Date:   Fri, 09 Dec 2016 01:09:21 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Dave Stevenson <linux-media@...tevenson.freeserve.co.uk>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg KH <greg@...ah.com>
Subject: Re: uvcvideo logging kernel warnings on device disconnect

Hi Dave,

(CC'ing LKML and Greg KH)

On Thursday 08 Dec 2016 12:31:55 Dave Stevenson wrote:
> Hi All.
> 
> I'm working with a USB webcam which has been seen to spontaneously
> disconnect when in use. That's a separate issue, but when it does it
> throws a load of warnings into the kernel log if there is a file handle
> on the device open at the time, even if not streaming.
> 
> I've reproduced this with a generic Logitech C270 webcam on:
> - Ubuntu 16.04 (kernel 4.4.0-51) vanilla, and with the latest media tree
> from linuxtv.org
> - Ubuntu 14.04 (kernel 4.4.0-42) vanilla
> - an old 3.10.x tree on an embedded device.
> 
> To reproduce:
> - connect USB webcam.
> - run a simple app that opens /dev/videoX, sleeps for a while, and then
> closes the handle.
> - disconnect the webcam whilst the app is running.
> - read kernel logs - observe warnings. We get the disconnect logged as
> it occurs, but the warnings all occur when the file descriptor is
> closed. (A copy of the logs from my Ubuntu 14.04 machine are below).
> 
> I can fully appreciate that the open file descriptor is holding
> references to a now invalid device, but is there a way to avoid them? Or
> do we really not care and have to put up with the log noise when doing
> such silly things?

This is a known problem, caused by the driver core trying to remove the same 
sysfs attributes group twice.

The group is first removed when the USB device is disconnected. The input 
device and media device created by the uvcvideo driver are children of the USB 
interface device, which is deleted from the system when the camera is 
unplugged. Due to the parent-child relationship, all sysfs attribute groups of 
the children are removed.

Then, when the device node is closed, the media device and input device are 
unregistered, causing the corresponding devices to be deleted too. The driver 
core tries to remove the sysfs attributes groups related to those devices, and 
issues a warning as they have been removed already.

I'm not sure how to fix that, any hint from LKML would be appreciated.

> [157877.297617] usb 1-1: new high-speed USB device number 12 using xhci_hcd
> [157877.698744] usb 1-1: New USB device found, idVendor=046d, idProduct=0825
> [157877.698747] usb 1-1: New USB device strings: Mfr=0, Product=0,
> SerialNumber=2
> [157877.698749] usb 1-1: SerialNumber: E989E680
> [157877.699314] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825)
> [157877.789891] input: UVC Camera (046d:0825) as
> /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1:1.0/input/input688
> [157879.135333] usb 1-1: set resolution quirk: cval->res = 384
> 
> [157885.686043] usb 1-1: USB disconnect, device number 12
> 
> [157901.378104] ------------[ cut here ]------------
> [157901.378111] WARNING: CPU: 2 PID: 21082 at
