mutexfix.c

Vxworks的培训教程,大家分享下啊,

#include "vxWorks.h"
#include "stdio.h"
#include "taskLib.h"

#include "semLib.h"        /* Need to add this */

int v1;
int v2;
int count;
SEM_ID myMutexSem;

void makeMyMutexSem (void)
	{
	myMutexSem = semMCreate (SEM_Q_PRIORITY | SEM_INVERSION_SAFE |
				             SEM_DELETE_SAFE);
	if (myMutexSem == NULL)
		{
		perror ("makeMyMutexSem");
		exit (1);
		}

	}

void mutex1 (void)
	{

	/* Create semaphore to solve mutex problem */
	if (myMutexSem == NULL)
	        {
		printErr ("Error: semaphore not initialized\n");
		printErr ("To initialize, type \"makeMyMutexSem()\"\n");
		exit (1);
		}
		
        FOREVER
		{

		/* Must update v1 and v2 atomically */
		semTake (myMutexSem, WAIT_FOREVER);
		v1 = count;
		v2 = count;
		semGive (myMutexSem);

		count++;
		}
	}

void mutex2 (void)
	{
	int same;

	if (myMutexSem == NULL)
        {
		printErr ("Error: semaphore not initialized\n");
		printErr ("To initialize, type \"makeMyMutexSem()\"\n");
		exit (1);
		}

	FOREVER
		{
		
		/* 
		 * This instruction actually corresponds to
		 * several assembler instructions. We must
		 * make it atomic. 
		 */

		semTake (myMutexSem, WAIT_FOREVER);
		same = (v1 == v2);
		semGive (myMutexSem);

		if (!same)
			printf ("v1 = %d, v2 = %d\n", v1, v2);
		
		taskDelay (1);
		}
	}