(gdb) bt full
#0  transport_monitor_hash_fn (obj=<optimized out>, flags=<optimized out>) at res_pjsip/pjsip_transport_events.c:69
        object = <optimized out>
        key = <optimized out>
#1  0x0000000000466d9e in hash_ao2_find_first (self=0x7ffff4dcd080, flags=80, arg=0x7ffff747a7d8, state=0x7ffff4cce560) at astobj2_hash.c:363
        node = <optimized out>
        bucket_cur = <optimized out>
        cmp = <optimized out>
        __PRETTY_FUNCTION__ = "hash_ao2_find_first"
#2  0x0000000000464e5f in internal_ao2_traverse (self=self@entry=0x7ffff4dcd080, flags=flags@entry=80, cb_fn=<optimized out>, arg=arg@entry=0x7ffff747a7d8, data=data@entry=0x0, 
    type=type@entry=AO2_CALLBACK_DEFAULT, tag=0x0, file=0x7ffff5ebb150 "res_pjsip/pjsip_transport_events.c", line=411, func=0x7ffff5ebb640 <__PRETTY_FUNCTION__.21992> "ast_sip_transport_monitor_unregister")
    at astobj2_container.c:318
        ret = 0x0
        cb_default = 0x7ffff5e98720 <transport_monitor_cmp_fn>
        cb_withdata = 0x0
        node = <optimized out>
        traversal_state = 0x7ffff4cce560
        orig_lock = AO2_LOCK_REQ_MUTEX
        multi_container = 0x0
        multi_iterator = 0x0
        __PRETTY_FUNCTION__ = "internal_ao2_traverse"
#3  0x000000000046547c in __ao2_callback (func=<optimized out>, line=411, file=0x7ffff5ebb150 "res_pjsip/pjsip_transport_events.c", tag=0x0, arg=0x7ffff747a7d8, cb_fn=<optimized out>, flags=80, 
    c=0x7ffff4dcd080) at astobj2_container.c:437
No locals.
#4  __ao2_find (c=c@entry=0x7ffff4dcd080, arg=arg@entry=0x7ffff747a7d8, flags=flags@entry=80, tag=tag@entry=0x0, file=file@entry=0x7ffff5ebb150 "res_pjsip/pjsip_transport_events.c", line=line@entry=411, 
    func=0x7ffff5ebb640 <__PRETTY_FUNCTION__.21992> "ast_sip_transport_monitor_unregister") at astobj2_container.c:437
        arged = 0x7ffff747a7d8
#5  0x00007ffff5e98e9f in ast_sip_transport_monitor_unregister (transport=0x7ffff747a7d8, cb=cb@entry=0x7ffff5c5d620 <sub_tree_transport_cb>, data=data@entry=0x7ffff6dc8950, matches=matches@entry=0x0)
    at res_pjsip/pjsip_transport_events.c:411
        transports = 0x7ffff4dcd080
        monitored = <optimized out>
        __PRETTY_FUNCTION__ = "ast_sip_transport_monitor_unregister"
#6  0x00007ffff5c63740 in subscription_persistence_remove (sub_tree=0x7ffff6dc8950) at res_pjsip_pubsub.c:771
        __FUNCTION__ = "subscription_persistence_remove"
        __PRETTY_FUNCTION__ = "subscription_persistence_remove"
#7  pubsub_on_evsub_state (evsub=0x7ffff37547f8, event=<optimized out>) at res_pjsip_pubsub.c:3891
        sub_tree = 0x7ffff6dc8950
        __FUNCTION__ = "pubsub_on_evsub_state"
        __PRETTY_FUNCTION__ = "pubsub_on_evsub_state"
#8  0x00007ffff65d7318 in ?? () from /usr/lib/libpjsip-simple.so.2
No symbol table info available.
#9  0x00007ffff65d8300 in pjsip_evsub_terminate () from /usr/lib/libpjsip-simple.so.2
No symbol table info available.
#10 0x00007ffff5c5b037 in sub_tree_subscription_terminate_cb (data=0x7ffff6dc8950) at res_pjsip_pubsub.c:604
        sub_tree = 0x7ffff6dc8950
        __PRETTY_FUNCTION__ = "sub_tree_subscription_terminate_cb"
        __FUNCTION__ = "sub_tree_subscription_terminate_cb"
#11 0x00000000005925fa in ast_taskprocessor_execute (tps=tps@entry=0x7ffff4ad0d70) at taskprocessor.c:1302
        local = {local_data = 0x0, data = 0x0}
        t = 0x7ffff4706730
        size = <optimized out>
        __PRETTY_FUNCTION__ = "ast_taskprocessor_execute"
#12 0x0000000000599890 in execute_tasks (data=0x7ffff4ad0d70) at threadpool.c:1352
---Type <return> to continue, or q <return> to quit---
        tps = 0x7ffff4ad0d70
#13 0x00000000005925fa in ast_taskprocessor_execute (tps=0x7ffff5577970) at taskprocessor.c:1302
        local = {local_data = 0x7ffff5bee130, data = 0x7ffff55777f0}
        t = 0x7ffff378f6a0
        size = <optimized out>
        __PRETTY_FUNCTION__ = "ast_taskprocessor_execute"
#14 0x000000000059a148 in threadpool_execute (pool=0x7ffff55777f0) at threadpool.c:367
        __PRETTY_FUNCTION__ = "threadpool_execute"
#15 worker_active (worker=0x7ffff5bee130) at threadpool.c:1137
        alive = <optimized out>
#16 worker_start (arg=arg@entry=0x7ffff5bee130) at threadpool.c:1056
        worker = 0x7ffff5bee130
        saved_state = <optimized out>
        __PRETTY_FUNCTION__ = "worker_start"
#17 0x00000000005a1829 in dummy_start (data=<optimized out>) at utils.c:1574
        __cb = {__f = 0x460e90 <ast_unregister_thread>, __x = 0x7ffff4cceb30, __next = 0x0}
        ret = <optimized out>
        a = {start_routine = 0x599dc0 <worker_start>, data = 0x7ffff5bee130, name = 0x7ffff5574660 "worker_start         started at [ 1111] threadpool.c worker_thread_start()"}
        __PRETTY_FUNCTION__ = "dummy_start"
#18 0x00007ffff7fba0b9 in ?? () from /lib/ld-musl-x86_64.so.1
No symbol table info available.
#19 0x0000000000000000 in ?? ()
No symbol table info available.