> /build/linux-lts-xenial-Ev_ZZB/linux-lts-xenial-4.4.0/fs/sysfs/group.c:237
> sysfs_remove_group+0x8d/0x90()
> [157901.378113] sysfs group ffffffff81ecb6c0 not found for kobject 'event13'
> [157901.378114] Modules linked in: snd_usb_audio snd_usbmidi_lib uas
> usb_storage ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c drbg
> ansi_cprng ctr ccm dm_crypt cmac asus_nb_wmi asus_wmi sparse_keymap
> snd_soc_rt5640 snd_soc_rl6231 snd_soc_core arc4 snd_compress ac97_bus
> snd_pcm_dmaengine uvcvideo snd_seq_midi videobuf2_vmalloc
> videobuf2_memops snd_seq_midi_event videobuf2_v4l2 intel_rapl
> videobuf2_core v4l2_common x86_pkg_temp_thermal videodev
> intel_powerclamp media kvm_intel iwlmvm dm_multipath snd_rawmidi kvm
> mac80211 snd_hda_codec_hdmi irqbypass crct10dif_pclmul crc32_pclmul
> snd_hda_codec_conexant snd_hda_codec_generic btusb rfcomm btrtl btbcm
> bnep snd_hda_intel snd_hda_codec btintel iwlwifi bluetooth snd_seq
> snd_hda_core snd_hwdep aesni_intel aes_x86_64 lrw gf128mul glue_helper
> ablk_helper cryptd input_leds cfg80211 snd_pcm joydev nfsd serio_raw
> mei_me snd_seq_device auth_rpcgss nfs_acl mei processor_thermal_device
> intel_soc_dts_iosf lpc_ich snd_timer binfmt_misc shpchp
> intel_pch_thermal nfs lockd grace sunrpc fscache snd soundcore elan_i2c
> i2c_hid hid int3402_thermal int340x_thermal_zone nls_iso8859_1 dw_dmac
> int3400_thermal snd_soc_sst_acpi dw_dmac_core acpi_als acpi_pad
> i2c_designware_platform kfifo_buf i2c_designware_core 8250_dw
> spi_pxa2xx_platform parport_pc industrialio acpi_thermal_rel ppdev
> coretemp mac_hid lp parport btrfs xor raid6_pq dm_mirror dm_region_hash
> dm_log i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect
> sysimgblt fb_sys_fops drm ahci psmouse libahci wmi video sdhci_acpi
> sdhci fjes
> [157901.378184] CPU: 2 PID: 21082 Comm: a.out Not tainted
> 4.4.0-42-generic #62~14.04.1-Ubuntu
> [157901.378185] Hardware name: ASUSTeK COMPUTER INC.
> [157901.378186]  0000000000000000 ffff8800da3a7bb8 ffffffff813d51ec
> ffff8800da3a7c00
> [157901.378188]  ffffffff81cdd3b0 ffff8800da3a7bf0 ffffffff8107d886
> 0000000000000000
> [157901.378190]  ffffffff81ecb6c0 ffff8800bb2e08c0 ffff8800d93f6248
> ffff8801081b9540
> [157901.378192] Call Trace:
> [157901.378197]  [<ffffffff813d51ec>] dump_stack+0x63/0x87
> [157901.378200]  [<ffffffff8107d886>] warn_slowpath_common+0x86/0xc0
> [157901.378202]  [<ffffffff8107d90c>] warn_slowpath_fmt+0x4c/0x50
> [157901.378204]  [<ffffffff812781c8>] ? kernfs_find_and_get_ns+0x48/0x60
> [157901.378206]  [<ffffffff8127b7ad>] sysfs_remove_group+0x8d/0x90
> [157901.378209]  [<ffffffff81534e47>] dpm_sysfs_remove+0x57/0x60
> [157901.378211]  [<ffffffff815281c8>] device_del+0x58/0x260
> [157901.378213]  [<ffffffff814d5fd2>] ? kbd_disconnect+0x22/0x30
> [157901.378216]  [<ffffffff8164a093>] evdev_disconnect+0x23/0x60
> [157901.378218]  [<ffffffff81646348>] __input_unregister_device+0xb8/0x160
> [157901.378219]  [<ffffffff81646497>] input_unregister_device+0x47/0x70
> [157901.378223]  [<ffffffffc0a15a62>] uvc_status_cleanup+0x42/0x50
