i faced a similar crash at boot time of the Plasma desktop.

Application: plasma-desktop (4.11.11)
KDE Platform Version: 4.13.3
Qt Version: 4.8.6
Operating System: Linux 3.16.0-57-generic x86_64
Distribution: Ubuntu 14.04.3 LTS

-- Information about the crash:
- What I was doing when the application crashed: I was starting up my Kubuntu system. This is the first time that I have experienced this bug. I was engaging in updates before I shut down the last time. This crash of Plasma occurred after I had entered my credentials to log in but before the desktop appeared.

-- Backtrace:
Application: Plasma Desktop Shell (plasma-desktop), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fea8569e7c0 (LWP 2184))]

Thread 5 (Thread 0x7fea54dc6700 (LWP 2208)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fea7e33effb in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#2  0x00007fea7e33f039 in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#3  0x00007fea78bea182 in start_thread (arg=0x7fea54dc6700) at pthread_create.c:312
#4  0x00007fea84f8b47d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 4 (Thread 0x7fe9c9152700 (LWP 2218)):
#0  0x00007fea7851a61a in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#1  0x00007fea7851a9a9 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007fea784d8e9d in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007fea784d90ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4  0x00007fea81b547be in QEventDispatcherGlib::processEvents (this=0x7fe9c40008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:436
#5  0x00007fea81b260af in QEventLoop::processEvents (this=this@entry=0x7fe9c9151de0, flags=...) at kernel/qeventloop.cpp:149
#6  0x00007fea81b263a5 in QEventLoop::exec (this=this@entry=0x7fe9c9151de0, flags=...) at kernel/qeventloop.cpp:204
#7  0x00007fea81a22c5f in QThread::exec (this=this@entry=0x11d2430) at thread/qthread.cpp:537
#8  0x00007fea81b07823 in QInotifyFileSystemWatcherEngine::run (this=0x11d2430) at io/qfilesystemwatcher_inotify.cpp:265
#9  0x00007fea81a2532f in QThreadPrivate::start (arg=0x11d2430) at thread/qthread_unix.cpp:349
#10 0x00007fea78bea182 in start_thread (arg=0x7fe9c9152700) at pthread_create.c:312
#11 0x00007fea84f8b47d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 3 (Thread 0x7fe9bfd84700 (LWP 2220)):
#0  0x00007fea7851a629 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#1  0x00007fea7851a979 in g_mutex_lock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007fea784d8699 in g_main_context_prepare () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007fea784d8f03 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4  0x00007fea784d90ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5  0x00007fea81b547be in QEventDispatcherGlib::processEvents (this=0x7fe9b80008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:436
#6  0x00007fea81b260af in QEventLoop::processEvents (this=this@entry=0x7fe9bfd83de0, flags=...) at kernel/qeventloop.cpp:149
#7  0x00007fea81b263a5 in QEventLoop::exec (this=this@entry=0x7fe9bfd83de0, flags=...) at kernel/qeventloop.cpp:204
#8  0x00007fea81a22c5f in QThread::exec (this=<optimized out>) at thread/qthread.cpp:537
#9  0x00007fe9c80cc027 in KCupsConnection::run() () from /usr/lib/libkcupslib.so
#10 0x00007fea81a2532f in QThreadPrivate::start (arg=0x16567d0) at thread/qthread_unix.cpp:349
#11 0x00007fea78bea182 in start_thread (arg=0x7fe9bfd84700) at pthread_create.c:312
#12 0x00007fea84f8b47d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 2 (Thread 0x7fe9bee23700 (LWP 2222)):
#0  __pthread_mutex_unlock_usercnt (decr=1, mutex=0x7fe9b0000a60) at pthread_mutex_unlock.c:41
#1  __GI___pthread_mutex_unlock (mutex=0x7fe9b0000a60) at pthread_mutex_unlock.c:310
#2  0x00007fea7851a9b1 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007fea784d88f9 in g_main_context_query () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4  0x00007fea784d8f52 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5  0x00007fea784d90ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#6  0x00007fea81b547be in QEventDispatcherGlib::processEvents (this=0x7fe9b00008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:436
