sysfs warnings since kernel 3.13-rc1: "WARNING: ... at fs/sysfs/group.c:214 sysfs_remove_group"

Frank Schäfer
2014-01-07T17:44:01Z

Hi,

since

commit bcdde7e221a8750f9b62b6d0bd31b72ea4ad9309
Author: Tejun Heo <tj@kernel.org>
Date: Wed Sep 18 17:15:37 2013 -0400

sysfs: make __sysfs_remove_dir() recursive

Currently, sysfs directory removal is inconsistent in that it would
remove any files directly under it but wouldn't recurse into
directories. Thanks to group subdirectories, this doesn't even match
with kobject boundaries. sysfs is in the process of being separated
out so that it can be used by multiple subsystems and we want to have
a consistent behavior - either removal of a sysfs_dirent should remove
every descendant entries or none instead of something inbetween.

This patch implements proper recursive removal in
__sysfs_remove_dir(). The function now walks its subtree in a
post-order walk to remove all descendants.

This is a behavior change but kobject / driver layer, which currently
is the only consumer, has already been updated to handle duplicate
removal attempts, so nothing should be broken after this change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

I'm getting several sysfs related warnings when closing disconnected
em28xx USB devices:

[ 447.408658] ------------[ cut here ]------------
[ 447.408676] WARNING: CPU: 1 PID: 2489 at fs/sysfs/group.c:214
sysfs_remove_group+0xc9/0xd0()
[ 447.408681] sysfs group c0a10100 not found for kobject 'vbi1'
[ 447.408685] Modules linked in: em28xx_rc zl10353 em28xx_dvb dvb_core
snd_usb_audio snd_usbmidi_lib snd_rawmidi tuner_xc2028 tvp5150 em28xx
videobuf2_core videobuf2_vmalloc videobuf2_memops nls_iso8859_1
nls_cp437 vfat fat xt_tcpudp af_packet xt_pkttype xt_LOG xt_limit
ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT
iptable_raw xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns
nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables
xt_conntrack nf_conntrack ip6table_filter ip6_tables x_tables fuse
snd_hda_codec_hdmi arc4 snd_hda_codec_analog rtl8187 mac80211
snd_hda_intel snd_hda_codec snd_hwdep snd_pcm rc_hauppauge ir_kbd_i2c
snd_seq tuner_simple tuner_types cfg80211 tda9887 tda8290 tuner msp3400
bttv v4l2_common videodev snd_timer snd_seq_device videobuf_dma_sg
videobuf_core usb_storage btcx_risc rc_core snd tveeprom usblp rfkill
forcedeth sg soundcore i2c_nforce2 shpchp eeprom_93cx6 firewire_ohci
firewire_core crc_itu_t ppdev k8temp sr_mod cdrom powernow_k8 kvm_amd
button asus_atk0110 floppy parport_pc parport pcspkr snd_page_alloc kvm
serio_raw autofs4 radeon ttm drm_kms_helper drm i2c_algo_bit fan thermal
processor thermal_sys scsi_dh_alua scsi_dh_hp_sw scsi_dh_emc
scsi_dh_rdac scsi_dh ata_generic pata_amd pata_jmicron sata_nv
[ 447.408842] CPU: 1 PID: 2489 Comm: qv4l2 Tainted: G W
3.13.0-rc7-0.1-desktop+ #76
[ 447.408848] Hardware name: System manufacturer System Product
Name/M2N-VM DH, BIOS ASUS M2N-VM DH ACPI BIOS Revision 1503 09/16/2010
[ 447.408852] 00000000 00000000 e7205e38 c077985c e7205e78 e7205e68
