* [PATCH net-next-2.6] can: convert protocol handling to RCU
@ 2011-04-04 20:21 Oliver Hartkopp
2011-04-04 20:26 ` Eric Dumazet
2011-04-05 17:52 ` Oliver Hartkopp
0 siblings, 2 replies; 3+ messages in thread
From: Oliver Hartkopp @ 2011-04-04 20:21 UTC (permalink / raw)
To: David Miller
Cc: Linux Netdev List, Kurt Van Dijck, Eric Dumazet, Urs Thuermann
This patch removes spin_locks at CAN socket creation time by using RCU.
Inspired by the discussion with Kurt van Dijck and Eric Dumazet the RCU code
was partly derived from af_phonet.c
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 733d66f..551ebc1 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -85,7 +85,7 @@ static struct kmem_cache *rcv_cache __read_mostly;
/* table of registered CAN protocols */
static struct can_proto *proto_tab[CAN_NPROTO] __read_mostly;
-static DEFINE_SPINLOCK(proto_tab_lock);
+static DEFINE_MUTEX(proto_tab_lock);
struct timer_list can_stattimer; /* timer for statistics update */
struct s_stats can_stats; /* packet statistics */
@@ -115,6 +115,19 @@ static void can_sock_destruct(struct sock *sk)
skb_queue_purge(&sk->sk_receive_queue);
}
+static struct can_proto *can_try_module_get(int protocol)
+{
+ struct can_proto *cp;
+
+ rcu_read_lock();
+ cp = rcu_dereference(proto_tab[protocol]);
+ if (cp && !try_module_get(cp->prot->owner))
+ cp = NULL;
+ rcu_read_unlock();
+
+ return cp;
+}
+
static int can_create(struct net *net, struct socket *sock, int protocol,
int kern)
{
@@ -130,9 +143,12 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
if (!net_eq(net, &init_net))
return -EAFNOSUPPORT;
+ cp = can_try_module_get(protocol);
+
#ifdef CONFIG_MODULES
- /* try to load protocol module kernel is modular */
- if (!proto_tab[protocol]) {
+ if (!cp) {
+ /* try to load protocol module if kernel is modular */
+
err = request_module("can-proto-%d", protocol);
/*
@@ -143,22 +159,18 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
if (err && printk_ratelimit())
printk(KERN_ERR "can: request_module "
"(can-proto-%d) failed.\n", protocol);
+ else
+ cp = can_try_module_get(protocol);
}
#endif
- spin_lock(&proto_tab_lock);
- cp = proto_tab[protocol];
- if (cp && !try_module_get(cp->prot->owner))
- cp = NULL;
- spin_unlock(&proto_tab_lock);
-
/* check for available protocol and correct usage */
if (!cp)
return -EPROTONOSUPPORT;
if (cp->type != sock->type) {
- err = -EPROTONOSUPPORT;
+ err = -EPROTOTYPE;
goto errout;
}
@@ -694,15 +706,16 @@ int can_proto_register(struct can_proto *cp)
if (err < 0)
return err;
- spin_lock(&proto_tab_lock);
+ mutex_lock(&proto_tab_lock);
+
if (proto_tab[proto]) {
printk(KERN_ERR "can: protocol %d already registered\n",
proto);
err = -EBUSY;
} else
- proto_tab[proto] = cp;
+ rcu_assign_pointer(proto_tab[proto], cp);
- spin_unlock(&proto_tab_lock);
+ mutex_unlock(&proto_tab_lock);
if (err < 0)
proto_unregister(cp->prot);
@@ -719,13 +732,12 @@ void can_proto_unregister(struct can_proto *cp)
{
int proto = cp->protocol;
- spin_lock(&proto_tab_lock);
- if (!proto_tab[proto]) {
- printk(KERN_ERR "BUG: can: protocol %d is not registered\n",
- proto);
- }
- proto_tab[proto] = NULL;
- spin_unlock(&proto_tab_lock);
+ mutex_lock(&proto_tab_lock);
+ BUG_ON(proto_tab[proto] != cp);
+ rcu_assign_pointer(proto_tab[proto], NULL);
+ mutex_unlock(&proto_tab_lock);
+
+ synchronize_rcu();
proto_unregister(cp->prot);
}
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net-next-2.6] can: convert protocol handling to RCU
2011-04-04 20:21 [PATCH net-next-2.6] can: convert protocol handling to RCU Oliver Hartkopp
@ 2011-04-04 20:26 ` Eric Dumazet
2011-04-05 17:52 ` Oliver Hartkopp
1 sibling, 0 replies; 3+ messages in thread
From: Eric Dumazet @ 2011-04-04 20:26 UTC (permalink / raw)
To: Oliver Hartkopp
Cc: David Miller, Linux Netdev List, Kurt Van Dijck, Urs Thuermann
Le lundi 04 avril 2011 à 22:21 +0200, Oliver Hartkopp a écrit :
> This patch removes spin_locks at CAN socket creation time by using RCU.
>
> Inspired by the discussion with Kurt van Dijck and Eric Dumazet the RCU code
> was partly derived from af_phonet.c
>
> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
>
> ---
>
> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index 733d66f..551ebc1 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c
> @@ -85,7 +85,7 @@ static struct kmem_cache *rcv_cache __read_mostly;
Seems good to me, thanks !
Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net-next-2.6] can: convert protocol handling to RCU
2011-04-04 20:21 [PATCH net-next-2.6] can: convert protocol handling to RCU Oliver Hartkopp
2011-04-04 20:26 ` Eric Dumazet
@ 2011-04-05 17:52 ` Oliver Hartkopp
1 sibling, 0 replies; 3+ messages in thread
From: Oliver Hartkopp @ 2011-04-05 17:52 UTC (permalink / raw)
To: David Miller
Cc: Linux Netdev List, Kurt Van Dijck, Eric Dumazet, Urs Thuermann
On 04.04.2011 22:21, Oliver Hartkopp wrote:
> This patch removes spin_locks at CAN socket creation time by using RCU.
>
> @@ -143,22 +159,18 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
> if (err && printk_ratelimit())
> printk(KERN_ERR "can: request_module "
> "(can-proto-%d) failed.\n", protocol);
> + else
> + cp = can_try_module_get(protocol);
> }
Hm, i just discovered a tiny issue here as putting can_try_module_get() into
the 'else' path is not needed.
Will send a V2 in a few minutes.
Regards,
Oliver
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-04-04 20:21 [PATCH net-next-2.6] can: convert protocol handling to RCU Oliver Hartkopp
2011-04-04 20:26 ` Eric Dumazet
2011-04-05 17:52 ` Oliver Hartkopp
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