#7  0x00007fea81b260af in QEventLoop::processEvents (this=this@entry=0x7fe9bee22de0, flags=...) at kernel/qeventloop.cpp:149
#8  0x00007fea81b263a5 in QEventLoop::exec (this=this@entry=0x7fe9bee22de0, flags=...) at kernel/qeventloop.cpp:204
#9  0x00007fea81a22c5f in QThread::exec (this=this@entry=0x2268270) at thread/qthread.cpp:537
#10 0x00007fea81b07823 in QInotifyFileSystemWatcherEngine::run (this=0x2268270) at io/qfilesystemwatcher_inotify.cpp:265
#11 0x00007fea81a2532f in QThreadPrivate::start (arg=0x2268270) at thread/qthread_unix.cpp:349
#12 0x00007fea78bea182 in start_thread (arg=0x7fe9bee23700) at pthread_create.c:312
#13 0x00007fea84f8b47d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7fea8569e7c0 (LWP 2184)):
[KCrash Handler]
#6  0x00007fe9c80e36f2 in JobModel::updateJob(int, KCupsJob const&) () from /usr/lib/libkcupslib.so
#7  0x00007fe9c80e72b9 in JobModel::getJobFinished() () from /usr/lib/libkcupslib.so
#8  0x00007fe9c80e7905 in ?? () from /usr/lib/libkcupslib.so
#9  0x00007fea81b3fc1e in QObject::event (this=0x18c1c00, e=<optimized out>) at kernel/qobject.cpp:1194
#10 0x00007fea80ec0e2c in QApplicationPrivate::notify_helper (this=this@entry=0x70f280, receiver=receiver@entry=0x18c1c00, e=e@entry=0x7fe9b8057470) at kernel/qapplication.cpp:4567
#11 0x00007fea80ec74a0 in QApplication::notify (this=this@entry=0x703ed0, receiver=receiver@entry=0x18c1c00, e=e@entry=0x7fe9b8057470) at kernel/qapplication.cpp:4353
#12 0x00007fea827ecd1a in KApplication::notify (this=0x703ed0, receiver=0x18c1c00, event=0x7fe9b8057470) at ../../kdeui/kernel/kapplication.cpp:311
#13 0x00007fea81b274dd in QCoreApplication::notifyInternal (this=0x703ed0, receiver=receiver@entry=0x18c1c00, event=event@entry=0x7fe9b8057470) at kernel/qcoreapplication.cpp:953
#14 0x00007fea81b2ab3d in sendEvent (event=0x7fe9b8057470, receiver=0x18c1c00) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#15 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x6881f0) at kernel/qcoreapplication.cpp:1577
#16 0x00007fea81b2afe3 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1470
#17 0x00007fea81b54f83 in sendPostedEvents () at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:236
#18 postEventSourceDispatch (s=0x711130) at kernel/qeventdispatcher_glib.cpp:287
#19 0x00007fea784d8e04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#20 0x00007fea784d9048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#21 0x00007fea784d90ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#22 0x00007fea81b547a1 in QEventDispatcherGlib::processEvents (this=0x689af0, flags=...) at kernel/qeventdispatcher_glib.cpp:434
#23 0x00007fea80f62be6 in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#24 0x00007fea81b260af in QEventLoop::processEvents (this=this@entry=0x7ffd896e3a70, flags=...) at kernel/qeventloop.cpp:149
#25 0x00007fea81b263a5 in QEventLoop::exec (this=this@entry=0x7ffd896e3a70, flags=...) at kernel/qeventloop.cpp:204
#26 0x00007fea81b2bb79 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1225
#27 0x00007fea80ebf37c in QApplication::exec () at kernel/qapplication.cpp:3828
#28 0x00007fea8529267c in kdemain (argc=1, argv=0x7ffd896e3cc8) at ../../../../plasma/desktop/shell/main.cpp:126
#29 0x00007fea84eb2ec5 in __libc_start_main (main=0x4006e0 <main(int, char**)>, argc=1, argv=0x7ffd896e3cc8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd896e3cb8) at libc-start.c:287
#30 0x000000000040070e in _start ()

Report to https://bugs.kde.org/

Comment #1 is bug 326289.

Hello!

This bug report was filed for KDE Plasma 4, which reached end-of-support status in August 2015. KDE Plasma 5's desktop shell has been almost completely rewritten for better performance and usability, so it is likely that this bug has already been resolved in Plasma 5.

Accordingly, we hope you understand why we must close this bug report. If the issue described  here is still present in KDE Plasma 5.12 or later, please feel free to open a new ticket in the "plasmashell" product after reading https://community.kde.org/Get_Involved/Bug_Reporting

If you would like to get involved in KDE's bug triaging effort so that future mass bug closes like this are less likely, please read https://community.kde.org/Get_Involved#Bug_Triaging

Thanks for your understanding!

Nate Graham