WARNING: CPU: 2 PID: 42 at drivers/gpu/drm/drm_modeset_lock.c:276

[Stefan Wahren]

Hi,

if i enable PROVE_LOCKING on the Raspberry Pi 3 B+ 
(arm/multi_v7_defconfig) using v6.1 (didn't test older versions) i'm 
getting the following warning:

[  204.043396] WARNING: CPU: 2 PID: 42 at 
drivers/gpu/drm/drm_modeset_lock.c:276 drm_modeset_drop_locks+0x6c/0x70
[  204.043426] Modules linked in: aes_arm aes_generic cmac 
bcm2835_v4l2(C) bcm2835_mmal_vchiq(C) videobuf2_vmalloc videobuf2_memops 
videobuf2_v4l2 videobuf2_common videodev mc snd_bcm2835(C) crc32_arm_ce 
brcmfmac brcmutil vc4 snd_soc_hdmi_codec sha256_generic libsha256 
snd_soc_core ac97_bus snd_pcm_dmaengine snd_pcm sha256_arm snd_timer 
cfg80211 onboard_usb_hub snd hci_uart raspberrypi_hwmon soundcore 
drm_dma_helper btbcm bluetooth ecdh_generic bcm2835_thermal ecc libaes 
vchiq(C) microchip lan78xx
[  204.043820] CPU: 2 PID: 42 Comm: kworker/2:1 Tainted: G C         
6.1.0-00007-g22fada783b9f #31
[  204.043833] Hardware name: BCM2835
[  204.043842] Workqueue: events output_poll_execute
[  204.043866]  unwind_backtrace from show_stack+0x10/0x14
[  204.043886]  show_stack from dump_stack_lvl+0x58/0x70
[  204.043903]  dump_stack_lvl from __warn+0xc8/0x1e8
[  204.043920]  __warn from warn_slowpath_fmt+0x5c/0xb8
[  204.043936]  warn_slowpath_fmt from drm_modeset_drop_locks+0x6c/0x70
[  204.043952]  drm_modeset_drop_locks from 
drm_helper_probe_detect_ctx+0xd4/0x124
[  204.043969]  drm_helper_probe_detect_ctx from 
output_poll_execute+0x154/0x230
[  204.043986]  output_poll_execute from process_one_work+0x288/0x708
[  204.044004]  process_one_work from worker_thread+0x54/0x50c
[  204.044020]  worker_thread from kthread+0xe8/0x104
[  204.044034]  kthread from ret_from_fork+0x14/0x2c
[  204.044048] Exception stack(0xf0915fb0 to 0xf0915ff8)
[  204.044059] 5fa0:                                     00000000 
00000000 00000000 00000000
[  204.044070] 5fc0: 00000000 00000000 00000000 00000000 00000000 
00000000 00000000 00000000
[  204.044080] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[  204.044090] irq event stamp: 33189
[  204.044100] hardirqs last  enabled at (33195): [<c03ba3b4>] 
__up_console_sem+0x50/0x60
[  204.044120] hardirqs last disabled at (33200): [<c03ba3a0>] 
__up_console_sem+0x3c/0x60
[  204.044136] softirqs last  enabled at (32836): [<c0366478>] 
process_one_work+0x288/0x708
[  204.044152] softirqs last disabled at (32832): [<c0fb7134>] 
neigh_managed_work+0x18/0xa4
[  204.044168] ---[ end trace 0000000000000000 ]---

Best regards