c02401df c092bedc
[ 447.408866] e7205e94 000009b9 c0935e02 000000d6 c03afe89 c03afe89
00000000 c0a10100
[ 447.408876] e81a180c e7205e80 c024027e 00000009 e7205e78 c092bedc
e7205e94 e7205ea8
[ 447.408887] Call Trace:
[ 447.408901] [<c077985c>] dump_stack+0x48/0x69
[ 447.408911] [<c02401df>] warn_slowpath_common+0x7f/0xa0
[ 447.408920] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.408927] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.408934] [<c024027e>] warn_slowpath_fmt+0x2e/0x30
[ 447.408942] [<c03afe89>] sysfs_remove_group+0xc9/0xd0
[ 447.408951] [<c059c32d>] dpm_sysfs_remove+0x2d/0x30
[ 447.408959] [<c05940ac>] device_del+0x2c/0x150
[ 447.408965] [<c05941ec>] device_unregister+0x1c/0x60
[ 447.408972] [<c077644a>] ? printk+0x48/0x4a
[ 447.408998] [<f8b576e8>] video_unregister_device+0x38/0x40 [videodev]
[ 447.409092] [<f9a028a4>] em28xx_release_analog_resources+0xc4/0x100
[em28xx]
[ 447.409122] [<f9a0572b>] em28xx_release_resources+0xb/0x70 [em28xx]
[ 447.409132] [<f9a00c6f>] em28xx_v4l2_close+0xcf/0x150 [em28xx]
[ 447.409141] [<c0360ce5>] ? dput+0x15/0xe0
[ 447.409160] [<f8b5802e>] v4l2_release+0x2e/0x70 [videodev]
[ 447.409170] [<c034df2b>] __fput+0xab/0x1d0
[ 447.409177] [<c034e088>] ____fput+0x8/0x10
[ 447.409186] [<c025a709>] task_work_run+0x79/0x90
[ 447.409193] [<c0202141>] do_notify_resume+0x51/0x80
[ 447.409201] [<c077fffb>] work_notifysig+0x24/0x29
[ 447.409206] ---[ end trace 1e95e1c9d6c9c835 ]---
[ 447.411141] em2882/3 #0: V4L2 device video1 deregistered
[ 447.411145] ------------[ cut here ]------------
[ 447.411152] WARNING: CPU: 1 PID: 2489 at fs/sysfs/group.c:214
sysfs_remove_group+0xc9/0xd0()
[ 447.411154] sysfs group c0a10100 not found for kobject 'video1'
[ 447.411202] Modules linked in: em28xx_rc zl10353 em28xx_dvb dvb_core
snd_usb_audio snd_usbmidi_lib snd_rawmidi tuner_xc2028 tvp5150 em28xx
videobuf2_core videobuf2_vmalloc videobuf2_memops nls_iso8859_1
nls_cp437 vfat fat xt_tcpudp af_packet xt_pkttype xt_LOG xt_limit
ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT
iptable_raw xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns
nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables
xt_conntrack nf_conntrack ip6table_filter ip6_tables x_tables fuse
snd_hda_codec_hdmi arc4 snd_hda_codec_analog rtl8187 mac80211
snd_hda_intel snd_hda_codec snd_hwdep snd_pcm rc_hauppauge ir_kbd_i2c
snd_seq tuner_simple tuner_types cfg80211 tda9887 tda8290 tuner msp3400
bttv v4l2_common videodev snd_timer snd_seq_device videobuf_dma_sg
videobuf_core usb_storage btcx_risc rc_core snd tveeprom usblp rfkill
forcedeth sg soundcore i2c_nforce2 shpchp eeprom_93cx6 firewire_ohci
firewire_core crc_itu_t ppdev k8temp sr_mod cdrom powernow_k8 kvm_amd
button asus_atk0110 floppy parport_pc parport pcspkr snd_page_alloc kvm
serio_raw autofs4 radeon ttm drm_kms_helper drm i2c_algo_bit fan thermal
processor thermal_sys scsi_dh_alua scsi_dh_hp_sw scsi_dh_emc
scsi_dh_rdac scsi_dh ata_generic pata_amd pata_jmicron sata_nv
[ 447.411243] CPU: 1 PID: 2489 Comm: qv4l2 Tainted: G W
3.13.0-rc7-0.1-desktop+ #76
[ 447.411246] Hardware name: System manufacturer System Product
Name/M2N-VM DH, BIOS ASUS M2N-VM DH ACPI BIOS Revision 1503 09/16/2010
[ 447.411253] 00000000 00000000 e7205e38 c077985c e7205e78 e7205e68
c02401df c092bedc
[ 447.411260] e7205e94 000009b9 c0935e02 000000d6 c03afe89 c03afe89
00000000 c0a10100
[ 447.411266] f526780c e7205e80 c024027e 00000009 e7205e78 c092bedc
e7205e94 e7205ea8
[ 447.411267] Call Trace:
[ 447.411273] [<c077985c>] dump_stack+0x48/0x69
[ 447.411278] [<c02401df>] warn_slowpath_common+0x7f/0xa0
[ 447.411284] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.411289] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.411293] [<c024027e>] warn_slowpath_fmt+0x2e/0x30
[ 447.411298] [<c03afe89>] sysfs_remove_group+0xc9/0xd0
[ 447.411303] [<c059c32d>] dpm_sysfs_remove+0x2d/0x30
[ 447.411307] [<c05940ac>] device_del+0x2c/0x150
[ 447.411311] [<c05941ec>] device_unregister+0x1c/0x60
[ 447.411315] [<c077644a>] ? printk+0x48/0x4a
[ 447.411334] [<f8b576e8>] video_unregister_device+0x38/0x40 [videodev]
[ 447.411344] [<f9a02867>] em28xx_release_analog_resources+0x87/0x100
[em28xx]
[ 447.411353] [<f9a0572b>] em28xx_release_resources+0xb/0x70 [em28xx]
[ 447.411360] [<f9a00c6f>] em28xx_v4l2_close+0xcf/0x150 [em28xx]
[ 447.411365] [<c0360ce5>] ? dput+0x15/0xe0
[ 447.411380] [<f8b5802e>] v4l2_release+0x2e/0x70 [videodev]
[ 447.411385] [<c034df2b>] __fput+0xab/0x1d0
[ 447.411391] [<c034e088>] ____fput+0x8/0x10
[ 447.411397] [<c025a709>] task_work_run+0x79/0x90
[ 447.411401] [<c0202141>] do_notify_resume+0x51/0x80
[ 447.411406] [<c077fffb>] work_notifysig+0x24/0x29
[ 447.411408] ---[ end trace 1e95e1c9d6c9c836 ]---
[ 447.411730] ------------[ cut here ]------------
[ 447.411737] WARNING: CPU: 1 PID: 2489 at fs/sysfs/group.c:214
sysfs_remove_group+0xc9/0xd0()
[ 447.411739] sysfs group c0a10100 not found for kobject '10-005c'
[ 447.411787] Modules linked in: em28xx_rc zl10353 em28xx_dvb dvb_core
snd_usb_audio snd_usbmidi_lib snd_rawmidi tuner_xc2028 tvp5150 em28xx
videobuf2_core videobuf2_vmalloc videobuf2_memops nls_iso8859_1
nls_cp437 vfat fat xt_tcpudp af_packet xt_pkttype xt_LOG xt_limit
ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT
iptable_raw xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns
nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables
xt_conntrack nf_conntrack ip6table_filter ip6_tables x_tables fuse
snd_hda_codec_hdmi arc4 snd_hda_codec_analog rtl8187 mac80211
snd_hda_intel snd_hda_codec snd_hwdep snd_pcm rc_hauppauge ir_kbd_i2c
snd_seq tuner_simple tuner_types cfg80211 tda9887 tda8290 tuner msp3400
bttv v4l2_common videodev snd_timer snd_seq_device videobuf_dma_sg
videobuf_core usb_storage btcx_risc rc_core snd tveeprom usblp rfkill
forcedeth sg soundcore i2c_nforce2 shpchp eeprom_93cx6 firewire_ohci
firewire_core crc_itu_t ppdev k8temp sr_mod cdrom powernow_k8 kvm_amd
button asus_atk0110 floppy parport_pc parport pcspkr snd_page_alloc kvm
serio_raw autofs4 radeon ttm drm_kms_helper drm i2c_algo_bit fan thermal
