The error begun with

[  421.502977] [IGT] kms_pipe_crc_basic: starting subtest nonblocking-crc-pipe-B-frame-sequence

igt@kms_pipe_crc_basic@nonblocking-crc-pipe-c is an innocent victim.

I consider this bug to be about all softdog incompletes on CFL. I have to file the bug on something, so don't stare at the tests so far implicated. 

Reproduced also on igt@kms_flip@basic-flip-vs-dpm.
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3165/fi-cfl-s/igt@kms_flip@basic-flip-vs-dpms.html

This from dmesg appear frequently just before the softdog times out:

<3>[  354.277367] [drm:drm_atomic_helper_wait_for_flip_done] *ERROR* [CRTC:46:pipe B] flip_done timed out
<7>[  354.277608] [drm:verify_connector_state.isra.72 [i915]] [CONNECTOR:48:eDP-1]
<7>[  354.277718] [drm:intel_atomic_commit_tail [i915]] [CRTC:46:pipe B]
<7>[  354.277912] [drm:verify_single_dpll_state.isra.73 [i915]] DPLL 0
<14>[  354.289994] [IGT] kms_flip: exiting, ret=99
<3>[  364.517139] [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:46:pipe B] flip_done timed out
<3>[  374.757352] [drm:drm_atomic_helper_wait_for_flip_done] *ERROR* [CRTC:46:pipe B] flip_done timed out
<6>[  386.728770] [drm] GPU HANG: ecode 9:1:0xfffffffe, reason: Hang on bcs0, vcs0, vecs0, action: reset
<5>[  386.729156] i915 0000:00:02.0: Resetting bcs0 after gpu hang
<7>[  386.729960] [drm:gen8_init_common_ring [i915]] Execlists enabled for bcs0
<5>[  386.730083] i915 0000:00:02.0: Resetting vcs0 after gpu hang
<7>[  386.730312] [drm:gen8_init_common_ring [i915]] Execlists enabled for vcs0
<5>[  386.730320] i915 0000:00:02.0: Resetting vecs0 after gpu hang
<7>[  386.730458] [drm:gen8_init_common_ring [i915]] Execlists enabled for vecs0
<5>[  390.693538] i915 0000:00:02.0: Resetting rcs0 after gpu hang
<7>[  390.693959] [drm:gen8_init_common_ring [i915]] Execlists enabled for rcs0
<7>[  390.694170] [drm:init_workarounds_ring [i915]] rcs0: Number of context specific w/a: 16
<3>[  392.806459] [drm:i915_gem_idle_work_handler [i915]] *ERROR* Timeout waiting for engines to idle
<7>[  392.808157] [drm:missed_breadcrumb [i915]] rcs0 missed breadcrumb at intel_engine_disarm_breadcrumbs+0xb4/0xe0 [i915], irq posted? yes, current seqno=295740, last=295740
<7>[  392.833212] [drm:intel_atomic_check [i915]] New cdclk calculated to be logical 337500 kHz, actual 337500 kHz
<3>[  402.917171] [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:46:pipe B] flip_done timed out
<2>[  412.592339] softdog: Initiating panic

Also:
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3171/fi-cfl-s/igt@drv_module_reload@basic-reload-inject.html
and:
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3179/fi-cfl-s/igt@drv_module_reload@basic-no-display.html

Note: before softdog is triggered dmesg:



