Version:            (using Devel)
Installed from:    Compiled sources

I think the actions that caused it were:

I told the device notifier to remove a USB stick by clicking the eject icon.  It didn't react very quickly (possibly because I had copied a lot of files across and they hadn't been synced yet), so I opened Dolphin (using the K menu, so it hadn't deadlocked at this point) and used the places bar there to eject it, then closed Dolphin.  Then at some point it deadlocked.

Backtrace:

Thread 2 (Thread 0x7fab054f4950 (LWP 6497)):
#0  0x00007fab1dfa6d69 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1  0x00007fab1e22ae51 in QWaitConditionPrivate::wait (this=0x1ebec20, time=18446744073709551615)
    at /home/kde-devel/src/qt-copy/src/corelib/thread/qwaitcondition_unix.cpp:87                 
#2  0x00007fab1e22a9ae in QWaitCondition::wait (this=0x1efeda0, mutex=0x1efed98,                 
    time=18446744073709551615)                                                                   
    at /home/kde-devel/src/qt-copy/src/corelib/thread/qwaitcondition_unix.cpp:159                
#3  0x00007fab219bc617 in QHostInfoAgent::run (this=0x1efed80)                                   
    at /home/kde-devel/src/qt-copy/src/network/kernel/qhostinfo.cpp:260                          
#4  0x00007fab1e22a605 in QThreadPrivate::start (arg=0x1efed80)                                  
    at /home/kde-devel/src/qt-copy/src/corelib/thread/qthread_unix.cpp:189                       
#5  0x00007fab1dfa2fc7 in start_thread () from /lib/libpthread.so.0                              
#6  0x00007fab1d5715dd in clone () from /lib/libc.so.6                                           
#7  0x0000000000000000 in ?? ()                                                                  

Thread 1 (Thread 0x7fab230a7760 (LWP 6496)):
#0  0x00007fab1dfa6d69 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
#1  0x00007fab1e22941d in QMutexPrivate::wait (this=0x1dd3ef0, timeout=-1)           
    at /home/kde-devel/src/qt-copy/src/corelib/thread/qmutex_unix.cpp:80             
#2  0x00007fab1e224587 in QMutex::lock (this=0x1dd3d38)                              
    at /home/kde-devel/src/qt-copy/src/corelib/thread/qmutex.cpp:207                 
#3  0x00007fab1e6588a8 in QDBusMutexLocker (this=0x7fff2b1eb4d0, a=DoDispatchAction, s=0x1dd3cd0, 
    m=0x1dd3d38) at /home/kde-devel/src/qt-copy/src/dbus/qdbusthreaddebug_p.h:183                 
#4  0x00007fab1e6588ef in QDBusDispatchLocker (this=0x7fff2b1eb4d0, a=DoDispatchAction, s=0x1dd3cd0)
    at /home/kde-devel/src/qt-copy/src/dbus/qdbusthreaddebug_p.h:198                                
#5  0x00007fab1e64b346 in QDBusConnectionPrivate::doDispatch (this=0x1dd3cd0)                       
    at /home/kde-devel/src/qt-copy/src/dbus/qdbusintegrator.cpp:1065                                
#6  0x00007fab1e6814f3 in QDBusConnectionPrivate::qt_metacall (this=0x1dd3cd0,                      
    _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0x2630100)                                          
    at .moc/debug-shared/moc_qdbusconnection_p.cpp:88                                               
---Type <return> to continue, or q <return> to quit---                                              
#7  0x00007fab1e328bd3 in QMetaCallEvent::placeMetaCall (this=0x25a2560, object=0x1dd3cd0)          
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:489                               
#8  0x00007fab1e32d202 in QObject::event (this=0x1dd3cd0, e=0x25a2560)                              
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:1106                              
#9  0x00007fab1ea99fd1 in QApplicationPrivate::notify_helper (this=0x18d1540, receiver=0x1dd3cd0,   
    e=0x25a2560) at /home/kde-devel/src/qt-copy/src/gui/kernel/qapplication.cpp:4084                
#10 0x00007fab1ea9a388 in QApplication::notify (this=0x18bbfb0, receiver=0x1dd3cd0, e=0x25a2560)    
    at /home/kde-devel/src/qt-copy/src/gui/kernel/qapplication.cpp:3631                             
#11 0x00007fab21299617 in KApplication::notify (this=0x18bbfb0, receiver=0x1dd3cd0, event=0x25a2560)
    at /home/kde-devel/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:307                            
#12 0x00007fab1e31909b in QCoreApplication::notifyInternal (this=0x18bbfb0, receiver=0x1dd3cd0,     
    event=0x25a2560) at /home/kde-devel/src/qt-copy/src/corelib/kernel/qcoreapplication.cpp:598     
#13 0x00007fab1ea96ea5 in QCoreApplication::sendEvent (receiver=0x1dd3cd0, event=0x25a2560)         
    at ../../include/QtCore/../../../src/qt-copy/src/corelib/kernel/qcoreapplication.h:213          
