Calls:
->DetectEngineHCBDGetBufferForTX
->            htud->tsflags |= HTP_REQ_BODY_COMPLETE;
->    htud->request_body.body_inspected = htud->request_body.last->stream_offset + htud->request_body.last->len;

Which means the RDLOCK above is insufficient. Need a WRLOCK for client and server bodies at least.