I see similar kernel warnings when removing any bnep interface. 
Typically this happens on shutdown/reboot, but any time the bnep 
interface is taken down.  I reported this to the kernel Bluetooth 
maintainers back in March (March 1, 2018), but that was apparently the 
wrong place to do so.

Each time a bnep interface is disconnected, three kernel WARNINGs are 
emitted on the console.  I see this with the 4.4 and 4.9 kernels.  A 
search (https://patchwork.kernel.org/patch/6450921/) turned up a similar 
issue in a different driver, but I am at a loss to figure out how to fix 
the Bluetooth issue.  It appears that the sys fs entries are being 
deleted twice when the bnep connection is disconnected.  Any ideas on 
how to fix this?

WARNING: CPU: 0 PID: 1618 at fs/sysfs/group.c:237 
sysfs_remove_group+0x4c/0x94
sysfs group 'byte_queue_limits' not found for kobject 'tx-0'
Modules linked in: bnep hci_uart btqca bluetooth rt2800usb rt2800lib 
rt2x00usb rt2x00lib option usb_wwan usbserial
CPU: 0 PID: 1618 Comm: kbnepd bnep0 Tainted: G        W 4.9.83-r5041+ #123
Hardware name: Atmel AT91SAM9
[<c010ca10>] (unwind_backtrace) from [<c010a074>] (show_stack+0x10/0x14)
[<c010a074>] (show_stack) from [<c011df38>] (__warn+0xcc/0xf8)
[<c011df38>] (__warn) from [<c011df98>] (warn_slowpath_fmt+0x34/0x44)
[<c011df98>] (warn_slowpath_fmt) from [<c020d814>] 
(sysfs_remove_group+0x4c/0x94)
[<c020d814>] (sysfs_remove_group) from [<c045d910>] 
(netdev_queue_update_kobjects+0xe4/0x114)
[<c045d910>] (netdev_queue_update_kobjects) from [<c045d9a4>] 
(netdev_unregister_kobject+0x38/0x58)
[<c045d9a4>] (netdev_unregister_kobject) from [<c0442768>] 
(rollback_registered_many+0x29c/0x324)
[<c0442768>] (rollback_registered_many) from [<c0442810>] 
(rollback_registered+0x20/0x34)
[<c0442810>] (rollback_registered) from [<c044288c>] 
(unregister_netdevice_queue+0x68/0xb0)
[<c044288c>] (unregister_netdevice_queue) from [<c04428ec>] 
(unregister_netdev+0x18/0x20)
[<c04428ec>] (unregister_netdev) from [<bf15ca30>] 
(bnep_session+0x660/0x724 [bnep])
[<bf15ca30>] (bnep_session [bnep]) from [<c0136dfc>] (kthread+0xc4/0xd8)
[<c0136dfc>] (kthread) from [<c0106f98>] (ret_from_fork+0x14/0x3c)
---[ end trace d15771e874a78fbc ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1618 at fs/sysfs/group.c:237 
sysfs_remove_group+0x4c/0x94
sysfs group 'power' not found for kobject 'bnep0'
Modules linked in: bnep hci_uart btqca bluetooth rt2800usb rt2800lib 
rt2x00usb rt2x00lib option usb_wwan usbserial
CPU: 0 PID: 1618 Comm: kbnepd bnep0 Tainted: G        W 4.9.83-r5041+ #123
Hardware name: Atmel AT91SAM9
[<c010ca10>] (unwind_backtrace) from [<c010a074>] (show_stack+0x10/0x14)
[<c010a074>] (show_stack) from [<c011df38>] (__warn+0xcc/0xf8)
[<c011df38>] (__warn) from [<c011df98>] (warn_slowpath_fmt+0x34/0x44)
[<c011df98>] (warn_slowpath_fmt) from [<c020d814>] 
(sysfs_remove_group+0x4c/0x94)
[<c020d814>] (sysfs_remove_group) from [<c0356a94>] (device_del+0x44/0x1f4)
[<c0356a94>] (device_del) from [<c0442768>] 
(rollback_registered_many+0x29c/0x324)