#14 0x00007fab1e3195ed in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0,    
    data=0x187e550) at /home/kde-devel/src/qt-copy/src/corelib/kernel/qcoreapplication.cpp:1236     
#15 0x00007fab1e3197c4 in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0)           
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qcoreapplication.cpp:1132                     
#16 0x00007fab1eb427b5 in QCoreApplication::sendPostedEvents ()                                     
    at ../../include/QtCore/../../../src/qt-copy/src/corelib/kernel/qcoreapplication.h:218          
#17 0x00007fab1e347924 in postEventSourceDispatch (s=0x18d4c10)                                     
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventdispatcher_glib.cpp:209                 
#18 0x00007fab19d7aeda in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0                 
#19 0x00007fab19d7e5a0 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0                  
#20 0x00007fab19d7e73c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0                
#21 0x00007fab1e346c66 in QEventDispatcherGlib::processEvents (this=0x18d1070, flags={i = 723435712})
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventdispatcher_glib.cpp:323                  
#22 0x00007fab1eb4105b in QGuiEventDispatcherGlib::processEvents (this=0x18d1070, flags={i = 723435808})
    at /home/kde-devel/src/qt-copy/src/gui/kernel/qguieventdispatcher_glib.cpp:202                      
#23 0x00007fab1e31631f in QEventLoop::processEvents (this=0x7fff2b1ec1f0, flags={i = 723435904})        
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventloop.cpp:149                                
---Type <return> to continue, or q <return> to quit---                                                  
#24 0x00007fab1e31652c in QEventLoop::exec (this=0x7fff2b1ec1f0, flags={i = 723436032})                 
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventloop.cpp:196                                
#25 0x00007fab1efbf536 in QDialog::exec (this=0x25da1b0)                                                
    at /home/kde-devel/src/qt-copy/src/gui/dialogs/qdialog.cpp:498                                      
#26 0x00007fab212216d3 in KMessageBox::createKMessageBox (dialog=0x25da1b0, icon=@0x7fff2b1ec730,       
    text=@0x7fff2b1ec920, strlist=@0x7fff2b1ec8c0, ask=@0x7fff2b1ec840, checkboxReturn=0x0, options=    
      {i = 723437344}, details=@0x7fff2b1ec820, notifyType=QMessageBox::Critical)                       
    at /home/kde-devel/src/KDE/kdelibs/kdeui/dialogs/kmessagebox.cpp:330                                
#27 0x00007fab21221c90 in KMessageBox::createKMessageBox (dialog=0x25da1b0, icon=QMessageBox::Critical, 
    text=@0x7fff2b1ec920, strlist=@0x7fff2b1ec8c0, ask=@0x7fff2b1ec840, checkboxReturn=0x0, options=    
      {i = 723437616}, details=@0x7fff2b1ec820)                                                         
    at /home/kde-devel/src/KDE/kdelibs/kdeui/dialogs/kmessagebox.cpp:151                                
#28 0x00007fab21222cf4 in KMessageBox::errorListWId (parent_id=0, text=@0x7fff2b1ec920,                 
    strlist=@0x7fff2b1ec8c0, caption=@0x7fff2b1ec910, options={i = 723437744})                          
    at /home/kde-devel/src/KDE/kdelibs/kdeui/dialogs/kmessagebox.cpp:848                                
#29 0x00007fab21222e36 in KMessageBox::error (parent=0x0, text=@0x7fff2b1ec920,                         
    caption=@0x7fff2b1ec910, options={i = 723437824})                                                   
    at /home/kde-devel/src/KDE/kdelibs/kdeui/dialogs/kmessagebox.cpp:812                                
#30 0x00007fab06f66d72 in Notifier::NotifierDialog::storageTeardownDone (this=0x1be4450,                
    error=Solid::UnauthorizedOperation, errorData=                                                      
        {d = {data = {c = -64 '�', i = 723438016, u = 723438016, b = 192, d = 6.9531793508429679e-310, ll = 140733916826048, ull = 140733916826048, ptr = 0x7fff2b1ec9c0, shared = 0x7fff2b1ec9c0}, type = 723438496, is_shared = 0, is_null = 0}})                                                                        
    at /home/kde-devel/src/KDE/kdebase/workspace/plasma/applets/devicenotifier/notifierdialog.cpp:297    
#31 0x00007fab06f66f51 in Notifier::NotifierDialog::qt_metacall (this=0x1be4450,                         
    _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0x7fff2b1ecb30)                                          
