(gdb) bt full
#0  0xffffffff in syscall () at ../sysdeps/unix/sysv/linux/arm/syscall.S:37
#1  0xffffffff in QBasicMutex::lockInternal() (op=0, val=3, timeout=0x0, addr=<optimized out>) at thread/qmutex_linux.cpp:146
        addr2 = 0x0
        val2 = 0
#2  0xffffffff in QBasicMutex::lockInternal() (timeout=-1, elapsedTimer=0x0, d_ptr=...) at thread/qmutex_linux.cpp:187
#3  0xffffffff in QBasicMutex::lockInternal() (this=this@entry=0x1b6ab44) at thread/qmutex_linux.cpp:203
#4  0xffffffff in QMutex::lock() (this=0x1b6ab44) at thread/qmutex.h:59
        self = 0xb6f5b000
        success = true
        current = 0x1b6ab38
#5  0xffffffff in QMutex::lock() (timeout=-1, this=0x1b6ab38) at thread/qmutex.cpp:620
        self = 0xb6f5b000
        success = true
        current = 0x1b6ab38
#6  0xffffffff in QMutex::lock() (this=this@entry=0x1b6ad6c) at thread/qmutex.cpp:215
        current = 0x1b6ab38
#7  0xffffffff in qDBusRealToggleWatch(QDBusConnectionPrivate*, DBusWatch*, int) (m=0x1b6ad6c, s=
    0x1b6ad48, a=ToggleWatchAction, this=<synthetic pointer>) at qdbusthreaddebug_p.h:183
        locker = 
            {<QDBusMutexLocker> = {<QDBusLockerBase> = {<No data fields>}, self = 0x1b6ad48, mutex = 0x1b6ad6c, action = ToggleWatchAction}, <No data fields>}
        i = <optimized out>
#8  0xffffffff in qDBusRealToggleWatch(QDBusConnectionPrivate*, DBusWatch*, int) (s=0x1b6ad48, a=ToggleWatchAction, this=<synthetic pointer>) at qdbusthreaddebug_p.h:198
        locker = 
            {<QDBusMutexLocker> = {<QDBusLockerBase> = {<No data fields>}, self = 0x1b6ad48, mutex = 0x1b6ad6c, action = ToggleWatchAction}, <No data fields>}
        i = <optimized out>
#9  0xffffffff in qDBusRealToggleWatch(QDBusConnectionPrivate*, DBusWatch*, int) (d=0x1b6ad48, watch=0x1b6bdd0, fd=46)
    at qdbusintegrator.cpp:346
        locker = 
            {<QDBusMutexLocker> = {<QDBusLockerBase> = {<No data fields>}, self = 0x1b6ad48, mutex = 0x1b6ad6c, action = ToggleWatchAction}, <No data fields>}
        i = <optimized out>
#10 0xffffffff in check_write_watch (transport=0x1b6bd38) at ../../dbus/dbus-transport-socket.c:167
        needed = <optimized out>
        transport = 0x1b6bd38
        socket_transport = 0x1b6bd38
#11 0xffffffff in socket_do_iteration (transport=0x1b6bd38, flags=1, timeout_milliseconds=<optimized out>)
    at ../../dbus/dbus-transport-socket.c:1210
        socket_transport = 0x1b6bd38
        poll_fd = {fd = 46, events = 0, revents = 2527}
         poll_res = <optimized out>
        poll_timeout = <optimized out>
#12 0xffffffff in _dbus_transport_do_iteration (transport=0x1b6bd38, flags=1, timeout_milliseconds=-1)
    at ../../dbus/dbus-transport.c:1001
#13 0xffffffff in _dbus_connection_do_iteration_unlocked (connection=connection@entry=0x1b6c140, pending=pending@entry=0x0, flags=flags@entry=1, timeout_milliseconds=timeout_milliseconds@entry=-1) at ../../dbus/dbus-connection.c:1227
#14 0xffffffff in _dbus_connection_send_preallocated_unlocked_no_update (connection=connection@entry=0x1b6c140, preallocated=0x0, message=message@entry=0x1d34fa8, client_serial=client_serial@entry=0x0) at ../../dbus/dbus-connection.c:2057
#15 0xffffffff in _dbus_connection_send_and_unlock (client_serial=0x0, message=0x1d34fa8, preallocated=<optimized out>, connection=0x1b6c140) at ../../dbus/dbus-connection.c:2077
        status = <optimized out>
        preallocated = <optimized out>
#16 0xffffffff in _dbus_connection_send_and_unlock (connection=0x1b6c140, message=0x1d34fa8, client_serial=0x0)
    at ../../dbus/dbus-connection.c:2114
        preallocated = <optimized out>
#17 0xffffffff in dbus_bus_add_match (connection=0x1b6c140, rule=0x1c423f8 "type='signal',sender='com.canonical.UserMetrics',path='/com/canonical/UserMetrics/DataSource/1',interface='com.canonical.usermetrics.DataSource',member='formatStringChanged'", error=0x0)
    at ../../dbus/dbus-bus.c:1553
        msg = 0x1d34fa8
        __FUNCTION__ = "dbus_bus_add_match"
#18 0xffffffff in QDBusConnectionPrivate::connectSignal(QString const&, QDBusConnectionPrivate::SignalHook const&) (error=0x0, rule=<optimized out>, connection=<optimized out>) at qdbus_symbols_p.h:87
        it = <optimized out>
#19 0xffffffff in QDBusConnectionPrivate::connectSignal(QString const&, QDBusConnectionPrivate::SignalHook const&) (this=this@entry=0x1b6ad48, key=..., hook=...) at qdbusintegrator.cpp:2268
        it = <optimized out>
#20 0xffffffff in QDBusConnectionPrivate::connectRelay(QString const&, QString const&, QString const&, QDBusAbstractInterface*, QMetaMethod const&) (this=0x1b6ad48, service=..., path=..., interface=..., receiver=receiver@entry=0x1c41090, signal=...)
