During shutdown of desktop running SuSE Tumbleweed(Release:20161010) sometimes receiving following kernel BUG messages and system is not shutdown. 
Seems to be regression from previous kernel,tested this with kernel 4.6.3-1-default, and system shutdown/reboot is completed without hang.
I have found two BUG messages (both __ww_mutex_lock) in shutdown logs from whole history of journalctl , however shutdown is never completed with kernel 4.7.6-1-default. 

00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b) (prog-if 00 [VGA controller])
        Subsystem: Hewlett-Packard Company Device 198f
        Flags: bus master, fast devsel, latency 0, IRQ 48
        Memory at d0000000 (64-bit, non-prefetchable) [size=4M]
        Memory at c0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at 3000 [size=64]
        [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
        Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Capabilities: [d0] Power Management version 2
        Capabilities: [a4] PCI Advanced Features
        Kernel driver in use: i915
        Kernel modules: i915


I have external display connected via displayport on docking station. 

Oct 21 13:40:48 m.site systemd-logind[1376]: System is powering down.
Oct 21 13:40:48 m.site gnome-session[25988]: gnome-session-binary[25988]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 21 13:40:48 m.site gnome-session-binary[25988]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 21 13:40:48 m.site systemd[1]: Stopping User Manager for UID 473...
Oct 21 13:40:48 m.site evolution-alarm[26364]: Error reading events from display: Broken pipe
Oct 21 13:40:48 m.site kernel: traps: gnome-shell-por[27673] trap int3 ip:7f598b56a0e1 sp:7ffc3b8c9220 error:0
Oct 21 13:40:48 m.site kernel: traps: gnome-software[26340] trap int3 ip:7f075f1950e1 sp:7ffecf9a2900 error:0
Oct 21 13:40:48 m.site audit[26364]: ANOM_ABEND auid=1000 uid=1000 gid=100 ses=2 pid=26364 comm="evolution-alarm" exe="/usr/lib/evolution/evolution-alarm-
Oct 21 13:40:48 m.site polkitd[1401]: Unregistered Authentication Agent for unix-session:2 (system bus name :1.5081, object path /org/freedesktop/PolicyKi
Oct 21 13:40:48 m.site gnome-shell-por[27673]: Error reading events from display: Broken pipe
Oct 21 13:40:48 m.site audit[27673]: ANOM_ABEND auid=1000 uid=1000 gid=100 ses=2 pid=27673 comm="gnome-shell-por" exe="/usr/lib/gnome-shell/gnome-shell-po
Oct 21 13:40:48 m.site gnome-software[26340]: Error reading events from display: Broken pipe
Oct 21 13:40:48 m.site audit[26340]: ANOM_ABEND auid=1000 uid=1000 gid=100 ses=2 pid=26340 comm="gnome-software" exe="/usr/bin/gnome-software" sig=5
Oct 21 13:40:48 m.site systemd[1]: Stopping Login and scanning of iSCSI devices...

Oct 21 13:40:49 m.site kernel: traps: gnome-shell[2210] trap int3 ip:7fc3fa8f90e1 sp:7ffe25b5e6e0 error:0
Oct 21 13:40:49 m.site kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000250
Oct 21 13:40:59 m.site kernel: IP: [<ffffffff816b9b6a>] __ww_mutex_lock+0xa/0x80
Oct 21 13:41:00 m.site kernel: PGD 0 
Oct 21 13:41:00 m.site kernel: Oops: 0002 [#1] PREEMPT SMP
Oct 21 13:41:00 m.site kernel: Modules linked in: vhost_net vhost macvtap macvlan fuse cmac rfcomm xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables af_packet bnep msr snd_hda_codec_idt snd_hda_codec_hdmi snd_hda_codec_generic snd_usb_audio snd_usbmidi_lib snd_hda_intel snd_hda_codec snd_hda_core snd_rawmidi snd_hwdep snd_seq_device snd_pcm snd_timer snd arc4 intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp soundcore kvm_intel btusb iwlmvm mac80211 btrtl kvm btbcm btintel iwlwifi irqbypass tpm_infineon bluetooth crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel
Oct 21 13:41:00 m.site kernel:  aes_x86_64 lrw gf128mul mei_wdt glue_helper cfg80211 hp_wmi sparse_keymap rfkill uvcvideo videobuf2_vmalloc videobuf2_memops rtsx_pci_ms videobuf2_v4l2 hp_accel videobuf2_core memstick videodev lis3lv02d mei_me tpm_tis ppdev e1000e parport_pc ptp parport pps_core i2c_i801 thermal ablk_helper joydev input_polldev battery iTCO_wdt iTCO_vendor_support lpc_ich mei shpchp wmi pcspkr tpm fjes ac intel_smartconnect cryptd hp_wireless hid_generic usbhid rtsx_pci_sdmmc mmc_core serio_raw i915 ehci_pci i2c_algo_bit ehci_hcd xhci_pci drm_kms_helper syscopyarea sysfillrect xhci_hcd sysimgblt fb_sys_fops rtsx_pci mfd_core usbcore drm usb_common video button raid0 raid456 async_raid6_recov async_memcpy async_pq async_xor xor async_tx raid6_pq raid10 raid1 md_mod dm_cache_smq dm_cache dm_persistent_data
Oct 21 13:41:00 m.site kernel:  sg dm_bio_prison dm_bufio libcrc32c crc32c_intel dm_mirror dm_region_hash dm_log dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua
Oct 21 13:41:00 m.site kernel: CPU: 1 PID: 1376 Comm: systemd-logind Not tainted 4.7.6-1-default #1
Oct 21 13:41:00 m.site kernel: Hardware name: Hewlett-Packard HP EliteBook 840 G1/198F, BIOS L71 Ver. 01.07 02/09/2014
Oct 21 13:41:00 m.site kernel: task: ffff88017da4c080 ti: ffff88042bbc4000 task.ti: ffff88042bbc4000
Oct 21 13:41:00 m.site kernel: RIP: 0010:[<ffffffff816b9b6a>]  [<ffffffff816b9b6a>] __ww_mutex_lock+0xa/0x80
Oct 21 13:41:00 m.site kernel: RSP: 0018:ffff88042bbc7a38  EFLAGS: 00010246
Oct 21 13:41:00 m.site kernel: RAX: 00000000ffffffff RBX: ffff88031b6ee840 RCX: 0000000000000005
Oct 21 13:41:00 m.site kernel: RDX: ffff88042c53c500 RSI: ffff88031b6ee840 RDI: 0000000000000250
Oct 21 13:41:00 m.site kernel: RBP: 0000000000000250 R08: 0000000000000360 R09: 0000000000000640
Oct 21 13:41:00 m.site kernel: R10: 0000000000000480 R11: 0000000000000640 R12: ffff8800b5cb4c00
Oct 21 13:41:00 m.site kernel: R13: ffff88042b306800 R14: ffff880423fce800 R15: ffff8800b5a9d000
Oct 21 13:41:00 m.site kernel: FS:  00007f05fc653280(0000) GS:ffff88043ea40000(0000) knlGS:0000000000000000
Oct 21 13:41:00 m.site kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Oct 21 13:41:00 m.site kernel: CR2: 0000000000000250 CR3: 0000000424296000 CR4: 00000000001406e0
Oct 21 13:41:00 m.site kernel: Stack:
Oct 21 13:41:00 m.site kernel:  ffffffffc0199177 ffffffffc0199177 0000000000000000 ffff8800b5cb4c00
Oct 21 13:41:00 m.site kernel:  ffff8800b5cb4c00 ffffffffc0199bcf ffff88042c254e80 ffff8800b5cb4c00
Oct 21 13:41:00 m.site kernel:  0000000000000000 0000000000000000 ffff880423fce800 ffffffffc02c89ee
Oct 21 13:41:00 m.site kernel: Call Trace:
Oct 21 13:41:00 m.site kernel:  [<ffffffffc0199177>] drm_modeset_lock+0x47/0xd0 [drm]
Oct 21 13:41:00 m.site kernel:  [<ffffffffc0199bcf>] drm_atomic_get_connector_state+0x2f/0x1c0 [drm]
Oct 21 13:41:00 m.site kernel:  [<ffffffffc02c89ee>] __drm_atomic_helper_set_config+0x24e/0x320 [drm_kms_helper]
Oct 21 13:41:00 m.site kernel:  [<ffffffffc02c9a6e>] restore_fbdev_mode+0x21e/0x260 [drm_kms_helper]
Oct 21 13:41:00 m.site kernel:  [<ffffffffc02cbd6e>] drm_fb_helper_restore_fbdev_mode_unlocked+0x2e/0x70 [drm_kms_helper]
Oct 21 13:41:00 m.site kernel:  [<ffffffffc02cbdd9>] drm_fb_helper_set_par+0x29/0x50 [drm_kms_helper]
Oct 21 13:41:00 m.site kernel:  [<ffffffffc03b5536>] intel_fbdev_set_par+0x16/0x60 [i915]
Oct 21 13:41:00 m.site kernel:  [<ffffffff8140bc40>] fb_set_var+0x200/0x3e0
Oct 21 13:41:00 m.site kernel:  [<ffffffff81402a18>] fbcon_blank+0x2b8/0x2f0
Oct 21 13:41:00 m.site kernel:  [<ffffffff814939d7>] do_unblank_screen+0xc7/0x190
Oct 21 13:41:00 m.site kernel:  [<ffffffff81489e59>] vt_ioctl+0x4c9/0x1250
Oct 21 13:41:00 m.site kernel:  [<ffffffff8147e9be>] tty_ioctl+0x33e/0xc20
Oct 21 13:41:00 m.site kernel:  [<ffffffff81222f80>] do_vfs_ioctl+0x90/0x5c0
Oct 21 13:41:00 m.site kernel:  [<ffffffff81223524>] SyS_ioctl+0x74/0x80
Oct 21 13:41:00 m.site kernel:  [<ffffffff816bc276>] entry_SYSCALL_64_fastpath+0x1e/0xa8
Oct 21 13:41:00 m.site kernel: DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x1e/0xa8
Oct 21 13:41:00 m.site kernel: 
Oct 21 13:41:00 m.site kernel: Leftover inexact backtrace:
Oct 21 13:41:00 m.site kernel: Code: 18 48 8b 54 24 10 48 89 42 08 48 89 10 49 8b 47 08 48 39 44 24 08 75 8d 41 c7 07 00 00 00 00 eb 84 0f 1f 44 00 00 b8 ff ff ff ff <f0> 0f c1 07 83 e8 01 78 30 41 55 83 46 10 01 41 54 55 53 48 89 
Oct 21 13:41:00 m.site kernel: RIP  [<ffffffff816b9b6a>] __ww_mutex_lock+0xa/0x80
Oct 21 13:41:00 m.site kernel:  RSP <ffff88042bbc7a38>
Oct 21 13:41:00 m.site kernel: CR2: 0000000000000250
Oct 21 13:41:00 m.site kernel: ---[ end trace 4708ce1374460817 ]---