lockdep reports invalid wait context, dmar fault and serial console related.

[Ben Greear <greearb@candelatech.com>]

Hello,

I saw this splat while running a lockdep kernel.  The DMAR warning is related to mtk7915
driver, but aside from filling logs, it appears to not be a serious problem.  I have also
not seen any obvious actual problems related to the serial console in this case.  Never
the less, maybe someone with knowledge in this area with have a more informed understanding
of how important this is.

[    2.706497] DMAR: DRHD: handling fault status reg 3

[    2.706552] =============================
[    2.706552] [ BUG: Invalid wait context ]
[    2.706553] 6.7.5+ #3 Not tainted
[    2.706554] -----------------------------
[    2.706555] swapper/0/0 is trying to lock:
[    2.706556] ffffffff83db4cf8 (&port_lock_key){-.-.}-{3:3}, at: serial8250_console_write+0x82/0x480
[    2.706563] other info that might help us debug this:
[    2.706563] context-{2:2}
[    2.706564] 4 locks held by swapper/0/0:
[    2.706565]  #0: ffff888108065c70 (&iommu->register_lock){-...}-{2:2}, at: dmar_fault+0x1d/0x310
[    2.706568]  #1: ffffffff8296a480 (console_lock){+.+.}-{0:0}, at: _printk+0x53/0x70
[    2.706572]  #2: ffffffff8296a4d0 (console_srcu){....}-{0:0}, at: console_flush_all+0x84/0x510
[    2.706576]  #3: ffffffff8288a260 (console_owner){-...}-{0:0}, at: console_flush_all+0x1fa/0x510
[    2.706579] stack backtrace:
[    2.706579] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.7.5+ #3
[    2.706581] Hardware name: Default string Default string/SKYBAY, BIOS 5.12 08/04/2020
[    2.706581] Call Trace:
[    2.706582]  <IRQ>
[    2.706583]  dump_stack_lvl+0x57/0x90
[    2.706588]  __lock_acquire+0x9cc/0x2380
[    2.706590]  ? stack_trace_save+0x46/0x70
[    2.706595]  ? save_trace+0x4e/0x330
[    2.706597]  lock_acquire+0xc6/0x2b0
[    2.706598]  ? serial8250_console_write+0x82/0x480
[    2.706600]  _raw_spin_lock_irqsave+0x3f/0x60
[    2.706604]  ? serial8250_console_write+0x82/0x480
[    2.706605]  serial8250_console_write+0x82/0x480
[    2.706606]  ? console_flush_all+0x1fa/0x510
[    2.706608]  ? console_flush_all+0x1e8/0x510
[    2.706610]  ? lock_release+0xc5/0x270
[    2.706612]  console_flush_all+0x222/0x510
[    2.706613]  ? console_flush_all+0x1fa/0x510
[    2.706615]  ? console_flush_all+0x1fa/0x510
[    2.706617]  console_unlock+0x3f/0x140
[    2.706619]  vprintk_emit+0xa1/0x320
[    2.706621]  ? lock_release+0xc5/0x270
[    2.706622]  _printk+0x53/0x70
[    2.706624]  ? ___ratelimit+0x85/0x110
[    2.706626]  dmar_fault+0x2f0/0x310
[    2.706627]  ? find_held_lock+0x2b/0x80
[    2.706628]  __handle_irq_event_percpu+0x7c/0x230
[    2.706630]  handle_irq_event+0x2f/0x70
[    2.706631]  handle_edge_irq+0x7c/0x210
[    2.706634]  __common_interrupt+0x3d/0xe0
[    2.706636]  common_interrupt+0x7d/0xa0
[    2.706639]  </IRQ>
[    2.706639]  <TASK>
[    2.706640]  asm_common_interrupt+0x22/0x40
[    2.706641] RIP: 0010:cpuidle_enter_state+0xf6/0x4f0
[    2.706643] Code: c0 48 0f a3 05 fb fd c0 00 0f 82 f8 02 00 00 31 ff e8 4e 55 30 ff 45 84 ff 0f 85 c8 02 00 00 e8 30 9c 3e ff fb 0f 1f 44 00 00 <45> 85 f6 0f 
88 e7 01 00 00 49 63 d6 48 8d 04 52 48 8d 04 82 49 8d
[    2.706645] RSP: 0018:ffffffff82803e28 EFLAGS: 00000206
[    2.706646] RAX: 0000000000008a3f RBX: ffffe8ffffa262f0 RCX: 000000000000001f
[    2.706647] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff81ee0ef0
[    2.706647] RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000001
[    2.706648] R10: ffffffff828254c0 R11: ffffffff82825ed0 R12: ffffffff829ee520
[    2.706649] R13: 00000000a15167b5 R14: 0000000000000004 R15: 0000000000000000
[    2.706650]  ? cpuidle_enter_state+0xf0/0x4f0
[    2.706652]  ? cpuidle_enter_state+0xf0/0x4f0
[    2.706653]  cpuidle_enter+0x24/0x40
[    2.706656]  do_idle+0x1e8/0x240
[    2.706660]  cpu_startup_entry+0x21/0x30
[    2.706662]  rest_init+0xe0/0x180
[    2.706663]  arch_call_rest_init+0x5/0x20
[    2.706667]  start_kernel+0x860/0xa70
[    2.706669]  ? load_ucode_intel_bsp+0x46/0x80
[    2.706671]  x86_64_start_reservations+0x14/0x30
[    2.706674]  x86_64_start_kernel+0x79/0x80
[    2.706676]  secondary_startup_64_no_verify+0x178/0x17b
[    2.706681]  </TASK>
[    2.708867] systemd-journald[267]: /etc/systemd/journald.conf:1: Assignment outside of section. Ignoring.
[    2.710908] DMAR: [DMA Read NO_PASID] Request device [15:00.0] fault addr 0xffff1000 [fault reason 0x06] PTE Read access is not set

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com