(gdb) bt full
#0  0x08082a42 in ast_channel_spy_read_frame (spy=0x9af2610, samples=160) at channel.c:4210
        result = (struct ast_frame *) 0x0
        read_buf = {-354, -112}
        write_buf = {197, -246}
        read_frame = (struct ast_frame *) 0x32
        write_frame = (struct ast_frame *) 0x42349
        need_dup = 1157047854
        stack_read_frame = {frametype = AST_FRAME_VOICE, subclass = 64, datalen = 320, samples = 160, mallocd = 0, mallocd_hdr_len = 0, offset = 0,
  src = 0x0, data = 0xb761e170, delivery = {tv_sec = 0, tv_usec = 0}, frame_list = {next = 0x0}, has_timing_info = 0, ts = 0, len = 0, seqno = 0}
        stack_write_frame = {frametype = AST_FRAME_VOICE, subclass = 64, datalen = 320, samples = 160, mallocd = 0, mallocd_hdr_len = 0, offset = 0,
  src = 0x0, data = 0xb761e020, delivery = {tv_sec = 0, tv_usec = 0}, frame_list = {next = 0x0}, has_timing_info = 0, ts = 0, len = 0, seqno = 0}
#1  0x00a81684 in mixmonitor_thread (obj=0x9af2610) at app_mixmonitor.c:184
        next = (struct ast_frame *) 0x0
        write = 1
        mixmonitor = (struct mixmonitor *) 0x9af2610
        f = (struct ast_frame *) 0x0
#2  0x080e5dab in dummy_start (data=0x9addc78) at utils.c:538
        _buffer = {__routine = 0x8067a09 <ast_unregister_thread>, __arg = 0xb761ebb0, __canceltype = -1218321320, __prev = 0x0}
        ret = (void *) 0x8e166c
        a = {start_routine = 0xa815ec <mixmonitor_thread>, data = 0x9af2610,
  name = 0x9af3988 "mixmonitor_thread    started at [  315] app_mixmonitor.c launch_monitor_thread()"}
#3  0x0092b371 in start_thread () from /lib/tls/libpthread.so.0
No symbol table info available.
#4  0x008849be in clone () from /lib/tls/libc.so.6
No symbol table info available.