(gdb) bt full
#0  0xb4d2abc1 in __ast_pthread_mutex_lock (filename=0xb4d7d464 "chan_sip.c", lineno=7909, 
func=0xb4d8296c "expire_register", mutex_name=0xb4d7e66b "&(peer)->_lock", t=0x5c)
    at /usr/src/asterisk-1.4.19.2/include/asterisk/lock.h:302
        res = 0
        canlog = 1
        __PRETTY_FUNCTION__ = "__ast_pthread_mutex_lock"
#1  0xb4d4808f in expire_register (data=0x832f3f0) at chan_sip.c:7909
        newcount = 0
        peer = (struct sip_peer *) 0x0
        __PRETTY_FUNCTION__ = "expire_register"
#2  0x08103f84 in ast_sched_runq (con=0x82aac28) at sched.c:359
        current = (struct sched *) 0x82fac58
        tv = {tv_sec = 1211030731, tv_usec = 253425}
        numevents = 0
        res = 1
        __PRETTY_FUNCTION__ = "ast_sched_runq"
#3  0xb4d6fa1a in do_monitor (data=0x0) at chan_sip.c:15695
        res = 0
        sip = (struct sip_pvt *) 0x0
        peer = (struct sip_peer *) 0x0
        t = 1211030730
        fastrestart = 0
        lastpeernum = -1
        curpeernum = 60
        reloading = 0
        __PRETTY_FUNCTION__ = "do_monitor"
#4  0x08115e26 in dummy_start (data=0x82adb78) at utils.c:865
        _buffer = {__routine = 0x806a34b <ast_unregister_thread>, __arg = 0xb4d22bb0, __canceltype = 0, 
__prev = 0x0}
        ret = (void *) 0x0
        a = {start_routine = 0xb4d6f233 <do_monitor>, data = 0x0, name = 0x82ade28 "do_monitor", ' ' 
<repeats 11 times>, "started at [15749] chan_sip.c restart_monitor()"}
        lock_info = (struct thr_lock_info *) 0x82aee10
        mutex_attr = {__mutexkind = 1}
#5  0xb7f68240 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
No symbol table info available.
#6  0xb705749e in clone () from /lib/tls/i686/cmov/libc.so.6
No symbol table info available.
(gdb)