(gdb) 
(gdb) bt full
#0  0xb7509bfe in __ast_pthread_mutex_lock (filename=0xb755bdf4 "chan_sip.c", lineno=1900, func=0xb755c318 "retrans_pkt", 
    mutex_name=0xb755c324 "&pkt->owner->lock", t=0x0) at /usr/src/asterisk-1.4/include/asterisk/lock.h:302
        res = -1208696809
        canlog = -1219489176
        __PRETTY_FUNCTION__ = "__ast_pthread_mutex_lock"
#1  0xb75090b6 in retrans_pkt (data=0xb6626a00) at chan_sip.c:1900
        pkt = (struct sip_pkt *) 0xb6626a00
        prev = (struct sip_pkt *) 0x81618c9
        cur = (struct sip_pkt *) 0x0
        reschedule = 1000
        xmitres = 0
        __PRETTY_FUNCTION__ = "retrans_pkt"
#2  0x081012ce in ast_sched_runq (con=0x822f478) at sched.c:359
        current = (struct sched *) 0xb6600a70
        tv = {tv_sec = 1204213222, tv_usec = 775338}
        numevents = 0
        res = 1
        __PRETTY_FUNCTION__ = "ast_sched_runq"
#3  0xb754e24a in do_monitor (data=0x0) at chan_sip.c:15647
        res = 0
        sip = (struct sip_pvt *) 0x0
        peer = (struct sip_peer *) 0x0
        t = 1204213222
        fastrestart = 0
        lastpeernum = -1
        curpeernum = 5
        reloading = 0
        __PRETTY_FUNCTION__ = "do_monitor"
#4  0x081126c3 in dummy_start (data=0x8232b78) at utils.c:861
        _buffer = {__routine = 0x806a1e9 <ast_unregister_thread>, __arg = 0xb7501bb0, __canceltype = 0, __prev = 0x0}
        ret = (void *) 0x0
        a = {start_routine = 0xb754dab5 <do_monitor>, data = 0x0, 
  name = 0x8232b88 "do_monitor", ' ' <repeats 11 times>, "started at [15701] chan_sip.c restart_monitor()"}
        lock_info = (struct thr_lock_info *) 0x8233c38
        mutex_attr = {__mutexkind = 1}
#5  0xb7f4a240 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
No symbol table info available.
#6  0xb7e6549e in clone () from /lib/tls/i686/cmov/libc.so.6
No symbol table info available.