[<c0442768>] (rollback_registered_many) from [<c0442810>] 
(rollback_registered+0x20/0x34)
[<c0442810>] (rollback_registered) from [<c044288c>] 
(unregister_netdevice_queue+0x68/0xb0)
[<c044288c>] (unregister_netdevice_queue) from [<c04428ec>] 
(unregister_netdev+0x18/0x20)
[<c04428ec>] (unregister_netdev) from [<bf15ca30>] 
(bnep_session+0x660/0x724 [bnep])
[<bf15ca30>] (bnep_session [bnep]) from [<c0136dfc>] (kthread+0xc4/0xd8)
[<c0136dfc>] (kthread) from [<c0106f98>] (ret_from_fork+0x14/0x3c)
---[ end trace d15771e874a78fbd ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1618 at fs/sysfs/group.c:237 
sysfs_remove_group+0x4c/0x94
sysfs group 'statistics' not found for kobject 'bnep0'
Modules linked in: bnep hci_uart btqca bluetooth rt2800usb rt2800lib 
rt2x00usb rt2x00lib option usb_wwan usbserial
CPU: 0 PID: 1618 Comm: kbnepd bnep0 Tainted: G        W 4.9.83-r5041+ #123
Hardware name: Atmel AT91SAM9
[<c010ca10>] (unwind_backtrace) from [<c010a074>] (show_stack+0x10/0x14)
[<c010a074>] (show_stack) from [<c011df38>] (__warn+0xcc/0xf8)
[<c011df38>] (__warn) from [<c011df98>] (warn_slowpath_fmt+0x34/0x44)
[<c011df98>] (warn_slowpath_fmt) from [<c020d814>] 
(sysfs_remove_group+0x4c/0x94)
[<c020d814>] (sysfs_remove_group) from [<c020d900>] 
(sysfs_remove_groups+0x20/0x30)
[<c020d900>] (sysfs_remove_groups) from [<c035650c>] 
(device_remove_attrs+0x28/0x58)
[<c035650c>] (device_remove_attrs) from [<c0356b8c>] 
(device_del+0x13c/0x1f4)
[<c0356b8c>] (device_del) from [<c0442768>] 
(rollback_registered_many+0x29c/0x324)
[<c0442768>] (rollback_registered_many) from [<c0442810>] 
(rollback_registered+0x20/0x34)
[<c0442810>] (rollback_registered) from [<c044288c>] 
(unregister_netdevice_queue+0x68/0xb0)
[<c044288c>] (unregister_netdevice_queue) from [<c04428ec>] 
(unregister_netdev+0x18/0x20)
[<c04428ec>] (unregister_netdev) from [<bf15ca30>] 
(bnep_session+0x660/0x724 [bnep])
[<bf15ca30>] (bnep_session [bnep]) from [<c0136dfc>] (kthread+0xc4/0xd8)
[<c0136dfc>] (kthread) from [<c0106f98>] (ret_from_fork+0x14/0x3c)
---[ end trace d15771e874a78fbe ]---

Jay

On 9/28/2018 7:26 AM, bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=201269
>
>              Bug ID: 201269
>             Summary: sysfs_remove_group warning in kbnepd
>             Product: Drivers
>             Version: 2.5
>      Kernel Version: 4.9.129
>            Hardware: All
>                  OS: Linux
>                Tree: Mainline
>              Status: NEW
>            Severity: normal
>            Priority: P1
>           Component: Bluetooth
>            Assignee: linux-bluetooth@vger.kernel.org
>            Reporter: kai.ruhnau@live.com
>          Regression: No
>
> I've just gotten a warning in the kernel logs (see below). I was using Bluez
> 5.43 and a manual busctl call to start a NAP Bluetooth-tethering session to
> an
> iPhone, but the iPhone hadn't turned on tethering.
>
> The busctl returned successfully and I had the bnep0 network interface for a
> brief moment before the connection was closed again. I tried to reproduce a
> couple of times without success.
