.
Thread 2 (LWP 3946):
#0  0x00007fb471cf63cd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007fb47301b15c in g_main_context_poll (n_fds=1, fds=0x7fb45c0008c0, timeout=-1, context=0x286f5b0, priority=<optimized out>) at /build/buildd/glib2.0-2.35.8/./glib/gmain.c:3995
        poll_func = 0x7fb473029550 <g_poll>
#2  g_main_context_iterate (context=context@entry=0x286f5b0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.35.8/./glib/gmain.c:3696
        max_priority = 2147483647
        timeout = -1
        some_ready = <optimized out>
        allocated_nfds = <optimized out>
        fds = 0x7fb45c0008c0
        nfds = 1
#3  0x00007fb47301b284 in g_main_context_iteration (context=0x286f5b0, may_block=may_block@entry=1) at /build/buildd/glib2.0-2.35.8/./glib/gmain.c:3762
        retval = <optimized out>
#4  0x00007fb47301b2e1 in glib_worker_main (data=<optimized out>) at /build/buildd/glib2.0-2.35.8/./glib/gmain.c:5427
No locals.
#5  0x00007fb47303f075 in g_thread_proxy (data=0x27ffde0) at /build/buildd/glib2.0-2.35.8/./glib/gthread.c:798
        thread = 0x27ffde0
#6  0x00007fb472b1af8e in start_thread (arg=0x7fb4633f1700) at pthread_create.c:311
        __res = <optimized out>
        pd = 0x7fb4633f1700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140412735919872, -902633930929912676, 0, 140413031010400, 140733993730384, 4096, 869745888230458524, 869711892579042460}, 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  0x00007fb471d02e1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113
No locals.
.
Thread 1 (LWP 3935):
#0  ~basic_string (this=0x7fff2fb42c70, __in_chrg=<optimized out>) at /usr/include/c++/4.7/bits/basic_string.h:536
No locals.
#1  pkgProblemResolver::DoUpgrade (this=0x7fff2fb42ca0, Pkg=...) at algorithms.cc:730
        P = {<pkgCache::Iterator<pkgCache::Package, pkgCache::PkgIterator>> = {<std::iterator<std::forward_iterator_tag, pkgCache::Package, long, pkgCache::Package*, pkgCache::Package&>> = {<No data fields>}, _vptr.Iterator = 0x4641af8, S = 0x456f8d8, Owner = 0x44e7b78}, HashIndex = 0}
        Start = {<pkgCache::Iterator<pkgCache::Dependency, pkgCache::DepIterator>> = {<std::iterator<std::forward_iterator_tag, pkgCache::Dependency, long, pkgCache::Dependency*, pkgCache::Dependency&>> = {<No data fields>}, _vptr.Iterator = 0x2cc, S = 0x4, Owner = 0x7fff2fb42d0f}, Type = (unknown: 800337640)}
        End = {<pkgCache::Iterator<pkgCache::Dependency, pkgCache::DepIterator>> = {<std::iterator<std::forward_iterator_tag, pkgCache::Dependency, long, pkgCache::Dependency*, pkgCache::Dependency&>> = {<No data fields>}, _vptr.Iterator = 0x61044e7860, S = 0x26b42c8, Owner = 0x6b1d58}, Type = (unknown: 38622368)}
        D = {<pkgCache::Iterator<pkgCache::Dependency, pkgCache::DepIterator>> = {<std::iterator<std::forward_iterator_tag, pkgCache::Dependency, long, pkgCache::Dependency*, pkgCache::Dependency&>> = {<No data fields>}, _vptr.Iterator = 0x44e7b60, S = 0x4242e70, Owner = 0x25fc000}, Type = (unknown: 4466924)}
        group = {cache = @0x292b8e0, released = false}
        WasKept = false
        Fail = <optimized out>
#2  0x0000000000000000 in ?? ()
No symbol table info available.