From: Linus Torvalds <torvalds@linux-foundation.org>Date: Tue, 17 Dec 2013 11:06:15 -0800> this seems to be due to __udp4_lib_rcv() doing udp_sk_rx_dst_set(),> which takes the 'sk->sk_dst_lock' spinlock. This all happens in a> software irq context.I have a fix for this from Eric that I'll send to you today.