The driver may sleep under a read spin lock, and the function call path is:
send_socklist (acquire the lock by read_lock)
  skb_copy(GFP_KERNEL) --> may sleep
To fix it, the "GFP_KERNEL" is replaced with "GFP_ATOMIC".
Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
                if (sk->sk_state != MISDN_BOUND)
                        continue;
                if (!cskb)
-                       cskb = skb_copy(skb, GFP_KERNEL);
+                       cskb = skb_copy(skb, GFP_ATOMIC);
                if (!cskb) {
                        printk(KERN_WARNING "%s no skb\n", __func__);
                        break;