linux-kernel - Re: power-off delay/hang due to commit 6d25be57 (mainline)

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Date:   Tue, 11 Aug 2020 12:27:35 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Stephen Berman <stephen.berman@....net>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@...ica.org>
Subject: Re: power-off delay/hang due to commit 6d25be57 (mainline)

On 2020-07-14 17:53:15 [+0200], Rafael J. Wysocki wrote:
> acpi_evaluate_integer() doesn't show up in the trace, though, AFAICS.
> 
> > I assumed acpi_ex_opcode_2A_0T_0R() since the other
> > candidate was acpi_ev_asynch_execute_gpe_method().
> 
> Which probably is the case.  Specifically
> 
> acpi_ev_asynch_execute_gpe_method: Evaluate _L66
> 
> is likely to cause the Notify() to be dispatched.
…
> > Rafael, are you also interested in an ACPI dump?
> 
> That might help a bit.
> 
> So what probably happens is that poking at the TZ causes a GPE to
> trigger and a Notify() to be dispatched which then goes into the
> workqueue for execution.
> 
> Now, I'm not sure what happens to those Notify() items, though.  They
> each should cause a handler (in the thermal driver) to be executed,
> but does that happen?

Stephen's trace contains a few backtraces, all of them look like this:

| Call Trace:
|  acpi_ex_opcode_2A_0T_0R+0x93/0xdf
|  acpi_ds_exec_end_op+0x10d/0x701
|  acpi_ps_parse_loop+0x7f2/0x8c3
|  acpi_ps_parse_aml+0x1a5/0x540
|  acpi_ps_execute_method+0x1fe/0x2ba
|  acpi_ns_evaluate+0x345/0x4e2
|  acpi_evaluate_object+0x177/0x39f
|  acpi_evaluate_integer+0x4f/0x110
|  acpi_thermal_get_temperature.part.0+0x45/0xc4
|  thermal_get_temp.cold+0xc/0x2e
|  thermal_zone_get_temp+0x4c/0x70
|  thermal_zone_device_update.part.0+0x2a/0x110
|  acpi_thermal_notify+0xcf/0x140
|  acpi_ev_notify_dispatch+0x45/0x5a
|  acpi_os_execute_deferred_notify+0x34/0x60
|  process_one_work+0x1d2/0x3a0
|  worker_thread+0x45/0x3c0
|  kthread+0xf6/0x130
|  ret_from_fork+0x35/0x40

so no GPE and it comes the notify callback while parsing the ACPI table.
Any ideas? I guess acpi_ex_opcode_2A_0T_0R() uses the workqueue because
it may sleep and it might be invoked from non-preemptible context.

Sebastian