netdev - Re: possible recursive locking in udp4_lib

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Date:	Fri, 8 Aug 2008 22:37:42 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Michael S. Tsirkin" <m.s.tsirkin@...il.com>
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

On Fri, Aug 08, 2008 at 10:28:41PM +0800, Herbert Xu wrote:
>
> @@ -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?

Never mind, I see the reason why it's there.  What we should do
is drop the lock when we hit an encapsulated socket since they
don't need it at all.

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