4.14.44: BUG_ON(!list_empty(&sem->wait_list));

[Daniel J Blueman]

Plugging in a USB-C power source on my Dell XPS 9550 trips an ACPI
BUG_ON [1], reproducible with mainline 4.14.44, suggesting other
threads are waiting for semaphore acquisition due to
"BUG_ON(!list_empty(&sem->wait_list))".

This is the current 1.7.0 BIOS with Ubuntu 18.04 userspace, plugging
in an LG 27UD88 (also with the current firmware) monitor USB-C
connection which apparently advertises 60W charging (x1,
PowerDelivery, DisplayPort alternative mode, data). The same issues
reproduce on a Dell Precision 5510 with Ubuntu 16.04, the shipped
kernel and 4.14.44.

I can enable ACPI debugging if useful? Perhaps ACPI_DB_MUTEX or other
levels would be appropriate?

Thanks,
  Daniel

-- [1]

kernel BUG at /home/kernel/COD/linux/drivers/acpi/osl.c:1201
invalid opcode: 0000 [#1] SMP PTI
Modules linked in: [...]
CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 4.14.44-041444-generic
#201805251612
Hardware name: Dell Inc. XPS 15 9550/, BIOS 1.7.0 02/23/2018
task: ffff9bc2ab6b9740 task.stack: ffffbOca80034000
RIP: 0010:acpi_os_delete_semaphore+0x6d/0x70
RSP: 0018:ffffbOca80037be8 EFLAGS: 00010283
RAX: ffffbOca83f8fc40 RBX: ffff9bc238b5dbe0 RCX: 0000000000000000
RDX: ffff9bc238b5dbe8 RSI: 0000000000000000 RDI: ffff9bc238b5dbe0
RBP: ffff9bc2adlc0990 ROB: ffff9bc2bdc25f20 R09: ffff9bc29ee56300
R10: ffffe03bd2796440 R11: ffff9bc2ad183fa0 R12: ffff9bc22f1321e0
R13: 0000000000000001 R14: 0000000000000001 R15: ffff9bc22f132eb0
FS: 00007fc03886f940(0000) GS:ffff9bc2bdc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CRO: 0000000080050033
CR2: 00007ffc645e70f8 CR3: 000000049e120001 CR4: 00000000003606f0
Call Trace:
acpi_ex_system_reset_event+0x3f/0x65
acpi_ex_opcode_1A_OT_0R+0x70/0xfa
acpi_ds_exec_end_op+0x15d/0x71b
acpi_ps_parse_loop+0x929/0x9d6
? acpi_ds_result_push+0x82/0x1d2
acpi_ps_parse_aml+0x1a2/0x4af
acpi_ps_execute_method+0x1ef/0x2ab
acpi_ns_evaluate+0x2e4/0x41d
acpi_evaluate_object+0x1cb/0x38e
acpi_enter_sleep_state_prep+0xae/0x13a
acpi_sleep_prepare.part.2+0x2e/0x40
acpi_power_off_prepare+0xf/0x20
[38871.1925361 kernel_power_off+0x42/0x70
SYSC_reboot+0x12f/0x210
? handle_mm_fault+0xea/0x1e0
[38871.1925861 ? do_writev+0x5e/0xf0
? do_writev+0x5e/0xf0
do_syscall_64+0x6e/0x120
entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x7fc03839b373
RSP: 002b:00007ffc645e70f8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9
RAX: ffffffffffffffda RBX: 000000004321fedc RCX: 00007fc03839b373
ROX: 000000004321fedc RSI: 0000000028121969 RDI: 00000000fee1dead
RBP: 00007ffc645e7160 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000202 R12: 00007ffc645e7168
R13: 0000000000000000 R14: 0000001b00000004 R15: 00007ffc645e7458
Code: b8 00 04 00 00 48 c7 c1 c3 91 28 ab 48 c7 c2 20 91 28 ab be of
04 00 00 bf 00 00 00 01 03 41 85 04 00 58 eb b0 b8 01 10 00 00 c3 <Of>
Ob 90 Of if 44 00 00 80 3d 74 CO 97 01 00 41 54 55 53 Of 84
RIP: acpi_os_delete_semaphore+0x6d/0x70 RSP: ffffb0ca80037be8
-- 
Daniel J Blueman