The problem is that there is no operation extention. This triggers a PR_ASSERT. Note that I am surprise it leads to a SIGSEV

(gdb) list
235	    PR_ASSERT(ident);
236	    /* First mark the operation as completed/failed
237	     * the param to be used once the operation will be pushed
238	     * on the listeners queue
239	     */
240	    for (curr_op = prim_op; curr_op; curr_op = curr_op->next) {
241	        if (curr_op->idx_pl == ident->idx_pl) {
242	            /* The operation extension (ident) refers this operation (currop in the pending list)
243	             * This is called during sync_repl postop. At this moment
244	             * the operation in the pending list (identified by idx_pl in the operation extension)
(gdb) print prim_op
$1 = (OPERATION_PL_CTX_T *) 0x7f8f1c8af980
(gdb) print curr_op
$2 = (OPERATION_PL_CTX_T *) 0x7f8f1c8af980
(gdb) print curr_op->next
$3 = (struct OPERATION_PL_CTX *) 0x7f8f1c8afe30
(gdb) print ident
$4 = (op_ext_ident_t *) 0x0


'ident' is retrieved from:
233	    ident = sync_persist_get_operation_extension(pb);

At a first look, this internal operation (add a cenotaph) have not added an operation extention. I do not known how it is possible :(

I think the problem is that the ADD of a cenotaph is an internal_add flagged 'OP_FLAG_NOOP'.
As a consequence POST operation plugins are called (e.g. sync_update_persist_op) BUT not PRE/POST BETXN operation plugins (e.g. sync_update_persist_betxn_pre_op). Operation extension (for sync_repl) being initialized in PRE BETXN, it is no initialized at the time POST op are called.

Needs to confirm this, rerunning the test. A possible fix is to test NOOP flag if the operation ext is not set.

Fix pushed upstream => POST

Marking as verified: tested as per comment 10 and comment 11

# PYTHONPATH=src/lib389/ py.test -s -v dirsrvtests/tests/suites/syncrepl_plugin/basic_test.py::test_sync_repl_cenotaph
re-exec with libfaketime dependencies
================================================================== test session starts ==================================================================
platform linux -- Python 3.6.8, pytest-6.2.2, py-1.10.0, pluggy-0.13.1 -- /usr/bin/python3.6
cachedir: .pytest_cache
metadata: {'Python': '3.6.8', 'Platform': 'Linux-4.18.0-293.el8.x86_64-x86_64-with-redhat-8.5-Ootpa', 'Packages': {'pytest': '6.2.2', 'py': '1.10.0', 'pluggy': '0.13.1'}, 'Plugins': {'metadata': '1.11.0', 'html': '3.1.1', 'libfaketime': '0.1.2'}}
389-ds-base: 1.4.3.16-13.module+el8.4.0+10307+74bbfb4e
nss: 3.53.1-17.el8_3
nspr: 4.25.0-2.el8_2
openldap: 2.4.46-16.el8
cyrus-sasl: 2.1.27-5.el8
FIPS: disabled
rootdir: /mnt/tests/rhds/tests/upstream/ds/dirsrvtests, configfile: pytest.ini
plugins: metadata-1.11.0, html-3.1.1, libfaketime-0.1.2
collected 1 item
PASSED
    ================================================ 1 passed in 159.82s (0:02:39) ==================================================           

marking as VERIFIED

*** Bug 1937855 has been marked as a duplicate of this bug. ***

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (389-ds:1.4 bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:1835