#197 Problems with scheduler locking in QP/C/C++ ports to ThreadX

[Quantum Leaps]

The QFSchedLock_() implementation in the QP/C/C++ port to ThreadX might change thread preemption threshold with lower priority than the one of the thread itself. This causes an error in ThreadX and assertion in the QP port.
--MMS

[Quantum Leaps]

Fixed in QP/C/C++ 6.0.4. The selective scheduler locking for ThreadX is implemented as follows:

void QFSchedLock_(QFSchedLock * const lockStat, uint_fast8_t prio) {
    UINT tx_err;

    lockStat->lockHolder = tx_thread_identify();

    /* this must be thread level, so current TX thread must be valid */
    Q_REQUIRE_ID(800, lockStat->lockHolder != (TX_THREAD *)0);

    /* change the preemption threshold of the current thread */
    tx_err = tx_thread_preemption_change(lockStat->lockHolder,
                     (QF_TX_PRIO_OFFSET + QF_MAX_ACTIVE - prio),
                     &lockStat->prevThre);

    if (tx_err == TX_SUCCESS) {
        QS_CRIT_STAT_
        lockStat->lockPrio = prio;
        . . .
    }
    else if (tx_err == TX_THRESH_ERROR) {
        /* threshold was greater than (lower prio) than the current prio */
        lockStat->lockPrio = (uint_fast8_t)0; /* threshold not changed */
    }
    else {
        /* no other errors are tolerated */
        Q_ERROR_ID(810);
    }
}