<4>[  536.788670] DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
<4>[  536.788683] ------------[ cut here ]------------
<4>[  536.788723] WARNING: CPU: 0 PID: 4959 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x4e/0x60
<4>[  536.788748] Modules linked in: i915(-) snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic snd_hda_codec snd_hwdep snd_hda_core snd_pcm vgem ax88179_178a usbnet x86_pkg_temp_thermal mii intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel e1000e ptp pps_core prime_numbers i2c_hid [last unloaded: snd_hda_intel]
<4>[  536.788878] CPU: 0 PID: 4959 Comm: drv_module_relo Tainted: G     U          4.14.0-rc3-CI-CI_DRM_3171+ #1
<4>[  536.788905] Hardware name: Intel Corporation CoffeeLake Client Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWX1.R00.X104.A03.1709140524 09/14/2017
<4>[  536.788939] task: ffff8804146b5440 task.stack: ffffc9000054c000
<4>[  536.788959] RIP: 0010:mutex_destroy+0x4e/0x60
<4>[  536.788974] RSP: 0018:ffffc9000054fd58 EFLAGS: 00010292
<4>[  536.788992] RAX: 000000000000002a RBX: ffff88044d8be108 RCX: 0000000000000000
<4>[  536.789013] RDX: 0000000080000001 RSI: 0000000000000001 RDI: ffffffff810f0cf0
<4>[  536.789033] RBP: ffffc9000054fd60 R08: 0000000000000001 R09: 0000000000000001
<4>[  536.789054] R10: 000000000f21cb81 R11: 0000000000000000 R12: ffff8803f5d12e98
<4>[  536.789074] R13: ffffffffa02c1d20 R14: ffffffffa02c1d90 R15: ffff880459b29308
<4>[  536.789095] FS:  00007f3c5d91f8c0(0000) GS:ffff88045d200000(0000) knlGS:0000000000000000
<4>[  536.789119] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[  536.789137] CR2: 000055967e4cf090 CR3: 00000004579f7006 CR4: 00000000003606f0
<4>[  536.789157] Call Trace:
<4>[  536.789172]  drm_fb_helper_fini+0xd9/0x130
<4>[  536.789264]  intel_fbdev_destroy+0x12/0x60 [i915]
<4>[  536.789349]  intel_fbdev_fini+0x28/0x30 [i915]
<4>[  536.789432]  intel_modeset_cleanup+0x45/0xa0 [i915]
<4>[  536.789492]  i915_driver_unload+0x92/0x180 [i915]
<4>[  536.789554]  i915_pci_remove+0x19/0x30 [i915]
<4>[  536.789607]  pci_device_remove+0x39/0xb0
<4>[  536.789625]  device_release_driver_internal+0x15d/0x220
<4>[  536.789653]  driver_detach+0x40/0x80
<4>[  536.789673]  bus_remove_driver+0x58/0xd0
<4>[  536.789694]  driver_unregister+0x2c/0x40
<4>[  536.789715]  pci_unregister_driver+0x36/0xb0
<4>[  536.789799]  i915_exit+0x1a/0x8b [i915]
<4>[  536.789821]  SyS_delete_module+0x18c/0x1e0
<4>[  536.789842]  entry_SYSCALL_64_fastpath+0x1c/0xb1
<4>[  536.789858] RIP: 0033:0x7f3c5be37287
<4>[  536.789871] RSP: 002b:00007ffdf2f1f208 EFLAGS: 00000246 ORIG_RAX: 00000000000000b0
<4>[  536.789896] RAX: ffffffffffffffda RBX: ffffffff81493a03 RCX: 00007f3c5be37287
<4>[  536.789917] RDX: 0000000000000001 RSI: 0000000000000800 RDI: 00005641d2708e48
<4>[  536.789938] RBP: ffffc9000054ff88 R08: 0000000000000000 R09: 0000000000000080
<4>[  536.789958] R10: 00007f3c5d91f8c0 R11: 0000000000000246 R12: 0000000000000000
<4>[  536.789978] R13: 00007ffdf2f1f3f0 R14: 0000000000000000 R15: 0000000000000000
<4>[  536.790003]  ? __this_cpu_preempt_check+0x13/0x20
<4>[  536.790024] Code: 00 00 5b 5d c3 e8 93 b9 3a 00 85 c0 74 ec 8b 05 e1 53 c3 01 85 c0 75 e2 48 c7 c6 86 a6 c7 81 48 c7 c7 8b 8d c6 81 e8 03 ae 01 00 <0f> ff eb cb 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 b8 
<4>[  536.790210] ---[ end trace 824a7d8ce15a77b4 ]---
<7>[  536.829138] [drm:gmbus_xfer [i915]] GMBUS [i915 gmbus dpb] timed out, falling back to bit banging on pin 1
<7>[  536.843505] [drm:drm_do_probe_ddc_edid] drm: skipping non-existent adapter i915 gmbus dpb
<7>[  536.895952] [drm:gmbus_xfer [i915]] GMBUS [i915 gmbus dpb] timed out, falling back to bit banging on pin 1
<7>[  536.910417] [drm:drm_dp_dual_mode_detect] DP dual mode HDMI ID:  (err -6)