    at qdbusintegrator.cpp:2439
        key = {static null = {<No data fields>}, d = 0x1c420c0}
        sig = {static MaxSize = 1073741808, d = 0x1d2cf28}
        locker = {<QDBusLockerBase> = {<No data fields>}, self = 0x1b6ad48, action = ConnectRelayAction}
        end = {i = 0x1b6de98}
        hook = 
            {service = {static null = {<No data fields>}, d = 0x1d347a8}, path = {static null = {<No data fields>}, d = 0x1c41b10}, signature = {static null = {<No data fields>}, d = 0x1e832a0}, obj = 0x1c41090, midx = 7, params = {d = 0x1d45cd8}, argumentMatch = {<QList<QString>> = {<QListSpecialMethods<QString>> = {<No data fields>}, {p = {static shared_null = {ref = {atomic = {_q_value = -1}}, alloc = 0, begin = 0, end = 0, array = {0x0}}, d = 0xb6565c48 <QListData::shared_null>}, d = 0xb6565c48 <QListData::shared_null>}}, <No data fields>}, matchRule = {static MaxSize = 1073741808, d = 0x1c423e8}}
        it = {i = 0x1b6de98}
#21 0xffffffff in QDBusAbstractInterface::connectNotify(QMetaMethod const&) (this=0x1c41090, signal=...)
    at qdbusabstractinterface.cpp:604
         destroyedSignal = {mobj = 0x2a2e0 <QObject::staticMetaObject>, handle = 14}
#22 0xffffffff in QMetaObjectPrivate::connect(QObject const*, int, QMetaObject const*, QObject const*, int, QMetaObject const*, int, int*) (sender=0x1c41090, signal_index=4, smeta=0xa8d17cf0 <ComCanonicalUsermetricsDataSourceInterface::staticMetaObject>, receiver=<optimized out>, method_index=5, rmeta=0xa8d17540 <UserMetricsOutput::DataSource::staticMetaObject>, type=0, types=0x0)
    at kernel/qobject.cpp:3273
        s = 0x1c41090
        callFunction = 0xa8d0b1e1 <UserMetricsOutput::DataSource::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>
        locker = {mtx1 = 0xb66679a0 <_q_ObjectMutexPool+76>, mtx2 = 0xb6667af8 <_q_ObjectMutexPool+420>, locked = false}
        c = {d = 0x1c42090}
        r = <optimized out>
        smethod = {mobj = 0xa8d17cf0 <ComCanonicalUsermetricsDataSourceInterface::staticMetaObject>, handle = 19}
#23 0xffffffff in QObject::connect(QObject const*, char const*, QObject const*, char const*, Qt::ConnectionType) (sender=0x1c41090, signal=<optimized out>, receiver=receiver@entry=0x1d444e0, method=<optimized out>, type=type@entry=Qt::AutoConnection)
    at kernel/qobject.cpp:2727
        signalTypes = 
            {a = 10, s = 1, ptr = 0xbed70e58, {array = "\n\000\000\000(P\323\001\207\b\000\000\320_\362\001\350\020\304\001\020o\366\266\000\000\000\000\334\316\322\001\020\037f\266@F\323\001\020o\366\266\000\260\037\266\020\000\000\000\003\000\000\000\260\016\327\276\020o\366\266@F\323\001\307ZN\266\350\020\304\001H9/\266", q_for_alignment_1 = 131536946852790282, q_for_alignment_2 = 7.2096893005004902e-300}}
        tmp_method_name = {static MaxSize = 1073741808, d = 0x1d23f88}
        method_arg = <optimized out>
        methodName = {static MaxSize = 1073741808, d = 0x1d45538}
        types = 0x0
        handle = {d_ptr = 0x1b0b4c8}
        tmp_signal_name = {static MaxSize = 1073741808, d = 0x1d53908}
        rmeta = 0xa8d17540 <UserMetricsOutput::DataSource::staticMetaObject>
        method_index_relative = 5
        smeta = 0xa8d17cf0 <ComCanonicalUsermetricsDataSourceInterface::staticMetaObject>
        signal_arg = <optimized out>
        signalName = {static MaxSize = 1073741808, d = 0x1d31250}
        signal_index = 4
        methodTypes = 
