Description of problem:

from sf case number 02148976 (RH-IT)
"
The dirsrv service of our IdM servers were all hanging at the same time. I assume it was replication of data. I had to kill -9 the dirsrv service, after which things began to function as normal
"

->
the 389-ds "hang" situation happened on all 4 IPA LDAP servers during a "mass" import of 1500+ groups
4 IPA replica:
nsds50ruv: {replica 8 ldap://idm03.core.dev.int.phx1.redhat.com:389} 5a722845000000080000 5b305961003900080000
nsds50ruv: {replica 4 ldap://idm-admin.core.dev.int.phx1.redhat.com:389} 5a72232a000100040000 5b305962000100040000
nsds50ruv: {replica 3 ldap://idm01.core.dev.int.phx1.redhat.com:389} 5a722330000000030000 5b305961003600030000
nsds50ruv: {replica 11 ldap://idm02.core.dev.int.phx1.redhat.com:389} 5a72394a0000000b0000 5b305961003b000b0000


a pstack shows some SASL bind for incremental updates, waiting for a result.


attaching a stack trace for review, short version:

Thread 90
pthread_cond_wait pthread_cond_wait [IDLE worker_thread_func start_thread clone

...

Thread 59
pthread_cond_wait pthread_cond_wait [IDLE worker_thread_func start_thread clone

Thread 58
epoll_wait epoll_wait epoll_dispatch event_base_loop ns_event_fw_loop event_loop_thread_func start_thread clone

Thread 49
poll poll poll ldap_int_select wait4msg ldap_result ldap_sasl_interactive_bind_s slapd_ldap_sasl_interactive_bind slapi_ldap_bind bind_and_check_pwp conn_connect acquire_replica repl5_inc_run prot_thread_main _pt_root start_thread clone

Thread 48
poll poll poll ldap_int_select wait4msg ldap_result ldap_sasl_interactive_bind_s slapd_ldap_sasl_interactive_bind slapi_ldap_bind bind_and_check_pwp conn_connect acquire_replica repl5_inc_run prot_thread_main _pt_root start_thread clone

Thread 45
poll poll poll ldap_int_select wait4msg ldap_result ldap_sasl_interactive_bind_s slapd_ldap_sasl_interactive_bind slapi_ldap_bind bind_and_check_pwp conn_connect acquire_replica repl5_inc_run prot_thread_main _pt_root start_thread clone

Thread 44
poll poll poll ldap_int_select wait4msg ldap_result ldap_sasl_interactive_bind_s slapd_ldap_sasl_interactive_bind slapi_ldap_bind bind_and_check_pwp conn_connect acquire_replica repl5_inc_run prot_thread_main _pt_root start_thread clone

Thread 1
pthread_join pthread_join ns_thrpool_wait slapd_daemon main



Version-Release number of selected component (if applicable):

389-ds-base-1.3.7.5-21.el7_5.x86_64
ipa-server-4.5.4-10.el7_5.1.x86_64
redhat-release-server-7.5-8.el7.x86_64


How reproducible:
was a one time event so far.

Steps to Reproduce:
1. N/A
2.
3.

Actual results:


Expected results:


Additional info: