netpoll: Fix RCU usage
The use of RCU in netpoll is incorrect in a number of places:
1) The initial setting is lacking a write barrier.
2) The synchronize_rcu is in the wrong place.
3) Read barriers are missing.
4) Some places are even missing rcu_read_lock.
5) npinfo is zeroed after freeing.
This patch fixes those issues. As most users are in BH context,
this also converts the RCU usage to the BH variant.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index e9e2312..95c9f7e 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -57,12 +57,15 @@
#ifdef CONFIG_NETPOLL
static inline bool netpoll_rx(struct sk_buff *skb)
{
- struct netpoll_info *npinfo = skb->dev->npinfo;
+ struct netpoll_info *npinfo;
unsigned long flags;
bool ret = false;
+ rcu_read_lock_bh();
+ npinfo = rcu_dereference(skb->dev->npinfo);
+
if (!npinfo || (list_empty(&npinfo->rx_np) && !npinfo->rx_flags))
- return false;
+ goto out;
spin_lock_irqsave(&npinfo->rx_lock, flags);
/* check rx_flags again with the lock held */
@@ -70,12 +73,14 @@
ret = true;
spin_unlock_irqrestore(&npinfo->rx_lock, flags);
+out:
+ rcu_read_unlock_bh();
return ret;
}
static inline int netpoll_rx_on(struct sk_buff *skb)
{
- struct netpoll_info *npinfo = skb->dev->npinfo;
+ struct netpoll_info *npinfo = rcu_dereference(skb->dev->npinfo);
return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
}
@@ -91,7 +96,6 @@
{
struct net_device *dev = napi->dev;
- rcu_read_lock(); /* deal with race on ->npinfo */
if (dev && dev->npinfo) {
spin_lock(&napi->poll_lock);
napi->poll_owner = smp_processor_id();
@@ -108,7 +112,6 @@
napi->poll_owner = -1;
spin_unlock(&napi->poll_lock);
}
- rcu_read_unlock();
}
#else