[IPV6]: Fix illegal dst locking in softirq context.

On Tue, Jan 31, 2006 at 10:24:32PM +0100, Ingo Molnar wrote:
>
>  [<c04de9e8>] _write_lock+0x8/0x10
>  [<c0499015>] inet6_destroy_sock+0x25/0x100
>  [<c04b8672>] tcp_v6_destroy_sock+0x12/0x20
>  [<c046bbda>] inet_csk_destroy_sock+0x4a/0x150
>  [<c047625c>] tcp_rcv_state_process+0xd4c/0xdd0
>  [<c047d8e9>] tcp_v4_do_rcv+0xa9/0x340
>  [<c047eabb>] tcp_v4_rcv+0x8eb/0x9d0

OK this is definitely broken.  We should never touch the dst lock in
softirq context.  Since inet6_destroy_sock may be called from that
context due to the asynchronous nature of sockets, we can't take the
lock there.

In fact this sk_dst_reset is totally redundant since all IPv6 sockets
use inet_sock_destruct as their socket destructor which always cleans
up the dst anyway.  So the solution is to simply remove the call.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/af_inet6.c

@@ -369,12 +369,6 @@ int inet6_destroy_sock(struct sock *sk)
 	struct sk_buff *skb;
 	struct ipv6_txoptions *opt;
 
-	/*
-	 *	Release destination entry
-	 */
-
-	sk_dst_reset(sk);
-
 	/* Release rx options */
 
 	if ((skb = xchg(&np->pktoptions, NULL)) != NULL)