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netpoll: Fix RCU usage

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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>
This commit is contained in:
Herbert Xu
2010-06-10 16:12:44 +00:00
committed by David S. Miller
parent 36655042f9
commit de85d99eb7
2 changed files with 20 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/core/netpoll.c
+12 -8
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@@ -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;
}
}