Application: Plasma Desktop Shell (plasma-desktop), signal: Aborted
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f765e9c7780 (LWP 1704))]

Thread 5 (Thread 0x7f763954e700 (LWP 1706)):
#0 0x00007f7652d4ef69 in pthread_mutex_lock () from /lib/x86_64-linux-gnu/libpthread.so.0
#1 0x00007f7652483561 in g_mutex_lock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007f7652447ef5 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3 0x00007f7652448124 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4 0x00007f765b468426 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#5 0x00007f765b437c82 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#6 0x00007f765b437ed7 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#7 0x00007f765b336fa7 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#8 0x00007f765b4179ff in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#9 0x00007f765b339fcb in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#10 0x00007f7652d4ce9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#11 0x00007f765e2964bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#12 0x0000000000000000 in ?? ()

Thread 4 (Thread 0x7f7633da0700 (LWP 1707)):
#0 0x00007f765e2a40f0 in pthread_mutex_unlock () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007f7652483591 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007f7652447713 in g_main_context_prepare () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3 0x00007f7652447f1b in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4 0x00007f7652448124 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5 0x00007f765b468426 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#6 0x00007f765b437c82 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#7 0x00007f765b437ed7 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#8 0x00007f765b336fa7 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#9 0x00007f765b4179ff in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#10 0x00007f765b339fcb in ?? () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#11 0x00007f7652d4ce9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#12 0x00007f765e2964bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#13 0x0000000000000000 in ?? ()

Thread 3 (Thread 0x7f7630cc0700 (LWP 1710)):
#0 0x00007f7652d50d84 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1 0x00007f765821c222 in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#2 0x00007f765821c259 in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#3 0x00007f7652d4ce9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#4 0x00007f765e2964bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#5 0x0000000000000000 in ?? ()

Thread 2 (Thread 0x7f762996f700 (LWP 1715)):
#0 0x00007f7652d5005d in pthread_mutex_unlock () from /lib/x86_64-linux-gnu/libpthread.so.0
#1 0x00007f7652483591 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2 0x00007f76524470d8 in g_main_context_acquire () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3 0x00007f7652447ec4 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4 0x00007f765244845a in g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5 0x00007f762a4592c6 in ?? () from /usr/lib/x86_64-linux-gnu/libgio-2.0.so.0
#6 0x00007f76524699a5 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#7 0x00007f7652d4ce9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#8 0x00007f765e2964bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#9 0x0000000000000000 in ?? ()

Thread 1 (Thread 0x7f765e9c7780 (LWP 1704)):
[KCrash Handler]
#6 0x00007f765e1da445 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#7 0x00007f765e1ddbab in abort () from /lib/x86_64-linux-gnu/libc.so.6
#8 0x00007f765a3a769d in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#9 0x00007f765a3a5846 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#10 0x00007f765a3a5873 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#11 0x00007f765a3a59b6 in __cxa_rethrow () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#12 0x00007f765b43816c in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#13 0x00007f765b43cf67 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#14 0x00007f765e5a2a13 in kdemain () from /usr/lib/kde4/libkdeinit/libkdeinit4_plasma-desktop.so
#15 0x00007f765e1c576d in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#16 0x0000000000400671 in _start ()

Reproducible: Sometimes

Steps to Reproduce:
1. log into kde
2. lock screen, leave system idle for a time period
3. unlock screen
Actual Results:  
Sometimes, a plasma desktop crash notification. Sometimes plasma-desktop restarted. Display renders badly, shadows around all active windows, fonts do not display correctly. Sometimes, manually restarting plasma-desktop works. Sometimes, I have no window manager. Sometimes, I have to reboot or even power cycle to get the system back. 

Expected Results:  
Restore to a functional plasma desktop.