Bug 1319002

I have similar issue with plasma 5, but in my setup, the mouse can still move (but nothing happens if I click something).

This hang is usually for about 30 seconds. After that period, everything is usable again. I don't see a log message in journalctl or dmesg.
"mpstat -P ALL 1" shows that one core, during the hangs, is at 100%, most of the time 95% usr and 5% sys, in one second in the period sys goes up to 55% (with usr having the rest)

I can trigger the issue with various things:
* lock screen (this almost always triggers the bug)
* hover over the previews in the taskbar, especially with konsole and thunderbird
* change volume using hardware keys (the OSD showing the volume control appears, but gets stuck on fade in)

I will try to reset to 2.99.917-16.20150729 and see if the problems disappear.

I am using a dual-display setup with laptop as primary display and an external monitor connected via displayport in dockingstation (Dell Latitude E7440).

Switching back to 2.99.917-16.20150729 solves the issue for me.

Any suggestions on how to further debug this?
I tried to run a perf record while forcing a hang (start record, lock screen, unlock screen, stop record), but the symbols found are not very meaningful.

On the first page of perf report, only Xort and swapper lines are visible.
The top lines are:

* 45% of all samples at symbol 0x0000000000000001 (which sounds like a bug somewhere?)
* 36% at symbol 0x00007f0cdfdf2000 (which is within a map of 1032MB in /proc/PID/maps)
entry from /proc/PID/maps:
7f0cdfdd0000-7f0cdfed8000 rw-p 00000000 00:00 0 

* 30% at symbol 0x0000000001d09e70 (which is an address within the heap of Xorg)
entry from /proc/PID/maps:
01ce2000-02242000 rw-p 00000000 00:00 0                                  [heap]
* 10% at symbol 0xffff80f327c2ec79 (shared object intel_drv.so)

Want to add a 'me too' here. Typically happens for me when the external monitor for my laptop (x220) is asleep.

I accidentally left it doing its thing whilst I was AFK for a few hours and the OOM killer triggered for xorg. The laptop was back at the GDM login screen. I'll attach that shortly.

Created attachment 1152140 [details]
DMESG for OOM killer

confirmed that downgrading to 2.99.917-16.20150729 solved it for me, as did switching to Intel's own xorg-x11-drv-intel-2.99.917-23.intel20154

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