processor thermal_sys scsi_dh_alua scsi_dh_hp_sw scsi_dh_emc
scsi_dh_rdac scsi_dh ata_generic pata_amd pata_jmicron sata_nv
[ 447.411826] CPU: 1 PID: 2489 Comm: qv4l2 Tainted: G W
3.13.0-rc7-0.1-desktop+ #76
[ 447.411828] Hardware name: System manufacturer System Product
Name/M2N-VM DH, BIOS ASUS M2N-VM DH ACPI BIOS Revision 1503 09/16/2010
[ 447.411836] 00000000 00000000 e7205de8 c077985c e7205e28 e7205e18
c02401df c092bedc
[ 447.411842] e7205e44 000009b9 c0935e02 000000d6 c03afe89 c03afe89
00000000 c0a10100
[ 447.411848] e4ccce24 e7205e30 c024027e 00000009 e7205e28 c092bedc
e7205e44 e7205e58
[ 447.411849] Call Trace:
[ 447.411855] [<c077985c>] dump_stack+0x48/0x69
[ 447.411860] [<c02401df>] warn_slowpath_common+0x7f/0xa0
[ 447.411865] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.411870] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.411874] [<c024027e>] warn_slowpath_fmt+0x2e/0x30
[ 447.411880] [<c03afe89>] sysfs_remove_group+0xc9/0xd0
[ 447.411885] [<c059c32d>] dpm_sysfs_remove+0x2d/0x30
[ 447.411889] [<c05940ac>] device_del+0x2c/0x150
[ 447.411895] [<c064b8f0>] ? __unregister_dummy+0x30/0x30
[ 447.411899] [<c05941ec>] device_unregister+0x1c/0x60
[ 447.411903] [<c064b60b>] i2c_unregister_device+0xb/0x10
[ 447.411908] [<c064b923>] __unregister_client+0x33/0x40
[ 447.411912] [<c05936bc>] device_for_each_child+0x2c/0x60
[ 447.411917] [<c064cba8>] i2c_del_adapter+0x158/0x2c0
[ 447.411921] [<c064b8b0>] ? __process_removed_driver+0x30/0x30
[ 447.411925] [<c077644a>] ? printk+0x48/0x4a
[ 447.411936] [<f9a042b7>] em28xx_i2c_unregister+0x17/0x30 [em28xx]
[ 447.411944] [<f9a0573e>] em28xx_release_resources+0x1e/0x70 [em28xx]
[ 447.411952] [<f9a00c6f>] em28xx_v4l2_close+0xcf/0x150 [em28xx]
[ 447.411956] [<c0360ce5>] ? dput+0x15/0xe0
[ 447.411974] [<f8b5802e>] v4l2_release+0x2e/0x70 [videodev]
[ 447.411979] [<c034df2b>] __fput+0xab/0x1d0
[ 447.411984] [<c034e088>] ____fput+0x8/0x10
[ 447.411990] [<c025a709>] task_work_run+0x79/0x90
[ 447.411994] [<c0202141>] do_notify_resume+0x51/0x80
[ 447.411999] [<c077fffb>] work_notifysig+0x24/0x29
[ 447.412029] ---[ end trace 1e95e1c9d6c9c837 ]---
[ 447.412076] ------------[ cut here ]------------
[ 447.412083] WARNING: CPU: 1 PID: 2489 at fs/sysfs/group.c:214
sysfs_remove_group+0xc9/0xd0()
[ 447.412085] sysfs group c0a10100 not found for kobject '10-0061'
[ 447.412130] Modules linked in: em28xx_rc zl10353 em28xx_dvb dvb_core
snd_usb_audio snd_usbmidi_lib snd_rawmidi tuner_xc2028 tvp5150 em28xx
videobuf2_core videobuf2_vmalloc videobuf2_memops nls_iso8859_1
nls_cp437 vfat fat xt_tcpudp af_packet xt_pkttype xt_LOG xt_limit
ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT
iptable_raw xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns
nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables
xt_conntrack nf_conntrack ip6table_filter ip6_tables x_tables fuse
snd_hda_codec_hdmi arc4 snd_hda_codec_analog rtl8187 mac80211
snd_hda_intel snd_hda_codec snd_hwdep snd_pcm rc_hauppauge ir_kbd_i2c
snd_seq tuner_simple tuner_types cfg80211 tda9887 tda8290 tuner msp3400
