netdev - Re: possible recursive locking in udp4_lib

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Date:	Fri, 08 Aug 2008 22:28:41 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	m.s.tsirkin@...il.com (Michael S. Tsirkin)
Cc:	linux-kernel@...r.kernel.org, davem@...emloft.net,
	yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org, haoki@...hat.com
Subject: Re: possible recursive locking in udp4_lib_rcv

Michael S. Tsirkin <m.s.tsirkin@...il.com> wrote:
> I noticed the following warnings when running on 2.6.27-rc2
> with lockdep checker enabled:
> 
> [ 2912.004106] Initializing XFRM netlink socket

Argh, this was added by

commit 95766fff6b9a78d11fc2d3812dd035381690b55d
Author: Hideo Aoki <haoki@...hat.com>
Date:   Mon Dec 31 00:29:24 2007 -0800

    [UDP]: Add memory accounting.

@@ -1165,7 +1189,13 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
                               inet_iif(skb), udptable);

        if (sk != NULL) {
-               int ret = udp_queue_rcv_skb(sk, skb);
+               int ret = 0;
+               bh_lock_sock_nested(sk);
+               if (!sock_owned_by_user(sk))
+                       ret = udp_queue_rcv_skb(sk, skb);
+               else
+                       sk_add_backlog(sk, skb);
+               bh_unlock_sock(sk);

Hmm, what was the reason for that lock?

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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