From 068c6e98bc7ec4419299b38cd40be26ebf4bdeda Mon Sep 17 00:00:00 2001 From: Neil Horman Date: Mon, 26 Jun 2006 00:04:27 -0700 Subject: [PATCH] [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 Acked-by: Matt Mackall Signed-off-by: Andrew Morton Signed-off-by: David S. Miller --- include/linux/netpoll.h | 1 + net/core/netpoll.c | 26 ++++++++++++++++++++++++-- 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h index ca5a8733000f..1efe60c5c00c 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -31,6 +31,7 @@ struct netpoll_info { 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 377d1e7257b5..471da451cd48 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -54,6 +54,7 @@ static atomic_t trapped; 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 poll_napi(struct netpoll *np) } } +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 @@ void netpoll_poll(struct netpoll *np) if (np->dev->poll) poll_napi(np); + service_arp_queue(np->dev->npinfo); + zap_completion_queue(); } @@ -442,7 +461,9 @@ int __netpoll_rx(struct sk_buff *skb) 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 @@ int __netpoll_rx(struct sk_buff *skb) /* 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 @@ int netpoll_setup(struct netpoll *np) 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;