> [uvcvideo]
> [157901.378226]  [<ffffffffc0a0b1f8>] uvc_delete+0x18/0x150 [uvcvideo]
> [157901.378228]  [<ffffffffc0a0b403>] uvc_release+0x23/0x30 [uvcvideo]
> [157901.378233]  [<ffffffffc09df7bb>] v4l2_device_release+0xcb/0x100
> [videodev]
> [157901.378236]  [<ffffffff81527a02>] device_release+0x32/0xa0
> [157901.378237]  [<ffffffff813d7697>] kobject_cleanup+0x77/0x190
> [157901.378239]  [<ffffffff813d77e5>] kobject_put+0x25/0x50
> [157901.378240]  [<ffffffff81527cf7>] put_device+0x17/0x20
> [157901.378244]  [<ffffffffc09de46d>] v4l2_release+0x4d/0x80 [videodev]
> [157901.378246]  [<ffffffff811ffcc4>] __fput+0xe4/0x210
> [157901.378248]  [<ffffffff811ffe2e>] ____fput+0xe/0x10
> [157901.378251]  [<ffffffff81099fc6>] task_work_run+0x86/0xb0
> [157901.378253]  [<ffffffff81078806>] exit_to_usermode_loop+0x73/0xa2
> [157901.378255]  [<ffffffff81003a6e>] syscall_return_slowpath+0x4e/0x60
> [157901.378258]  [<ffffffff817fa658>] int_ret_from_sys_call+0x25/0x8f
> [157901.378259] ---[ end trace f6d203eeef04d0d8 ]---
> [157901.398109] ------------[ cut here ]------------
> [157901.398117] WARNING: CPU: 2 PID: 21082 at
> /build/linux-lts-xenial-Ev_ZZB/linux-lts-xenial-4.4.0/fs/sysfs/group.c:237
> sysfs_remove_group+0x8d/0x90()
> [157901.398119] sysfs group ffffffff81ecb6c0 not found for kobject
> 'input688'
> [157901.398120] Modules linked in: snd_usb_audio snd_usbmidi_lib uas
> usb_storage ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c drbg
> ansi_cprng ctr ccm dm_crypt cmac asus_nb_wmi asus_wmi sparse_keymap
> snd_soc_rt5640 snd_soc_rl6231 snd_soc_core arc4 snd_compress ac97_bus
> snd_pcm_dmaengine uvcvideo snd_seq_midi videobuf2_vmalloc
> videobuf2_memops snd_seq_midi_event videobuf2_v4l2 intel_rapl
> videobuf2_core v4l2_common x86_pkg_temp_thermal videodev
> intel_powerclamp media kvm_intel iwlmvm dm_multipath snd_rawmidi kvm
> mac80211 snd_hda_codec_hdmi irqbypass crct10dif_pclmul crc32_pclmul
> snd_hda_codec_conexant snd_hda_codec_generic btusb rfcomm btrtl btbcm
> bnep snd_hda_intel snd_hda_codec btintel iwlwifi bluetooth snd_seq
> snd_hda_core snd_hwdep aesni_intel aes_x86_64 lrw gf128mul glue_helper
> ablk_helper cryptd input_leds cfg80211 snd_pcm joydev nfsd serio_raw
> mei_me snd_seq_device auth_rpcgss nfs_acl mei processor_thermal_device
> intel_soc_dts_iosf lpc_ich snd_timer binfmt_misc shpchp
> intel_pch_thermal nfs lockd grace sunrpc fscache snd soundcore elan_i2c
> i2c_hid hid int3402_thermal int340x_thermal_zone nls_iso8859_1 dw_dmac
> int3400_thermal snd_soc_sst_acpi dw_dmac_core acpi_als acpi_pad
> i2c_designware_platform kfifo_buf i2c_designware_core 8250_dw
> spi_pxa2xx_platform parport_pc industrialio acpi_thermal_rel ppdev
> coretemp mac_hid lp parport btrfs xor raid6_pq dm_mirror dm_region_hash
> dm_log i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect
> sysimgblt fb_sys_fops drm ahci psmouse libahci wmi video sdhci_acpi
> sdhci fjes
> [157901.398205] CPU: 2 PID: 21082 Comm: a.out Tainted: G W
> 4.4.0-42-generic #62~14.04.1-Ubuntu
> [157901.398207] Hardware name: ASUSTeK COMPUTER INC.
