一．实验原理：掌握在基于嵌入式实时操作系统μC/OS-II的应用中，任务使用信号量的一般原理。
通过哲学家问题实验，了解如何利用信号量来对共享资源进行互斥访问。
二．实验平台：PC、XP操作系统、ADS集成开发环境三．实验目的复习对进程同步的机制，并加强学生动手能力，不仅让学生从原理上懂得操作系统，而且让学生实践，让学生自己动手写操作系统部分代码。
四：实验内容：哲学家动作：thinkinghungryeatingph 1 thinking! ph 2 thinking! ……….ph 1 hungry! ph 2 hungry! ……….ph 1 eating! ph 2 eating! ………..实现：while( 1 ) {显示ph x thinking；OSTimeDly()随机延时；显示ph x hungry；OSTimeDly()随机延时；显示ph x eating；OSTimeDly()随机延时；}五：实验要求：能在屏幕上输出5个哲学家的动作，分别是thinking，hungry，eating，如下所示：哲学家1 thinking, 哲学家2 thinking, ...哲学家1 hungry, 哲学家2 hungry, ...哲学家1 eating, 哲学家2 eating, ...六：实验代码：在ADS1.2中先后导入一下文件最后编写主函数main的程序，代码如下：#include "../ucos-ii/includes.h" /* uC/OS interface */#include "string.h"#include "gui.h"//task stack size#ifdef SEMIHOSTED#define TASK_STACK_SIZE (64+SEMIHOSTED_STACK_NEEDS) #else#define TASK_STACK_SIZE 10*1024#endif///***********define task************************/#define TASK_PRIO 2#define TASK_STK_SIZE 512INT8U *err; //用于退出的键OS_EVENT *SEM[5]; //定义对应的信号量指针数组extern char keyflag;OS_STK MyTaskStk1[TASK_STK_SIZE]; //定义任务堆栈区OS_STK MyTaskStk2[TASK_STK_SIZE];OS_STK MyTaskStk3[TASK_STK_SIZE];OS_STK MyTaskStk4[TASK_STK_SIZE];OS_STK MyTaskStk5[TASK_STK_SIZE];void Mytask1(void *pd){char buf[128];while(1){sprintf(buf,"ph%d is thinking\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPend(SEM[0],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is hungry\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[1]); //发送一个信号量OSSemPend(SEM[0],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is eating\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[1]); //发送一个信号量OSTimeDlyHMSM(0,0,0,200); //等待200ms}}void Mytask2(void *pd){char buf[128];while(1){sprintf(buf,"ph%d is thinking\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPend(SEM[1],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is hungry\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[2]); //发送一个信号量OSSemPend(SEM[1],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is eating\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[2]); //发送一个信号量OSTimeDlyHMSM(0,0,0,200); //等待200ms}}void Mytask3(void *pd){char buf[128];while(1){sprintf(buf,"ph%d is thinking\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPend(SEM[2],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is hungry\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[3]); //发送一个信号量OSSemPend(SEM[2],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is eating\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[3]); //发送一个信号量OSTimeDlyHMSM(0,0,0,200); //等待200ms}}void Mytask4(void *pd){char buf[128];while(1){sprintf(buf,"ph%d is thinking\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPend(SEM[3],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is hungry\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[4]); //发送一个信号量OSSemPend(SEM[3],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is eating\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[4]); //发送一个信号量OSTimeDlyHMSM(0,0,0,200); //等待200ms}}void Mytask5(void *pd){char buf[128];while(1){sprintf(buf,"ph%d is thinking\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[0]); //发送一个信号量OSSemPend(SEM[4],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is hungry\n",(unsigned int )pd+1);armulPrintf(buf);OSSemPost(SEM[0]); //发送一个信号量OSSemPend(SEM[4],0,err); //请求一个信号量，没有时间限制sprintf(buf,"ph%d is eating\n",(unsigned int )pd+1);armulPrintf(buf);OSTimeDlyHMSM(0,0,0,200); //等待200ms}}///****************************************/// main function///****************************************/int Main(int argc, char **argv){int i;//Init ARM hardwareARMTargetInit();//Init uCOS-IIOSInit();for(i=0;i<5;i++)SEM[i]=OSSemCreate(0); //建立计数器初值为0的信号量//for(i=0;i<NUM;i++)//OSTaskCreate(Mytask,(void*)i,&MyTaskStk[TASK_STK_SIZE-1],TASK_PRIO+i);OSTaskCreate(Mytask1,(void*)0,&MyTaskStk1[TASK_STK_SIZE-1],TASK_PRIO);OSTaskCreate(Mytask2,(void*)1,&MyTaskStk2[TASK_STK_SIZE-1],TASK_PRIO+1);OSTaskCreate(Mytask3,(void*)2,&MyTaskStk3[TASK_STK_SIZE-1],TASK_PRIO+2);OSTaskCreate(Mytask4,(void*)3,&MyTaskStk4[TASK_STK_SIZE-1],TASK_PRIO+3);OSTaskCreate(Mytask5,(void*)4,&MyTaskStk5[TASK_STK_SIZE-1],TASK_PRIO+4);//Create TaskARMTargetStart();//Start uCOS-IIOSStart();//*/while(1){};return 0; // can't run into here}运行本程序后可以得到期望的结果五：实验结果和总结：通过本实验，我对进程间的同步更熟悉，熟悉了信号量的运用，消除了对操作系统源代码的畏惧心理，受益匪浅。