    at /home/kde-devel/build/KDE/kdebase/workspace/plasma/applets/devicenotifier/notifierdialog.moc:81   
#32 0x00007fab1e32f384 in QMetaObject::activate (sender=0x2573450, from_signal_index=6,                  
    to_signal_index=6, argv=0x7fff2b1ecb30)                                                              
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:3057                                   
#33 0x00007fab1e330769 in QMetaObject::activate (sender=0x2573450, m=0x7fab1bdebfe0,                     
---Type <return> to continue, or q <return> to quit---                                                   
    local_signal_index=2, argv=0x7fff2b1ecb30)                                                           
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:3134                                   
#34 0x00007fab1bb92b46 in Solid::StorageAccess::teardownDone (this=0x2573450,                            
    _t1=Solid::UnauthorizedOperation, _t2=                                                               
        {d = {data = {c = -96 '�', i = 723438496, u = 723438496, b = 160, d = 6.9531793508666831e-310, ll = 140733916826528, ull = 140733916826528, ptr = 0x7fff2b1ecba0, shared = 0x7fff2b1ecba0}, type = 723438496, is_shared = 0, is_null = 0}}, _t3=@0x7fff2b1ecdd0)                                                   
    at /home/kde-devel/build/KDE/kdelibs/solid/solid/storageaccess.moc:129                               
#35 0x00007fab1bb92ef2 in Solid::StorageAccess::qt_metacall (this=0x2573450,                             
    _c=QMetaObject::InvokeMetaMethod, _id=2, _a=0x7fff2b1ecd30)                                          
    at /home/kde-devel/build/KDE/kdelibs/solid/solid/storageaccess.moc:79                                
#36 0x00007fab1e32f384 in QMetaObject::activate (sender=0x21921c0, from_signal_index=6,                  
    to_signal_index=6, argv=0x7fff2b1ecd30)                                                              
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:3057                                   
#37 0x00007fab1e330769 in QMetaObject::activate (sender=0x21921c0, m=0x7fab1bdf5840,                     
    local_signal_index=2, argv=0x7fff2b1ecd30)                                                           
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:3134                                   
#38 0x00007fab1bbc332e in Solid::Backends::Hal::StorageAccess::teardownDone (this=0x21921c0,             
    _t1=Solid::UnauthorizedOperation, _t2=                                                               
        {d = {data = {c = -32 '�', i = 723439072, u = 723439072, b = 224, d = 6.9531793508951412e-310, ll = 140733916827104, ull = 140733916827104, ptr = 0x7fff2b1ecde0, shared = 0x7fff2b1ecde0}, type = 723439104, is_shared = 0, is_null = 0}}, _t3=@0x7fff2b1ecdd0)                                                   
    at /home/kde-devel/build/KDE/kdelibs/solid/solid/backends/hal/halstorageaccess.moc:122               
#39 0x00007fab1bbc4c90 in Solid::Backends::Hal::StorageAccess::slotDBusError (this=0x21921c0,            
    error=@0x7fff2b1ed050)                                                                               
    at /home/kde-devel/src/KDE/kdelibs/solid/solid/backends/hal/halstorageaccess.cpp:183                 
#40 0x00007fab1bbc5326 in Solid::Backends::Hal::StorageAccess::qt_metacall (this=0x21921c0,              
    _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0x7fff2b1ed000)                                          
    at /home/kde-devel/build/KDE/kdelibs/solid/solid/backends/hal/halstorageaccess.moc:94                
#41 0x00007fab1e32f384 in QMetaObject::activate (sender=0x26ff0b0, from_signal_index=6,                  
    to_signal_index=6, argv=0x7fff2b1ed000)                                                              
---Type <return> to continue, or q <return> to quit---                                                   
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:3057                                   
#42 0x00007fab1e330769 in QMetaObject::activate (sender=0x26ff0b0, m=0x7fab1e89fe20,                     
    local_signal_index=2, argv=0x7fff2b1ed000)                                                           
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:3134                                   
#43 0x00007fab1e68168f in QDBusPendingCallWatcherHelper::error (this=0x26ff0b0, _t1=@0x7fff2b1ed050,     
    _t2=@0x199a7d8) at .moc/debug-shared/moc_qdbuspendingcall_p.cpp:97                                   
#44 0x00007fab1e658b1c in QDBusPendingCallWatcherHelper::emitSignals (this=0x26ff0b0,                    
