From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: Lockdep warning in vxlan Date: Thu, 20 Dec 2012 10:16:00 -0800 Message-ID: <1356027360.21834.2973.camel@edumazet-glaptop> References: <50D31A00.7060905@mellanox.com> <20121220083436.0c7fc33f@nehalam.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Yan Burman , netdev@vger.kernel.org To: Stephen Hemminger Return-path: Received: from mail-pb0-f53.google.com ([209.85.160.53]:54156 "EHLO mail-pb0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751274Ab2LTSQG (ORCPT ); Thu, 20 Dec 2012 13:16:06 -0500 Received: by mail-pb0-f53.google.com with SMTP id jt11so2153641pbb.26 for ; Thu, 20 Dec 2012 10:16:05 -0800 (PST) In-Reply-To: <20121220083436.0c7fc33f@nehalam.linuxnetplumber.net> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2012-12-20 at 08:34 -0800, Stephen Hemminger wrote: > On Thu, 20 Dec 2012 16:00:32 +0200 > Yan Burman wrote: > > > Hi. > > > > When working with vxlan from current net-next, I got a lockdep warning > > (below). > > It seems to happen when I have host B pinging host A and while the pings > > continue, > > I do "ip link del" on the vxlan interface on host A. The lockdep warning > > is on host A. > > Tell me if you need some more info. > > > > Looks like the case of nested ARP requests, the initial request is coming > from neigh_timer (ARP retransmit), but inside neigh_probe the lock > is dropped? Bug is from arp_solicit(), releasing the lock after arp_send() Its used to protect neigh->ha We could instead copy neigh->ha, without taking n->lock but ha_lock seqlock, using neigh_ha_snapshot() helper Yan, could you test the following patch ? Thanks diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index ce6fbdf..1169ed4 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -321,7 +321,7 @@ static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb) static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb) { __be32 saddr = 0; - u8 *dst_ha = NULL; + u8 dst_ha[MAX_ADDR_LEN]; struct net_device *dev = neigh->dev; __be32 target = *(__be32 *)neigh->primary_key; int probes = atomic_read(&neigh->probes); @@ -363,9 +363,9 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb) if (probes < 0) { if (!(neigh->nud_state & NUD_VALID)) pr_debug("trying to ucast probe in NUD_INVALID\n"); - dst_ha = neigh->ha; - read_lock_bh(&neigh->lock); + neigh_ha_snapshot(dst_ha, neigh, dev); } else { + memset(dst_ha, 0, dev->addr_len); probes -= neigh->parms->app_probes; if (probes < 0) { #ifdef CONFIG_ARPD @@ -377,8 +377,6 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb) arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr, dst_ha, dev->dev_addr, NULL); - if (dst_ha) - read_unlock_bh(&neigh->lock); } static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)