>
>
> [ 4136.114230] ------------[ cut here ]------------
> [ 4136.114260] WARNING: CPU: 0 PID: 427 at fs/sysfs/group.c:237
> sysfs_remove_group+0x90/0x9c
> [ 4136.114265] sysfs group 'byte_queue_limits' not found for kobject 'tx-0'
> [ 4136.114271] Modules linked in:
> [ 4136.114284] CPU: 0 PID: 427 Comm: kbnepd bnep0 Not tainted
> 4.9.129-00093-g98220ccd50ff #180
> [ 4136.114288] Hardware name: Freescale i.MX6 SoloX (Device Tree)
> [ 4136.114292] Backtrace:
> [ 4136.114315] [<c010bbc4>] (dump_backtrace) from [<c010be70>]
> (show_stack+0x18/0x1c)
> [ 4136.114324]  r7:00000009 r6:60070013 r5:00000000 r4:c0e1c230
> [ 4136.114338] [<c010be58>] (show_stack) from [<c03d9ce8>]
> (dump_stack+0x94/0xb0)
> [ 4136.114355] [<c03d9c54>] (dump_stack) from [<c012359c>]
> (__warn+0xd8/0x104)
> [ 4136.114362]  r7:00000009 r6:c0bfe9f8 r5:00000000 r4:ee747da8
> [ 4136.114374] [<c01234c4>] (__warn) from [<c0123604>]
> (warn_slowpath_fmt+0x3c/0x44)
> [ 4136.114383]  r9:00000000 r8:00000000 r7:ee416000 r6:eebc540c r5:c0e605ec
> r4:c0bfea34
> [ 4136.114396] [<c01235cc>] (warn_slowpath_fmt) from [<c027647c>]
> (sysfs_remove_group+0x90/0x9c)
> [ 4136.114401]  r3:c0c8290c r2:c0bfea34
> [ 4136.114405]  r4:00000000
> [ 4136.114419] [<c02763ec>] (sysfs_remove_group) from [<c0788324>]
> (netdev_queue_update_kobjects+0xb4/0x15c)
> [ 4136.114425]  r6:c0e605ec r5:eebc540c r4:00000000
> [ 4136.114435] [<c0788270>] (netdev_queue_update_kobjects) from [<c0788408>]
> (netdev_unregister_kobject+0x3c/0x60)
> [ 4136.114444]  r10:00001ac4 r9:ffffffff r8:00000006 r7:024000c0 r6:eeb703c0
> r5:00000001
> [ 4136.114448]  r4:ee416000
> [ 4136.114464] [<c07883cc>] (netdev_unregister_kobject) from [<c0764858>]
> (rollback_registered_many+0x240/0x3b0)
> [ 4136.114470]  r5:ee747e98 r4:ee416000
> [ 4136.114483] [<c0764618>] (rollback_registered_many) from [<c0767674>]
> (unregister_netdevice_queue+0x78/0xe8)
> [ 4136.114492]  r10:eea53684 r9:ee4164c0 r8:00000002 r7:00000145 r6:00000009
> r5:00000000
> [ 4136.114495]  r4:ee416000
> [ 4136.114504] [<c07675fc>] (unregister_netdevice_queue) from [<c0767704>]
> (unregister_netdev+0x20/0x28)
> [ 4136.114509]  r5:00000000 r4:ee416000
> [ 4136.114521] [<c07676e4>] (unregister_netdev) from [<c0891360>]
> (bnep_session+0x4cc/0x880)
> [ 4136.114525]  r5:00000000 r4:ee416000
> [ 4136.114538] [<c0890e94>] (bnep_session) from [<c0141474>]
> (kthread+0xf0/0x110)
> [ 4136.114547]  r10:00000000 r9:00000000 r8:c0890e94 r7:ee4164c0 r6:ee746000
> r5:ee6fea80
> [ 4136.114550]  r4:00000000
> [ 4136.114562] [<c0141384>] (kthread) from [<c0107b70>]
> (ret_from_fork+0x14/0x24)
> [ 4136.114570]  r8:00000000 r7:00000000 r6:00000000 r5:c0141384 r4:ee6fea80
> [ 4136.114574] ---[ end trace 79b76e2cb188c011 ]---
> [ 4136.114629] ------------[ cut here ]------------
> [ 4136.114646] WARNING: CPU: 0 PID: 427 at fs/sysfs/group.c:237