> [157901.398209]  0000000000000000 ffff8800da3a7be0 ffffffff813d51ec
> ffff8800da3a7c28
> [157901.398213]  ffffffff81cdd3b0 ffff8800da3a7c18 ffffffff8107d886
> 0000000000000000
> [157901.398216]  ffffffff81ecb6c0 ffff8800d93f6258 ffff8801322ef430
> ffff8801081b9540
> [157901.398218] Call Trace:
> [157901.398224]  [<ffffffff813d51ec>] dump_stack+0x63/0x87
> [157901.398228]  [<ffffffff8107d886>] warn_slowpath_common+0x86/0xc0
> [157901.398231]  [<ffffffff8107d90c>] warn_slowpath_fmt+0x4c/0x50
> [157901.398234]  [<ffffffff812781c8>] ? kernfs_find_and_get_ns+0x48/0x60
> [157901.398237]  [<ffffffff8127b7ad>] sysfs_remove_group+0x8d/0x90
> [157901.398241]  [<ffffffff81534e47>] dpm_sysfs_remove+0x57/0x60
> [157901.398244]  [<ffffffff815281c8>] device_del+0x58/0x260
> [157901.398248]  [<ffffffff810bd8e4>] ? __wake_up+0x44/0x50
> [157901.398251]  [<ffffffff816463d2>] __input_unregister_device+0x142/0x160
> [157901.398254]  [<ffffffff81646497>] input_unregister_device+0x47/0x70
> [157901.398261]  [<ffffffffc0a15a62>] uvc_status_cleanup+0x42/0x50
> [uvcvideo]
> [157901.398264]  [<ffffffffc0a0b1f8>] uvc_delete+0x18/0x150 [uvcvideo]
> [157901.398267]  [<ffffffffc0a0b403>] uvc_release+0x23/0x30 [uvcvideo]
> [157901.398274]  [<ffffffffc09df7bb>] v4l2_device_release+0xcb/0x100
> [videodev]
> [157901.398277]  [<ffffffff81527a02>] device_release+0x32/0xa0
> [157901.398280]  [<ffffffff813d7697>] kobject_cleanup+0x77/0x190
> [157901.398282]  [<ffffffff813d77e5>] kobject_put+0x25/0x50
> [157901.398283]  [<ffffffff81527cf7>] put_device+0x17/0x20
> [157901.398290]  [<ffffffffc09de46d>] v4l2_release+0x4d/0x80 [videodev]
> [157901.398293]  [<ffffffff811ffcc4>] __fput+0xe4/0x210
> [157901.398296]  [<ffffffff811ffe2e>] ____fput+0xe/0x10
> [157901.398299]  [<ffffffff81099fc6>] task_work_run+0x86/0xb0
> [157901.398302]  [<ffffffff81078806>] exit_to_usermode_loop+0x73/0xa2
> [157901.398305]  [<ffffffff81003a6e>] syscall_return_slowpath+0x4e/0x60
> [157901.398309]  [<ffffffff817fa658>] int_ret_from_sys_call+0x25/0x8f
> [157901.398312] ---[ end trace f6d203eeef04d0d9 ]---
> [157901.398320] ------------[ cut here ]------------
> [157901.398323] WARNING: CPU: 2 PID: 21082 at
> /build/linux-lts-xenial-Ev_ZZB/linux-lts-xenial-4.4.0/fs/sysfs/group.c:237
> sysfs_remove_group+0x8d/0x90()
> [157901.398325] sysfs group ffffffff81ee8de0 not found for kobject
> 'input688'
> [157901.398326] Modules linked in: snd_usb_audio snd_usbmidi_lib uas
> usb_storage ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c drbg
> ansi_cprng ctr ccm dm_crypt cmac asus_nb_wmi asus_wmi sparse_keymap
> snd_soc_rt5640 snd_soc_rl6231 snd_soc_core arc4 snd_compress ac97_bus
> snd_pcm_dmaengine uvcvideo snd_seq_midi videobuf2_vmalloc
> videobuf2_memops snd_seq_midi_event videobuf2_v4l2 intel_rapl