            {a = 10, s = 1, ptr = 0xbed70eb8, {array = "\n\000\000\000 \366\362\001\270\026\325\001\250\267\037\266\000\240-\266\020\000\000\000\270\026\325\001\374\017\327\276\000\000\000\000pN\324\001}\233Ш_I\026\266@\031\304\001\000\000\000\000\020\000\000\000\000\240-\266\bE\324\001\221 '\266\000\270\037\223\000\000\000", q_for_alignment_1 = 140445155701293066, q_for_alignment_2 = 2.8313614138543411e-299}}
#24 0xffffffff in UserMetricsOutput::SyncedDataSource::SyncedDataSource(QSharedPointer<ComCanonicalUsermetricsDataSourceInterface>, QObject*) (this=0x1d444e0, interface=..., parent=0x0)
    at /build/buildd/libusermetrics-1.1.1+15.04.20150219/src/libusermetricsoutput/SyncedDataSource.cpp:29
#25 0xffffffff in UserMetricsOutput::SyncedUserMetricsStore::addDataSource(QDBusObjectPath const&) (this=this@entry=0x1d44e70, path=...) at /build/buildd/libusermetrics-1.1.1+15.04.20150219/src/libusermetricsoutput/SyncedUserMetricsStore.cpp:135
        dataSource = {value = <optimized out>, d = 0x1d347f0}
 #26 0xffffffff in UserMetricsOutput::SyncedUserMetricsStore::sync() (this=0x1d44e70)
    at /build/buildd/libusermetrics-1.1.1+15.04.20150219/src/libusermetricsoutput/SyncedUserMetricsStore.cpp:64
        path = <optimized out>
        __for_range = <unknown type in /usr/lib/debug/.build-id/f4/f5bd5102094e6c2bc81062aa781a5cb328d45e.debug, CU 0x1140c6, DIE 0x1518a8>
        interface = <optimized out>
        systemData = <optimized out>
#27 0xffffffff in QObject::event(QEvent*) (this=<optimized out>, e=<optimized out>) at kernel/qobject.cpp:1245
        mce = <optimized out>
        sw = {receiver = 0x1d44e70, previousSender = 0x0, currentSender = {sender = 0x0, signal = -1, ref = 1}, switched = true}
#28 0xffffffff in QCoreApplication::notify(QObject*, QEvent*) (this=<optimized out>, receiver=<optimized out>, event=<optimized out>) at kernel/qcoreapplication.cpp:997
        d = <optimized out>
#29 0xffffffff in QCoreApplication::notifyInternal(QObject*, QEvent*) (this=
    0x1b0af00, receiver=receiver@entry=0x1d44e70, event=event@entry=0x1d45a30) at kernel/qcoreapplication.cpp:935
        threadData = 0x1b0b4c8
        loopLevelCounter = {threadData = 0x1b0b4c8}
        result = false
        cbdata = {0x1d44e70, 0x1d45a30, 0xbed7121f}
        d = <optimized out>
#30 0xffffffff in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (event=0x1d45a30, receiver=0x1d44e70)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:228
        e = 0x1d45a30
        pe = <optimized out>
        r = 0x1d44e70
        unlocker = {m = <synthetic pointer>}
        event_deleter = {d = 0x1d45a30}
        locker = {val = 28357860}
        startOffset = 0
        i = <optimized out>
        cleanup = {receiver = 0x0, event_type = 0, data = 0x1b0b4c8, exceptionCaught = true}
#31 0xffffffff in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x1b0b4c8) at kernel/qcoreapplication.cpp:1552
        e = 0x1d45a30
        pe = <optimized out>
        r = 0x1d44e70
        unlocker = {m = <synthetic pointer>}
        event_deleter = {d = 0x1d45a30}
        locker = {val = 28357860}
        startOffset = 0
        i = <optimized out>
        cleanup = {receiver = 0x0, event_type = 0, data = 0x1b0b4c8, exceptionCaught = true}
 #32 0xffffffff in QCoreApplication::sendPostedEvents(QObject*, int) (receiver=receiver@entry=0x0, event_type=event_type@entry=0)
    at kernel/qcoreapplication.cpp:1410
        data = <optimized out>
#33 0xffffffff in postEventSourceDispatch(GSource*, GSourceFunc, gpointer) (s=0x1b28f78) at kernel/qeventdispatcher_glib.cpp:271
        source = 0x1b28f78
#34 0xffffffff in g_main_context_dispatch (context=0x1b29560) at /build/buildd/glib2.0-2.44.0/./glib/gmain.c:3122