> sysfs_remove_group+0x90/0x9c
> [ 4136.114650] sysfs group 'power' not found for kobject 'bnep0'
> [ 4136.114653] Modules linked in:
> [ 4136.114664] CPU: 0 PID: 427 Comm: kbnepd bnep0 Tainted: G        W
> 4.9.129-00093-g98220ccd50ff #180
> [ 4136.114668] Hardware name: Freescale i.MX6 SoloX (Device Tree)
> [ 4136.114670] Backtrace:
> [ 4136.114686] [<c010bbc4>] (dump_backtrace) from [<c010be70>]
> (show_stack+0x18/0x1c)
> [ 4136.114694]  r7:00000009 r6:60070013 r5:00000000 r4:c0e1c230
> [ 4136.114704] [<c010be58>] (show_stack) from [<c03d9ce8>]
> (dump_stack+0x94/0xb0)
> [ 4136.114717] [<c03d9c54>] (dump_stack) from [<c012359c>]
> (__warn+0xd8/0x104)
> [ 4136.114724]  r7:00000009 r6:c0bfe9f8 r5:00000000 r4:ee747d90
> [ 4136.114734] [<c01234c4>] (__warn) from [<c0123604>]
> (warn_slowpath_fmt+0x3c/0x44)
> [ 4136.114743]  r9:ffffffff r8:00000006 r7:eeb9a198 r6:ee4162b0 r5:c0e303f0
> r4:c0bfea34
> [ 4136.114755] [<c01235cc>] (warn_slowpath_fmt) from [<c027647c>]
> (sysfs_remove_group+0x90/0x9c)
> [ 4136.114760]  r3:c0a51798 r2:c0bfea34
> [ 4136.114764]  r4:00000000
> [ 4136.114782] [<c02763ec>] (sysfs_remove_group) from [<c05002b0>]
> (dpm_sysfs_remove+0x50/0x58)
> [ 4136.114788]  r6:ee4162a8 r5:c0e303f0 r4:ee4162b0
> [ 4136.114801] [<c0500260>] (dpm_sysfs_remove) from [<c04f41c4>]
> (device_del+0x40/0x224)
> [ 4136.114808]  r7:eeb9a198 r6:eeb703c0 r5:ee4162a8 r4:ee416000
> [ 4136.114818] [<c04f4184>] (device_del) from [<c0788428>]
> (netdev_unregister_kobject+0x5c/0x60)
> [ 4136.114826]  r8:00000006 r7:024000c0 r6:eeb703c0 r5:ee4162a8 r4:ee416000
> [ 4136.114840] [<c07883cc>] (netdev_unregister_kobject) from [<c0764858>]
> (rollback_registered_many+0x240/0x3b0)
> [ 4136.114845]  r5:ee747e98 r4:ee416000
> [ 4136.114856] [<c0764618>] (rollback_registered_many) from [<c0767674>]
> (unregister_netdevice_queue+0x78/0xe8)
> [ 4136.114865]  r10:eea53684 r9:ee4164c0 r8:00000002 r7:00000145 r6:00000009
> r5:00000000
> [ 4136.114868]  r4:ee416000
> [ 4136.114877] [<c07675fc>] (unregister_netdevice_queue) from [<c0767704>]
> (unregister_netdev+0x20/0x28)
> [ 4136.114881]  r5:00000000 r4:ee416000
> [ 4136.114891] [<c07676e4>] (unregister_netdev) from [<c0891360>]
> (bnep_session+0x4cc/0x880)
> [ 4136.114896]  r5:00000000 r4:ee416000
> [ 4136.114907] [<c0890e94>] (bnep_session) from [<c0141474>]
> (kthread+0xf0/0x110)
> [ 4136.114915]  r10:00000000 r9:00000000 r8:c0890e94 r7:ee4164c0 r6:ee746000
> r5:ee6fea80
> [ 4136.114919]  r4:00000000
> [ 4136.114930] [<c0141384>] (kthread) from [<c0107b70>]
> (ret_from_fork+0x14/0x24)
> [ 4136.114937]  r8:00000000 r7:00000000 r6:00000000 r5:c0141384 r4:ee6fea80
> [ 4136.114941] ---[ end trace 79b76e2cb188c012 ]---
> [ 4136.114959] ------------[ cut here ]------------
> [ 4136.114970] WARNING: CPU: 0 PID: 427 at fs/sysfs/group.c:237
