DescriptionStuart D Gathman
2016-12-18 03:54:01 UTC
Description of problem:
Changing screen brightness by any means instantly freezes xorg.
Version-Release number of selected component (if applicable):
All 4.8.x releases, last freeze that got me:
kernel-4.8.13-200.fc24.x86_64
xorg-x11-drv-intel-2.99.917-24.20160712.fc24.x86_64
00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c)
How reproducible:
always
Steps to Reproduce:
1. press brightness key OR click on brightness slider in power manager
2. OR plug in laptop after it's been on battery
3. OR boot laptop (it restores screen brightness at boot)
Actual results:
xorg freezes anywhere from 10 secs to infinity. Even if xorg isn't running, the kernel sits in a spin lock for the 10 secs before timing out.
Expected results:
Normal operation. Earlier kernels were logging a kernel oops since early 2016, but didn't crash xorg.
Additional info:
bz#1342755 is the report of the kernel oops. This more serious regression has made 4.8 kernels unusable.
Work around: try to disable all adjustments of screen brightness. Unfortunately, cinnamon has started insisting on dimming the screen when plugging in the AC adapter - which often permanently freezes xorg.
I'm working on disabling the systemd unit that sets screen brightness
as boot time (which it does twice, adding at least 20 seconds to boot time).
Also, when xorg freezes permanently, while the network is still active, and you can log in remotely, systemctl reboot (or poweroff) will not complete. It freezes trying to shutdown. You have to force power off.
Still broken in 4.8.14. Switching from text console back to GUI console also sets brightness (and hangs xorg). Logging in to GUI sets brightness and hangs xorg (usually not permanently). I haven't found a way to globally disable changes in brightness.