[PATCH 7/7] netpoll: take rcu_read_lock_bh() in netpoll_send_skb_on_dev()

Cong Wang
2012-07-27T15:39:48Z

This patch fixes several problems in the call path of
netpoll_send_skb_on_dev():

1. We already disable IRQ's before calling netpoll_send_skb_on_dev(),
so we don't need to disable IRQ's again.
2. All the callees of netpoll_send_skb_on_dev() should use
rcu_dereference_bh() to dereference ->npinfo.
3. Rename arp_reply() to netpoll_arp_reply(), the former is too generic.

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
---
net/core/netpoll.c | 31 +++++++++++++++++--------------
1 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 3965fdb..d6e192b 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -54,7 +54,7 @@ static atomic_t trapped;
MAX_UDP_CHUNK)

static void zap_completion_queue(void);
-static void arp_reply(struct sk_buff *skb);
+static void netpoll_arp_reply(struct sk_buff *skb, struct netpoll_info *npinfo);

static unsigned int carrier_timeout = 4;
module_param(carrier_timeout, uint, 0644);
@@ -170,7 +170,8 @@ static void poll_napi(struct net_device *dev)
list_for_each_entry(napi, &dev->napi_list, dev_list) {
if (napi->poll_owner != smp_processor_id() &&
spin_trylock(&napi->poll_lock)) {
- budget = poll_one_napi(dev->npinfo, napi, budget);
+ budget = poll_one_napi(rcu_dereference_bh(dev->npinfo),
+ napi, budget);
spin_unlock(&napi->poll_lock);

if (!budget)
@@ -185,13 +186,14 @@ static void service_arp_queue(struct netpoll_info *npi)
struct sk_buff *skb;

while ((skb = skb_dequeue(&npi->arp_tx)))
- arp_reply(skb);
+ netpoll_arp_reply(skb, npi);
}
}

static void netpoll_poll_dev(struct net_device *dev)
{
const struct net_device_ops *ops;
+ struct netpoll_info *ni = rcu_dereference_bh(dev->npinfo);

if (!dev || !netif_running(dev))
return;
@@ -206,17 +208,18 @@ static void netpoll_poll_dev(struct net_device *dev)
poll_napi(dev);

if (dev->flags & IFF_SLAVE) {
- if (dev->npinfo) {
+ if (ni) {
struct net_device *bond_dev = dev->master;
struct sk_buff *skb;
- while ((skb = skb_dequeue(&dev->npinfo->arp_tx))) {
+ struct netpoll_info *bond_ni = rcu_dereference_bh(bond_dev->npinfo);
+ while ((skb = skb_dequeue(&ni->arp_tx))) {
skb->dev = bond_dev;
- skb_queue_tail(&bond_dev->npinfo->arp_tx, skb);
+ skb_queue_tail(&bond_ni->arp_tx, skb);
}
}
}

- service_arp_queue(dev->npinfo);
+ service_arp_queue(ni);

zap_completion_queue();
}
@@ -302,6 +305,7 @@ static int netpoll_owner_active(struct net_device *dev)
return 0;
}

+/* call with IRQ disabled */
void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
struct net_device *dev)
{
@@ -309,8 +313,11 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
unsigned long tries;
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;
+ struct netpoll_info *npinfo;
+
+ WARN_ON_ONCE(!irqs_disabled());

+ npinfo = rcu_dereference_bh(np->dev->npinfo);
if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) {
__kfree_skb(skb);
return;
@@ -319,11 +326,9 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
/* don't get messages out of order, and no recursion */
if (skb_queue_len(&npinfo->txq) == 0 && !netpoll_owner_active(dev)) {
struct netdev_queue *txq;
- unsigned long flags;

txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));

- local_irq_save(flags);
/* try until next clock tick */
for (tries = jiffies_to_usecs(1)/USEC_PER_POLL;
tries > 0; --tries) {
@@ -347,10 +352,9 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
}

WARN_ONCE(!irqs_disabled(),
- "netpoll_send_skb(): %s enabled interrupts in poll (%pF)\n",
+ "netpoll_send_skb_on_dev(): %s enabled interrupts in poll (%pF)\n",
dev->name, ops->ndo_start_xmit);

- local_irq_restore(flags);
}

if (status != NETDEV_TX_OK) {
@@ -423,9 +427,8 @@ void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
}
EXPORT_SYMBOL(netpoll_send_udp);

-static void arp_reply(struct sk_buff *skb)
+static void netpoll_arp_reply(struct sk_buff *skb, struct netpoll_info *npinfo)
{
- struct netpoll_info *npinfo = skb->dev->npinfo;
struct arphdr *arp;
unsigned char *arp_ptr;
int size, type = ARPOP_REPLY, ptype = ETH_P_ARP;
--
1.7.7.6