ThreadSanitizer: data race lib/dns/zone.c:10272:7 in zone_maintenance

TSAN error on v9_11 (ff463f37):

S:notify:Wed Mar 17 04:43:32 UTC 2021
T:notify:1:A
A:notify:System test notify
I:notify:PORTRANGE:10000 - 10099
I:notify:checking initial status (1)
I:notify:checking startup notify rate limit (2)
I:notify:reloading with example2 using HUP and waiting up to 45 seconds
I:notify:checking notify message was logged (3)
I:notify:checking example2 loaded (4)
I:notify:checking example2 contents have been transferred after HUP reload (5)
I:notify:stopping master and restarting with example4 then waiting up to 45 seconds
I:notify:checking notify message was logged (6)
I:notify:checking example4 loaded (7)
I:notify:checking example4 contents have been transferred after restart (8)
I:notify:checking notify to alternate port with master inheritance (9)
I:notify:checking notify to multiple views using tsig (10)
I:notify:exit status: 0
I:notify:1 sanitizer report(s) found
R:notify:FAIL
E:notify:Wed Mar 17 04:44:05 UTC 2021

WARNING: ThreadSanitizer: data race 
  Read of size 4 at 0x000000000001 by thread T1:
    #0 zone_maintenance lib/dns/zone.c:10272:7
    #1 zone_timer lib/dns/zone.c:13569:2
    #2 dispatch lib/isc/task.c:1157:7
    #3 run lib/isc/task.c:1331:2

  Previous write of size 4 at 0x000000000001 by thread T2 (mutexes: write M1):
    #0 dns_zone_notifyreceive2 lib/dns/zone.c:14053:3
    #1 ns_notify_start bin/named/notify.c:150:13
    #2 client_request bin/named/client.c:3150:3
    #3 dispatch lib/isc/task.c:1157:7
    #4 run lib/isc/task.c:1331:2

  Location is heap block of size 2841 at 0x000000000009 allocated by thread T3:
    #0 malloc <null>
    #1 internal_memalloc lib/isc/mem.c:887:8
    #2 mem_get lib/isc/mem.c:792:8
    #3 mem_allocateunlocked lib/isc/mem.c:1545:8
    #4 isc___mem_allocate lib/isc/mem.c:1566:7
    #5 isc__mem_allocate lib/isc/mem.c:3048:11
    #6 isc___mem_get lib/isc/mem.c:1304:11
    #7 isc__mem_get lib/isc/mem.c:3012:11
    #8 dns_zone_create lib/dns/zone.c:930:9
    #9 dns_zonemgr_createzone lib/dns/zone.c:16916:11
    #10 configure_zone bin/named/./server.c:5637:3
    #11 configure_view bin/named/./server.c:3435:3
    #12 load_configuration bin/named/./server.c:8179:3
    #13 run_server bin/named/./server.c
    #14 dispatch lib/isc/task.c:1157:7
    #15 run lib/isc/task.c:1331:2

  Mutex M1 is already destroyed.

  Thread T3 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:60:8
    #2 isc__taskmgr_create lib/isc/task.c:1468:7
    #3 isc_taskmgr_create lib/isc/task.c:2109:11
    #4 create_managers bin/named/./main.c:886:11
    #5 setup bin/named/./main.c:1305:11
    #6 main bin/named/./main.c:1556:2

  Thread T2 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:60:8
    #2 isc__taskmgr_create lib/isc/task.c:1468:7
    #3 isc_taskmgr_create lib/isc/task.c:2109:11
    #4 create_managers bin/named/./main.c:886:11
    #5 setup bin/named/./main.c:1305:11
    #6 main bin/named/./main.c:1556:2

  Thread T3 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:60:8
    #2 isc__taskmgr_create lib/isc/task.c:1468:7
    #3 isc_taskmgr_create lib/isc/task.c:2109:11
    #4 create_managers bin/named/./main.c:886:11
    #5 setup bin/named/./main.c:1305:11
    #6 main bin/named/./main.c:1556:2

SUMMARY: ThreadSanitizer: data race lib/dns/zone.c:10272:7 in zone_maintenance

There's this similar TSAN on v9_11: #2261 (closed).