[asterisk-bugs] [JIRA] (ASTERISK-25468) Deadlock in chan_sip - core show locks shows do_monitor lock

[Barry Flanagan (JIRA)]

Barry Flanagan created ASTERISK-25468:
-----------------------------------------

             Summary: Deadlock in chan_sip - core show locks shows do_monitor lock
                 Key: ASTERISK-25468
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-25468
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Channels/chan_sip/General
    Affects Versions: 13.6.0
         Environment: Debian 8 and Ubuntu 14.04.3.
Asterisk latest 13.6.0 from Git.
Realtime using odbc/mysql

            Reporter: Barry Flanagan


I am trying to bring a new server into an existing cluster of Asterisk boxes and I keep getting the same problem.

Servers are all behind a Kamailio LB, and when I add this new server to the dispatcher group, kamailio starts sending REGISTER and  SUBSCRIBE requests to the new server. After a few minutes chan_sip just hangs, no longer processing any traffic at all. Nothing shows up in the logs, and Asterisk itself is still running. I can see the incoming SIP packets using sngrep, but Asterisk does not see them.

I have tried this on KVM and Openvz virtual servers as well as physical servers, and have tried both Debian 8 and Ubuntu 14.04 with the exact same results.

When chan_sip freezes, 'core show locks' shows the following every time:

{code}
=======================================================================
=== GIT-13-f8707ae
=== Currently Held Locks
=======================================================================
===
=== <pending> <lock#> (<file>): <lock type> <line num> <function> <lock name> <lock addr> (times locked)
===
=== Thread ID: 0x7fba21a4c700 LWP:13423 (do_monitor           started at [28932] chan_sip.c restart_monitor())
=== ---> Lock #0 (chan_sip.c): MUTEX 28903 do_monitor &monlock 0x7fba319054a0 (1)
        main/backtrace.c:59 __ast_bt_get_addresses() (0x46777f+1D)
        main/lock.c:258 __ast_pthread_mutex_lock() (0x5379ef+C7)
        channels/chan_sip.c:28904 do_monitor()
        main/utils.c:1237 dummy_start()
        :0 start_thread()
        libc.so.6 clone() (0x7fbab9e25410+6D)
=== -------------------------------------------------------------------
{code}

There is no core sump when this happens. SIP simply stops responding, peers do not expire, etc.

I have managed to get a gdb backtrace from the running process using 
{code}
gdb -ex "thread apply all bt" --batch /usr/sbin/asterisk <pid>
{code}

Hopefully that will give some clue. I will upload it as an attachment.

Any help much appreciated.




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