Bug 286963

Application: plasma-desktop (0.4)
KDE Platform Version: 4.7.3 (4.7.3)
Qt Version: 4.8.0
Operating System: Linux 3.1.1-1.fc16.x86_64 x86_64
Distribution: "Fedora release 16 (Verne)"

-- Information about the crash:
- What I was doing when the application crashed:

I was using kdiff3 to diff two files and merge changes from one file to another. Somewhere between, or right after, saving the changes in kdiff3 and using Alt-tab to change back to another app, plasma crashed and drkonqi caught it.

I had done a clean install of Fedora16 and was impressed with KDE 4,.7.2(?) that shipped with it. After the udpate to 4.7.3, I've had frequent plasma crashes, typically upon switching apps via Ctrl-tab, but also when clicking on the KDE menu in the taskbar. I've installed the debug libs over the last few of these crashes. So I'm glad that this crash reported a useable backtrace. I've compared my trace to others, but don't find a certain duplicate.

- Unusual behavior I noticed:

Each of these crashes has left my apps still running, but no "taskbar", so only the Desktop background is seen. I can Alt-tab betweeen my running apps, but when I select any of them, their window is temporarily outlined, but the app does not show its window when selected. This even made drkonqi useless.

I used Ctrl-Alt-F2 to switch to another virtual terminal and logged in at the command line to look for clues. I didn't find any in the hoped-for places (/var/log/*, or ~/.xsession-errors), but I noticed that there are TWO instances of /usr/bin/plasma-desktop running: one started when I logged in, and a second:

/usr/bin/plasma-desktop --nocrashhandler

By trial-n-error  over a few crashes, I figured out that if I kill THAT process, when I go back to the GUI via Ctrl-Alt-F1, I can *then* use Ctrl-Alt to bring the apps to the foreground and use them. That's how I'm able to use drkonqi right now.

This occurs frequently enough (daily) that I could collect more info if told how, and am also interested in helping you get the info you need. Please contact me if there's anything I can do here. Thanks.

PS: Not only has KDE come so far in a couple years, but your crash collection and reporting tool here is also impressive. Kudos to you all!

The crash can be reproduced some of the time.

-- Backtrace:
Application: Plasma Desktop Shell (plasma-desktop), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
82	T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
[KCrash Handler]
#6  operator== (value=0, this=0xc2) at /usr/include/QtCore/qbasicatomic.h:70
#7  isNull (this=0x200000f) at /usr/include/QtCore/qsharedpointer_impl.h:580
#8  operator! (this=0x200000f) at /usr/include/QtCore/qsharedpointer_impl.h:586
#9  TaskManager::TaskItem::task (this=0x29a3fd0) at /usr/src/debug/kde-workspace-4.7.3/libs/taskmanager/taskitem.cpp:113
#10 0x00007f8803c2e218 in WindowTaskItem::publishIconGeometry (this=0x2a094c0, rect=...) at /usr/src/debug/kde-workspace-4.7.3/plasma/desktop/applets/tasks/windowtaskitem.cpp:130
#11 0x00007f8803c3dd64 in TaskGroupItem::publishIconGeometry (this=<optimized out>, rect=...) at /usr/src/debug/kde-workspace-4.7.3/plasma/desktop/applets/tasks/taskgroupitem.cpp:1432
#12 0x00007f8803c3db75 in publishIconGeometry (this=0x27a3680) at /usr/src/debug/kde-workspace-4.7.3/plasma/desktop/applets/tasks/taskgroupitem.cpp:1424
#13 TaskGroupItem::publishIconGeometry (this=0x27a3680) at /usr/src/debug/kde-workspace-4.7.3/plasma/desktop/applets/tasks/taskgroupitem.cpp:1416
#14 0x00007f8803c3cbbc in AbstractTaskItem::timerEvent (this=0x27a3680, event=<optimized out>) at /usr/src/debug/kde-workspace-4.7.3/plasma/desktop/applets/tasks/abstracttaskitem.cpp:439
#15 0x00000031c4f90719 in QObject::event (this=0x27a3680, e=<optimized out>) at kernel/qobject.cpp:1156
#16 0x00000031c6df9f1b in QGraphicsWidget::event (this=0x27a3680, event=0x7ffff4641c70) at graphicsview/qgraphicswidget.cpp:1461
#17 0x00000031c67c96f4 in notify_helper (e=0x7ffff4641c70, receiver=0x27a3680, this=0x904d50) at kernel/qapplication.cpp:4518
#18 QApplicationPrivate::notify_helper (this=0x904d50, receiver=0x27a3680, e=0x7ffff4641c70) at kernel/qapplication.cpp:4490
#19 0x00000031c67ce573 in QApplication::notify (this=0x8fa050, receiver=0x27a3680, e=0x7ffff4641c70) at kernel/qapplication.cpp:4379
#20 0x00000031c7e50396 in KApplication::notify (this=0x8fa050, receiver=0x27a3680, event=0x7ffff4641c70) at /usr/src/debug/kdelibs-4.7.3/kdeui/kernel/kapplication.cpp:311
#21 0x00000031c4f77b4c in QCoreApplication::notifyInternal (this=0x8fa050, receiver=0x27a3680, event=0x7ffff4641c70) at kernel/qcoreapplication.cpp:876
#22 0x00000031c4fa8622 in sendEvent (event=0x7ffff4641c70, receiver=<optimized out>) at kernel/qcoreapplication.h:231
#23 QTimerInfoList::activateTimers (this=0x90b6b0) at kernel/qeventdispatcher_unix.cpp:611
#24 0x00000031c4fa5ffd in timerSourceDispatch (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:186
#25 timerSourceDispatch (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:180
#26 0x00000031c4fa6021 in idleTimerSourceDispatch (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:233
#27 0x0000003c11844a7d in g_main_context_dispatch () from /lib64/libglib-2.0.so.0
#28 0x0000003c11845278 in ?? () from /lib64/libglib-2.0.so.0
#29 0x0000003c1184544c in g_main_context_iteration () from /lib64/libglib-2.0.so.0
#30 0x00000031c4fa682f in QEventDispatcherGlib::processEvents (this=0x8a1c00, flags=<optimized out>) at kernel/qeventdispatcher_glib.cpp:424
#31 0x00000031c686c43e in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=<optimized out>) at kernel/qguieventdispatcher_glib.cpp:207
#32 0x00000031c4f76c82 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#33 0x00000031c4f76ed7 in QEventLoop::exec (this=0x7ffff4641f10, flags=...) at kernel/qeventloop.cpp:204
#34 0x00000031c4f7b8d5 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1148
#35 0x0000003702641243 in kdemain (argc=1, argv=0x7ffff46422f8) at /usr/src/debug/kde-workspace-4.7.3/plasma/desktop/shell/main.cpp:120
#36 0x0000003c11c2169d in __libc_start_main (main=0x400850 <main(int, char**)>, argc=1, ubp_av=0x7ffff46422f8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffff46422e8) at libc-start.c:226
#37 0x0000000000400881 in _start ()

Possible duplicates by query: bug 286920, bug 286823, bug 286785, bug 286723, bug 286695.

Reported using DrKonqi