Description of problem:
When memberof plugin is enabled, an update of a group can trigger many nested updates of its members. The value of 'memberof' is changed in those members. As a consequence many database pages associated to the index 'memberof' are held (write) by the parent TXN (update of the group).

Any search request, that need access to those pages (i.e. filter contains (memberof=cn=my_group,dc=com)) is stuck until the update TXN commits.

If the number of such searches requests is as high as the number of workers, all workers may be busy+locked until the TXN commits. During that time the server may receive new requests that will not be processed until the TXN commits. As a consequence the LDAP server appears unresponsive.

Version-Release number of selected component (if applicable):
All versions RHEL7/8/9

How reproducible:
Systematically. See next update

Actual results:
The server becomes unresponsive

Expected results:
The server should stay responsive