[NET] netpoll: break recursive loop in netpoll rx path
The netpoll system currently has a rx to tx path via:
netpoll_rx
__netpoll_rx
arp_reply
netpoll_send_skb
dev->hard_start_tx
This rx->tx loop places network drivers at risk of inadvertently causing a
deadlock or BUG halt by recursively trying to acquire a spinlock that is
used in both their rx and tx paths (this problem was origionally reported
to me in the 3c59x driver, which shares a spinlock between the
boomerang_interrupt and boomerang_start_xmit routines).
This patch breaks this loop, by queueing arp frames, so that they can be
responded to after all receive operations have been completed. Tested by
myself and the reported with successful results.
Specifically it was tested with netdump. Heres the BZ with details:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=194055
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index ca5a873..1efe60c 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -31,6 +31,7 @@
int rx_flags;
spinlock_t rx_lock;
struct netpoll *rx_np; /* netpoll that registered an rx_hook */
+ struct sk_buff_head arp_tx; /* list of arp requests to reply to */
};
void netpoll_poll(struct netpoll *np);
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 377d1e7..471da45 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -54,6 +54,7 @@
sizeof(struct iphdr) + sizeof(struct ethhdr))
static void zap_completion_queue(void);
+static void arp_reply(struct sk_buff *skb);
static void queue_process(void *p)
{
@@ -153,6 +154,22 @@
}
}
+static void service_arp_queue(struct netpoll_info *npi)
+{
+ struct sk_buff *skb;
+
+ if (unlikely(!npi))
+ return;
+
+ skb = skb_dequeue(&npi->arp_tx);
+
+ while (skb != NULL) {
+ arp_reply(skb);
+ skb = skb_dequeue(&npi->arp_tx);
+ }
+ return;
+}
+
void netpoll_poll(struct netpoll *np)
{
if(!np->dev || !netif_running(np->dev) || !np->dev->poll_controller)
@@ -163,6 +180,8 @@
if (np->dev->poll)
poll_napi(np);
+ service_arp_queue(np->dev->npinfo);
+
zap_completion_queue();
}
@@ -442,7 +461,9 @@
int proto, len, ulen;
struct iphdr *iph;
struct udphdr *uh;
- struct netpoll *np = skb->dev->npinfo->rx_np;
+ struct netpoll_info *npi = skb->dev->npinfo;
+ struct netpoll *np = npi->rx_np;
+
if (!np)
goto out;
@@ -452,7 +473,7 @@
/* check if netpoll clients need ARP */
if (skb->protocol == __constant_htons(ETH_P_ARP) &&
atomic_read(&trapped)) {
- arp_reply(skb);
+ skb_queue_tail(&npi->arp_tx, skb);
return 1;
}
@@ -647,6 +668,7 @@
npinfo->poll_owner = -1;
npinfo->tries = MAX_RETRIES;
spin_lock_init(&npinfo->rx_lock);
+ skb_queue_head_init(&npinfo->arp_tx);
} else
npinfo = ndev->npinfo;