Event Flag Vs Semaphore: Refer Status/Deletion/Clear Event Flag

①Event Flags: Clear/Refer/Delete event flags

As, these functions are not holding much share of programming, let me put all these in one post. And, these functions are exactly same as of Semaphore, though Semaphore does not have a function equivalent to clr_flg().

② uITRON implementation to clear event flag

ER clr_flg(ID flgid, FLGPTN clrptn)
{
        Sanity check on arguments
        Enter critical section (Interrupt Disable)
        existing flag pattern &= clrptn;
        Exit critical section (Interrupt Restore)
        return E_OK;
}

③ uITRON implementation to refer event flag information

ER ref_flg(ID flgid, T_RFLG *pk_rflg)
{
        Sanity check on arguments
        Enter critical section (Interrupt Disable)
        Store event flag's current bit pattern
        Store ID number of task which is at the head of flag's wait queue
        Exit critical section (Interrupt Restore)
        return E_OK;
}

④ uITRON implementation to delete flag

ER del_mtx(ID mtxid)
{
        Check context. If called from ISR,
                return E_CTX;
        Sanity check on arguments
        Enter critical section (Interrupt Disable)
        For each task waiting on the event flag's queue {
                Set E_DLT at the error code register of task's context
                If task is waiting for timeout {
                        Delete task from timer queue
                }
                Set task's status as Ready
                If task is not in suspended state {
                        Change the task from event flag's queue to ready queue
                        If executing task's priority is lower than the waiting,
                           set to execute scheduler when quitting this function
                }
                else {
                        Delete the task from the event flag queue
                }
        }
        Release resources allocated when creating event flag(Release event flag's queue)
        If scheduler has to be executed {
                Call scheduler
                Return the error code in the context's error code register
        }
        Exit critical section (Interrupt Restore)
        return E_OK;
}
Please visit other posts under RTOS label.