Re: possible recursive locking in udp4_lib_rcv

[Herbert Xu]

Michael S. Tsirkin <m.s.tsirkin@xxxxxxxxx> 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@xxxxxxxxxx>
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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