https://bugs.kde.org/show_bug.cgi?id=501285
Bug ID: 501285
Summary: kscreenlocker (sometimes) crashes when screen turns
off/on
Classification: Plasma
Product: plasmashell
Version: git-stable-Plasma/6.3
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: crash
Priority: NOR
Component: Screen locking
Assignee: plasma-b...@kde.org
Reporter: knights_of...@gmx.com
Target Milestone: 1.0
SUMMARY
So, I know that this is not quite a full bug report with a nice backtrace yet,
but I need some help to get there because I'm running out of ideas. Here is
what I got so far:
- This bug is hardware-specific. I get it on one machine (desktop using an AMD
Ryzen 5 5600G's integrated graphics, connected to a Philips 272B7QPTK screen)
but not on another (MSI Alpha A4DEK laptop using an AMD Ryzen 7 4800H + RX
5600M hybrid setup + unknown screen model), with otherwise similar hardware
configuration.
- This bug is related to GPU or screen power management. In the default
powerdevil configuration, where the screen automatically turns off, when I wake
up the computer I face the message telling me that I need to log in to a VT and
run "loginctl unlock-session 2" to unlock the screen. And in journalctl, it
says that kscreenlocker_greet segfaulted. If I disable screen poweroff, then
the bug never happens, however long I keep the login screen on. I sometimes
manage to reproduce the bug by running "sleep 10 && kscreen-doctor --dpms off"
on one terminal and "/usr/lib/kscreenlocker_greet --testing" on another
terminal, but not always, and it's not clear to me what are the precise
circumstances that cause it to trigger. This makes it harder for me to analyze
the bug further.
- This bug is not related to libddc. Although there were tons of promising
libddc warnings/errors in the journalctl logs, turning off libddc as directed
by the powerdevil readme silences the warnings but does not stop the crashes.
Along the way, I also tried to increase the powerdevil log verbosity as
directed in the powerdevil readme, but that did not turn up anything useful.
- This bug comes from some sort of memory corruption. One time I managed to get
/usr/lib/kscreenlocker_greet to reproduce the bug under GDB, which gave me a
stack trace where the code was attempting to dereference a QWeakPointer with a
target address of 0x6d1 or something blatantly invalid like that. I hoped to
find out who overwrote the address of that pointer with rr, but the bug does
not reproduce under either rr or valgrind. That being said, valgrind does
report many out-of-bounds issues in KSVG, but judging by the very different
memory addresses and the fact that these errors are reported even if the screen
does not turn off, this seems to be an unrelated issue.
STEPS TO REPRODUCE
1. Get the same hardware as I do?
2. Set "Shutdown screen after..." to anything other than "Never" in powerdevil.
3. Wait for screen to lock and turn off, maybe some extra time (it seems the
crash is not always right at the point where the screen turns off).
OBSERVED RESULT
Wiggle mouse, face a kscreenlocker crash report, need to switch to VT to get
back to my desktop.
EXPECTED RESULT
Screen locker shows up normally and lets me unlock my session without dirty VT
tricks.
SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.3.2
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.13.5-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 5600G with Radeon Graphics
Memory: 62.2 Gio of RAM
Graphics Processor: AMD Radeon Graphics
ADDITIONAL INFORMATION
I reliably get a plasma shell crash report dialog on the same system when
resuming from sleep. I do not know if this is related or not.
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