backtrace for iceweasel related hangup

(gdb) bt
#0  0x00007fc68928b99d in pthread_join (threadid=1404900385100136, thread_return=0x0) at pthread_join.c:89

#16 0x00007fc68773d8e8 in XRE_main (argc=, argv=, aAppData=) at nsAppRunner.cpp:3331
#17 0x00000000004024df in main (argc=1, argv=0x7fffaa9352c8) at nsXULStub.cpp:493