/* synchronizeDemo.c - Demonstrates intertask synchronization using binary  *                     semaphores. *//* Copyright 1984-1997 Wind River Systems, Inc. *//*modification history--------------------01c,06nov97,mm  added copyright.01b,16sep97,ram included stdio.h,sysLib.h01a,14feb94,ms   written.*/#include "vxWorks.h"#include "taskLib.h"#include "semLib.h"#include "stdio.h"#include "sysLib.h"#define  TASK_PRI                 98     /* Priority of the spawned tasks */#define  TASK_STACK_SIZE          5000   /* stack size for spawned tasks */LOCAL SEM_ID semId1;            /* semaphore id of binary semaphore 1 */LOCAL SEM_ID semId2;            /* semaphore id of binary semaphore 2 */LOCAL int numTimes = 3;         /* Number of iterations */LOCAL BOOL notDone;                /* flag to indicate completion */LOCAL STATUS taskA ();LOCAL STATUS taskB ();/***************************************************************************** *  synchronizeDemo - Demonstrates intertask synchronization using binary  *                    semaphores. * *  DESCRIPTION *  Creates two (semId1 and semId2) binary semaphores for intertask *  synchronization between two tasks (taskA and taskB). taskA need to execute *  an event (event A). On completion of event A, taskB needs to execute *  another event (event B). On completion of the event B, taskA needs to  *  execute event A. This process needs to be done iteratively. synchronizeDemo *  executes this process. * *  RETURNS: OK or ERROR * *  EXAMPLE * *  -> sp synchronizeDemo * */STATUS synchronizeDemo ()    {    notDone = TRUE;     /* semaphore semId1 is availble  after creation*/    if ((semId1 = semBCreate (SEM_Q_PRIORITY, SEM_FULL)) == NULL)        {        perror ("synchronizeDemo: Error in creating semId1 semaphore");        return (ERROR);        }    /* semaphore semId2 is not available  after creation*/    if ((semId2 = semBCreate (SEM_Q_PRIORITY, SEM_EMPTY)) == NULL)        {        perror ("synchronizeDemo: Error in creating semId2 semaphore");        return (ERROR);        }    /* Spwan taskA*/    if (taskSpawn ("tTaskA", TASK_PRI, 0, TASK_STACK_SIZE, (FUNCPTR) taskA, 0,                    0, 0, 0, 0, 0, 0, 0, 0, 0) == ERROR)        {        perror ("synchronizeDemo: Error in spawning taskA");        return (ERROR);        }    /* Spwan taskB*/    if (taskSpawn ("tTaskB", TASK_PRI, 0, TASK_STACK_SIZE, (FUNCPTR) taskB, 0,                   0, 0, 0, 0, 0, 0, 0, 0, 0) == ERROR)        {        perror ("synchronizeDemo: Error in spawning taskB");        return (ERROR);        }        /* Polling is not recommended. But used for simple demonstration purpose */    while (notDone)         taskDelay (sysClkRateGet());  /* wait here until done */        /* Delete the created semaphores */    if (semDelete (semId1) == ERROR)        {        perror ("syncronizeDemo: Error in deleting semId1 semaphore");        return (ERROR);        }    if (semDelete (semId2) == ERROR)       {       perror ("syncronizeDemo: Error in deleting semId1 semaphore");       return (ERROR);       }    printf ("\n\n synchronizeDemo now completed \n");        return (OK);    }/***************************************************************************** *  taskA - executes event A first and wakes up taskB to excute event B next *          using binary semaphores for synchronization. * *  RETURNS: OK or ERROR * */LOCAL STATUS taskA ()    {    int count;    for (count = 0; count < numTimes; count++)        {        if (semTake (semId1, WAIT_FOREVER) == ERROR)            {            perror ("taskA: Error in semTake");            return (ERROR);            }         printf ("taskA: Started first by taking the semId1 semaphore - %d times\n",                (count + 1));        printf("This is task  <%s> : Event A now done\n", taskName (taskIdSelf()));        printf("taskA: I'm done, taskB can now proceed; Releasing semId2 semaphore\n\n");        if (semGive (semId2) == ERROR)            {            perror ("taskA: Error in semGive");            return (ERROR);            }        }        return (OK);    }/***************************************************************************** *  taskB - executes event B first and wakes up taskA to excute event A next *          using binary semaphores for synchronization. * *  RETURNS: OK or ERROR * */LOCAL STATUS taskB()    {    int count;    for (count = 0; count < numTimes; count++)        {        if (semTake (semId2,WAIT_FOREVER) == ERROR)            {            perror ("taskB: Error in semTake");            return (ERROR);            }         printf ("taskB: Synchronized with taskA's release of semId2 - %d times\n",                (count + 1 ));        printf("This is task  <%s> : Event B now done\n", taskName (taskIdSelf()));        printf("taskB: I'm done, taskA can now proceed; Releasing semId1 semaphore\n\n\n");        if (semGive (semId1) == ERROR)            {            perror ("taskB: Error in semGive");            return (ERROR);            }        }        notDone = FALSE;        return (OK);    }