luci is blocked when invoking shell commands（c source can also find similar error）

[truelv]

platform：
openwrt CC / mips ( 4 cpu core)

Repetition frequency：
sometimes happen

wrong lines：
luci/modules/admin-full/luasrc/view/admin_status/index.html line97
mac = luci.sys.exec("ifconfig eth0 | awk '/HWaddr/{print $5}'")

PS info：
15 treebear 0 SW [ksoftirqd/2]
16 treebear 0 SW [kworker/2:0]
17 treebear 0 SW< [kworker/2:0H]
18 treebear 0 SW [migration/3]
19 treebear 0 SW [ksoftirqd/3]
20 treebear 0 SW [kworker/3:0]
21 treebear 0 SW< [kworker/3:0H]
22 treebear 0 SW< [khelper]
100 treebear 0 SW< [writeback]
102 treebear 0 SW< [bioset]
104 treebear 0 SW< [kblockd]
117 treebear 0 SW [khubd]
144 treebear 0 RW [kworker/0:1]
150 treebear 0 SW [kswapd0]
194 treebear 0 SW [fsnotify_mark]
266 treebear 0 SW [kworker/3:1]
267 treebear 0 SW [kworker/2:1]
268 treebear 0 SW [kworker/1:1]
280 treebear 0 SW< [deferwq]
382 treebear 0 SWN [jffs2_gcd_mtd6]
461 treebear 888 S /sbin/ubusd
470 treebear 768 S /sbin/askfirst ttyS0 /bin/ash --login
912 treebear 0 SW< [rpciod]
933 treebear 0 SW< [nfsiod]
1164 treebear 1504 S /sbin/klogd
1165 treebear 1528 S /sbin/syslogd -l 7 -O /etc/log/system.log -s 1000 -b 10 -U /tmp/user.log
1166 treebear 0 SW [kworker/0:2]
1202 treebear 1544 S /sbin/netifd
1353 treebear 1508 S udhcpc -R -p /var/run/udhcpc-eth0.5.pid -s /lib/netifd/dhcp.script -f -t 0 -i eth0.5 -H Witown -V #AP:Tre
1466 treebear 1208 S /usr/sbin/dnsmasq -C /var/etc/dnsmasq.conf -k -u treebear
1468 treebear 0 SW< [kworker/1:1H]
1486 treebear 0 SW [RtmpCmdQTask]
1487 treebear 0 SW [RtmpWscTask]
1488 treebear 0 SW [RtmpMlmeTask]
1650 treebear 0 SW [RtmpCmdQTask]
1651 treebear 0 SW [RtmpWscTask]
1652 treebear 0 SW [RtmpMlmeTask]
1745 treebear 1508 S /usr/sbin/telnetd
1769 treebear 1084 S /sbin/mountd -f
1791 treebear 1508 S /usr/sbin/ntpd -n -u 86400 -r 600 -p 0.cn.pool.ntp.org -p 1.cn.pool.ntp.org -p 2.cn.pool.ntp.org -p 3.cn.
1815 treebear 4032 S /usr/sbin/lighttpd -f /etc/lighttpd/lighttpd.conf
1819 treebear 1504 S {runing_status_m} /bin/sh /usr/sbin/runing_status_monitor
1833 treebear 1520 S {update_cur_stat} /bin/sh /usr/sbin/update_cur_status
1870 treebear 1508 S {witownapp.sh} /bin/sh /usr/sbin/witownapp.sh
1905 treebear 980 S arp_broadcast lan
1911 treebear 1508 S /usr/sbin/crond start
1930 treebear 37408 S /usr/bin/ppcloud
2005 treebear 0 SW [kworker/u8:2]
6786 treebear 1520 S -ash
15051 treebear 3320 S {luci} /usr/bin/lua /www/cgi-bin/luci //these three lines below are bocked one bye one
15120 treebear 1512 S sh -c ifconfig eth0 | awk '/HWaddr/{print $5}'
15122 treebear 1512 R sh -c ifconfig eth0 | awk '/HWaddr/{print $5}'
22209 treebear 1500 S sleep 10
22214 treebear 1508 R ps w

Top info：
Mem: 83636K used, 172364K free, 0K shrd, 5748K buff, 22196K cached
CPU: 4% usr 29% sys 0% nic 50% idle 0% io 0% irq 15% sirq
Load average: 1.23 1.33 1.45 2/77 24291
PID PPID USER STAT VSZ %VSZ %CPU COMMAND
15122 15120 treebear R 1512 1% 25% sh -c ifconfig eth0 | awk '/HWaddr/{p //wrong line 1
3 2 treebear SW 0 0% 7% [ksoftirqd/0]
1930 1870 treebear S 37412 15% 2% /usr/bin/ppcloud
24289 6786 treebear R 1512 1% 2% top
1815 1 treebear S 4032 2% 0% /usr/sbin/lighttpd -f /etc/lighttpd/l
15051 1815 treebear S 3320 1% 0% {luci} /usr/bin/lua /www/cgi-bin/luci //wrong line 3
1202 1 treebear S 1544 1% 0% /sbin/netifd
1165 1 treebear S 1528 1% 0% /sbin/syslogd -l 7 -O /etc/log/system
1833 1819 treebear S 1520 1% 0% {update_cur_stat} /bin/sh /usr/sbin/u
6786 1745 treebear S 1520 1% 0% -ash
15120 15051 treebear S 1512 1% 0% sh -c ifconfig eth0 | awk '/HWaddr/{p //wrong line 2
1745 1 treebear S 1508 1% 0% /usr/sbin/telnetd
1911 1 treebear S 1508 1% 0% /usr/sbin/crond start
1353 1202 treebear S 1508 1% 0% udhcpc -R -p /var/run/udhcpc-eth0.5.p
1791 1 treebear S 1508 1% 0% /usr/sbin/ntpd -n -u 86400 -r 600 -p
1870 1 treebear S 1508 1% 0% {witownapp.sh} /bin/sh /usr/sbin/wito
1164 1 treebear S 1504 1% 0% /sbin/klogd
1819 1 treebear S 1504 1% 0% {runing_status_m} /bin/sh /usr/sbin/r
24282 1833 treebear S 1500 1% 0% sleep 10
1 0 treebear S 1360 1% 0% /sbin/procd

wrong line 3 is blocked by wrong line 2 and wrong line 2 is blocked by wrong line 1.

Hopes for your reply soon.
Thanks a lot.