> videobuf2_core v4l2_common x86_pkg_temp_thermal videodev
> intel_powerclamp media kvm_intel iwlmvm dm_multipath snd_rawmidi kvm
> mac80211 snd_hda_codec_hdmi irqbypass crct10dif_pclmul crc32_pclmul
> snd_hda_codec_conexant snd_hda_codec_generic btusb rfcomm btrtl btbcm
> bnep snd_hda_intel snd_hda_codec btintel iwlwifi bluetooth snd_seq
> snd_hda_core snd_hwdep aesni_intel aes_x86_64 lrw gf128mul glue_helper
> ablk_helper cryptd input_leds cfg80211 snd_pcm joydev nfsd serio_raw
> mei_me snd_seq_device auth_rpcgss nfs_acl mei processor_thermal_device
> intel_soc_dts_iosf lpc_ich snd_timer binfmt_misc shpchp
> intel_pch_thermal nfs lockd grace sunrpc fscache snd soundcore elan_i2c
> i2c_hid hid int3402_thermal int340x_thermal_zone nls_iso8859_1 dw_dmac
> int3400_thermal snd_soc_sst_acpi dw_dmac_core acpi_als acpi_pad
> i2c_designware_platform kfifo_buf i2c_designware_core 8250_dw
> spi_pxa2xx_platform parport_pc industrialio acpi_thermal_rel ppdev
> coretemp mac_hid lp parport btrfs xor raid6_pq dm_mirror dm_region_hash
> dm_log i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect
> sysimgblt fb_sys_fops drm ahci psmouse libahci wmi video sdhci_acpi
> sdhci fjes
> [157901.398381] CPU: 2 PID: 21082 Comm: a.out Tainted: G W
> 4.4.0-42-generic #62~14.04.1-Ubuntu
> [157901.398382] Hardware name: ASUSTeK COMPUTER INC.
> [157901.398383]  0000000000000000 ffff8800da3a7ba8 ffffffff813d51ec
> ffff8800da3a7bf0
> [157901.398385]  ffffffff81cdd3b0 ffff8800da3a7be0 ffffffff8107d886
> 0000000000000000
> [157901.398387]  ffffffff81ee8de0 ffff8800d93f6258 ffffffff81ee8bc0
> ffff8801081b9540
> [157901.398388] Call Trace:
> [157901.398391]  [<ffffffff813d51ec>] dump_stack+0x63/0x87
> [157901.398393]  [<ffffffff8107d886>] warn_slowpath_common+0x86/0xc0
> [157901.398395]  [<ffffffff8107d90c>] warn_slowpath_fmt+0x4c/0x50
> [157901.398397]  [<ffffffff812781c8>] ? kernfs_find_and_get_ns+0x48/0x60
> [157901.398399]  [<ffffffff8127b7ad>] sysfs_remove_group+0x8d/0x90
> [157901.398400]  [<ffffffff8127b85e>] sysfs_remove_groups+0x2e/0x50
> [157901.398403]  [<ffffffff8152794e>] device_remove_attrs+0x5e/0x80
> [157901.398404]  [<ffffffff815282a1>] device_del+0x131/0x260
> [157901.398406]  [<ffffffff810bd8e4>] ? __wake_up+0x44/0x50
> [157901.398408]  [<ffffffff816463d2>] __input_unregister_device+0x142/0x160
> [157901.398409]  [<ffffffff81646497>] input_unregister_device+0x47/0x70
> [157901.398412]  [<ffffffffc0a15a62>] uvc_status_cleanup+0x42/0x50
> [uvcvideo]
> [157901.398415]  [<ffffffffc0a0b1f8>] uvc_delete+0x18/0x150 [uvcvideo]
> [157901.398417]  [<ffffffffc0a0b403>] uvc_release+0x23/0x30 [uvcvideo]
> [157901.398421]  [<ffffffffc09df7bb>] v4l2_device_release+0xcb/0x100
> [videodev]
> [157901.398423]  [<ffffffff81527a02>] device_release+0x32/0xa0
