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Subject[BUG] dev_pm_opp refcount issue on Arm Juno r0
Date
Hi,

While running some hotplug torture test [1] on my Juno r0 I came across
the follow splat:

[ 716.561862] ------------[ cut here ]------------
[ 716.566451] refcount_t: underflow; use-after-free.
[ 716.571240] WARNING: CPU: 2 PID: 18 at lib/refcount.c:280 refcount_dec_not_one+0x9c/0xc0
[ 716.579246] Modules linked in:
[ 716.582269] CPU: 2 PID: 18 Comm: cpuhp/2 Not tainted 4.20.0-rc7 #39
[ 716.588469] Hardware name: ARM Juno development board (r0) (DT)
[ 716.594326] pstate: 40000005 (nZcv daif -PAN -UAO)
[ 716.599065] pc : refcount_dec_not_one+0x9c/0xc0
[ 716.603546] lr : refcount_dec_not_one+0x9c/0xc0
[ 716.608024] sp : ffff00000a063c70
[ 716.611299] x29: ffff00000a063c70 x28: 0000000000000000
[ 716.616555] x27: 0000000000000000 x26: 0000000000000002
[ 716.621810] x25: ffff000009169000 x24: ffff000008f8e1b0
[ 716.627065] x23: ffff000008ce0920 x22: 00000000ffffffff
[ 716.632319] x21: ffff000009169000 x20: ffff8009762a2664
[ 716.637574] x19: ffff000009294a90 x18: 0000000000000400
[ 716.642828] x17: 0000000000000000 x16: 0000000000000000
[ 716.648082] x15: 0000000000000000 x14: 0000000000000400
[ 716.653336] x13: 000000000000023f x12: 0000000000043705
[ 716.658590] x11: 0000000000000108 x10: 0000000000000960
[ 716.663844] x9 : ffff00000a063970 x8 : ffff800976943ec0
[ 716.669098] x7 : 0000000000000000 x6 : ffff80097ff720b8
[ 716.674353] x5 : ffff80097ff720b8 x4 : 0000000000000000
[ 716.679607] x3 : ffff80097ff78e68 x2 : ffff80097ff720b8
[ 716.684861] x1 : 6374e2a7925c1100 x0 : 0000000000000000
[ 716.690115] Call trace:
[ 716.692532] refcount_dec_not_one+0x9c/0xc0
[ 716.696669] refcount_dec_and_mutex_lock+0x18/0x70
[ 716.701409] _put_opp_list_kref+0x28/0x50
[ 716.705373] _dev_pm_opp_find_and_remove_table+0x24/0x88
[ 716.710628] _dev_pm_opp_cpumask_remove_table+0x50/0xa0
[ 716.715796] dev_pm_opp_cpumask_remove_table+0x10/0x18
[ 716.720879] scpi_cpufreq_exit+0x40/0x50
[ 716.724758] cpufreq_offline+0x108/0x1e0
[ 716.728637] cpuhp_cpufreq_offline+0xc/0x18
[ 716.732775] cpuhp_invoke_callback+0x84/0x248
[ 716.737084] cpuhp_thread_fun+0xc4/0x148
[ 716.740963] smpboot_thread_fn+0x168/0x268
[ 716.745013] kthread+0x128/0x130
[ 716.748204] ret_from_fork+0x10/0x18
[ 716.751738] ---[ end trace 0c658e0103aac29d ]---

The test produces a script [2] that can be found at the end of this email.

Kernel:
7566ec393f41 ("Linux 4.20-rc7")
Config:
arm64 defconfig w/ CONFIG_MOUSE_PS2=n
Firmware:
ARM V2M_Juno Firmware v1.4.4
Build Date: Jul 26 2016

NOTICE: BL31: v1.3(debug):v1.3-567-g3fb340a2
NOTICE: BL31: Built : 18:52:35, Apr 25 2017

Cheers,
Valentin

---

[1]: https://github.com/ARM-software/lisa/blob/next/lisa/tests/kernel/hotplug/torture.py

[2]: random_cpuhp.sh
#!/bin/sh
set -e
while true
do
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.055
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.084
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.014
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.069
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.037
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.075
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.088
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.064
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.049
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.024
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.097
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.013
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.094
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.073
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.022
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.057
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.054
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.022
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.018
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.057
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.046
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.018
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.016
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.016
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.044
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.046
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.093
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.098
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.072
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.013
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.099
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.07
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.022
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.041
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.098
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.032
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.043
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.076
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.072
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.036
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.042
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.016
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.07
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.018
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.055
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.096
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.012
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.093
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.086
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.09
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.077
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.01
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.026
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.049
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.083
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.096
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.067
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.083
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.089
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.065
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.066
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.099
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.08
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.076
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.01
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.017
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.049
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.057
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.083
echo 0 > /sys/devices/system/cpu/cpu4/online
sleep 0.037
echo 0 > /sys/devices/system/cpu/cpu0/online
sleep 0.04
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.051
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.03
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.067
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.011
echo 1 > /sys/devices/system/cpu/cpu4/online
sleep 0.041
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.057
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.082
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.067
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.069
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.062
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.074
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.025
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.016
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.017
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.025
echo 0 > /sys/devices/system/cpu/cpu3/online
sleep 0.016
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.082
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.021
echo 0 > /sys/devices/system/cpu/cpu5/online
sleep 0.02
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.035
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.063
echo 0 > /sys/devices/system/cpu/cpu1/online
sleep 0.064
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.029
echo 1 > /sys/devices/system/cpu/cpu1/online
sleep 0.096
echo 1 > /sys/devices/system/cpu/cpu3/online
sleep 0.073
echo 1 > /sys/devices/system/cpu/cpu0/online
sleep 0.049
echo 1 > /sys/devices/system/cpu/cpu5/online
sleep 0.065
echo 0 > /sys/devices/system/cpu/cpu2/online
sleep 0.024
echo 1 > /sys/devices/system/cpu/cpu2/online
sleep 0.092
done &
LOOP_PID=$!
sleep 10
[ $(ps -q $LOOP_PID | wc -l) -gt 1 ] && kill -9 $LOOP_PID
set +e

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