(ITS#8752) MMR delta-sync deadlock using slapd.conf

[quanah@openldap.org]

Full_Name: Quanah Gibson-Mount
Version: 2.4.45
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (47.208.148.239)


There is a reproducible lockup with delta-sync based multimaster replication. 
The more masters exist the easier it is to trigger, with 100% reproducibility at
4 masters.

Generally:

Load a database onto a server with no syncprov/accesslog configuration.

Stop slapd

Reconfigure slapd.conf to include syncprov/accesslog overlays, and cn=accesslog
DB for changes, and replication agreements with other servers

Configure other servers for syncprov/accesslog, but no database

start slapd on all servers

execute a MOD operation sequentially across the servers (1, 2, 3, 4)

slapd will deadlock on server 3 or 4 100% of the time