Comment 16 for bug 1578011

A short update on that: I am running 4.4.0-31-generic now, and although i can not see from the changelog what would have changed in that regard, recognizing an external display connected to a docking station is no problem anymore. But after asuspend/resume-Cycle, the internal monitor will not switch on again anymore, and kernel seems non-responding to requests via sysrq. As such, I currently can not help with any kernel output in that case. If you could give me any advice in how to collect kernel output in that case, I'd be happy to deliver it.
Attached is a kernel warning, which happens after unplugging from the docking station:

Jul 24 21:06:03 synlap01 kernel: [84597.934350] ------------[ cut here ]------------
Jul 24 21:06:03 synlap01 kernel: [84597.934388] WARNING: CPU: 2 PID: 21878 at /build/linux-dcxD3m/linux-4.4.0/ubuntu/i915/intel_dp_mst.c:522 intel_dp_destroy_mst_connector+0xec/0x100 [i915_
bpo]()
Jul 24 21:06:03 synlap01 kernel: [84597.934390] Disabling mst crtc failed with -22
Jul 24 21:06:03 synlap01 kernel: [84597.934392] Modules linked in: hid_logitech_hidpp hid_logitech_dj hid_generic usbhid snd_usb_audio hid snd_usbmidi_lib ctr ccm pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) ip6t_REJECT nf_reject_ipv6 xt_CHECKSUM ipt_REJECT nf_reject_ipv4 ebtable_filter ebtables ip6table_filter ip6_tables ipt_MASQUERADE nf_nat_masquerade_ipv4 xt_addrtype br_netfilter bridge stp llc aufs iptable_nat nf_nat_ipv4 nf_nat xt_tcpudp nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack iptable_filter iptable_mangle ip_tables x_tables rfcomm bnep binfmt_misc zfs(PO) zunicode(PO) zcommon(PO) znvpair(PO) spl(O) zavl(PO) arc4 intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp snd_hda_codec_hdmi snd_soc_skl snd_soc_skl_ipc snd_hda_codec_realtek snd_hda_codec_generic snd_hda_ext_core snd_soc_sst_ipc snd_soc_sst_dsp snd_soc_core snd_compress ac97_bus snd_pcm_dmaengine dw_dmac_core joydev input_leds snd_hda_intel cdc_mbim serio_raw iwlmvm cdc_wdm snd_hda_codec cdc_ncm snd_hda_core usbnet snd_hwdep mii mac80211 btusb btrtl btbcm btintel qcserial usb_wwan bluetooth usbserial snd_pcm iwlwifi rtsx_pci_ms memstick cfg80211 thinkpad_acpi nvram snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer snd soundcore mac_hid shpchp mei_me mei kvm_intel kvm irqbypass parport_pc ppdev lp parport autofs4 xfs btrfs drbg ansi_cprng algif_skcipher af_alg dm_crypt raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear rtsx_pci_sdmmc crct10dif_pclmul crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd i915_bpo intel_ips rtsx_pci i2c_algo_bit psmouse drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt e1000e fb_sys_fops drm ptp pps_core wmi video fjes
Jul 24 21:06:03 synlap01 kernel: [84597.934597] CPU: 2 PID: 21878 Comm: kworker/2:3 Tainted: P OE 4.4.0-31-generic #50-Ubuntu
Jul 24 21:06:03 synlap01 kernel: [84597.934599] Hardware name: LENOVO 20FAS05Q00/20FAS05Q00, BIOS N1CET37W (1.05 ) 01/15/2016
Jul 24 21:06:03 synlap01 kernel: [84597.934610] Workqueue: events drm_dp_destroy_connector_work [drm_kms_helper]
Jul 24 21:06:03 synlap01 kernel: [84597.934612] 0000000000000286 000000004e977f58 ffff880291d63cd8 ffffffff813f1143
Jul 24 21:06:03 synlap01 kernel: [84597.934616] ffff880291d63d20 ffffffffc0282738 ffff880291d63d10 ffffffff81081102
Jul 24 21:06:03 synlap01 kernel: [84597.934619] ffff880424a02800 ffff880503d77800 ffff8800b413aa58 ffff8800b413a658
Jul 24 21:06:03 synlap01 kernel: [84597.934622] Call Trace:
Jul 24 21:06:03 synlap01 kernel: [84597.934629] [<ffffffff813f1143>] dump_stack+0x63/0x90
Jul 24 21:06:03 synlap01 kernel: [84597.934634] [<ffffffff81081102>] warn_slowpath_common+0x82/0xc0
Jul 24 21:06:03 synlap01 kernel: [84597.934637] [<ffffffff8108119c>] warn_slowpath_fmt+0x5c/0x80
Jul 24 21:06:03 synlap01 kernel: [84597.934647] [<ffffffffc013ab32>] ? drm_atomic_helper_set_config+0x92/0xb0 [drm_kms_helper]
Jul 24 21:06:03 synlap01 kernel: [84597.934669] [<ffffffffc005710e>] ? drm_atomic_state_free+0x4e/0x70 [drm]
Jul 24 21:06:03 synlap01 kernel: [84597.934702] [<ffffffffc023047c>] intel_dp_destroy_mst_connector+0xec/0x100 [i915_bpo]
Jul 24 21:06:03 synlap01 kernel: [84597.934712] [<ffffffffc013694d>] drm_dp_destroy_connector_work+0xad/0x150 [drm_kms_helper]
Jul 24 21:06:03 synlap01 kernel: [84597.934717] [<ffffffff8109a2c5>] process_one_work+0x165/0x480
Jul 24 21:06:03 synlap01 kernel: [84597.934720] [<ffffffff8109a62b>] worker_thread+0x4b/0x4c0
Jul 24 21:06:03 synlap01 kernel: [84597.934724] [<ffffffff8109a5e0>] ? process_one_work+0x480/0x480
Jul 24 21:06:03 synlap01 kernel: [84597.934727] [<ffffffff810a0808>] kthread+0xd8/0xf0
Jul 24 21:06:03 synlap01 kernel: [84597.934729] [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
Jul 24 21:06:03 synlap01 kernel: [84597.934734] [<ffffffff8182decf>] ret_from_fork+0x3f/0x70
Jul 24 21:06:03 synlap01 kernel: [84597.934737] [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
Jul 24 21:06:03 synlap01 kernel: [84597.934741] ---[ end trace b87d7a74c9a0e017 ]---