TSAN error: lib/dns/rbtdb.c

Job #1434050 failed for e6064e7c:

WARNING: ThreadSanitizer: data race 
  Write of size 4 at 0x000000000001 by thread T1 (mutexes: read M1, read M2):
    #0 check_stale_header lib/dns/rbtdb.c:4573
    #1 cache_find lib/dns/rbtdb.c:5061
    #2 dns_db_findext lib/dns/db.c:536
    #3 query_lookup lib/ns/query.c:5805
    #4 query_gotanswer lib/ns/query.c:7556
    #5 query_resume lib/ns/query.c:6614
    #6 fetch_callback lib/ns/query.c:6161
    #7 dispatch lib/isc/task.c:1152
    #8 run lib/isc/task.c:1344
    #9 <null> <null>

  Previous write of size 4 at 0x000000000001 by thread T2 (mutexes: read M1, read M2):
    #0 check_stale_header lib/dns/rbtdb.c:4573
    #1 cache_find lib/dns/rbtdb.c:5061
    #2 dns_db_findext lib/dns/db.c:536
    #3 query_lookup lib/ns/query.c:5805
    #4 query_gotanswer lib/ns/query.c:7556
    #5 query_resume lib/ns/query.c:6614
    #6 fetch_callback lib/ns/query.c:6161
    #7 dispatch lib/isc/task.c:1152
    #8 run lib/isc/task.c:1344
    #9 <null> <null>

  Location is heap block of size 209 at 0x000000000011 allocated by thread T3:
    #0 malloc <null>
    #1 default_memalloc lib/isc/mem.c:713
    #2 mem_get lib/isc/mem.c:622
    #3 mem_allocateunlocked lib/isc/mem.c:1268
    #4 isc___mem_allocate lib/isc/mem.c:1288
    #5 isc__mem_allocate lib/isc/mem.c:2453
    #6 isc___mem_get lib/isc/mem.c:1037
    #7 isc__mem_get lib/isc/mem.c:2432
    #8 dns_rdataslab_fromrdataset lib/dns/rdataslab.c:270
    #9 addrdataset lib/dns/rbtdb.c:6813
    #10 dns_db_addrdataset lib/dns/db.c:719
    #11 addoptout lib/dns/ncache.c:281
    #12 dns_ncache_add lib/dns/ncache.c:101
    #13 ncache_adderesult lib/dns/resolver.c:6795
    #14 ncache_message lib/dns/resolver.c:6972
    #15 rctx_ncache lib/dns/resolver.c:9350
    #16 resquery_response lib/dns/resolver.c:8063
    #17 dispatch lib/isc/task.c:1152
    #18 run lib/isc/task.c:1344
    #19 <null> <null>

  Mutex M1 is already destroyed.

  Mutex M2 is already destroyed.

  Thread T1 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create pthreads/thread.c:73
    #2 isc_taskmgr_create lib/isc/task.c:1434
    #3 create_managers bin/named/main.c:940
    #4 setup bin/named/main.c:1248
    #5 main bin/named/main.c:1548

  Thread T2 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create pthreads/thread.c:73
    #2 isc_taskmgr_create lib/isc/task.c:1434
    #3 create_managers bin/named/main.c:940
    #4 setup bin/named/main.c:1248
    #5 main bin/named/main.c:1548

  Thread T3 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create pthreads/thread.c:73
    #2 isc_taskmgr_create lib/isc/task.c:1434
    #3 create_managers bin/named/main.c:940
    #4 setup bin/named/main.c:1248
    #5 main bin/named/main.c:1548

SUMMARY: ThreadSanitizer: data race lib/dns/rbtdb.c:4573 in check_stale_header