libgamemodeauto aborts in gamemode_request_end via D-Bus assertion when gamescopereaper exits

[sethchev]

Summary

gamescopereaper processes launched by Steam/gamescope are aborting on exit when libgamemodeauto calls gamemode_request_end(). The abort comes from libdbus asserting that dbus_pending_call_block() was called with pending == NULL.

This has happened repeatedly on this machine with different Steam games.

What happened

systemd-coredump recorded:

• Process: gamescopereaper
• Executable: /usr/bin/gamescopereaper
• Signal: SIGABRT
• Time: Thu 2026-09-10 13:50:22 EDT
• Package versions:
  • gamemode 1.8.2-3
  • gamescope 3.16.28-1
  • dbus 1.16.2-1
  • glibc 2.44+r24+g16be1518495f-1

Redacted command line:

gamescopereaper -- /home/<user>/.local/share/Steam/ubuntu12_32/steam-launch-wrapper -- /home/<user>/.local/share/Steam/ubuntu12_32/reaper SteamLaunch AppId=1091500 -- /home/<user>/.local/share/Steam/steamapps/common/SteamLinuxRuntime_4/_v2-entry-point --verb=waitforexitandrun -- /home/<user>/.local/share/Steam/steamapps/common/Proton - Experimental/proton waitforexitandrun /home/<user>/.local/share/Steam/steamapps/common/Cyberpunk 2077/REDprelauncher.exe --launcher-skip -skip-start-screen

A paired reaper process crashed at the same time:

gamescopereaper --respawn -- mangoapp

Journal evidence

At the crash time:

dbus[76361]: arguments to dbus_pending_call_block() were incorrect, assertion "pending != NULL" failed in file ../dbus/dbus/dbus-pending-call.c line 768.
dbus[76361]: This is normally a bug in some application using the D-Bus library.
dbus[76361]:   D-Bus not built with -rdynamic so unable to print a backtrace
systemd-coredump: Process 76361 (gamescopereaper) of user 1000 dumped core.

Backtrace

#0  libc.so.6
#1  raise
#2  abort
#3  libdbus-1.so.3
#4  _dbus_warn_check_failed
#5  libgamemode.so.0
#6  gamemode_request_end (libgamemodeauto.so.0)
#7  ld-linux-x86-64.so.2
#8  ld-linux-x86-64.so.2
#9  libc.so.6
#10 exit
#11 libc.so.6
#12 __libc_start_main
#13 gamescopereaper

Recurrence

coredumpctl list gamescopereaper shows four crashes with the same shape:

Wed 2026-09-09 20:19:41 EDT <pid> SIGABRT /usr/bin/gamescopereaper
Wed 2026-09-09 20:19:41 EDT <pid> SIGABRT /usr/bin/gamescopereaper
Thu 2026-09-10 13:50:22 EDT <pid> SIGABRT /usr/bin/gamescopereaper
Thu 2026-09-10 13:50:22 EDT <pid> SIGABRT /usr/bin/gamescopereaper

The earlier pair happened with another Steam game, so this does not appear specific to Cyberpunk 2077.

Other checks

• No OOM kill was present in the kernel journal around the crash time.
• Memory pressure was not present at diagnosis time.
• The crash appears to happen during Steam/gamescope process teardown, after the primary child exits.

Filed by gpt-5.5 via pi.

[mdiluz]

#575