jy_droopy:

This problem also occurs in cc version 15.04.

1. system info

root@LEDE:/# cat /proc/cpuinfo
system type : MediaTek MT7628AN ver:1 eco:2
machine : MiWiFi Nano
processor : 0
cpu model : MIPS 24KEc V5.5
BogoMIPS : 385.84
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa : mips1 mips2 mips32r1 mips32r2
ASEs implemented : mips16 dsp
shadow register sets : 1
kscratch registers : 0
package : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available

root@LEDE:/# uname -a
Linux LEDE 4.4.92 #0 Tue Oct 17 17:46:20 2017 mips GNU/Linux

2. trace log
   root@LEDE:/#
   [ 60.915441] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
   [ 60.931769] device wlan0 entered promiscuous mode
   [ 60.965229] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
   [ 60.971937] br-lan: port 2(wlan0) entered forwarding state
   [ 60.977586] br-lan: port 2(wlan0) entered forwarding state
   [ 62.975771] br-lan: port 2(wlan0) entered forwarding state
   [ 63.436041] random: nonblocking pool is initialized

root@LEDE:/# uname -a
Linux LEDE 4.4.92 #0 Tue Oct 17 17:46:20 2017 mips GNU/Linux
root@LEDE:/# [ 71.259540] device wlan0 left promiscuous mode
[ 71.264171] br-lan: port 2(wlan0) entered disabled state
[ 72.180390] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
[ 72.208932] device wlan0 entered promiscuous mode
[ 72.213810] br-lan: port 2(wlan0) entered forwarding state
[ 72.219479] br-lan: port 2(wlan0) entered forwarding state
[ 72.307245] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 74.215791] br-lan: port 2(wlan0) entered forwarding state
======[ 75.565774] ------------[ cut here ]------------
[ 75.570530] WARNING: CPU: 0 PID: 7 at /srv/repository/77.lede/openwrt-444add1/build_dir/target-mipsel_24kc_musl-1.1.16/linux-ramips_mt7628/mt76-2017-10-12-1be430fc/mt7603_mac.c:1279 mt7603_mac_work+0xf0/0x290 mt7603e
[ 75.590375] Modules linked in: pppoe ppp_async iptable_nat pppox ppp_generic nf_nat_ipv4 nf_conntrack_ipv6 nf_conntrack_ipv4 ipt_REJECT ipt_MASQUERADE xt_time xt_tcpudp xt_state xt_nat xt_multiport xt_mark xt_mac xt_limit xt_conntrack xt_comment xt_TCPMSS xt_REDIRECT xt_LOG slhc nf_reject_ipv4 nf_nat_redirect nf_nat_masquerade_ipv4 nf_nat nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache nf_conntrack iptable_mangle iptable_filter ip_tables crc_ccitt mt76x2e mt7603e ledtrig_usbport mt76 mac80211 cfg80211 compat ip6t_REJECT nf_reject_ipv6 nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables x_tables leds_gpio ohci_platform ohci_hcd ehci_platform ehci_hcd gpio_button_hotplug usbcore nls_base usb_common
[ 75.656193] CPU: 0 PID: 7 Comm: kworker/u2:1 Not tainted 4.4.92 #0
[ 75.662836] Workqueue: phy0 mt7603_mac_work [mt7603e]
[ 75.668031] Stack : 83803410 838a7198 00000088 8004afbc 8382e0b4 8038ad23 80328bd4 00000007
80350878 838b3d64 80380000 80048f28 00000088 8004afbc 8032e104 80380000
00000003 838b3d64 80380000 80038f18 00000088 838b3d9c 000000bc 00000000
00000001 00000000 83115420 83b54900 83b54800 30796870 00000000 00000000
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
...
[ 75.704622] Call Trace:
[ 75.707135] [<800148c8>] show_stack+0x54/0x88
[ 75.711563] [<80025440>] warn_slowpath_common+0xa0/0xd0
[ 75.716888] [<800254f8>] warn_slowpath_null+0x18/0x24
[ 75.722036] [<83115510>] mt7603_mac_work+0xf0/0x290 [mt7603e]
[ 75.727906] [<80036e14>] process_one_work+0x1f8/0x334
[ 75.733045] [<80037c3c>] worker_thread+0x2b0/0x404
[ 75.737925] [<8003c01c>] kthread+0xd8/0xec
[ 75.742098] [<80004478>] ret_from_kernel_thread+0x14/0x1c
[ 75.747581]
[ 75.749096] ---[ end trace e8bec1608a59628f ]---======

root@LEDE:/# [ 87.742860] done.
[ 87.744871] jffs2: notice: (1006) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.