data race in rdataset_addglue

WARNING: ThreadSanitizer: data race 
  Read of size 8 at 0x000000000001 by thread T1:
    #0 rdataset_addglue lib/dns/rbtdb.c:10254
    #1 dns_rdataset_addglue lib/dns/rdataset.c:747
    #2 query_additional lib/ns/query.c:2105
    #3 query_addrrset lib/ns/query.c:2194
    #4 query_addanswer lib/ns/query.c:7342
    #5 query_respond lib/ns/query.c:7432
    #6 query_prepresponse lib/ns/query.c:9946
    #7 query_gotanswer lib/ns/query.c:6863
    #8 query_lookup lib/ns/query.c:5624
    #9 ns__query_start lib/ns/query.c:5500
    #10 query_setup lib/ns/query.c:5224
    #11 ns_query_start lib/ns/query.c:11351
    #12 ns__client_request lib/ns/client.c:2178
    #13 udp_recv_cb netmgr/udp.c:377
    #14 <null> <null>
    #15 <null> <null>

  Previous write of size 8 at 0x000000000001 by thread T2 (mutexes: write M1):
    #0 rehash_gluetable lib/dns/rbtdb.c:10070
    #1 rdataset_addglue lib/dns/rbtdb.c:10426
    #2 dns_rdataset_addglue lib/dns/rdataset.c:747
    #3 query_additional lib/ns/query.c:2105
    #4 query_addrrset lib/ns/query.c:2194
    #5 query_prepare_delegation_response lib/ns/query.c:7932
    #6 query_zone_delegation lib/ns/query.c:8039
    #7 query_delegation lib/ns/query.c:8064
    #8 query_gotanswer lib/ns/query.c:6875
    #9 query_lookup lib/ns/query.c:5624
    #10 ns__query_start lib/ns/query.c:5500
    #11 query_setup lib/ns/query.c:5224
    #12 ns_query_start lib/ns/query.c:11351
    #13 ns__client_request lib/ns/client.c:2178
    #14 udp_recv_cb netmgr/udp.c:377
    #15 <null> <null>
    #16 <null> <null>

  Location is heap block of size 537 at 0x000000000019 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 allocate_version lib/dns/rbtdb.c:1302
    #9 dns_rbtdb_create lib/dns/rbtdb.c:8707
    #10 dns_db_create lib/dns/db.c:118
    #11 zone_load lib/dns/zone.c:2225
    #12 zone_asyncload lib/dns/zone.c:2314
    #13 dispatch lib/isc/task.c:1152
    #14 run lib/isc/task.c:1344
    #15 <null> <null>

  Mutex M1 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_nm_start netmgr/netmgr.c:215
    #3 create_managers bin/named/main.c:907
    #4 setup bin/named/main.c:1221
    #5 main bin/named/main.c:1521

  Thread T2 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create pthreads/thread.c:73
    #2 isc_nm_start netmgr/netmgr.c:215
    #3 create_managers bin/named/main.c:907
    #4 setup bin/named/main.c:1221
    #5 main bin/named/main.c:1521

  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:913
    #4 setup bin/named/main.c:1221
    #5 main bin/named/main.c:1521

SUMMARY: ThreadSanitizer: data race lib/dns/rbtdb.c:10254 in rdataset_addglue