> [157901.398425]  [<ffffffff813d7697>] kobject_cleanup+0x77/0x190
> [157901.398426]  [<ffffffff813d77e5>] kobject_put+0x25/0x50
> [157901.398427]  [<ffffffff81527cf7>] put_device+0x17/0x20
> [157901.398431]  [<ffffffffc09de46d>] v4l2_release+0x4d/0x80 [videodev]
> [157901.398433]  [<ffffffff811ffcc4>] __fput+0xe4/0x210
> [157901.398435]  [<ffffffff811ffe2e>] ____fput+0xe/0x10
> [157901.398437]  [<ffffffff81099fc6>] task_work_run+0x86/0xb0
> [157901.398439]  [<ffffffff81078806>] exit_to_usermode_loop+0x73/0xa2
> [157901.398441]  [<ffffffff81003a6e>] syscall_return_slowpath+0x4e/0x60
> [157901.398443]  [<ffffffff817fa658>] int_ret_from_sys_call+0x25/0x8f
> [157901.398444] ---[ end trace f6d203eeef04d0da ]---
> [157901.398445] ------------[ cut here ]------------
> [157901.398447] WARNING: CPU: 2 PID: 21082 at
> /build/linux-lts-xenial-Ev_ZZB/linux-lts-xenial-4.4.0/fs/sysfs/group.c:237
> sysfs_remove_group+0x8d/0x90()
> [157901.398448] sysfs group ffffffff81ee8c20 not found for kobject
> 'input688'
> [157901.398449] Modules linked in: snd_usb_audio snd_usbmidi_lib uas
> usb_storage ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c drbg
> ansi_cprng ctr ccm dm_crypt cmac asus_nb_wmi asus_wmi sparse_keymap
> snd_soc_rt5640 snd_soc_rl6231 snd_soc_core arc4 snd_compress ac97_bus
> snd_pcm_dmaengine uvcvideo snd_seq_midi videobuf2_vmalloc
> videobuf2_memops snd_seq_midi_event videobuf2_v4l2 intel_rapl
> videobuf2_core v4l2_common x86_pkg_temp_thermal videodev
> intel_powerclamp media kvm_intel iwlmvm dm_multipath snd_rawmidi kvm
> mac80211 snd_hda_codec_hdmi irqbypass crct10dif_pclmul crc32_pclmul
> snd_hda_codec_conexant snd_hda_codec_generic btusb rfcomm btrtl btbcm
> bnep snd_hda_intel snd_hda_codec btintel iwlwifi bluetooth snd_seq
> snd_hda_core snd_hwdep aesni_intel aes_x86_64 lrw gf128mul glue_helper
> ablk_helper cryptd input_leds cfg80211 snd_pcm joydev nfsd serio_raw
> mei_me snd_seq_device auth_rpcgss nfs_acl mei processor_thermal_device
> intel_soc_dts_iosf lpc_ich snd_timer binfmt_misc shpchp
> intel_pch_thermal nfs lockd grace sunrpc fscache snd soundcore elan_i2c
> i2c_hid hid int3402_thermal int340x_thermal_zone nls_iso8859_1 dw_dmac
> int3400_thermal snd_soc_sst_acpi dw_dmac_core acpi_als acpi_pad
> i2c_designware_platform kfifo_buf i2c_designware_core 8250_dw
> spi_pxa2xx_platform parport_pc industrialio acpi_thermal_rel ppdev
> coretemp mac_hid lp parport btrfs xor raid6_pq dm_mirror dm_region_hash
> dm_log i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect
> sysimgblt fb_sys_fops drm ahci psmouse libahci wmi video sdhci_acpi
> sdhci fjes
> [157901.398495] CPU: 2 PID: 21082 Comm: a.out Tainted: G W
> 4.4.0-42-generic #62~14.04.1-Ubuntu
> [157901.398496] Hardware name: ASUSTeK COMPUTER INC.