        dispatch = 0xb64fb5f1 <postEventSourceDispatch(GSource*, GSourceFunc, gpointer)>
        prev_source = 0x0
        was_in_call = 0
        user_data = 0x0
        callback = 0x0
        cb_funcs = <optimized out>
        cb_data = 0x0
        need_destroy = <optimized out>
        source = 0x1b28f78
        current = 0x1bf9330
        i = 0
#35 0xffffffff in g_main_context_dispatch (context=context@entry=0x1b29560) at /build/buildd/glib2.0-2.44.0/./glib/gmain.c:3737
#36 0xffffffff in g_main_context_iterate (context=context@entry=0x1b29560, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.44.0/./glib/gmain.c:3808
        max_priority = 0
        timeout = 0
        some_ready = 1
        nfds = <optimized out>
        allocated_nfds = <optimized out>
        fds = 0x1e83508
#37 0xffffffff in g_main_context_iteration (context=0x1b29560, may_block=1) at /build/buildd/glib2.0-2.44.0/./glib/gmain.c:3869
        retval = <optimized out>
#38 0xffffffff in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x1b29338, flags=...)
    at kernel/qeventdispatcher_glib.cpp:418
        d = 0x1b29348
        canWait = true
        savedFlags = {i = 0}
        result = <optimized out>
#39 0xffffffff in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0xbed713d0, flags=..., flags@entry=...)
    at kernel/qeventloop.cpp:204
        locker = {val = 28357984}
        ref = {d = 0x1e834b0, locker = @0xbed71394, exceptionCaught = true}
        d = 0x1e834b0
#40 0xffffffff in QCoreApplication::exec() () at kernel/qcoreapplication.cpp:1188
        threadData = 0x1b0b4c8
        eventLoop = 
               {<QObject> = {_vptr.QObject = 0xb6663788 <vtable for QEventLoop+8>, static staticMetaObject = {d = {superdata = 0x0, stringdata = 0xb6605dd0 <qt_meta_stringdata_QObject>, data = 0xb6605ea8 <qt_meta_data_QObject>, static_metacall = 0xb64e64b1 <QObject::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, extradata = 0x0}}, d_ptr = {d = 0x1e834b0}, static staticQtMetaObject = {d = {superdata = 0x0, stringdata = 0xb664b080 <qt_meta_stringdata_Qt>, data = 0xb664881c <qt_meta_data_Qt>, static_metacall = 0x0, relatedMetaObjects = 0x0, extradata = 0x0}}}, static staticMetaObject = {d = {superdata = 0x2a2e0 <QObject::staticMetaObject>, stringdata = 0xb665acfc <qt_meta_stringdata_QEventLoop>, data = 0xb665ad40 <qt_meta_data_QEventLoop>, static_metacall = 0xb6531215 <QEventLoop::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, extradata = 0x0}}}
        returnCode = <optimized out>
#41 0x000140aa in  ()
#42 0xffffffff in __libc_start_main (main=
    0x13bfd, argc=1, argv=0xbed71674, init=<optimized out>, fini=0x188f9 <__libc_csu_fini>, rtld_fini=0xb6f4aadd <_dl_fini>, stack_end=0xbed71674) at libc-start.c:289
        self = <optimized out>
        result = <optimized out>
        unwind_buf = 
              {cancel_jmp_buf = {{jmp_buf = {586643298, 707925259, 296, 0, 100541, 0, 0, 0, -1225363456, 0 <repeats 18 times>, 28340280, -1093200392, -1225360624, -1093200448, -1225360624, -1, -1236991459, -1240347092, -1225381040, 0, -1234807556, -1231522064, -1234810136, 1, -1234807556, 1, -1225363696, -1231525608, -1234807524, -1234807524, 0, 172192, 0, 70496, -1225412608, -1225411392, 1, 0, -1225482273, -1225403216, 1, 1, 0, -1233784832, -1240347092, 0, 0}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0xb6f67000, 0xb6f4eafc <_dl_runtime_resolve+24>}, data = {prev = 0x0, cleanup = 0x0, canceltype = -1225363456}}}
        not_first_call = <optimized out>
#43 0x0001461c in _start ()