linux-kernel - Re: [GIT PULL] ACPI fixes for v5.16-rc3

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Message-ID: <CAJZ5v0janj--CTeVndJAwiaset5tP8XYdXmeW1hHREcO4BefZw@mail.gmail.com>
Date:   Sat, 4 Dec 2021 21:11:27 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [GIT PULL] ACPI fixes for v5.16-rc3

On Sat, Dec 4, 2021 at 6:04 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Fri, Nov 26, 2021 at 11:38 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> >  git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git \
> >  acpi-5.16-rc3
>
> Hmm. This may be unrelated, but I don't think I've seen this before..

No, this is not related.  It shows up because of the drain_workqueue()
in __acpi_ec_flush_work().

> On my laptop, I get
>
>   WARNING: CPU: 4 PID: 95940 at kernel/workqueue.c:1441 __queue_work+0x2f9/0x3b0
>   Workqueue: kec_query acpi_ec_event_processor
>   ..
>   Call Trace:
>    <TASK>
>    queue_work_on+0x20/0x30

So this tries to add work to ec_wq while it is draining AFAICS.

>    advance_transaction+0x1a1/0x500
>    acpi_ec_transaction+0x15c/0x410
>    acpi_ec_space_handler+0xd2/0x270
>    acpi_ev_address_space_dispatch+0x216/0x2a3
>    ? acpi_ec_resume+0x20/0x20
>    acpi_ex_access_region+0x1dc/0x255
>    ? acpi_os_wait_semaphore+0x48/0x70
>    acpi_ex_field_datum_io+0xfd/0x178
>    acpi_ex_read_data_from_field+0x12e/0x171
>    acpi_ex_resolve_node_to_value+0x1fe/0x281
>    acpi_ds_evaluate_name_path+0x75/0xe9
>    acpi_ds_exec_end_op+0x8f/0x411
>    acpi_ps_parse_loop+0x495/0x5bc
>    acpi_ps_parse_aml+0x94/0x2c2
>    acpi_ps_execute_method+0x15e/0x193
>    acpi_ns_evaluate+0x1c6/0x25d
>    acpi_evaluate_object+0x12e/0x226
>    acpi_ec_event_processor+0x63/0x90
>    process_one_work+0x217/0x3c0
>
> and it seems to be happening at resume time.
>
> This was when running a51e3ac43ddb, so not the very latest git tree,
> but recent.
>
> Maybe I've missed a report of this?

It's not been reported or at least I can't recall that, but it is not
a new issue.

There is a commit to address this in my linux-next branch:

https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=4a9af6cac050dce2e895ec3205c4615383ad9112

but it is interesting that you can reproduce it.  I thought it would
be rather theoretical.