> [157901.398497]  0000000000000000 ffff8800da3a7ba8 ffffffff813d51ec
> ffff8800da3a7bf0
> [157901.398498]  ffffffff81cdd3b0 ffff8800da3a7be0 ffffffff8107d886
> 0000000000000000
> [157901.398500]  ffffffff81ee8c20 ffff8800d93f6258 ffffffff81ee8bc0
> ffff8801081b9540
> [157901.398502] Call Trace:
> [157901.398504]  [<ffffffff813d51ec>] dump_stack+0x63/0x87
> [157901.398506]  [<ffffffff8107d886>] warn_slowpath_common+0x86/0xc0
> [157901.398508]  [<ffffffff8107d90c>] warn_slowpath_fmt+0x4c/0x50
> [157901.398509]  [<ffffffff812781c8>] ? kernfs_find_and_get_ns+0x48/0x60
> [157901.398511]  [<ffffffff8127b7ad>] sysfs_remove_group+0x8d/0x90
> [157901.398513]  [<ffffffff8127b85e>] sysfs_remove_groups+0x2e/0x50
> [157901.398515]  [<ffffffff8152794e>] device_remove_attrs+0x5e/0x80
> [157901.398517]  [<ffffffff815282a1>] device_del+0x131/0x260
> [157901.398519]  [<ffffffff810bd8e4>] ? __wake_up+0x44/0x50
> [157901.398520]  [<ffffffff816463d2>] __input_unregister_device+0x142/0x160
> [157901.398522]  [<ffffffff81646497>] input_unregister_device+0x47/0x70
> [157901.398524]  [<ffffffffc0a15a62>] uvc_status_cleanup+0x42/0x50
> [uvcvideo]
> [157901.398526]  [<ffffffffc0a0b1f8>] uvc_delete+0x18/0x150 [uvcvideo]
> [157901.398528]  [<ffffffffc0a0b403>] uvc_release+0x23/0x30 [uvcvideo]
> [157901.398532]  [<ffffffffc09df7bb>] v4l2_device_release+0xcb/0x100
> [videodev]
> [157901.398535]  [<ffffffff81527a02>] device_release+0x32/0xa0
> [157901.398536]  [<ffffffff813d7697>] kobject_cleanup+0x77/0x190
> [157901.398537]  [<ffffffff813d77e5>] kobject_put+0x25/0x50
> [157901.398538]  [<ffffffff81527cf7>] put_device+0x17/0x20
> [157901.398542]  [<ffffffffc09de46d>] v4l2_release+0x4d/0x80 [videodev]
> [157901.398544]  [<ffffffff811ffcc4>] __fput+0xe4/0x210
> [157901.398546]  [<ffffffff811ffe2e>] ____fput+0xe/0x10
> [157901.398548]  [<ffffffff81099fc6>] task_work_run+0x86/0xb0
> [157901.398549]  [<ffffffff81078806>] exit_to_usermode_loop+0x73/0xa2
> [157901.398551]  [<ffffffff81003a6e>] syscall_return_slowpath+0x4e/0x60
> [157901.398553]  [<ffffffff817fa658>] int_ret_from_sys_call+0x25/0x8f
> [157901.398554] ---[ end trace f6d203eeef04d0db ]---
> [157901.398600] ------------[ cut here ]------------
> [157901.398603] WARNING: CPU: 2 PID: 21082 at
> /build/linux-lts-xenial-Ev_ZZB/linux-lts-xenial-4.4.0/fs/sysfs/group.c:237
> sysfs_remove_group+0x8d/0x90()
> [157901.398605] sysfs group ffffffff81ecb6c0 not found for kobject 'media1'
> [157901.398606] Modules linked in: snd_usb_audio snd_usbmidi_lib uas
> usb_storage ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c drbg
> ansi_cprng ctr ccm dm_crypt cmac asus_nb_wmi asus_wmi sparse_keymap
> snd_soc_rt5640 snd_soc_rl6231 snd_soc_core arc4 snd_compress ac97_bus
> snd_pcm_dmaengine uvcvideo snd_seq_midi videobuf2_vmalloc
> videobuf2_memops snd_seq_midi_event videobuf2_v4l2 intel_rapl
> videobuf2_core v4l2_common x86_pkg_temp_thermal videodev
> intel_powerclamp media kvm_intel iwlmvm dm_multipath snd_rawmidi kvm
> mac80211 snd_hda_codec_hdmi irqbypass crct10dif_pclmul crc32_pclmul
> snd_hda_codec_conexant snd_hda_codec_generic btusb rfcomm btrtl btbcm
> bnep snd_hda_intel snd_hda_codec btintel iwlwifi bluetooth snd_seq
> snd_hda_core snd_hwdep aesni_intel aes_x86_64 lrw gf128mul glue_helper
> ablk_helper cryptd input_leds cfg80211 snd_pcm joydev nfsd serio_raw
> mei_me snd_seq_device auth_rpcgss nfs_acl mei processor_thermal_device
> intel_soc_dts_iosf lpc_ich snd_timer binfmt_misc shpchp
> intel_pch_thermal nfs lockd grace sunrpc fscache snd soundcore elan_i2c
> i2c_hid hid int3402_thermal int340x_thermal_zone nls_iso8859_1 dw_dmac
> int3400_thermal snd_soc_sst_acpi dw_dmac_core acpi_als acpi_pad
> i2c_designware_platform kfifo_buf i2c_designware_core 8250_dw
> spi_pxa2xx_platform parport_pc industrialio acpi_thermal_rel ppdev
> coretemp mac_hid lp parport btrfs xor raid6_pq dm_mirror dm_region_hash
> dm_log i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect
> sysimgblt fb_sys_fops drm ahci psmouse libahci wmi video sdhci_acpi
> sdhci fjes
> [157901.398654] CPU: 2 PID: 21082 Comm: a.out Tainted: G W
> 4.4.0-42-generic #62~14.04.1-Ubuntu
> [157901.398655] Hardware name: ASUSTeK COMPUTER INC.
