Dash frozen while the rest of unity8 still functional (can't change scopes)

[Ricardo Salveti]

phablet@ubuntu-phablet:~$ system-image-cli -i
current build number: 214
device name: krillin
channel: ubuntu-touch/ubuntu-rtm/14.09-proposed
last update: 2015-01-26 18:10:46
version version: 214
version ubuntu: 20150126.1
version device: 20150121-61768b8
version custom: 20150121-510-24-178

Got this before going to bed, and noticed today that the dash was still completely frozen.

Checking unity8-dash, it seems to be stuck in a futex:
phablet@ubuntu-phablet:/tmp$ sudo strace -p 2617
[sudo] password for phablet:
Process 2617 attached
futex(0x408a98, FUTEX_WAIT_PRIVATE, 2, NULL
^CProcess 2617 detached
 <detached ...>

Log attached.

Video: http://people.canonical.com/~rsalveti/VID_20150127_161410.mp4

[Ricardo Salveti (rsalveti)]

The backgrace of unity8-dash:
(gdb) bt full
#0 __libc_do_syscall () at ../ports/sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:43
No locals.
#1 0xb5f9b1e4 in __lll_lock_wait (futex=futex@entry=0x408a98, private=<optimized out>) at ../ports/sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.c:46
        _a2 = 128
        _a3 = 2
        _a1 = 4229784
        _a1tmp = 4229784
        _a4 = 0
        _name = 240
        __ret = 4229784
        oldval = <optimized out>
#2 0xb5f979a6 in __GI___pthread_mutex_lock (mutex=0x408a98) at pthread_mutex_lock.c:114
        __futex = 0x408a98
        id = <optimized out>
        __PRETTY_FUNCTION__ = "__pthread_mutex_lock"
        type = <optimized out>
        id = <optimized out>
#3 0xb3dd1532 in _dbus_connection_lock (connection=0x408a00) at ../../dbus/dbus-connection.c:397
No locals.
#4 0xb3ddecfe in _dbus_pending_call_get_connection_and_lock (pending=pending@entry=0x9403d940) at ../../dbus/dbus-pending-call.c:334
No locals.
#5 0xb3dd3fcc in reply_handler_timeout (data=0x9403d940) at ../../dbus/dbus-connection.c:3292
        connection = <optimized out>
        status = <optimized out>
        pending = 0x9403d940
#6 0xb3e3a28e in q_dbus_timeout_handle (timeout=<optimized out>) at qdbus_symbols_p.h:174
No locals.
#7 QDBusConnectionPrivate::timerEvent (this=0x407c20, e=0xbed54144) at qdbusintegrator.cpp:1134
        locker = {<QDBusMutexLocker> = {<QDBusLockerBase> = {<No data fields>}, self = 0x407c20, mutex = 0x407c4c, action = TimerEventAction}, <No data fields>}
#8 0xb6492ef2 in QObject::event (this=0x407c20, e=0xbed54144) at kernel/qobject.cpp:1263
No locals.
#9 0xb6472318 in QCoreApplication::notify (this=<optimized out>, receiver=<optimized out>, event=<optimized out>) at kernel/qcoreapplication.cpp:997
        d = <optimized out>
#10 0xb64723f4 in QCoreApplication::notifyInternal (this=0x2cf410, receiver=0x407c20, event=event@entry=0xbed54144) at kernel/qcoreapplication.cpp:935
        threadData = 0x2cf4b8
        loopLevelCounter = {threadData = 0x2cf4b8}
        result = false
        cbdata = {0x407c20, 0xbed54144, 0xbed540df}
        d = <optimized out>
#11 0xb64acc2e in sendEvent (event=0xbed54144, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:237
No locals.
#12 QTimerInfoList::activateTimers (this=0x31e174) at kernel/qtimerinfo_unix.cpp:643
        e = {<QEvent> = {_vptr.QEvent = 0xb6628f38 <vtable for QTimerEvent+8>, static staticMetaObject = {d = {superdata = 0x0, stringdata = 0xb65ec118 <qt_meta_stringdata_QEvent>, data = 0xb65ebb94 <qt_meta_data_QEvent>, static_metacall = 0x0, relatedMetaObjects = 0x0,
                extradata = 0x0}}, d = 0x0, t = 1, posted = 0, spont = 0, m_accept = 1, reserved = 0}, id = 7}
        currentTimerInfo = 0x1f72420
        n_act = 1
        maxCount = <optimized out>
        currentTime = {tv_sec = 12034, tv_nsec = <optimized out>}
#13 0xb64acf46 in timerSourceDispatch (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:185
        timerSource = <optimized out>
#14 0xb5c7af50 in g_main_dispatch (context=0x31e0c0) at /build/buildd/glib2.0-2.41.5/./glib/gmain.c:3064
        dispatch = 0xb64acf3...

[Michał Sawicz (saviq)]

Calling this a dupe, the other bug is about unity8, not unity8-dash, but the trace is very similar.