[Wayland-bugs] [Bug 106179] weston-launch does not restore the interface

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106179

--- Comment #5 from Pekka Paalanen <ppaalanen at gmail.com> ---
Thank you. It's a little bit along the lines I suspected, but in a surprising
way. The below is my analysis for the record:

Main details from the log:
- atomic modesetting is in use

The interesting sequence:

[07:07:31.718] activating session
...
[07:07:31.797] DRM: expected property DPMS to not be an enum, but it is;
ignoring
[07:07:31.797] DRM: expected property DPMS to not be an enum, but it is;
ignoring
[07:07:31.817] unexpectedly large timestamp jump (from 31925138 to 31934769)
[07:13:57.726] atomic: couldn't commit new state: Permission denied
[07:13:57.727] deactivating session

Judging by the timestamps, it seems that EPERM might result from a sequence
like this:
- user hits Ctrl+Alt+F#
- that ends up calling launcher_logind_activate_vt()
- logind revokes DRM access
- libweston core hits repaint and fails atomic flip with EPERM
- logind signals VT deactivation
- session_notify() gets called, prints "deactivating session"

If an atomic flip fails, I think libweston will never try again, which leads to
no screen updates. Looks like two things: fix the race (libweston or logind?),
and maybe find a way to recover from atomic failures.

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