evc.c

test file nucleus source

        if (preempt)

            /* Transfer control to the system if the resumed task function
               detects a preemption condition.  */
            TCT_Control_To_System();
    }

    /* Release protection of the event_group.  */
    TCT_Unprotect();

    /* Return to user mode */
    NU_USER_MODE();

    /* Return a successful status.  */
    return(NU_SUCCESS);
}



/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      EVC_Retrieve_Events                                              */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function retrieves various combinations of event flags from */
/*      the specified event group.  If the group does not contain the    */
/*      necessary flags, suspension of the calling task is possible.     */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      EVCE_Retrieve_Events                Error checking shell         */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      CSC_Place_On_List                   Place on suspend list        */
/*      [HIC_Make_History_Entry]            Make entry in history log    */
/*      TCC_Suspend_Task                    Suspend calling task         */
/*      [TCT_Check_Stack]                   Stack checking function      */
/*      TCT_Current_Thread                  Pickup current thread pointer*/
/*      TCT_System_Protect                  Protect event group          */
/*      TCT_Unprotect                       Release protection           */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      event_group_ptr                     Event Group control block ptr*/
/*      requested_events                    Requested event flags        */
/*      operation                           AND/OR selection of flags    */
/*      retrieved_events                    Pointer to destination for   */
/*                                            actual flags retrieved     */
/*      suspend                             Suspension option            */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_SUCCESS                          If successful completion     */
/*      NU_TIMEOUT                          If timeout on suspension     */
/*      NU_NOT_PRESENT                      If event flags are not       */
/*                                            present                    */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      03-01-1994      Changed function interfaces to                   */
/*                      match those in prototype,                        */
/*                      added register options, changed                  */
/*                      protection logic to reduce                       */
/*                      overhead, resulting in                           */
/*                      version 1.1                                      */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
STATUS  EVC_Retrieve_Events(NU_EVENT_GROUP *event_group_ptr,
                        UNSIGNED requested_events, OPTION operation,
                        UNSIGNED *retrieved_events, UNSIGNED suspend)
{

R1 EV_GCB      *event_group;                /* Event control block ptr   */
R2 EV_SUSPEND  *suspend_ptr;                /* Pointer to suspend block  */
EV_SUSPEND      suspend_block;              /* Suspension block          */
R3 UNSIGNED     compare;                    /* Event comparison variable */
TC_TCB         *task;                       /* Pointer to task           */
STATUS          status;                     /* Completion status         */
NU_SUPERV_USER_VARIABLES

    /* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

    /* Move input event group pointer into internal pointer.  */
    event_group =  (EV_GCB *) event_group_ptr;


#ifdef  NU_ENABLE_STACK_CHECK

    /* Call stack checking function to check for an overflow condition.  */
    TCT_Check_Stack();

#endif

#ifdef  NU_ENABLE_HISTORY

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_RETRIEVE_EVENTS_ID, (UNSIGNED) event_group,
                            (UNSIGNED) requested_events, (UNSIGNED) operation);

#endif

    /* Initialize the status as successful.  */
    status =  NU_SUCCESS;

    /* Protect against simultaneous access to the event group.  */
    TCT_System_Protect();

    /* Determine if the events requested are present.  */

    /* Isolate common event flags.  */
    compare =  event_group -> ev_current_events & requested_events;

    /* Determine if all of the events must be present.  */
    if (operation & EV_AND)

        /* Yes, all events must be present.  See if the compare value is
           the same as the requested value.  */
        compare =  (compare == requested_events);

    /* Determine if the requested combination of event flags are present.  */
    if (compare)
    {

        /* Yes, necessary event flags are present.  */

        /* Copy the current event flags into the appropriate destination.  */
        *retrieved_events =  event_group -> ev_current_events;

        /* Determine if consumption is required.  If so, consume the event
           flags present in the group.  */
        if (operation & EV_CONSUME)

            event_group -> ev_current_events =
                event_group -> ev_current_events & ~requested_events;

