[PATCH] 2.5.27 fix potential spinlocking race.

In case of socket transmission errors etc. kfree_skb(), and hence
xprt_write_space() can potentially get called outside of a bh-safe
context.

net/sunrpc/xprt.c

@@ -966,10 +966,10 @@ xprt_write_space(struct sock *sk)
 		return;
 
 	if (!xprt_test_and_set_wspace(xprt)) {
-		spin_lock(&xprt->sock_lock);
+		spin_lock_bh(&xprt->sock_lock);
 		if (xprt->snd_task && xprt->snd_task->tk_rpcwait == &xprt->pending)
 			rpc_wake_up_task(xprt->snd_task);
-		spin_unlock(&xprt->sock_lock);
+		spin_unlock_bh(&xprt->sock_lock);
 	}
 
 	if (test_bit(SOCK_NOSPACE, &sock->flags)) {