While running CPU hotplug testing on arm64 db410c device the following kernel warning noticed on linux stable-rc 4.19 branch. I did not bisect this problem yet.

Kernel Warning log: ------------------------------ [ 290.463053] CPU1: shutdown [ 290.463107] psci: CPU1 killed (polled 0 ms) [ 290.527026] CPU2: shutdown [ 290.527072] psci: CPU2 killed (polled 0 ms) [ 290.579064] CPU3: shutdown [ 290.579098] psci: CPU3 killed (polled 0 ms) [ 290.612295] Detected VIPT I-cache on CPU1 [ 290.612361] CPU1: Booted secondary processor 0x0000000001 [0x410fd030] [ 290.684091] Detected VIPT I-cache on CPU2 [ 290.684158] CPU2: Booted secondary processor 0x0000000002 [0x410fd030] [ 290.684464] WARNING: CPU: 2 PID: 20 at /usr/src/kernel/kernel/workqueue.c:4762 workqueue_online_cpu+0x18c/0x428 [ 290.697731] Modules linked in: sch_ingress algif_hash test_bpf snd_soc_hdmi_codec crc32_ce adv7511 cec rfkill msm snd_soc_msm8916_analog snd_soc_lpass_apq8016 mdt_loader snd_soc_lpass_cpu snd_soc_msm8916_digital snd_soc_apq8016_sbc drm_kms_helper snd_soc_lpass_platform drm drm_panel_orientation_quirks fuse [last unloaded: test_bpf] [ 290.714992] CPU: 2 PID: 20 Comm: cpuhp/2 Tainted: G D 4.19.156-rc1 #1 [ 290.737221] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT) [ 290.745033] pstate: 40000005 (nZcv daif -PAN -UAO) [ 290.751718] pc : workqueue_online_cpu+0x18c/0x428 [ 290.756316] lr : workqueue_online_cpu+0x140/0x428 [ 290.761086] sp : ffff00000a90bc90 [ 290.765774] x29: ffff00000a90bc90 x28: ffff00000989bfc8 [ 290.769074] x27: ffff80003ac81a00 x26: ffff000009914a00 [ 290.774456] x25: ffff00000989c068 x24: ffff00000a90bd24 [ 290.779752] x23: 0000000000000002 x22: ffff80003fe7a4d0 [ 290.785047] x21: ffff000009914000 x20: ffff00000989bf68 [ 290.790341] x19: ffff80003fe7a1c0 x18: ffffffffffffffff [ 290.795636] x17: 0000000000000000 x16: 0000000000000000 [ 290.800932] x15: ffff00000987fa48 x14: ffff00000a69c530 [ 290.806227] x13: 0000000000000040 x12: 0000000000000228 [ 290.811522] x11: 0000000000000000 x10: ffff00000987fa48 [ 290.816816] x9 : ffff000009914000 x8 : ffff00000987fa48 [ 290.822112] x7 : ffff00000812d338 x6 : 0000000000000000 [ 290.827407] x5 : 0000000000000000 x4 : ffff80003c59ad00 [ 290.832702] x3 : ffff000009880000 x2 : 8b427f82388e4a00 [ 290.837997] x1 : 0000000000000000 x0 : 00000000ffffffea [ 290.843293] Call trace: [ 290.848588] workqueue_online_cpu+0x18c/0x428 [ 290.850762] cpuhp_invoke_callback+0xe8/0xd18 [ 290.855274] cpuhp_thread_fun+0x1a8/0x250 [ 290.859613] smpboot_thread_fn+0x1c4/0x2d0 [ 290.863606] kthread+0x150/0x168 [ 290.867600] ret_from_fork+0x10/0x1c [ 290.870983] irq event stamp: 158 [ 290.874546] hardirqs last enabled at (157): [<ffff000009001784>] _raw_spin_unlock_irqrestore+0x74/0xb0 [ 290.877765] hardirqs last disabled at (158): [<ffff000008ffa1e0>] __schedule+0xc0/0xbc0 [ 290.886878] softirqs last enabled at (0): [<ffff0000080efac8>] copy_process.isra.5.part.6+0x490/0x1b20 [ 290.894861] softirqs last disabled at (0): [<0000000000000000>] (null) [ 290.904233] ---[ end trace 7a9cb6558129244f ]---

steps to reproduce: ---------------------------------- Total number of CPU[0-3] offline each CPU 1, 2 and 3 online each CPU 1, 2 and 3

echo 0 > /sys/devices/system/cpu/cpu1/online echo 0 > /sys/devices/system/cpu/cpu2/online echo 0 > /sys/devices/system/cpu/cpu3/online echo 1 > /sys/devices/system/cpu/cpu1/online echo 1 > /sys/devices/system/cpu/cpu2/online echo 1 > /sys/devices/system/cpu/cpu3/online

Reported-by: Naresh Kamboju naresh.kamboju@linaro.org

metadata: git branch: linux-4.19.y git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git git describe: v4.19.155-72-g4d10cdd4ac50 kernel-config: http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/dragonboard-410c/lkf...

ref: https://lkft.validation.linaro.org/scheduler/job/1927553#L3876 https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-4.19.y/build/v4.19....