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpEventGroup(RT_PROF_RETRIEVE_EVENTS,event_group, RT_PROF_OK);
#endif /*INCLUDE_PROVIEW*/

    }
    else
    {

        /* Determine if the task requested suspension.  */
        if (suspend)
        {

            /* Suspension is selected.  */

            /* Increment the number of tasks waiting.  */
            event_group -> ev_tasks_waiting++;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpEventGroup(RT_PROF_RETRIEVE_EVENTS,event_group, RT_PROF_WAIT);
#endif /*INCLUDE_PROVIEW*/

            /* Setup the suspend block and suspend the calling task.  */
            suspend_ptr =  &suspend_block;
            suspend_ptr -> ev_event_group =              event_group;
            suspend_ptr -> ev_suspend_link.cs_next =     NU_NULL;
            suspend_ptr -> ev_suspend_link.cs_previous = NU_NULL;
            task =                            (TC_TCB *) TCT_Current_Thread();
            suspend_ptr -> ev_suspended_task =           task;
            suspend_ptr -> ev_requested_events =         requested_events;
            suspend_ptr -> ev_operation =                operation;

            /* Link the suspend block into the list of suspended tasks on this
               event group.  */
            CSC_Place_On_List((CS_NODE **)
                        &(event_group -> ev_suspension_list),
                                        &(suspend_ptr -> ev_suspend_link));

            /* Finally, suspend the calling task. Note that the suspension call
               automatically clears the protection on the event group.  */
            TCC_Suspend_Task((NU_TASK *) task, NU_EVENT_SUSPEND,
                                        EVC_Cleanup, suspend_ptr, suspend);

            /* Pickup the return status and the actual retrieved events.  */
            status =             suspend_ptr -> ev_return_status;
            *retrieved_events =  suspend_ptr -> ev_actual_events;
        }
        else
        {

            /* No suspension requested.  Simply return an error status
               and zero the retrieved events variable.  */
            status =             NU_NOT_PRESENT;
            *retrieved_events =  0;
#ifdef INCLUDE_PROVIEW
            _RTProf_DumpEventGroup(RT_PROF_RETRIEVE_EVENTS,event_group,RT_PROF_FAIL);
#endif /*INCLUDE_PROVIEW*/
        }
    }

    /* Release protection of the event_group.  */
    TCT_Unprotect();

    /* Return to user mode */
    NU_USER_MODE();

    /* Return the completion status.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      EVC_Cleanup                                                      */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function is responsible for removing a suspension block     */
/*      from a event group.  It is not called unless a timeout or a task */
/*      terminate is in progress.  Note that protection is already in    */
/*      effect - the same protection at suspension time.  This routine   */
/*      must be called from Supervisor mode in Supervisor/User mode      */
/*      switching kernels.                                               */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      TCC_Timeout                         Task timeout                 */
/*      TCC_Terminate                       Task terminate               */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      CSC_Remove_From_List                Remove suspend block from    */
/*                                            the suspension list        */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      information                         Pointer to suspend block     */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      None                                                             */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*                                                                       */
/*************************************************************************/
VOID  EVC_Cleanup(VOID *information)
{

EV_SUSPEND      *suspend_ptr;               /* Suspension block pointer  */
NU_SUPERV_USER_VARIABLES

    /* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

    /* Use the information pointer as a suspend pointer.  */
    suspend_ptr =  (EV_SUSPEND *) information;

    /* By default, indicate that the service timed-out.  It really does not
       matter if this function is called from a terminate request since
       the task does not resume.  */
    suspend_ptr -> ev_return_status =  NU_TIMEOUT;

    /* Decrement the number of tasks waiting counter.  */
    (suspend_ptr -> ev_event_group) -> ev_tasks_waiting--;

    /* Unlink the suspend block from the suspension list.  */
    CSC_Remove_From_List((CS_NODE **)
                &((suspend_ptr -> ev_event_group) -> ev_suspension_list),
                                &(suspend_ptr -> ev_suspend_link));

    /* Return to user mode */
    NU_USER_MODE();
}