(gdb) bt full
#0  0x00f13402 in __kernel_vsyscall ()
No symbol table info available.
#1  0x00a2edf0 in raise () from /lib/libc.so.6
No symbol table info available.
#2  0x00a30701 in abort () from /lib/libc.so.6
No symbol table info available.
#3  0x00a6728b in __libc_message () from /lib/libc.so.6
No symbol table info available.
#4  0x00a6f595 in _int_free () from /lib/libc.so.6
No symbol table info available.
#5  0x00a6f9d9 in free () from /lib/libc.so.6
No symbol table info available.
#6  0x08080fb4 in __ao2_ref (user_data=0xa03d730, delta=-1) at astobj2.c:290
        obj = (struct astobj2 *) 0xa03d0f8
        current_value = -1
        ret = 0
        __PRETTY_FUNCTION__ = "__ao2_ref"
#7  0x08080eb2 in _ao2_ref (user_data=0xa03d730, delta=-1) at astobj2.c:251
        obj = (struct astobj2 *) 0xa03d0f8
#8  0x00659900 in local_ast_moh_cleanup (chan=0xa041500) at res_musiconhold.c:1181
        state = (struct moh_files_state *) 0xa03ea38
#9  0x080a691f in ast_moh_cleanup (chan=0xa041500) at channel.c:5530
No locals.
#10 0x08098932 in ast_channel_free (chan=0xa041500) at channel.c:1423
        fd = 151494696
        vardata = (struct ast_var_t *) 0x815d9bf
        f = (struct ast_frame *) 0x4bca42f6
        headp = (struct varshead *) 0xa041c28
        datastore = (struct ast_datastore *) 0x0
        name = "SIP/chris\00000000003\000\t\204\035\004\n\204\035\004\n\220«\a\tè\237\a\t\t\000\000\000*ä\032\bTØ\032\b\000\000\000\0009ò\032\b3ç\032\b\000\000\000\000( \a\tá%\t\b\000\000\000\000\220«\a\t"
        dashptr = 0x9079fb1 ""
        inlist = 0
        __PRETTY_FUNCTION__ = "ast_channel_free"
#11 0x08099e02 in ast_hangup (chan=0xa041500) at channel.c:1767
        res = 0
        __PRETTY_FUNCTION__ = "ast_hangup"
#12 0x0811ec89 in __ast_pbx_run (c=0xa041500, args=0x0) at pbx.c:3966
        found = 1
        res = -1
        autoloopflag = 0
        error = 1
        __PRETTY_FUNCTION__ = "__ast_pbx_run"
#13 0x0811efcc in pbx_thread (data=0xa041500) at pbx.c:4058
        c = (struct ast_channel *) 0xa041500
#14 0x0817ae3a in dummy_start (data=0xa0253b0) at utils.c:968
        __cancel_buf = {__cancel_jmp_buf = {{__cancel_jmp_buf = {11964404, 0, 151497616, 151495608, -685830422, -703659886}, __mask_was_saved = 0}}, __pad = {0x907a470, 0x0, 
    0xa0842b8, 0xa03a9c8}}
        __cancel_routine = (void (*)(void *)) 0x807501d <ast_unregister_thread>
        __cancel_arg = (void *) 0x907ab90
        not_first_call = 0
---Type <return> to continue, or q <return> to quit---
        ret = (void *) 0xb58bdc
        a = {start_routine = 0x811efad <pbx_thread>, data = 0xa041500, name = 0x9f70560 "pbx_thread", ' ' <repeats 11 times>, "started at [ 4079] pbx.c ast_pbx_start()"}
        lock_info = (struct thr_lock_info *) 0xa048ce0
        mutex_attr = {__size = "\001\000\000", __align = 1}
#15 0x00b5973b in start_thread () from /lib/libpthread.so.0
No symbol table info available.
#16 0x00ad7cfe in clone () from /lib/libc.so.6
No symbol table info available.
(gdb) 
(gdb) 
(gdb) thread apply all bt

Thread 1 (process 26388):
#0  0x00f13402 in __kernel_vsyscall ()
#1  0x00a2edf0 in raise () from /lib/libc.so.6
#2  0x00a30701 in abort () from /lib/libc.so.6
#3  0x00a6728b in __libc_message () from /lib/libc.so.6
#4  0x00a6f595 in _int_free () from /lib/libc.so.6
#5  0x00a6f9d9 in free () from /lib/libc.so.6
#6  0x08080fb4 in __ao2_ref (user_data=0xa03d730, delta=-1) at astobj2.c:290
#7  0x08080eb2 in _ao2_ref (user_data=0xa03d730, delta=-1) at astobj2.c:251
#8  0x00659900 in local_ast_moh_cleanup (chan=0xa041500) at res_musiconhold.c:1181
#9  0x080a691f in ast_moh_cleanup (chan=0xa041500) at channel.c:5530
#10 0x08098932 in ast_channel_free (chan=0xa041500) at channel.c:1423
#11 0x08099e02 in ast_hangup (chan=0xa041500) at channel.c:1767
#12 0x0811ec89 in __ast_pbx_run (c=0xa041500, args=0x0) at pbx.c:3966
#13 0x0811efcc in pbx_thread (data=0xa041500) at pbx.c:4058
#14 0x0817ae3a in dummy_start (data=0xa0253b0) at utils.c:968
#15 0x00b5973b in start_thread () from /lib/libpthread.so.0
#16 0x00ad7cfe in clone () from /lib/libc.so.6
(gdb) q