Bug 401350

Summary:	kwin_wayland randomly segfault on libKF5WaylandServer.so.5.50.0
Product:	[Plasma] kwin	Reporter:	José Pekkarinen <koalinux>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	normal
Priority:	NOR
Version First Reported In:	5.13.5
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description José Pekkarinen 2018-11-23 21:10:45 UTC

SUMMARY

I recently migrated my gentoo to a ryzen 7 laptop, after
rebuilding full system I randomly keep having freezes that
forces me to reboot the machine by the power button. From
/var/log/messages I can read the following lines:

Nov 23 14:50:32 bee kernel: kwin_wayland[18524]: segfault at 10 ip 00007f8e44b63e90 sp 00007ffdbeb60218 error 4 in libKF5WaylandServer.so.5.50.0[7f8e44afc000+ee000]
Nov 23 14:50:32 bee kernel: Code: 48 3b 78 10 74 c4 49 83 c0 08 49 8b 00 48 3b 78 10 75 9a eb b5 4c 8d 42 18 eb af 90 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 <48> 8b 47 10 c3 90 66 2e 0f 1f 84 00 00 00 00 00 41 55 41 54 49 89

STEPS TO REPRODUCE
1. Start plasma, and run normal desktop tasks, specially if they consume
   loads of memory like chromium, firefox, and akonadiserver.

OBSERVED RESULT

Full laptop freezes having easily more than half of the swap yet available.

EXPECTED RESULT

Run without freezes until swap memory gets full.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Gentoo stable plasma ebuilds. 
(available in About System)
KDE Plasma Version: 5.13.5
KDE Frameworks Version: 5.50.0
Qt Version: 5.11.1-r1

ADDITIONAL INFORMATION

I'm not really familiar with debugging/providing better traces for
kwin_wayland, but I'm willing to help if guidance is offered, and spend time looking at documentation to learn, so any help would be greatly appreciated.

Thanks!

José.

Comment 1 Martin Flöser 2018-11-24 06:45:08 UTC

Best way is to ssh in from another system and attach gdb.

Comment 2 José Pekkarinen 2018-11-27 15:58:10 UTC

Though the signs of the segfault seems legit, I found the problem on the
continuous freezing kwin_wayland to be the clock source in the kernel
(preset to tsc)to be the root cause, so I feel I'd hardly ever be able to reproduce this issue anymore. The solution was to set the hpet clocksource
instead.

Thanks!

José.