> sysfs_remove_group+0x90/0x9c
> [ 4136.114974] sysfs group 'statistics' not found for kobject 'bnep0'
> [ 4136.114976] Modules linked in:
> [ 4136.114988] CPU: 0 PID: 427 Comm: kbnepd bnep0 Tainted: G        W
> 4.9.129-00093-g98220ccd50ff #180
> [ 4136.114991] Hardware name: Freescale i.MX6 SoloX (Device Tree)
> [ 4136.114994] Backtrace:
> [ 4136.115010] [<c010bbc4>] (dump_backtrace) from [<c010be70>]
> (show_stack+0x18/0x1c)
> [ 4136.115017]  r7:00000009 r6:60070013 r5:00000000 r4:c0e1c230
> [ 4136.115026] [<c010be58>] (show_stack) from [<c03d9ce8>]
> (dump_stack+0x94/0xb0)
> [ 4136.115039] [<c03d9c54>] (dump_stack) from [<c012359c>]
> (__warn+0xd8/0x104)
> [ 4136.115046]  r7:00000009 r6:c0bfe9f8 r5:00000000 r4:ee747d78
> [ 4136.115057] [<c01234c4>] (__warn) from [<c0123604>]
> (warn_slowpath_fmt+0x3c/0x44)
> [ 4136.115066]  r9:ffffffff r8:c0ec727c r7:c0e65724 r6:ee4162b0 r5:c0e60600
> r4:c0bfea34
> [ 4136.115078] [<c01235cc>] (warn_slowpath_fmt) from [<c027647c>]
> (sysfs_remove_group+0x90/0x9c)
> [ 4136.115083]  r3:c0c50684 r2:c0bfea34
> [ 4136.115086]  r4:00000000
> [ 4136.115096] [<c02763ec>] (sysfs_remove_group) from [<c02764b4>]
> (sysfs_remove_groups+0x2c/0x3c)
> [ 4136.115102]  r6:c0e6056c r5:ee4162b0 r4:ee416430
> [ 4136.115112] [<c0276488>] (sysfs_remove_groups) from [<c04f3734>]
> (device_remove_attrs+0x44/0x74)
> [ 4136.115117]  r5:ee4162b0 r4:ee4162a8
> [ 4136.115125] [<c04f36f0>] (device_remove_attrs) from [<c04f428c>]
> (device_del+0x108/0x224)
> [ 4136.115132]  r7:eeb9a198 r6:ee4162b0 r5:ee4162a8 r4:ef1c4238
> [ 4136.115142] [<c04f4184>] (device_del) from [<c0788428>]
> (netdev_unregister_kobject+0x5c/0x60)
> [ 4136.115149]  r8:00000006 r7:024000c0 r6:eeb703c0 r5:ee4162a8 r4:ee416000
> [ 4136.115161] [<c07883cc>] (netdev_unregister_kobject) from [<c0764858>]
> (rollback_registered_many+0x240/0x3b0)
> [ 4136.115166]  r5:ee747e98 r4:ee416000
> [ 4136.115177] [<c0764618>] (rollback_registered_many) from [<c0767674>]
> (unregister_netdevice_queue+0x78/0xe8)
> [ 4136.115186]  r10:eea53684 r9:ee4164c0 r8:00000002 r7:00000145 r6:00000009
> r5:00000000
> [ 4136.115189]  r4:ee416000
> [ 4136.115198] [<c07675fc>] (unregister_netdevice_queue) from [<c0767704>]
> (unregister_netdev+0x20/0x28)
> [ 4136.115202]  r5:00000000 r4:ee416000
> [ 4136.115212] [<c07676e4>] (unregister_netdev) from [<c0891360>]
> (bnep_session+0x4cc/0x880)
> [ 4136.115217]  r5:00000000 r4:ee416000
> [ 4136.115226] [<c0890e94>] (bnep_session) from [<c0141474>]
> (kthread+0xf0/0x110)
> [ 4136.115235]  r10:00000000 r9:00000000 r8:c0890e94 r7:ee4164c0 r6:ee746000
> r5:ee6fea80
> [ 4136.115239]  r4:00000000
> [ 4136.115249] [<c0141384>] (kthread) from [<c0107b70>]
> (ret_from_fork+0x14/0x24)
> [ 4136.115256]  r8:00000000 r7:00000000 r6:00000000 r5:c0141384 r4:ee6fea80
> [ 4136.115260] ---[ end trace 79b76e2cb188c013 ]---
>