I haven't narrowed down when this started, other than "sometime between 10/23 and 11/13". Looks to me like something in the i915/DRM arena doesn't play nice with mutex debugging.
The system still acts fine, but my /var partition filled up due to gigabytes of the following two warning calls repeating over and over. I'm not sure what triggers it, except that I know that it doesn't start when the Gnome login screen is displaying, but something after I login starts it complaining.
Nov 17 22:13:16 turing-police kernel: [ 163.835592] ------------[ cut here ]------------ Nov 17 22:13:16 turing-police kernel: [ 163.835712] WARNING: CPU: 0 PID: 0 at kernel/locking/mutex.c:1419 mutex_trylock+0x13a/0x150 Nov 17 22:13:16 turing-police kernel: [ 163.835717] Modules linked in: fuse nf_log_ipv6 ts_bm nf_log_ipv4 nf_log_common xt_string xt_LOG bpfilter sunrpc algif_hash algif_skcipher af_alg bnep vfat fat ath3k btusb btrtl btbcm btintel bluetooth ecdh_generic ecc uas intel_rapl_msr rtsx_pci_sdmmc ath9k ath9k_common ath9k_hw intel_rapl_common intel_soc_dts_thermal intel_soc_dts_iosf intel_powerclamp crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel cryptd serio_raw snd_hda_codec_realtek snd_hda_codec_hdmi ath rtsx_pci bfq fan toshiba_acpi toshiba_bluetooth mei_txe industrialio pwm_lpss_platform i2c_hid rfkill_gpio pwm_lpss sch_fq_codel Nov 17 22:13:16 turing-police kernel: [ 163.835795] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G T 5.4.0-rc7-next-20191113-dirty #701 Nov 17 22:13:16 turing-police kernel: [ 163.835799] Hardware name: TOSHIBA Satellite C55-B/ZBWAA, BIOS 5.00 07/23/2015 Nov 17 22:13:16 turing-police kernel: [ 163.835806] RIP: 0010:mutex_trylock+0x13a/0x150 Nov 17 22:13:16 turing-police kernel: [ 163.835813] Code: 7b 70 45 31 c9 41 b8 01 00 00 00 31 c9 ba 01 00 00 00 31 f6 e8 87 5e 21 ff 58 48 8d 65 e8 b8 01 00 00 00 5b 41 5c 41 5d 5d c3 <0f> 0b e9 f7 fe ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 Nov 17 22:13:16 turing-police kernel: [ 163.835817] RSP: 0018:ffff989080003d70 EFLAGS: 00010006 Nov 17 22:13:16 turing-police kernel: [ 163.835823] RAX: 0000000080010002 RBX: ffff974932946e08 RCX: 00000000ffffffff Nov 17 22:13:16 turing-police kernel: [ 163.835828] RDX: ffffffffb4a2b900 RSI: ffff974934107c88 RDI: ffff974932946e08 Nov 17 22:13:16 turing-police kernel: [ 163.835832] RBP: ffff989080003d90 R08: 0000000000000000 R09: 0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.835837] R10: 0000000000000000 R11: 0000000000000000 R12: ffff974932946e00 Nov 17 22:13:16 turing-police kernel: [ 163.835841] R13: ffff989080003e18 R14: ffff989080003e08 R15: ffff97493333ae08 Nov 17 22:13:16 turing-police kernel: [ 163.835846] FS: 0000000000000000(0000) GS:ffff974937800000(0000) knlGS:0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.835850] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Nov 17 22:13:16 turing-police kernel: [ 163.835855] CR2: 0000560c069bc708 CR3: 0000000088a24000 CR4: 00000000001006f0 Nov 17 22:13:16 turing-police kernel: [ 163.835859] Call Trace: Nov 17 22:13:16 turing-police kernel: [ 163.835864] <IRQ> Nov 17 22:13:16 turing-police kernel: [ 163.835878] active_retire+0x36/0x70 Nov 17 22:13:16 turing-police kernel: [ 163.835886] node_retire+0x19/0x20 