The OplogTruncaterThread acquires a global IX lock here. This calls WiredTigerRecordStore::reclaimOplog(), which calls WiredTigerKVEngine::getPinnedOplog(), which calls WiredTigerKVEngine::getOplogNeededForRollback(), which calls TransactionParticipant::getOldestActiveTimestamp(), which acquires a global IS lock in a different locker here. This can self-deadlock if there is a pending strong lock acquisition.