mbc.c

test file nucleus source

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_RECEIVE_FROM_MAILBOX_ID, (UNSIGNED) mailbox,
                                       (UNSIGNED) message, (UNSIGNED) suspend);

#endif

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

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

    /* Determine if the mailbox is empty or full.  */
    if (mailbox -> mb_message_present)
    {

        /* Copy message from mailbox into the caller's area.  */

        /* Setup the source and destination pointers.  */
        source_ptr =       &(mailbox -> mb_message_area[0]);
        destination_ptr =  (UNSIGNED *) message;

        /* Copy the message directly into the waiting task's
           destination.  */
        *destination_ptr =        *source_ptr;
        *(destination_ptr + 1) =  *(source_ptr + 1);
        *(destination_ptr + 2) =  *(source_ptr + 2);
        *(destination_ptr + 3) =  *(source_ptr + 3);

        /* Determine if another task is waiting to place something into the
           mailbox.  */
        if (mailbox -> mb_suspension_list)
        {

            /* Yes, another task is waiting to send something to the
               mailbox.  */

            /* Decrement the number of tasks waiting counter.  */
            mailbox -> mb_tasks_waiting--;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_RECEIVE_FROM_MAILBOX,mailbox,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */
            /* Remove the first suspended block from the list.  */
            suspend_ptr =  mailbox -> mb_suspension_list;
            CSC_Remove_From_List((CS_NODE **)
                &(mailbox -> mb_suspension_list),
                                &(suspend_ptr -> mb_suspend_link));

            /* Setup the source and destination pointers.  */
            source_ptr =       suspend_ptr -> mb_message_area;
            destination_ptr =  &(mailbox -> mb_message_area[0]);

            /* Copy the message directly into the waiting task's
               destination.  */
            *destination_ptr =        *source_ptr;
            *(destination_ptr + 1) =  *(source_ptr + 1);
            *(destination_ptr + 2) =  *(source_ptr + 2);
            *(destination_ptr + 3) =  *(source_ptr + 3);

            /* Setup the appropriate return value.  */
            suspend_ptr -> mb_return_status =  NU_SUCCESS;

            /* Resume the suspended task.  */
            preempt =
               TCC_Resume_Task((NU_TASK *) suspend_ptr -> mb_suspended_task,
                                                       NU_MAILBOX_SUSPEND);

            /* Determine if a preempt condition is present.  */
            if (preempt)

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

            /* Clear the message present flag.  */
            mailbox -> mb_message_present =  NU_FALSE;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_RECEIVE_FROM_MAILBOX,mailbox,RT_PROF_OK);
#endif /* INCLUDE_PROVIEW */

        }

    }
    else
    {

        /* Mailbox is empty.  Determine if suspension is required.  */
        if (suspend)
        {

            /* Suspension is required.  */

            /* Increment the number of tasks waiting on the mailbox counter. */
            mailbox -> mb_tasks_waiting++;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_RECEIVE_FROM_MAILBOX,mailbox,RT_PROF_WAIT);
#endif /* INCLUDE_PROVIEW */

            /* Setup the suspend block and suspend the calling task.  */
            suspend_ptr =  &suspend_block;
            suspend_ptr -> mb_mailbox =                  mailbox;
            suspend_ptr -> mb_suspend_link.cs_next =     NU_NULL;
            suspend_ptr -> mb_suspend_link.cs_previous = NU_NULL;
            suspend_ptr -> mb_message_area =             (UNSIGNED *) message;
            task =                            (TC_TCB *) TCT_Current_Thread();
            suspend_ptr -> mb_suspended_task =           task;

            /* Determine if priority or FIFO suspension is associated with the
               mailbox.  */
            if (mailbox -> mb_fifo_suspend)
            {

                /* FIFO suspension is required.  Link the suspend block into
                   the list of suspended tasks on this mailbox.  */
                CSC_Place_On_List((CS_NODE **) &(mailbox ->mb_suspension_list),
                                        &(suspend_ptr -> mb_suspend_link));
            }
            else
            {

                /* Get the priority of the current thread so the suspend block
                   can be placed in the appropriate place.  */
                suspend_ptr -> mb_suspend_link.cs_priority =
                                                       TCC_Task_Priority(task);

                CSC_Priority_Place_On_List((CS_NODE **)
                        &(mailbox -> mb_suspension_list),
                                        &(suspend_block.mb_suspend_link));
            }

            /* Finally, suspend the calling task. Note that the suspension call
               automatically clears the protection on the mailbox.  */
            TCC_Suspend_Task((NU_TASK *) task, NU_MAILBOX_SUSPEND,
                                        MBC_Cleanup, &suspend_block, suspend);

            /* Pickup the return status.  */
            status =  suspend_ptr -> mb_return_status;
        }
        else
        {

            /* Return a status of NU_MAILBOX_EMPTY because there is
               nothing in the mailbox.  */
            status =  NU_MAILBOX_EMPTY;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpMailBox(RT_PROF_RECEIVE_FROM_MAILBOX,mailbox,RT_PROF_FAIL);
#endif /* INCLUDE_PROVIEW */
        }

    }

    /* Release protection.  */
    TCT_Unprotect();

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

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


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      MBC_Cleanup                                                      */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function is responsible for removing a suspension block     */
/*      from a mailbox.  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.                 */
/*                                                                       */
/* 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  MBC_Cleanup(VOID *information)
{

MB_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 =  (MB_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 -> mb_return_status =  NU_TIMEOUT;

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

    /* Unlink the suspend block from the suspension list.  */
    CSC_Remove_From_List((CS_NODE **)
                &((suspend_ptr -> mb_mailbox) -> mb_suspension_list),
                                &(suspend_ptr -> mb_suspend_link));

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