Nov 17 22:13:16 turing-police kernel: [ 163.835898] intel_engine_breadcrumbs_irq+0x296/0x410 Nov 17 22:13:16 turing-police kernel: [ 163.835924] gen6_gt_irq_handler+0x5e/0x130 Nov 17 22:13:16 turing-police kernel: [ 163.835935] valleyview_irq_handler+0x2a1/0x2e0 Nov 17 22:13:16 turing-police kernel: [ 163.835956] __handle_irq_event_percpu+0x40/0x2c0 Nov 17 22:13:16 turing-police kernel: [ 163.835962] ? handle_irq_event+0x2c/0x53 Nov 17 22:13:16 turing-police kernel: [ 163.835977] handle_irq_event_percpu+0x32/0x90 Nov 17 22:13:16 turing-police kernel: [ 163.835990] handle_irq_event+0x34/0x53 Nov 17 22:13:16 turing-police kernel: [ 163.836002] handle_edge_irq+0x95/0x1d0 Nov 17 22:13:16 turing-police kernel: [ 163.836012] do_IRQ+0x83/0x190 Nov 17 22:13:16 turing-police kernel: [ 163.836023] common_interrupt+0xf/0xf Nov 17 22:13:16 turing-police kernel: [ 163.836029] </IRQ> Nov 17 22:13:16 turing-police kernel: [ 163.836036] RIP: 0010:cpuidle_enter_state+0xc3/0x610 Nov 17 22:13:16 turing-police kernel: [ 163.836041] Code: 00 00 31 ff e8 3e 0b 65 ff 80 7d c0 00 74 12 9c 58 f6 c4 02 0f 85 6e 03 00 00 31 ff e8 66 ff 6c ff e8 11 93 73 ff fb 45 85 ed <0f> 88 b4 02 00 00 4d 63 f5 49 83 fe 09 0f 87 83 04 00 00 49 6b c6 Nov 17 22:13:16 turing-police kernel: [ 163.836046] RSP: 0018:ffffffffb4a03d80 EFLAGS: 00000206 ORIG_RAX: ffffffffffffffdc Nov 17 22:13:16 turing-police kernel: [ 163.836052] RAX: ffffffffb4a2b900 RBX: ffffb8907fa10030 RCX: 0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.836056] RDX: 0000000000000019 RSI: 0000000000000006 RDI: ffffffffb4a2b900 Nov 17 22:13:16 turing-police kernel: [ 163.836060] RBP: ffffffffb4a03dd0 R08: 000000262554d345 R09: 0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.836065] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffb4b76560 Nov 17 22:13:16 turing-police kernel: [ 163.836069] R13: 0000000000000003 R14: 0000000000000003 R15: 0000000000000003 Nov 17 22:13:16 turing-police kernel: [ 163.836111] cpuidle_enter+0x29/0x40 Nov 17 22:13:16 turing-police kernel: [ 163.836122] call_cpuidle+0x36/0x60 Nov 17 22:13:16 turing-police kernel: [ 163.836132] do_idle+0x1c0/0x210 Nov 17 22:13:16 turing-police kernel: [ 163.836149] cpu_startup_entry+0x1b/0x1d Nov 17 22:13:16 turing-police kernel: [ 163.836158] rest_init+0x1bf/0x2eb Nov 17 22:13:16 turing-police kernel: [ 163.836170] arch_call_rest_init+0x11/0x63 Nov 17 22:13:16 turing-police kernel: [ 163.836179] start_kernel+0x7bf/0x7ef Nov 17 22:13:16 turing-police kernel: [ 163.836194] x86_64_start_reservations+0x4f/0x70 Nov 17 22:13:16 turing-police kernel: [ 163.836204] x86_64_start_kernel+0x7b/0x9e Nov 17 22:13:16 turing-police kernel: [ 163.836214] secondary_startup_64+0xa4/0xb0 Nov 17 22:13:16 turing-police kernel: [ 163.836242] irq event stamp: 451082 Nov 17 22:13:16 turing-police kernel: [ 163.836249] hardirqs last enabled at (451079): [<ffffffffb3b09bff>] cpuidle_enter_state+0xbf/0x610 Nov 17 22:13:16 turing-police kernel: [ 163.836254] hardirqs last disabled at (451080): [<ffffffffb3002e6a>] trace_hardirqs_off_thunk+0x1a/0x1c Nov 17 22:13:16 turing-police kernel: [ 163.836261] softirqs last enabled at (451082): [<ffffffffb3116f1c>] _local_bh_enable+0x1c/0x30 Nov 17 22:13:16 