bttv v4l2_common videodev snd_timer snd_seq_device videobuf_dma_sg
videobuf_core usb_storage btcx_risc rc_core snd tveeprom usblp rfkill
forcedeth sg soundcore i2c_nforce2 shpchp eeprom_93cx6 firewire_ohci
firewire_core crc_itu_t ppdev k8temp sr_mod cdrom powernow_k8 kvm_amd
button asus_atk0110 floppy parport_pc parport pcspkr snd_page_alloc kvm
serio_raw autofs4 radeon ttm drm_kms_helper drm i2c_algo_bit fan thermal
processor thermal_sys scsi_dh_alua scsi_dh_hp_sw scsi_dh_emc
scsi_dh_rdac scsi_dh ata_generic pata_amd pata_jmicron sata_nv
[ 447.412168] CPU: 1 PID: 2489 Comm: qv4l2 Tainted: G W
3.13.0-rc7-0.1-desktop+ #76
[ 447.412170] Hardware name: System manufacturer System Product
Name/M2N-VM DH, BIOS ASUS M2N-VM DH ACPI BIOS Revision 1503 09/16/2010
[ 447.412177] 00000000 00000000 e7205de8 c077985c e7205e28 e7205e18
c02401df c092bedc
[ 447.412184] e7205e44 000009b9 c0935e02 000000d6 c03afe89 c03afe89
00000000 c0a10100
[ 447.412190] e8314224 e7205e30 c024027e 00000009 e7205e28 c092bedc
e7205e44 e7205e58
[ 447.412191] Call Trace:
[ 447.412197] [<c077985c>] dump_stack+0x48/0x69
[ 447.412201] [<c02401df>] warn_slowpath_common+0x7f/0xa0
[ 447.412207] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.412212] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.412216] [<c024027e>] warn_slowpath_fmt+0x2e/0x30
[ 447.412221] [<c03afe89>] sysfs_remove_group+0xc9/0xd0
[ 447.412226] [<c059c32d>] dpm_sysfs_remove+0x2d/0x30
[ 447.412230] [<c05940ac>] device_del+0x2c/0x150
[ 447.412235] [<c064b8f0>] ? __unregister_dummy+0x30/0x30
[ 447.412238] [<c05941ec>] device_unregister+0x1c/0x60
[ 447.412242] [<c05933ff>] ? put_device+0xf/0x20
[ 447.412246] [<c059341b>] ? klist_children_put+0xb/0x10
[ 447.412250] [<c064b60b>] i2c_unregister_device+0xb/0x10
[ 447.412254] [<c064b923>] __unregister_client+0x33/0x40
[ 447.412258] [<c05936bc>] device_for_each_child+0x2c/0x60
[ 447.412263] [<c064cba8>] i2c_del_adapter+0x158/0x2c0
[ 447.412267] [<c064b8b0>] ? __process_removed_driver+0x30/0x30
[ 447.412271] [<c077644a>] ? printk+0x48/0x4a
[ 447.412281] [<f9a042b7>] em28xx_i2c_unregister+0x17/0x30 [em28xx]
[ 447.412290] [<f9a0573e>] em28xx_release_resources+0x1e/0x70 [em28xx]
[ 447.412297] [<f9a00c6f>] em28xx_v4l2_close+0xcf/0x150 [em28xx]
[ 447.412301] [<c0360ce5>] ? dput+0x15/0xe0
[ 447.412318] [<f8b5802e>] v4l2_release+0x2e/0x70 [videodev]
[ 447.412324] [<c034df2b>] __fput+0xab/0x1d0
[ 447.412329] [<c034e088>] ____fput+0x8/0x10
[ 447.412334] [<c025a709>] task_work_run+0x79/0x90
[ 447.412338] [<c0202141>] do_notify_resume+0x51/0x80
[ 447.412343] [<c077fffb>] work_notifysig+0x24/0x29
[ 447.412346] ---[ end trace 1e95e1c9d6c9c838 ]---
[ 447.412367] xc2028 10-0061: destroying instance
[ 447.412391] ------------[ cut here ]------------
[ 447.412398] WARNING: CPU: 1 PID: 2489 at fs/sysfs/group.c:214
sysfs_remove_group+0xc9/0xd0()
[ 447.412399] sysfs group c0a10100 not found for kobject 'i2c-10'
[ 447.412444] Modules linked in: em28xx_rc zl10353 em28xx_dvb dvb_core
snd_usb_audio snd_usbmidi_lib snd_rawmidi tuner_xc2028 tvp5150 em28xx
