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authorHerbert Xu <herbert@gondor.apana.org.au>2010-06-10 16:12:44 +0000
committerDavid S. Miller <davem@davemloft.net>2010-06-15 10:58:38 -0700
commitde85d99eb7b595f6751550184b94c1e2f74a828b (patch)
tree950eea4329bfb2b5d94f2e242a86c36cf1fd49fc
parent36655042f9873efc2a90d251b9aef9b6b79d75d8 (diff)
downloadop-kernel-dev-de85d99eb7b595f6751550184b94c1e2f74a828b.zip
op-kernel-dev-de85d99eb7b595f6751550184b94c1e2f74a828b.tar.gz
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>
-rw-r--r--include/linux/netpoll.h13
-rw-r--r--net/core/netpoll.c20
2 files changed, 20 insertions, 13 deletions
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 @@ void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb);
#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 @@ static inline bool netpoll_rx(struct sk_buff *skb)
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 @@ static inline void *netpoll_poll_lock(struct napi_struct *napi)
{
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 @@ static inline void netpoll_poll_unlock(void *have)
napi->poll_owner = -1;
spin_unlock(&napi->poll_lock);
}
- rcu_read_unlock();
}
#else
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 19ff660..e9ab4f0 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -261,6 +261,7 @@ void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
unsigned long tries;
struct net_device *dev = np->dev;
const struct net_device_ops *ops = dev->netdev_ops;
+ /* It is up to the caller to keep npinfo alive. */
struct netpoll_info *npinfo = np->dev->npinfo;
if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) {
@@ -810,10 +811,7 @@ int netpoll_setup(struct netpoll *np)
refill_skbs();
/* last thing to do is link it to the net device structure */
- ndev->npinfo = npinfo;
-
- /* avoid racing with NAPI reading npinfo */
- synchronize_rcu();
+ rcu_assign_pointer(ndev->npinfo, npinfo);
return 0;
@@ -857,6 +855,16 @@ void netpoll_cleanup(struct netpoll *np)
if (atomic_dec_and_test(&npinfo->refcnt)) {
const struct net_device_ops *ops;
+
+ ops = np->dev->netdev_ops;
+ if (ops->ndo_netpoll_cleanup)
+ ops->ndo_netpoll_cleanup(np->dev);
+
+ rcu_assign_pointer(np->dev->npinfo, NULL);
+
+ /* avoid racing with NAPI reading npinfo */
+ synchronize_rcu_bh();
+
skb_queue_purge(&npinfo->arp_tx);
skb_queue_purge(&npinfo->txq);
cancel_rearming_delayed_work(&npinfo->tx_work);
@@ -864,10 +872,6 @@ void netpoll_cleanup(struct netpoll *np)
/* clean after last, unfinished work */
__skb_queue_purge(&npinfo->txq);
kfree(npinfo);
- ops = np->dev->netdev_ops;
- if (ops->ndo_netpoll_cleanup)
- ops->ndo_netpoll_cleanup(np->dev);
- np->dev->npinfo = NULL;
}
}
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