turing-police kernel: [ 163.836267] softirqs last disabled at (451081): [<ffffffffb31174f0>] irq_enter+0x50/0x70 Nov 17 22:13:16 turing-police kernel: [ 163.836272] ---[ end trace 2e91f38e14c84d13 ]--- Nov 17 22:13:16 turing-police kernel: [ 163.836341] ------------[ cut here ]------------ Nov 17 22:13:16 turing-police kernel: [ 163.836455] WARNING: CPU: 0 PID: 0 at kernel/locking/mutex.c:737 mutex_unlock+0x27/0x40 Nov 17 22:13:16 turing-police kernel: [ 163.836459] Modules linked in: fuse nf_log_ipv6 ts_bm nf_log_ipv4 nf_log_common xt_string xt_LOG bpfilter sunrpc algif_hash algif_skcipher af_alg bnep vfat fat ath3k btusb btrtl btbcm btintel bluetooth ecdh_generic ecc uas intel_rapl_msr rtsx_pci_sdmmc ath9k ath9k_common ath9k_hw intel_rapl_common intel_soc_dts_thermal intel_soc_dts_iosf intel_powerclamp crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel cryptd serio_raw snd_hda_codec_realtek snd_hda_codec_hdmi ath rtsx_pci bfq fan toshiba_acpi toshiba_bluetooth mei_txe industrialio pwm_lpss_platform i2c_hid rfkill_gpio pwm_lpss sch_fq_codel Nov 17 22:13:16 turing-police kernel: [ 163.836518] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W T 5.4.0-rc7-next-20191113-dirty #701 Nov 17 22:13:16 turing-police kernel: [ 163.836522] Hardware name: TOSHIBA Satellite C55-B/ZBWAA, BIOS 5.00 07/23/2015 Nov 17 22:13:16 turing-police kernel: [ 163.836528] RIP: 0010:mutex_unlock+0x27/0x40 Nov 17 22:13:16 turing-police kernel: [ 163.836533] Code: 00 00 00 55 48 89 e5 41 54 49 89 fc 65 8b 05 d8 a6 09 4c a9 00 ff 1f 00 75 10 48 8b 75 08 4c 89 e7 e8 fd fc ff ff 41 5c 5d c3 <0f> 0b 48 8b 75 08 4c 89 e7 e8 eb fc ff ff 41 5c 5d c3 0f 1f 80 00 Nov 17 22:13:16 turing-police kernel: [ 163.836538] RSP: 0018:ffff989080003d50 EFLAGS: 00010006 Nov 17 22:13:16 turing-police kernel: [ 163.836543] RAX: 0000000080010002 RBX: ffff974934107c88 RCX: 00000000ffffffff Nov 17 22:13:16 turing-police kernel: [ 163.836548] RDX: ffffffffb4a2b900 RSI: ffff974932946e78 RDI: ffff974932946e08 Nov 17 22:13:16 turing-police kernel: [ 163.836552] RBP: ffff989080003d58 R08: 0000002625672d76 R09: 0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.836557] R10: 0000000000000001 R11: 0000000000000000 R12: ffff974932946e08 Nov 17 22:13:16 turing-police kernel: [ 163.836561] R13: ffff974932946e00 R14: ffff989080003e08 R15: ffff97493333ae08 Nov 17 22:13:16 turing-police kernel: [ 163.836566] FS: 0000000000000000(0000) GS:ffff974937800000(0000) knlGS:0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.836571] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Nov 17 22:13:16 turing-police kernel: [ 163.836575] CR2: 0000560c069bc708 CR3: 0000000088a24000 CR4: 00000000001006f0 Nov 17 22:13:16 turing-police kernel: [ 163.836579] Call Trace: Nov 17 22:13:16 turing-police kernel: [ 163.836583] <IRQ> Nov 17 22:13:16 turing-police kernel: [ 163.836593] __active_retire+0x67/0x140 Nov 17 22:13:16 turing-police kernel: [ 163.836605] active_retire+0x5f/0x70 Nov 17 22:13:16 turing-police kernel: [ 163.836614] node_retire+0x19/0x20 Nov 17 22:13:16 turing-police kernel: [ 163.836622] intel_engine_breadcrumbs_irq+0x296/0x410 Nov 17 22:13:16 turing-police kernel: [ 163.836649] gen6_gt_irq_handler+0x5e/0x130 Nov 17 22:13:16 