(gdb) bt full
#0  0xb707ec23 in strlen () from /lib/i686/libc.so.6
No symbol table info available.
#1  0xb707e945 in strdup () from /lib/i686/libc.so.6
No symbol table info available.
#2  0x0810d66b in ast_extension_state_add (context=0x82bf6c5 "linestates", exten=0x82bf60d "772", callback=0xb6d79664 <cb_extensionstate>, data=0x82f94a8) at pbx.c:3393
        hint = (struct ast_hint *) 0xb6ce0e08
        cblist = (struct ast_state_cb *) 0xb7f5e300
        e = (struct ast_exten *) 0x82dd3d8
        __PRETTY_FUNCTION__ = "ast_extension_state_add"
#3  0xb6d9f598 in ?? () from /usr/lib/asterisk/modules/chan_sip.so
No locals.
#4  0xb6da0b43 in ?? () from /usr/lib/asterisk/modules/chan_sip.so
No locals.
#5  0xb6da16c4 in ?? () from /usr/lib/asterisk/modules/chan_sip.so
No locals.
#6  0xb6da1042 in ?? () from /usr/lib/asterisk/modules/chan_sip.so
No locals.
#7  0x080e8fb3 in ast_io_wait (ioc=0x823bf58, howlong=97) at io.c:287
        res = 1
        x = 0
        origcnt = 1
#8  0xb6da2a4d in ?? () from /usr/lib/asterisk/modules/chan_sip.so
No locals.
#9  0x08167b52 in dummy_start (data=0x8247820) at utils.c:1024
        __cancel_buf = {__cancel_jmp_buf = {{__cancel_jmp_buf = {-1210679308, 0, 4001536, -1228008536, -496338954, 1387837067}, __mask_was_saved = 0}}, __pad = {0xb6ce1470, 0x0, 0x0,
    0x0}}
        __cancel_routine = (void (*)(void *)) 0x806fc58 <ast_unregister_thread>
        __cancel_arg = (void *) 0xb6ce1b90
        not_first_call = 0
        ret = (void *) 0x0
        a = {start_routine = 0xb6da27c2, data = 0x0, name = 0x8216028 "do_monitor", ' ' <repeats 11 times>, "started at [19591] chan_sip.c restart_monitor()"}
        lock_info = (struct thr_lock_info *) 0x82463e8
        mutex_attr = {__size = "\001\000\000", __align = 1}
#10 0xb7d59315 in start_thread () from /lib/i686/libpthread.so.0
No symbol table info available.
#11 0xb70e4dde in clone () from /lib/i686/libc.so.6
No symbol table info available.