videobuf2_core videobuf2_vmalloc videobuf2_memops nls_iso8859_1
nls_cp437 vfat fat xt_tcpudp af_packet xt_pkttype xt_LOG xt_limit
ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT
iptable_raw xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns
nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables
xt_conntrack nf_conntrack ip6table_filter ip6_tables x_tables fuse
snd_hda_codec_hdmi arc4 snd_hda_codec_analog rtl8187 mac80211
snd_hda_intel snd_hda_codec snd_hwdep snd_pcm rc_hauppauge ir_kbd_i2c
snd_seq tuner_simple tuner_types cfg80211 tda9887 tda8290 tuner msp3400
bttv v4l2_common videodev snd_timer snd_seq_device videobuf_dma_sg
videobuf_core usb_storage btcx_risc rc_core snd tveeprom usblp rfkill
forcedeth sg soundcore i2c_nforce2 shpchp eeprom_93cx6 firewire_ohci
firewire_core crc_itu_t ppdev k8temp sr_mod cdrom powernow_k8 kvm_amd
button asus_atk0110 floppy parport_pc parport pcspkr snd_page_alloc kvm
serio_raw autofs4 radeon ttm drm_kms_helper drm i2c_algo_bit fan thermal
processor thermal_sys scsi_dh_alua scsi_dh_hp_sw scsi_dh_emc
scsi_dh_rdac scsi_dh ata_generic pata_amd pata_jmicron sata_nv
[ 447.412482] CPU: 1 PID: 2489 Comm: qv4l2 Tainted: G W
3.13.0-rc7-0.1-desktop+ #76
[ 447.412484] Hardware name: System manufacturer System Product
Name/M2N-VM DH, BIOS ASUS M2N-VM DH ACPI BIOS Revision 1503 09/16/2010
[ 447.412491] 00000000 00000000 e7205e18 c077985c e7205e58 e7205e48
c02401df c092bedc
[ 447.412498] e7205e74 000009b9 c0935e02 000000d6 c03afe89 c03afe89
00000000 c0a10100
[ 447.412504] e8073220 e7205e60 c024027e 00000009 e7205e58 c092bedc
e7205e74 e7205e88
[ 447.412505] Call Trace:
[ 447.412511] [<c077985c>] dump_stack+0x48/0x69
[ 447.412515] [<c02401df>] warn_slowpath_common+0x7f/0xa0
[ 447.412521] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.412525] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 447.412530] [<c024027e>] warn_slowpath_fmt+0x2e/0x30
[ 447.412535] [<c03afe89>] sysfs_remove_group+0xc9/0xd0
[ 447.412540] [<c059c32d>] dpm_sysfs_remove+0x2d/0x30
[ 447.412544] [<c05940ac>] device_del+0x2c/0x150
[ 447.412548] [<c05941ec>] device_unregister+0x1c/0x60
[ 447.412553] [<c03af3b1>] ? sysfs_remove_link+0x11/0x30
[ 447.412558] [<c0597c5f>] ? class_compat_remove_link+0x2f/0x50
[ 447.412563] [<c064cc04>] i2c_del_adapter+0x1b4/0x2c0
[ 447.412567] [<c064b8b0>] ? __process_removed_driver+0x30/0x30
[ 447.412571] [<c077644a>] ? printk+0x48/0x4a
[ 447.412581] [<f9a042b7>] em28xx_i2c_unregister+0x17/0x30 [em28xx]
[ 447.412590] [<f9a0573e>] em28xx_release_resources+0x1e/0x70 [em28xx]
[ 447.412597] [<f9a00c6f>] em28xx_v4l2_close+0xcf/0x150 [em28xx]
[ 447.412601] [<c0360ce5>] ? dput+0x15/0xe0
[ 447.412618] [<f8b5802e>] v4l2_release+0x2e/0x70 [videodev]
[ 447.412623] [<c034df2b>] __fput+0xab/0x1d0
[ 447.412628] [<c034e088>] ____fput+0x8/0x10
[ 447.412634] [<c025a709>] task_work_run+0x79/0x90
[ 447.412638] [<c0202141>] do_notify_resume+0x51/0x80
[ 447.412643] [<c077fffb>] work_notifysig+0x24/0x29
[ 447.412645] ---[ end trace 1e95e1c9d6c9c839 ]---