turing-police kernel: [ 163.836659] valleyview_irq_handler+0x2a1/0x2e0 Nov 17 22:13:16 turing-police kernel: [ 163.836679] __handle_irq_event_percpu+0x40/0x2c0 Nov 17 22:13:16 turing-police kernel: [ 163.836685] ? handle_irq_event+0x2c/0x53 Nov 17 22:13:16 turing-police kernel: [ 163.836699] handle_irq_event_percpu+0x32/0x90 Nov 17 22:13:16 turing-police kernel: [ 163.836712] handle_irq_event+0x34/0x53 Nov 17 22:13:16 turing-police kernel: [ 163.836723] handle_edge_irq+0x95/0x1d0 Nov 17 22:13:16 turing-police kernel: [ 163.836733] do_IRQ+0x83/0x190 Nov 17 22:13:16 turing-police kernel: [ 163.836743] common_interrupt+0xf/0xf Nov 17 22:13:16 turing-police kernel: [ 163.836749] </IRQ> Nov 17 22:13:16 turing-police kernel: [ 163.836756] RIP: 0010:cpuidle_enter_state+0xc3/0x610 Nov 17 22:13:16 turing-police kernel: [ 163.836761] Code: 00 00 31 ff e8 3e 0b 65 ff 80 7d c0 00 74 12 9c 58 f6 c4 02 0f 85 6e 03 00 00 31 ff e8 66 ff 6c ff e8 11 93 73 ff fb 45 85 ed <0f> 88 b4 02 00 00 4d 63 f5 49 83 fe 09 0f 87 83 04 00 00 49 6b c6 Nov 17 22:13:16 turing-police kernel: [ 163.836766] RSP: 0018:ffffffffb4a03d80 EFLAGS: 00000206 ORIG_RAX: ffffffffffffffdc Nov 17 22:13:16 turing-police kernel: [ 163.836772] RAX: ffffffffb4a2b900 RBX: ffffb8907fa10030 RCX: 0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.836776] RDX: 0000000000000019 RSI: 0000000000000006 RDI: ffffffffb4a2b900 Nov 17 22:13:16 turing-police kernel: [ 163.836780] RBP: ffffffffb4a03dd0 R08: 000000262554d345 R09: 0000000000000000 Nov 17 22:13:16 turing-police kernel: [ 163.836785] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffb4b76560 Nov 17 22:13:16 turing-police kernel: [ 163.836789] R13: 0000000000000003 R14: 0000000000000003 R15: 0000000000000003 Nov 17 22:13:16 turing-police kernel: [ 163.836829] cpuidle_enter+0x29/0x40 Nov 17 22:13:16 turing-police kernel: [ 163.836840] call_cpuidle+0x36/0x60 Nov 17 22:13:16 turing-police kernel: [ 163.836850] do_idle+0x1c0/0x210 Nov 17 22:13:16 turing-police kernel: [ 163.836867] cpu_startup_entry+0x1b/0x1d Nov 17 22:13:16 turing-police kernel: [ 163.836875] rest_init+0x1bf/0x2eb Nov 17 22:13:16 turing-police kernel: [ 163.836886] arch_call_rest_init+0x11/0x63 Nov 17 22:13:16 turing-police kernel: [ 163.836895] start_kernel+0x7bf/0x7ef Nov 17 22:13:16 turing-police kernel: [ 163.836910] x86_64_start_reservations+0x4f/0x70 Nov 17 22:13:16 turing-police kernel: [ 163.836920] x86_64_start_kernel+0x7b/0x9e Nov 17 22:13:16 turing-police kernel: [ 163.836929] secondary_startup_64+0xa4/0xb0 Nov 17 22:13:16 turing-police kernel: [ 163.836956] irq event stamp: 451082 Nov 17 22:13:16 turing-police kernel: [ 163.836963] hardirqs last enabled at (451079): [<ffffffffb3b09bff>] cpuidle_enter_state+0xbf/0x610 Nov 17 22:13:16 turing-police kernel: [ 163.836969] hardirqs last disabled at (451080): [<ffffffffb3002e6a>] trace_hardirqs_off_thunk+0x1a/0x1c Nov 17 22:13:16 turing-police kernel: [ 163.836974] softirqs last enabled at (451082): [<ffffffffb3116f1c>] _local_bh_enable+0x1c/0x30 Nov 17 22:13:16 turing-police kernel: [ 163.836980] softirqs last disabled at (451081): [<ffffffffb31174f0>] irq_enter+0x50/0x70 Nov 17 22:13:16 turing-police kernel: [ 163.836984] ---[ end trace 2e91f38e14c84d14 ]---