    replyMessage=@0x199a7e0, sentMessage=@0x199a7d8)                                                     
    at /home/kde-devel/src/qt-copy/src/dbus/qdbuspendingcall_p.h:110                                     
#45 0x00007fab1e64e218 in QDBusConnectionPrivate::processFinishedCall (call=0x199a7d0)                   
    at /home/kde-devel/src/qt-copy/src/dbus/qdbusintegrator.cpp:1691                                     
#46 0x00007fab1e64e324 in qDBusResultReceived (pending=0x26b8970, user_data=0x199a7d0)                   
    at /home/kde-devel/src/qt-copy/src/dbus/qdbusintegrator.cpp:1644                                     
#47 0x00007fab16cb68aa in complete_pending_call_and_unlock () from /usr/lib/libdbus-1.so.3               
#48 0x00007fab16cb74b1 in dbus_connection_dispatch () from /usr/lib/libdbus-1.so.3                       
#49 0x00007fab1e64a904 in q_dbus_connection_dispatch (connection=0x1dd47a0)                              
    at /home/kde-devel/src/qt-copy/src/dbus/qdbus_symbols_p.h:113                                        
#50 0x00007fab1e64b36b in QDBusConnectionPrivate::doDispatch (this=0x1dd3cd0)                            
    at /home/kde-devel/src/qt-copy/src/dbus/qdbusintegrator.cpp:1067                                     
#51 0x00007fab1e64b3f1 in QDBusConnectionPrivate::timerEvent (this=0x1dd3cd0, e=0x7fff2b1edb60)          
    at /home/kde-devel/src/qt-copy/src/dbus/qdbusintegrator.cpp:1027                                     
#52 0x00007fab1e32d12e in QObject::event (this=0x1dd3cd0, e=0x7fff2b1edb60)                              
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qobject.cpp:1073                                   
#53 0x00007fab1ea99fd1 in QApplicationPrivate::notify_helper (this=0x18d1540, receiver=0x1dd3cd0,        
    e=0x7fff2b1edb60) at /home/kde-devel/src/qt-copy/src/gui/kernel/qapplication.cpp:4084                
#54 0x00007fab1ea9a388 in QApplication::notify (this=0x18bbfb0, receiver=0x1dd3cd0, e=0x7fff2b1edb60)    
    at /home/kde-devel/src/qt-copy/src/gui/kernel/qapplication.cpp:3631                                  
#55 0x00007fab21299617 in KApplication::notify (this=0x18bbfb0, receiver=0x1dd3cd0,
    event=0x7fff2b1edb60) at /home/kde-devel/src/KDE/kdelibs/kdeui/kernel/kapplication.cpp:307
#56 0x00007fab1e31909b in QCoreApplication::notifyInternal (this=0x18bbfb0, receiver=0x1dd3cd0,
    event=0x7fff2b1edb60) at /home/kde-devel/src/qt-copy/src/corelib/kernel/qcoreapplication.cpp:598
---Type <return> to continue, or q <return> to quit---
#57 0x00007fab1ea96ea5 in QCoreApplication::sendEvent (receiver=0x1dd3cd0, event=0x7fff2b1edb60)
    at ../../include/QtCore/../../../src/qt-copy/src/corelib/kernel/qcoreapplication.h:213
#58 0x00007fab1e34a221 in QTimerInfoList::activateTimers (this=0x18d4d70)
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventdispatcher_unix.cpp:572
#59 0x00007fab1e347a0a in timerSourceDispatch (source=0x18d4d10)
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventdispatcher_glib.cpp:164
#60 0x00007fab19d7aeda in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#61 0x00007fab19d7e5a0 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#62 0x00007fab19d7e73c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#63 0x00007fab1e346c66 in QEventDispatcherGlib::processEvents (this=0x18d1070, flags={i = 723443136})
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventdispatcher_glib.cpp:323
#64 0x00007fab1eb4105b in QGuiEventDispatcherGlib::processEvents (this=0x18d1070, flags={i = 723443232})
    at /home/kde-devel/src/qt-copy/src/gui/kernel/qguieventdispatcher_glib.cpp:202
#65 0x00007fab1e31631f in QEventLoop::processEvents (this=0x7fff2b1edee0, flags={i = 723443328})
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventloop.cpp:149
#66 0x00007fab1e31652c in QEventLoop::exec (this=0x7fff2b1edee0, flags={i = 723443440})
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qeventloop.cpp:196
#67 0x00007fab1e3198e6 in QCoreApplication::exec ()
    at /home/kde-devel/src/qt-copy/src/corelib/kernel/qcoreapplication.cpp:880
#68 0x00007fab1ea99d2e in QApplication::exec ()
    at /home/kde-devel/src/qt-copy/src/gui/kernel/qapplication.cpp:3553
#69 0x00007fab22d7b965 in kdemain (argc=1, argv=0x7fff2b1ee1e8)
    at /home/kde-devel/src/KDE/kdebase/workspace/plasma/shells/desktop/main.cpp:50
#70 0x00000000004008e7 in main (argc=1, argv=0x7fff2b1ee1e8)
    at /home/kde-devel/build/KDE/kdebase/workspace/plasma/shells/desktop/plasma-desktop_dummy.cpp:3
#0  0x00007fab1dfa6d69 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0