(gdb) bt full
#0  0x00007f60d78d5ad4 in pjsip_inv_send_msg (inv=inv@entry=0x7f60b81a4d98, tdata=tdata@entry=0x7f60b8144308)
    at ../src/pjsip-ua/sip_inv.c:3218
        cseq = 0x7f60b8144de0
        status = <optimized out>
#1  0x00007f60d5931279 in internal_pjsip_inv_send_msg (inv=0x7f60b81a4d98, transport_name=<optimized out>, 
    tdata=tdata@entry=0x7f60b8144308) at res_pjsip_session.c:996
        selector = {type = PJSIP_TPSELECTOR_NONE, u = {transport = 0x0, listener = 0x0, ptr = 0x0}}
#2  0x00007f60d5933a8e in ast_sip_session_send_response (session=session@entry=0x7f60b86218f8, tdata=0x7f60b8144308)
    at res_pjsip_session.c:1002
No locals.
#3  0x00007f60c17eec62 in answer (data=0x7f60b86218f8) at chan_pjsip.c:575
        status = 0
        packet = 0x7f60b8144308
        session = 0x7f60b86218f8
        __PRETTY_FUNCTION__ = "answer"
#4  0x00007f61340ee074 in sync_task (data=0x7f6085e21430) at res_pjsip.c:3861
        std = 0x7f6085e21430
        ret = <optimized out>
        __PRETTY_FUNCTION__ = "sync_task"
#5  0x00000000005b9f78 in ast_taskprocessor_execute (tps=tps@entry=0x3181218) at taskprocessor.c:967
        local = {local_data = 0x20, data = 0x3181218}
        t = 0x7f60ed590490
        size = <optimized out>
        __PRETTY_FUNCTION__ = "ast_taskprocessor_execute"
#6  0x00000000005c1788 in execute_tasks (data=0x3181218) at threadpool.c:1322
        tps = 0x3181218
#7  0x00000000005b9f78 in ast_taskprocessor_execute (tps=0x1c35b98) at taskprocessor.c:967
        local = {local_data = 0x7f60c347ede0, data = 0x7f60c4001610}
        t = 0x7f60cc0a3b60
        size = <optimized out>
        __PRETTY_FUNCTION__ = "ast_taskprocessor_execute"
#8  0x00000000005c1b7c in threadpool_execute (pool=0x1c37468) at threadpool.c:351
No locals.
#9  worker_active (worker=0x7f60c4001608) at threadpool.c:1105
No locals.
#10 worker_start (arg=arg@entry=0x7f60c4001608) at threadpool.c:1024
        worker = 0x7f60c4001608
        saved_state = <optimized out>
        __PRETTY_FUNCTION__ = "worker_start"
#11 0x00000000005cc299 in dummy_start (data=<optimized out>) at utils.c:1235
        __cancel_buf = {__cancel_jmp_buf = {{__cancel_jmp_buf = {140053581926624, 6629035796046559806, 140053855235248, 0, 
                140053569862080, 17, -6539624265827468738, 6629035141124340286}, __mask_was_saved = 0}}, __pad = {0x7f60c347eef0, 
            0x0, 0x7f6138044870 <__elf_set___libc_thread_subfreeres_element___rpc_thread_destroy__>, 0x7f6138044878}}
        __cancel_arg = 0x7f60c347f700
        __not_first_call = <optimized out>
        ret = <optimized out>
        a = {start_routine = 0x5c17c0 <worker_start>, data = 0x7f60c4001608, name = <optimized out>}
#12 0x00007f61387eece2 in start_thread () from /lib64/libpthread.so.0
No symbol table info available.
#13 0x00007f6137d7f8cd in clone () from /lib64/libc.so.6