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

Rafael J. Wysocki
2016-01-19T00:00:34Z

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.

Thanks,
Rafael