Re: 4.5 regression: ACPI hangs when backlight hotkeys are pressed

Andy Lutomirski
2016-01-19T00:09:47Z

On Mon, Jan 18, 2016 at 4:01 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Monday, January 18, 2016 03:57:49 PM Andy Lutomirski wrote:
>> On Mon, Jan 18, 2016 at 3:54 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>> > On Monday, January 18, 2016 03:04:28 PM Andy Lutomirski wrote:
>> >> On Mon, Jan 18, 2016 at 2:25 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>> >> > On Monday, January 18, 2016 12:52:53 PM Andy Lutomirski wrote:
>> >> >> I'm running 4.4 with the pm+acpi-4.5-rc1-1 merged in. After pressing
>> >> >> the backlight hotkeys a couple times, things start to break. Poking
>> >> >> at hung thread stacks, it appears that calls to
>> >> >> acpi_video_handles_brightness_key_presses never return.
>> >> >>
>> >> >> It appears that the culprit is:
>> >> >>
>> >> >> commit aecbd9b1bff6afbe349921b406b99d285b412820
>> >> >> Author: Adrien Schildknecht <adrien+dev@schischi.me>
>> >> >> Date: Mon Jan 4 23:22:28 2016 +0100
>> >> >>
>> >> >> ACPI / video: driver must be registered before checking for keypresses
>> >> >>
>> >> >> Reverting that patch makes my laptop work again.
>> >> >>
>> >> >> I don't know what that patch is trying to do, but it looks highly
>> >> >> questionable to me. Why should an accessor wait for a potential
>> >> >> different driver to register something? I see no guarantee that it
>> >> >> will eve happen.
>> >> >>
>> >> >> This is a Dell XPS 13 9350.
>> >> >
>> >> > Should be fixed in my linux-next branch, can you please try that one?
>> >> >
>> >>
>> >> To avoid churning my laptop tree too much, I cherry-picked:
>> >>
>> >> ACPI / video: Add disable_backlight_sysfs_if quirk for the Toshiba
>> >> Satellite R830
>> >> ACPI / video: Revert "thinkpad_acpi: Use
>> >> acpi_video_handles_brightness_key_presses()"
>> >> ACPI / video: Document acpi_video_handles_brightness_key_presses() a bit
>> >> ACPI / video: Fix using an uninitialized mutex / list_head in
>> >> acpi_video_handles_brightness_key_presses()
>> >> ACPI / video: Revert "ACPI / video: driver must be registered before
>> >> checking for keypresses"
>> >>
>> >> The result seems to work. Are you planning on sending these for 4.5?
>> >
>> > Yes, I am.
>> >
>> > Most likely on Wednesday (or Thursday if anything urgent shows up in the meantime).
>> >
>>
>> Sounds good. I'll keep testing.
>>
>> Some day my laptop will Just Work on a distro kernel :)
>
> Well, even then it'll help a lot if you run the mainline on it, so we know that
> it doesn't regress.
>

So far the only other change I noticed is that I stopped seeing
warnings about S1 and S2 being missing.

--Andy