* [PATCH net] vxlan: Use RCU apis to access sk_user_data.
@ 2013-09-24 5:28 Pravin B Shelar
2013-09-24 5:51 ` Eric Dumazet
2013-09-24 16:20 ` Stephen Hemminger
0 siblings, 2 replies; 4+ messages in thread
From: Pravin B Shelar @ 2013-09-24 5:28 UTC (permalink / raw)
To: netdev; +Cc: Pravin B Shelar, Jesse Gross
Use of RCU api makes vxlan code easier to understand. It also
fixes bug due to missing ACCESS_ONCE() on sk_user_data dereference.
In rare case without ACCESS_ONCE() compiler might omit vs on
sk_user_data dereference.
Compiler can use vs as alias for sk->sk_user_data, resulting in
multiple sk_user_data dereference in rcu read context which
could change.
CC: Jesse Gross <jesse@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
---
drivers/net/vxlan.c | 9 +++------
include/net/sock.h | 2 ++
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index d1292fe..3519a71 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -952,8 +952,7 @@ void vxlan_sock_release(struct vxlan_sock *vs)
spin_lock(&vn->sock_lock);
hlist_del_rcu(&vs->hlist);
- smp_wmb();
- vs->sock->sk->sk_user_data = NULL;
+ rcu_assign_pointer(sk_user_data_rcu(vs->sock->sk), NULL);
vxlan_notify_del_rx_port(sk);
spin_unlock(&vn->sock_lock);
@@ -1048,8 +1047,7 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
port = inet_sk(sk)->inet_sport;
- smp_read_barrier_depends();
- vs = (struct vxlan_sock *)sk->sk_user_data;
+ vs = rcu_dereference(sk_user_data_rcu(sk));
if (!vs)
goto drop;
@@ -2302,8 +2300,7 @@ static struct vxlan_sock *vxlan_socket_create(struct net *net, __be16 port,
atomic_set(&vs->refcnt, 1);
vs->rcv = rcv;
vs->data = data;
- smp_wmb();
- vs->sock->sk->sk_user_data = vs;
+ rcu_assign_pointer(sk_user_data_rcu(vs->sock->sk), vs);
spin_lock(&vn->sock_lock);
hlist_add_head_rcu(&vs->hlist, vs_head(net, port));
diff --git a/include/net/sock.h b/include/net/sock.h
index 6ba2e7b..ffd1356 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -409,6 +409,8 @@ struct sock {
void (*sk_destruct)(struct sock *sk);
};
+#define sk_user_data_rcu(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
+
/*
* SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK
* or not whether his port will be reused by someone else. SK_FORCE_REUSE
--
1.7.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net] vxlan: Use RCU apis to access sk_user_data.
2013-09-24 5:28 [PATCH net] vxlan: Use RCU apis to access sk_user_data Pravin B Shelar
@ 2013-09-24 5:51 ` Eric Dumazet
2013-09-24 16:20 ` Stephen Hemminger
1 sibling, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2013-09-24 5:51 UTC (permalink / raw)
To: Pravin B Shelar; +Cc: netdev, Jesse Gross
On Mon, 2013-09-23 at 22:28 -0700, Pravin B Shelar wrote:
> Use of RCU api makes vxlan code easier to understand. It also
> fixes bug due to missing ACCESS_ONCE() on sk_user_data dereference.
> In rare case without ACCESS_ONCE() compiler might omit vs on
> sk_user_data dereference.
> Compiler can use vs as alias for sk->sk_user_data, resulting in
> multiple sk_user_data dereference in rcu read context which
> could change.
>
> CC: Jesse Gross <jesse@nicira.com>
> Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
> ---
> drivers/net/vxlan.c | 9 +++------
> include/net/sock.h | 2 ++
> 2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> index d1292fe..3519a71 100644
> --- a/drivers/net/vxlan.c
> +++ b/drivers/net/vxlan.c
> @@ -952,8 +952,7 @@ void vxlan_sock_release(struct vxlan_sock *vs)
>
> spin_lock(&vn->sock_lock);
> hlist_del_rcu(&vs->hlist);
> - smp_wmb();
> - vs->sock->sk->sk_user_data = NULL;
> + rcu_assign_pointer(sk_user_data_rcu(vs->sock->sk), NULL);
RCU_INIT_POINTER(sk_user_data_rcu(vs->sock->sk), NULL)
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] vxlan: Use RCU apis to access sk_user_data.
2013-09-24 5:28 [PATCH net] vxlan: Use RCU apis to access sk_user_data Pravin B Shelar
2013-09-24 5:51 ` Eric Dumazet
@ 2013-09-24 16:20 ` Stephen Hemminger
2013-09-24 16:27 ` Pravin Shelar
1 sibling, 1 reply; 4+ messages in thread
From: Stephen Hemminger @ 2013-09-24 16:20 UTC (permalink / raw)
To: Pravin B Shelar; +Cc: netdev, Jesse Gross
On Mon, 23 Sep 2013 22:28:21 -0700
Pravin B Shelar <pshelar@nicira.com> wrote:
>
> +#define sk_user_data_rcu(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
I don't like the macro, is it just to keep sparse happy?
The name also implies that rcu_dereference() is built in.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] vxlan: Use RCU apis to access sk_user_data.
2013-09-24 16:20 ` Stephen Hemminger
@ 2013-09-24 16:27 ` Pravin Shelar
0 siblings, 0 replies; 4+ messages in thread
From: Pravin Shelar @ 2013-09-24 16:27 UTC (permalink / raw)
To: Stephen Hemminger; +Cc: netdev, Jesse Gross
On Tue, Sep 24, 2013 at 9:20 AM, Stephen Hemminger
<stephen@networkplumber.org> wrote:
> On Mon, 23 Sep 2013 22:28:21 -0700
> Pravin B Shelar <pshelar@nicira.com> wrote:
>
>>
>> +#define sk_user_data_rcu(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
>
> I don't like the macro, is it just to keep sparse happy?
yes, it is for sparse.
> The name also implies that rcu_dereference() is built in.
ok, I can right separate API for rcu-set and rcu-deref.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-09-24 16:27 UTC | newest]
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2013-09-24 5:28 [PATCH net] vxlan: Use RCU apis to access sk_user_data Pravin B Shelar
2013-09-24 5:51 ` Eric Dumazet
2013-09-24 16:20 ` Stephen Hemminger
2013-09-24 16:27 ` Pravin Shelar
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