<7>[  536.910442] [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:62:HDMI-A-1] disconnected
<4>[  536.910472] general protection fault: 0000 [#1] PREEMPT SMP
<4>[  536.910488] Modules linked in: i915(-) snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic snd_hda_codec snd_hwdep snd_hda_core snd_pcm vgem ax88179_178a usbnet x86_pkg_temp_thermal mii intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel e1000e ptp pps_core prime_numbers i2c_hid [last unloaded: snd_hda_intel]
<4>[  536.910601] CPU: 4 PID: 224 Comm: kworker/4:3 Tainted: G     U  W       4.14.0-rc3-CI-CI_DRM_3171+ #1
<4>[  536.910625] Hardware name: Intel Corporation CoffeeLake Client Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWX1.R00.X104.A03.1709140524 09/14/2017
<4>[  536.910718] Workqueue: events intel_dp_modeset_retry_work_fn [i915]
<4>[  536.910738] task: ffff8804573a8040 task.stack: ffffc9000121c000
<4>[  536.910757] RIP: 0010:drm_setup_crtcs+0x143/0xbf0
<4>[  536.910771] RSP: 0018:ffffc9000121fd20 EFLAGS: 00010202
<4>[  536.910787] RAX: 6b6b6b6b6b6b6b6b RBX: 0000000000000031 RCX: 0000000000000000
<4>[  536.910806] RDX: 0000000000000003 RSI: 0000000000000780 RDI: ffffc9000121fc98
<4>[  536.910824] RBP: ffffc9000121fdb8 R08: ffff8804533442f0 R09: ffff88044dae8e88
<4>[  536.910842] R10: ffffc9000121fb78 R11: 0000000000000000 R12: 0000000000000004
<4>[  536.910861] R13: ffff88044d8bdfa8 R14: 0000000000000780 R15: 0000000000000438
<4>[  536.910880] FS:  0000000000000000(0000) GS:ffff88045d300000(0000) knlGS:0000000000000000
<4>[  536.910901] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[  536.910917] CR2: 00007f0b3594e000 CR3: 0000000456b07004 CR4: 00000000003606e0
<4>[  536.910936] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
<4>[  536.910954] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
<4>[  536.910971] Call Trace:
<4>[  536.910990]  drm_fb_helper_hotplug_event.part.18+0x7e/0xc0
<4>[  536.911007]  drm_fb_helper_hotplug_event+0x1a/0x20
<4>[  536.911078]  intel_fbdev_output_poll_changed+0x1a/0x20 [i915]
<4>[  536.911096]  drm_kms_helper_hotplug_event+0x27/0x30
<4>[  536.911162]  intel_dp_modeset_retry_work_fn+0x77/0x80 [i915]
<4>[  536.911181]  process_one_work+0x233/0x660
<4>[  536.911199]  worker_thread+0x206/0x3b0
<4>[  536.911214]  kthread+0x152/0x190
<4>[  536.911226]  ? process_one_work+0x660/0x660
<4>[  536.911240]  ? kthread_create_on_node+0x40/0x40
<4>[  536.911257]  ret_from_fork+0x27/0x40
<4>[  536.911272] Code: 06 00 00 45 8b 45 20 31 db 45 31 e4 45 85 c0 0f 8e 91 06 00 00 44 8b 75 94 44 8b 7d 90 49 8b 45 28 49 63 d4 44 89 f6 41 83 c4 01 <48> 8b 04 d0 44 89 fa 48 8b 38 48 8b 87 a8 01 00 00 ff 50 20 01 
<1>[  536.911432] RIP: drm_setup_crtcs+0x143/0xbf0 RSP: ffffc9000121fd20
<4>[  536.911472] ---[ end trace 824a7d8ce15a77b5 ]---
<2>[  618.454192] softdog: Initiating panic
<0>[  618.454213] Kernel panic - not syncing: Software Watchdog Timer expired
<0>[  618.454308] Kernel Offset: disabled

again:
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3211/fi-cfl-s/igt@kms_pipe_crc_basic@nonblocking-crc-pipe-b.html

The drv_module_reload_basic hangs should be gone now with

commit 886c6b8692ba5f71b578097524b3b082e2e02119 (drm-intel/for-linux-next, drm-intel/drm-intel-next-queued)
Author: Manasi Navare <manasi.d.navare@intel.com>
Date:   Thu Oct 26 14:52:00 2017 -0700

    drm/i915: Cancel the modeset retry work during modeset cleanup

Integrated in https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3288/commits_short.log

There hasn't been any softdog incomplete on CFL-s since https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_3179/fi-cfl-s/igt@drv_module_reload@basic-no-display.html, so I am not sure the patch has anything to do with it. Anyways it is fine with me to close this.