> [157901.398656]  0000000000000000 ffff8800da3a7be0 ffffffff813d51ec
> ffff8800da3a7c28
> [157901.398658]  ffffffff81cdd3b0 ffff8800da3a7c18 ffffffff8107d886
> 0000000000000000
> [157901.398660]  ffffffff81ecb6c0 ffff8800d93f2090 ffff8801322ef430
> ffff8801081b9540
> [157901.398661] Call Trace:
> [157901.398664]  [<ffffffff813d51ec>] dump_stack+0x63/0x87
> [157901.398666]  [<ffffffff8107d886>] warn_slowpath_common+0x86/0xc0
> [157901.398668]  [<ffffffff8107d90c>] warn_slowpath_fmt+0x4c/0x50
> [157901.398669]  [<ffffffff812781c8>] ? kernfs_find_and_get_ns+0x48/0x60
> [157901.398671]  [<ffffffff8127b7ad>] sysfs_remove_group+0x8d/0x90
> [157901.398673]  [<ffffffff81534e47>] dpm_sysfs_remove+0x57/0x60
> [157901.398675]  [<ffffffff815281c8>] device_del+0x58/0x260
> [157901.398676]  [<ffffffff815283ee>] device_unregister+0x1e/0x60
> [157901.398680]  [<ffffffffc07c2f11>] media_devnode_unregister+0x41/0x50
> [media]
> [157901.398683]  [<ffffffffc07c2315>] media_device_unregister+0x55/0x60
> [media]
> [157901.398685]  [<ffffffffc0a0b31d>] uvc_delete+0x13d/0x150 [uvcvideo]
> [157901.398687]  [<ffffffffc0a0b403>] uvc_release+0x23/0x30 [uvcvideo]
> [157901.398691]  [<ffffffffc09df7bb>] v4l2_device_release+0xcb/0x100
> [videodev]
> [157901.398694]  [<ffffffff81527a02>] device_release+0x32/0xa0
> [157901.398695]  [<ffffffff813d7697>] kobject_cleanup+0x77/0x190
> [157901.398696]  [<ffffffff813d77e5>] kobject_put+0x25/0x50
> [157901.398698]  [<ffffffff81527cf7>] put_device+0x17/0x20
> [157901.398701]  [<ffffffffc09de46d>] v4l2_release+0x4d/0x80 [videodev]
> [157901.398706]  [<ffffffff811ffcc4>] __fput+0xe4/0x210
> [157901.398708]  [<ffffffff811ffe2e>] ____fput+0xe/0x10
> [157901.398710]  [<ffffffff81099fc6>] task_work_run+0x86/0xb0
> [157901.398711]  [<ffffffff81078806>] exit_to_usermode_loop+0x73/0xa2
> [157901.398713]  [<ffffffff81003a6e>] syscall_return_slowpath+0x4e/0x60
> [157901.398715]  [<ffffffff817fa658>] int_ret_from_sys_call+0x25/0x8f
> [157901.398716] ---[ end trace f6d203eeef04d0dc ]---

-- 
Regards,

Laurent Pinchart

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