I'm also getting this error when unmounting a disconnecting a USB mass
storage device:

[ 180.527140] WARNING: CPU: 0 PID: 2145 at fs/sysfs/group.c:214
sysfs_remove_group+0xc9/0xd0()
[ 180.527142] sysfs group c0a10100 not found for kobject 'target11:0:0'
[ 180.527144] Modules linked in: nls_iso8859_1 nls_cp437 vfat fat
xt_tcpudp af_packet xt_pkttype xt_LOG xt_limit ip6t_REJECT
nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_raw ipt_REJECT iptable_raw
xt_CT iptable_filter ip6table_mangle nf_conntrack_netbios_ns
nf_conntrack_broadcast nf_conntrack_ipv4 nf_defrag_ipv4 ip_tables
xt_conntrack nf_conntrack ip6table_filter ip6_tables x_tables fuse
snd_hda_codec_hdmi arc4 snd_hda_codec_analog rtl8187 mac80211
snd_hda_intel snd_hda_codec snd_hwdep snd_pcm rc_hauppauge ir_kbd_i2c
snd_seq tuner_simple tuner_types cfg80211 tda9887 tda8290 tuner msp3400
bttv v4l2_common videodev snd_timer snd_seq_device videobuf_dma_sg
videobuf_core usb_storage btcx_risc rc_core snd tveeprom usblp rfkill
forcedeth sg soundcore i2c_nforce2 shpchp eeprom_93cx6 firewire_ohci
firewire_core crc_itu_t ppdev k8temp sr_mod cdrom powernow_k8 kvm_amd
button asus_atk0110 floppy parport_pc parport pcspkr snd_page_alloc kvm
serio_raw autofs4 radeon ttm drm_kms_helper drm i2c_algo_bit fan thermal
processor thermal_sys scsi_dh_alua scsi_dh_hp_sw scsi_dh_emc
scsi_dh_rdac scsi_dh ata_generic pata_amd pata_jmicron sata_nv
[ 180.527204] CPU: 0 PID: 2145 Comm: bash Not tainted
3.13.0-rc7-0.1-desktop+ #76
[ 180.527206] Hardware name: System manufacturer System Product
Name/M2N-VM DH, BIOS ASUS M2N-VM DH ACPI BIOS Revision 1503 09/16/2010
[ 180.527208] 00000000 00000000 f6531bcc c077985c f6531c0c f6531bfc
c02401df c092bedc
[ 180.527213] f6531c28 00000861 c0935e02 000000d6 c03afe89 c03afe89
00000000 c0a10100
[ 180.527217] f527761c f6531c14 c024027e 00000009 f6531c0c c092bedc
f6531c28 f6531c3c
[ 180.527221] Call Trace:
[ 180.527227] [<c077985c>] dump_stack+0x48/0x69
[ 180.527231] [<c02401df>] warn_slowpath_common+0x7f/0xa0
[ 180.527234] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 180.527237] [<c03afe89>] ? sysfs_remove_group+0xc9/0xd0
[ 180.527240] [<c024027e>] warn_slowpath_fmt+0x2e/0x30
[ 180.527243] [<c03afe89>] sysfs_remove_group+0xc9/0xd0
[ 180.527246] [<c059c32d>] dpm_sysfs_remove+0x2d/0x30
