current amd64 crashes in usb_transfer_complete

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

Got KASSERT when a yubikey device was plugged in.

$ crash -M netbsd.9.core
Crash version 7.99.35, image version 7.99.35.
System panicked: kernel diagnostic assertion "xfer->ux_state == XFER_ONQU" failed: file "/home/alnsn/netbsd-current/clean/src/sys/dev/usb/usbdi.c", line 910
Backtrace from time of crash is available.
crash> bt
_KERNEL_OPT_NARCNET() at 0
_KERNEL_OPT_NARCNET() at 0
vpanic() at vpanic+0x149
cd_play_msf() at cd_play_msf
usb_transfer_complete() at usb_transfer_complete+0x24e
xhci_abort_xfer() at xhci_abort_xfer+0x15d
usbd_ar_pipe() at usbd_ar_pipe+0x3b
usbd_abort_pipe() at usbd_abort_pipe+0x27
uhidev_detach() at uhidev_detach+0x32
config_detach() at config_detach+0xf8
usb_disconnect_port() at usb_disconnect_port+0xae
uhub_explore() at uhub_explore+0x1fe
usb_discover.isra.2() at usb_discover.isra.2+0x4e
usb_event_thread() at usb_event_thread+0x7c


Kernel built from src updated about a week ago:

$ uname -a
NetBSD neva 7.99.35 NetBSD 7.99.35 (GENERIC) #0: Wed Aug  3 23:02:01 BST 2016  alnsn@nebeda.localdomain:/home/alnsn/netbsd-current/clean/src/sys/arch/amd64/compile/obj/GENERIC amd64

$ gunzip -c /netbsd |ident |grep usbdi.c
     $NetBSD: usbdi.c,v 1.171 2016/05/17 11:37:50 pooka Exp $

Alex