Additional info:
libreport version: 2.0.13
cmdline:        ro root=UUID=1dccc4dd-d113-4d9c-bc74-8f01e7602874 rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=croat rhgb quiet
kernel:         undefined
kernel_tainted_long: Taint on warning.

backtrace:
:WARNING: at lib/debugobjects.c:262 debug_print_object+0x74/0x82()
:Hardware name: To Be Filled By O.E.M.
:ODEBUG: free active (active state 0) object type: timer_list hint: wakeup_timer_fn+0x0/0x106
:Modules linked in: usb_storage uas 8021q garp stp llc bnep bluetooth rfkill fuse snd_hda_codec_hdmi snd_hda_codec_realtek ppdev parport_pc parport snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_timer snd iTCO_wdt microcode soundcore iTCO_vendor_support r8169 i2c_i801 mii snd_page_alloc i915 drm_kms_helper drm i2c_algo_bit i2c_core video [last unloaded: scsi_wait_scan]
:Pid: 1844, comm: umount Not tainted 3.1.0-0.rc8.git0.0.fc17.i686 #1
:Call Trace:
: [<c04402b0>] warn_slowpath_common+0x7c/0x91
: [<c05f60ad>] ? debug_print_object+0x74/0x82
: [<c05f60ad>] ? debug_print_object+0x74/0x82
: [<c0440350>] warn_slowpath_fmt+0x33/0x35
: [<c05f60ad>] debug_print_object+0x74/0x82
: [<c04d858b>] ? congestion_wait+0xec/0xec
: [<c05f67d1>] debug_check_no_obj_freed+0x8a/0x129
: [<c04f1db1>] slab_free_hook+0x5c/0x61
: [<c04f32d6>] kmem_cache_free+0x2b/0x109
: [<c05fbb68>] ? percpu_counter_destroy+0x48/0x52
: [<c05d6e88>] ? blk_release_queue+0x53/0x57
: [<c05ea87b>] ? prop_local_destroy_percpu+0x8/0xa
: [<c05d6e88>] blk_release_queue+0x53/0x57
: [<c05e8356>] kobject_release+0x121/0x15e
: [<c05e8235>] ? kobject_del+0x2c/0x2c
: [<c05e9517>] kref_put+0x39/0x42
: [<c05e81b2>] kobject_put+0x46/0x4c
: [<c04568e0>] ? __cancel_work_timer+0xc2/0xdf
: [<c05d2ebd>] blk_put_queue+0x12/0x14
: [<c06b41a8>] scsi_device_dev_release_usercontext+0xab/0xe9
: [<c06b40fd>] ? scsi_device_cls_release+0x14/0x14
: [<c0456bd9>] execute_in_process_context+0x23/0x6c
: [<c06b40e7>] scsi_device_dev_release+0x18/0x1a
: [<c069901a>] device_release+0x3f/0x77
: [<c05e838b>] ? kobject_release+0x156/0x15e
: [<c05e8356>] kobject_release+0x121/0x15e
: [<c05e838b>] ? kobject_release+0x156/0x15e
: [<c0856e7f>] ? __mutex_lock_common+0x30c/0x320
: [<c05e8235>] ? kobject_del+0x2c/0x2c
: [<c05e9517>] kref_put+0x39/0x42
: [<c05e81b2>] kobject_put+0x46/0x4c
: [<c0474f13>] ? module_refcount+0x6b/0x7c
: [<c0698e64>] put_device+0x14/0x16
: [<c06a9dd2>] scsi_device_put+0x37/0x3b
: [<c06b7f12>] scsi_disk_put+0x2a/0x38
: [<c06b881c>] sd_release+0xa8/0xb1
: [<c0527636>] ? bdev_inode_switch_bdi+0x80/0x86
: [<c0528348>] __blkdev_put+0xbc/0x14c
: [<c05283cd>] __blkdev_put+0x141/0x14c
: [<c05284cf>] blkdev_put+0xf7/0xfd
: [<c0502bb3>] kill_block_super+0x5c/0x60
: [<c0502e3d>] deactivate_locked_super+0x32/0x5e
: [<c05035b8>] deactivate_super+0x31/0x34
: [<c0516f7d>] mntput_no_expire+0xb5/0xb9
: [<c0517972>] sys_umount+0x270/0x297
: [<c08587ec>] syscall_call+0x7/0xb