3a55b..ed65da2 100644
> --- a/net/phonet/af_phonet.c
> +++ b/net/phonet/af_phonet.c
> @@ -35,7 +35,6 @@
> 
>  /* Transport protocol registration */
>  static struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;
> -static DEFINE_SPINLOCK(proto_tab_lock);
> 
>  static struct phonet_protocol *phonet_proto_get(int protocol)
>  {
> @@ -44,11 +43,11 @@ static struct phonet_protocol *phonet_proto_get(int protocol)
>  	if (protocol >= PHONET_NPROTO)
>  		return NULL;
> 
> -	spin_lock(&proto_tab_lock);
> +	rcu_read_lock();
>  	pp = proto_tab[protocol];

Don't we need an rcu_dereference() in here somewhere?

Perhaps something like the following?

	pp = rcu_dereference(proto_tab[protocol]);

							Thanx, Paul

>  	if (pp && !try_module_get(pp->prot->owner))
>  		pp = NULL;
> -	spin_unlock(&proto_tab_lock);
> +	rcu_read_unlock();
> 
>  	return pp;
>  }
> @@ -439,6 +438,8 @@ static struct packet_type phonet_packet_type __read_mostly = {
>  	.func = phonet_rcv,
>  };
> 
> +static DEFINE_MUTEX(proto_tab_lock);
> +
>  int __init_or_module phonet_proto_register(int protocol,
>  						struct phonet_protocol *pp)
>  {
> @@ -451,12 +452,12 @@ int __init_or_module phonet_proto_register(int protocol,
>  	if (err)
>  		return err;
> 
> -	spin_lock(&proto_tab_lock);
> +	mutex_lock(&proto_tab_lock);
>  	if (proto_tab[protocol])
>  		err = -EBUSY;
>  	else
> -		proto_tab[protocol] = pp;
> -	spin_unlock(&proto_tab_lock);
> +		rcu_assign_pointer(proto_tab[protocol], pp);
> +	mutex_unlock(&proto_tab_lock);
> 
>  	return err;
>  }
> @@ -464,10 +465,11 @@ EXPORT_SYMBOL(phonet_proto_register);
> 
>  void phonet_proto_unregister(int protocol, struct phonet_protocol *pp)
>  {
> -	spin_lock(&proto_tab_lock);
> +	mutex_lock(&proto_tab_lock);
>  	BUG_ON(proto_tab[protocol] != pp);
> -	proto_tab[protocol] = NULL;
> -	spin_unlock(&proto_tab_lock);
> +	rcu_assign_pointer(proto_tab[protocol], NULL);
> +	mutex_unlock(&proto_tab_lock);
> +	synchronize_rcu();
>  	proto_unregister(pp->prot);
>  }
>  EXPORT_SYMBOL(phonet_proto_unregister);
> -- 
> 1.6.3.3
> 
> --
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Re: [PATCH net-next 1/2] Phonet: put protocols array under RCU

[Rémi Denis-Courmont]

Le lundi 16 novembre 2009 19:26:17 Paul E. McKenney, vous avez écrit :
> On Fri, Nov 13, 2009 at 05:01:18PM +0200, Rémi Denis-Courmont wrote:
> > From: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
> >
> > Signed-off-by: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
> > ---
> >  net/phonet/af_phonet.c |   20 +++++++++++---------
> >  1 files changed, 11 insertions(+), 9 deletions(-)
> >
> > diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
> > index 8d3a55b..ed65da2 100644
> > --- a/net/phonet/af_phonet.c
> > +++ b/net/phonet/af_phonet.c
> > @@ -35,7 +35,6 @@
> >
> >  /* Transport protocol registration */
> >  static struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;
> > -static DEFINE_SPINLOCK(proto_tab_lock);
> >
> >  static struct phonet_protocol *phonet_proto_get(int protocol)
> >  {
> > @@ -44,11 +43,11 @@ static struct phonet_protocol *phonet_proto_get(int
> > protocol) if (protocol >= PHONET_NPROTO)
> >  		return NULL;
> >
> > -	spin_lock(&proto_tab_lock);
> > +	rcu_read_lock();
> >  	pp = proto_tab[protocol];
> 
> Don't we need an rcu_dereference() in here somewhere?
> 
> Perhaps something like the following?

Err yes, we do.

-- 
Rémi Denis-Courmont
http://www.remlab.net/