(gdb) info threads
  Id   Target Id         Frame
  2    Thread 0xb25d8b70 (LWP 19842) "python" 0xb782b424 in __kernel_vsyscall ()
* 1    Thread 0xb743c6c0 (LWP 4025) "python" 0xb782b424 in __kernel_vsyscall ()
(gdb) bt
#0  0xb782b424 in __kernel_vsyscall ()
#1  0xb7801619 in __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:142
#2  0xb77fcf7d in _L_lock_708 () from /lib/i386-linux-gnu/libpthread.so.0
#3  0xb77fcdc3 in __pthread_mutex_lock (mutex=0xa35eecc) at pthread_mutex_lock.c:61
#4  0xb6aec881 in boost::thread::interrupt() () from /usr/lib/libboost_thread.so.1.46.1
#5  0xb6b45537 in gruel::thread_group::interrupt_all() () from /usr/local/lib/libgruel-3.5.0rc0.so.0.0.0
#6  0xb6cea49e in gr_scheduler_tpb::stop() () from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#7  0xb6cefb76 in gr_top_block_impl::stop() () from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#8  0xb6cefbcd in gr_top_block_impl::restart() () from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#9  0xb6cf03cf in gr_top_block_impl::unlock() () from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#10 0xb6cef20e in gr_top_block::unlock() () from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#11 0xb70d7e70 in _wrap_gr_top_block_sptr_unlock ()
   from /usr/local/lib/python2.7/dist-packages/gnuradio/gr/_gnuradio_core_runtime.so
#12 0x080f77c3 in PyEval_EvalFrameEx ()
#13 0x080f7e20 in PyEval_EvalFrameEx ()
#14 0x080fd804 in PyEval_EvalCodeEx ()
#15 0x080fe177 in PyEval_EvalCode ()
#16 0x0811acd0 in ?? ()
#17 0x0811b8e9 in PyRun_FileExFlags ()
#18 0x0811c4cc in PyRun_SimpleFileExFlags ()
#19 0x0812c7c6 in Py_Main ()
#20 0x0805da0b in main ()
(gdb) thread 2
[Switching to thread 2 (Thread 0xb25d8b70 (LWP 19842))]
#0  0xb782b424 in __kernel_vsyscall ()
(gdb) bt
#0  0xb782b424 in __kernel_vsyscall ()
#1  0xb7801619 in __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:142
#2  0xb77fcf7d in _L_lock_708 () from /lib/i386-linux-gnu/libpthread.so.0
#3  0xb77fcdc3 in __pthread_mutex_lock (mutex=0xb1c022f8) at pthread_mutex_lock.c:61
#4  0xb6aecbdb in boost::this_thread::interruption_point() () from /usr/lib/libboost_thread.so.1.46.1
#5  0xb6cf158d in gr_tpb_thread_body::gr_tpb_thread_body(boost::shared_ptr<gr_block>) ()
   from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#6  0xb6cebc1b in boost::detail::function::void_function_obj_invoker0<gruel::thread_body_wrapper<tpb_container>, void>::invoke(boost::detail::function::function_buffer&) () from /usr/local/lib/libgnuradio-core-3.5.0rc0.so.0.0.0
#7  0xb6b461a6 in boost::detail::thread_data<boost::function0<void> >::run() ()
   from /usr/local/lib/libgruel-3.5.0rc0.so.0.0.0
#8  0xb6aec3cc in thread_proxy () from /usr/lib/libboost_thread.so.1.46.1
#9  0xb77fad31 in start_thread (arg=0xb25d8b70) at pthread_create.c:304
#10 0xb750f0ce in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130
Backtrace stopped: Not enough registers or memory available to unwind further