[ 180.527249] [<c05940ac>] device_del+0x2c/0x150
[ 180.527253] [<c05cb0d6>] scsi_target_reap_usercontext+0x26/0x40
[ 180.527257] [<c0256d44>] execute_in_process_context+0x44/0x50
[ 180.527260] [<c05cc6ec>] scsi_target_reap+0x8c/0xb0
[ 180.527263] [<c05ce372>] scsi_device_dev_release_usercontext+0x122/0x150
[ 180.527266] [<c0256d44>] execute_in_process_context+0x44/0x50
[ 180.527268] [<c05cdf13>] scsi_device_dev_release+0x13/0x20
[ 180.527271] [<c059362c>] device_release+0x2c/0x90
[ 180.527273] [<c0593633>] ? device_release+0x33/0x90
[ 180.527276] [<c04a8058>] kobject_cleanup+0x78/0x1b0
[ 180.527279] [<c04a8070>] ? kobject_cleanup+0x90/0x1b0
[ 180.527282] [<c04915f4>] ? part_release+0x24/0x30
[ 180.527286] [<c0317097>] ? free_percpu+0x77/0x100
[ 180.527290] [<c04a81c5>] kobject_put+0x25/0x60
[ 180.527293] [<c05c18b7>] ? scsi_device_put+0x47/0x50
[ 180.527296] [<c05933ff>] put_device+0xf/0x20
[ 180.527299] [<c05c189f>] scsi_device_put+0x2f/0x50
[ 180.527302] [<c05d138a>] scsi_disk_put+0x2a/0x40
[ 180.527305] [<c05d1c7f>] sd_release+0x3f/0xd0
[ 180.527308] [<c037e574>] __blkdev_put+0x124/0x170
[ 180.527311] [<c037e547>] __blkdev_put+0xf7/0x170
[ 180.527313] [<c037e604>] blkdev_put+0x44/0x110
[ 180.527318] [<c034f23c>] kill_block_super+0x3c/0x70
[ 180.527321] [<c034e81a>] deactivate_locked_super+0x3a/0x60
[ 180.527323] [<c034f4f2>] deactivate_super+0x42/0x60
[ 180.527326] [<c036779d>] mntput_no_expire+0xad/0x120
[ 180.527329] [<c0367828>] mntput+0x18/0x30
[ 180.527332] [<c0355085>] path_put+0x15/0x20
[ 180.527335] [<c0376756>] free_fs_struct+0x16/0x30
[ 180.527338] [<c03767df>] exit_fs+0x6f/0x80
[ 180.527341] [<c024203a>] do_exit+0x24a/0x980
[ 180.527344] [<c024d558>] ? dequeue_signal+0x78/0x180
[ 180.527347] [<c024285f>] do_group_exit+0x2f/0x90
[ 180.527350] [<c024fb39>] get_signal_to_deliver+0x239/0x5e0
[ 180.527354] [<c0202033>] do_signal+0x33/0xf0
[ 180.527357] [<c02017c5>] ? restore_sigcontext+0xe5/0x110
[ 180.527359] [<c0202397>] ? sys_sigreturn+0x97/0xa0
[ 180.527362] [<c0202155>] do_notify_resume+0x65/0x80
[ 180.527365] [<c077fffb>] work_notifysig+0x24/0x29
[ 180.527367] ---[ end trace 1e95e1c9d6c9c834 ]---

Both are 100% reproducable.

I assume the warning means that something unexpected happened.
So how can these warnings be fixed ?

Regards,
Frank Schäfer