.
Thread 3 (LWP 12134):
#0  0x00007f0235a023cd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f023627d394 in g_main_context_poll (priority=2147483647, n_fds=3, fds=0x7f02280010e0, timeout=-1, context=0x7f0238866190) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3999
        poll_func = 0x7f023628c030 <g_poll>
#2  g_main_context_iterate (context=0x7f0238866190, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3700
        max_priority = 2147483647
        timeout = -1
        some_ready = <optimized out>
        nfds = 3
        allocated_nfds = 3
        fds = 0x7f02280010e0
#3  0x00007f023627d7fa in g_main_loop_run (loop=0x7f0238866120) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3899
        __PRETTY_FUNCTION__ = "g_main_loop_run"
#4  0x00007f02368585f6 in gdbus_shared_thread_func (user_data=0x7f0238866160) at /build/buildd/glib2.0-2.37.3/./gio/gdbusprivate.c:278
        data = 0x7f0238866160
#5  0x00007f02362a1c25 in g_thread_proxy (data=0x7f023880ee30) at /build/buildd/glib2.0-2.37.3/./glib/gthread.c:798
        thread = 0x7f023880ee30
#6  0x00007f0235ce4f8e in start_thread (arg=0x7f022e178700) at pthread_create.c:311
        __res = <optimized out>
        pd = 0x7f022e178700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {139647339955968, -4875462305284160214, 0, 139647507308640, 140733869270576, 4096, 4779089909163689258, 4779035269222696234}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = 0
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#7  0x00007f0235a0ee1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113
No locals.
.
Thread 2 (LWP 12135):
#0  0x00007f0235a023cd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f023627d394 in g_main_context_poll (priority=2147483647, n_fds=1, fds=0x7f01f40010c0, timeout=-1, context=0x7f0238bcf180) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3999
        poll_func = 0x7f023628c030 <g_poll>
#2  g_main_context_iterate (context=context@entry=0x7f0238bcf180, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3700
        max_priority = 2147483647
        timeout = -1
        some_ready = <optimized out>
        nfds = 1
        allocated_nfds = 1
        fds = 0x7f01f40010c0
#3  0x00007f023627d49c in g_main_context_iteration (context=0x7f0238bcf180, may_block=1) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3766
        retval = <optimized out>
#4  0x00007f022e17fa1d in ?? () from /tmp/apport_sandbox_VnjPAp/usr/lib/x86_64-linux-gnu/gio/modules/libdconfsettings.so
No symbol table info available.
#5  0x00007f02362a1c25 in g_thread_proxy (data=0x7f0238b48770) at /build/buildd/glib2.0-2.37.3/./glib/gthread.c:798
        thread = 0x7f0238b48770
#6  0x00007f0235ce4f8e in start_thread (arg=0x7f01fc67e700) at pthread_create.c:311
        __res = <optimized out>
        pd = 0x7f01fc67e700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {139646506362624, -4875462305284160214, 0, 139647507308640, 140733869268832, 4096, 4779753048892966186, 4779035269222696234}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = 0
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#7  0x00007f0235a0ee1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113
No locals.
.
Thread 1 (LWP 12131):
#0  g_type_check_instance_cast (type_instance=type_instance@entry=0x7f0238c31030, iface_type=139647518830528) at /build/buildd/glib2.0-2.37.3/./gobject/gtype.c:4008
        is_instantiatable = <optimized out>
        check = <optimized out>
#1  0x00007f01fe438923 in dir_enum_async_ready (source=0x7f0238928b80, res=0x7f0238be2c10, user_data=user_data@entry=0x7f0238c31030) at bg-pictures-source.c:456
        priv = <optimized out>
        enumerator = <optimized out>
        err = 0x7f02362793a6 <g_list_prepend+22>
#2  0x00007f0236804a75 in g_task_return_now (task=0x7f0238be2c10) at /build/buildd/glib2.0-2.37.3/./gio/gtask.c:1108
No locals.
#3  0x00007f0236804a99 in complete_in_idle_cb (task=0x7f0238be2c10) at /build/buildd/glib2.0-2.37.3/./gio/gtask.c:1117
No locals.
#4  0x00007f023627d0a6 in g_main_dispatch (context=0x7f023881d0d0) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3058
        dispatch = 0x7f023627a0f0 <g_idle_dispatch>
        was_in_call = 0
        user_data = 0x7f0238be2c10
        callback = 0x7f0236804a90 <complete_in_idle_cb>
        cb_funcs = 0x7f0236533940 <g_source_callback_funcs>
        cb_data = 0x7f01f0009110
        need_destroy = <optimized out>
        current_source_link = {data = 0x7f01f0009ad0, next = 0x0}
        source = 0x7f01f0009ad0
        current = 0x7f0238867690
        i = 1
#5  g_main_context_dispatch (context=context@entry=0x7f023881d0d0) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3634
No locals.
#6  0x00007f023627d3f8 in g_main_context_iterate (context=context@entry=0x7f023881d0d0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3705
        max_priority = 300
        timeout = 0
        some_ready = 1
        nfds = <optimized out>
        allocated_nfds = 4
        fds = 0x7f02388df330
#7  0x00007f023627d49c in g_main_context_iteration (context=0x7f023881d0d0, context@entry=0x0, may_block=may_block@entry=1) at /build/buildd/glib2.0-2.37.3/./glib/gmain.c:3766
        retval = <optimized out>
#8  0x00007f0236825a1c in g_application_run (application=0x7f0238850e60, argc=argc@entry=2, argv=argv@entry=0x7fff284932c8) at /build/buildd/glib2.0-2.37.3/./gio/gapplication.c:1635
        arguments = 0x7f0238b96760
        status = 0
        i = <optimized out>
        __PRETTY_FUNCTION__ = "g_application_run"
#9  0x00007f023811b25a in main (argc=2, argv=0x7fff284932c8) at control-center.c:263
        shell = <optimized out>
        application = 0x7f0238850e60
        status = <optimized out>