(gdb) 
#0  0x002d58d0 in pthread_mutex_trylock () from /lib/libpthread.so.0
#1  0x006dbf83 in ast_mutex_trylock (pmutex=0x6573752c) at /root/yuxiaobo/asterisk-1.4.23-rc3/include/asterisk/lock.h:760
#2  0x0071f853 in do_monitor (data=0x0) at chan_sip.c:16145
#3  0x08106009 in dummy_start (data=0x9fe1378) at utils.c:856
#4  0x002d343b in start_thread () from /lib/libpthread.so.0
#5  0x0022afde in clone () from /lib/libc.so.6
(gdb) bt full
#0  0x002d58d0 in pthread_mutex_trylock () from /lib/libpthread.so.0
No symbol table info available.
#1  0x006dbf83 in ast_mutex_trylock (pmutex=0x6573752c) at /root/yuxiaobo/asterisk-1.4.23-rc3/include/asterisk/lock.h:760
No locals.
#2  0x0071f853 in do_monitor (data=0x0) at chan_sip.c:16145
        res = 0
        sip = (struct sip_pvt *) 0x6573752c
        peer = (struct sip_peer *) 0x0
        t = 1231379496
        fastrestart = 0
        lastpeernum = -1
        curpeernum = 74
        reloading = 0
        __PRETTY_FUNCTION__ = "do_monitor"
#3  0x08106009 in dummy_start (data=0x9fe1378) at utils.c:856
        __cancel_buf = {__cancel_jmp_buf = {{__cancel_jmp_buf = {3022836, 0, 10312592, 10310600, 1059984012, 933436981}, 
      __mask_was_saved = 0}}, __pad = {0x9d5480, 0x0, 0x0, 0x0}}
        __cancel_routine = (void (*)(void *)) 0x806a974 <ast_unregister_thread>
        __cancel_arg = (void *) 0x9d5b90
        not_first_call = 0
        ret = (void *) 0x0
        a = {start_routine = 0x71f690 <do_monitor>, data = 0x0, 
  name = 0x9fe13f8 "do_monitor", ' ' <repeats 11 times>, "started at [16281] chan_sip.c restart_monitor()"}
        __PRETTY_FUNCTION__ = "dummy_start"
#4  0x002d343b in start_thread () from /lib/libpthread.so.0
No symbol table info available.
#5  0x0022afde in clone () from /lib/libc.so.6
No symbol table info available.
(gdb) frame 2
#2  0x0071f853 in do_monitor (data=0x0) at chan_sip.c:16145
16145                           if (ast_mutex_trylock(&sip->lock))
(gdb) list
16140                           /*! \note If we can't get a lock on an interface, skip it and come
16141                            * back later. Note that there is the possibility of a deadlock with
16142                            * sip_hangup otherwise, because sip_hangup is called with the channel
16143                            * locked first, and the iface lock is attempted second.
16144                            */
16145                           if (ast_mutex_trylock(&sip->lock))
16146                                   continue;
16147
16148                           /* Check RTP timeouts and kill calls if we have a timeout set and do not get RTP */
16149                           if (sip->rtp && sip->owner &&
(gdb) p *sip
Cannot access memory at address 0x6573752c
(gdb) p sip->lock
Cannot access memory at address 0x6573752c
(gdb)