WARNING: ThreadSanitizer: lock-order-inversion (potential deadlock) 
  Cycle in lock order graph: M1 (0x000000000000) => M2 (0x000000000000) => M3 (0x000000000001) => M1

  Mutex M2 acquired here while holding mutex M1 in thread T1:
    #0 pthread_mutex_lock <null>
    #1 dns_zone_asyncload lib/dns/zone.c:2342:2
    #2 asyncload lib/dns/zt.c:371:11
    #3 dns_zt_apply lib/dns/zt.c:544:14
    #4 dns_zt_asyncload lib/dns/zt.c:344:11
    #5 dns_view_asyncload lib/dns/view.c:1575:10
    #6 load_zones bin/named/server.c:9686:12
    #7 run_server bin/named/server.c:9774:2
    #8 dispatch lib/isc/task.c:1152:7
    #9 run lib/isc/task.c:1344:2

  Mutex M1 previously acquired by the same thread here:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 dns_zt_asyncload lib/dns/zt.c:343:2
    #3 dns_view_asyncload lib/dns/view.c:1575:10
    #4 load_zones bin/named/server.c:9686:12
    #5 run_server bin/named/server.c:9774:2
    #6 dispatch lib/isc/task.c:1152:7
    #7 run lib/isc/task.c:1344:2

  Mutex M3 acquired here while holding mutex M2 in thread T1:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 dns_keytable_find lib/dns/keytable.c:522:2
    #3 check_dnskey_sigs lib/dns/zoneverify.c:1535:11
    #4 check_dnskey lib/dns/zoneverify.c:1657:4
    #5 dns_zoneverify_dnssec lib/dns/zoneverify.c:1991:11
    #6 dns_zone_verifydb lib/dns/zone.c:21044:11
    #7 zone_postload lib/dns/zone.c:4956:12
    #8 zone_load lib/dns/zone.c:2281:11
    #9 zone_asyncload lib/dns/zone.c:2314:11
    #10 dispatch lib/isc/task.c:1152:7
    #11 run lib/isc/task.c:1344:2

  Mutex M2 previously acquired by the same thread here:
    #0 pthread_mutex_lock <null>
    #1 zone_asyncload lib/dns/zone.c:2313:2
    #2 dispatch lib/isc/task.c:1152:7
    #3 run lib/isc/task.c:1344:2

  Mutex M1 acquired here while holding mutex M3 in thread T2:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 dns_zt_find lib/dns/zt.c:172:2
    #3 dns_view_findzonecut lib/dns/view.c:1315:12
    #4 dotat bin/named/server.c:7088:11
    #5 dns_keytable_forall lib/dns/keytable.c:786:4
    #6 tat_timer_tick bin/named/server.c:7143:9
    #7 dispatch lib/isc/task.c:1152:7
    #8 run lib/isc/task.c:1344:2

  Mutex M3 previously acquired by the same thread here:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 dns_keytable_forall lib/dns/keytable.c:770:2
    #3 tat_timer_tick bin/named/server.c:7143:9
    #4 dispatch lib/isc/task.c:1152:7
    #5 run lib/isc/task.c:1344:2

  Thread T1 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:73:8
    #2 isc_taskmgr_create lib/isc/task.c:1434:3
    #3 create_managers bin/named/main.c:915:11
    #4 setup bin/named/main.c:1223:11
    #5 main bin/named/main.c:1523:2

  Thread T2 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:73:8
    #2 isc_taskmgr_create lib/isc/task.c:1434:3
    #3 create_managers bin/named/main.c:915:11
    #4 setup bin/named/main.c:1223:11
    #5 main bin/named/main.c:1523:2

SUMMARY: ThreadSanitizer: lock-order-inversion (potential deadlock) in pthread_mutex_lock