linux过程协作-一个小例子
日期：2014-05-16 浏览次数：20973 次
linux进程协作-一个小例子
爸爸给女儿和儿子喂水果。爸爸随机挑选橘子或者苹果，将橘子剥皮或者将苹果削皮放在盘子中，剥皮的速度比较快，而削皮的时间比较慢。女儿只吃橘子，儿子只吃苹果（当然我们假设女儿和儿子永远也吃不饱）。盘子只能装下3个水果。儿子吃得比较快，女儿吃得比较慢。
编程模拟该过程：
简单分析
信号量：
int accessplate = 1; //表示访问盘子的信号量
int apple = 0; //苹果个数
int orange = 0; //橘子
int emptyplates = 3; //空盘子
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Father: P(emptyplates); produce a fruit if( is apple ) then P(accessplate) put apple in V(apple) V(accessplate) else P(accessplate) put orange in V(orange) V(accessplate) |
Boy: P(apple) P(accessplate) get an apple eat an apple V(emptyplates) V(accessplate)
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Girl: P(orange) P(accessplate) get an orange eat an orange V(emptyplates) V(accessplate)
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代码：
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <time.h>
#include <sys/ipc.h>
#include <sys/sem.h>
/*overall varible*/
int numOfEmptyPlate_sem_id = 0; //number of empty plates.
int numOfApple_sem_id = 0; //number of apple
int numOfOrange_sem_id = 0; //number of orange
int getAccesstoPlate = 0; //get plate
int *plate = NULL; //3 PLATES
struct sembuf P, V; // p,v opration
void printPlates(const char *arg)
{
int i = 0;
printf("%s\nFruits in plates:", arg);
for(i=0; i<3; i++)
{
printf("%d ", plate[i]);
}
printf("\n");
}
void father_do() // PUT FRUITS in
{// 1 == apple, 2 == range
int i = 0;
semop( numOfEmptyPlate_sem_id, &P, 1); // P(empty plates)
if( rand()%100+1 > 50) //get an orange
{
sleep(1); //get an orange,sleep 1 seconds
semop( getAccesstoPlate, &P, 1); //P(plate)
printf("Father get access to the plates.\n");
printPlates("father:");
for(i=0; i<3; i++)
{
if( 0 == plate[i]) //find an empty plate, and put the furit in
{
printf("%d ", plate[i]);
plate[i] = 2;
break;
}
}
semop( numOfOrange_sem_id, &V, 1); //V(oranges)
printf("Father put an orange in plate.\n");
semop( getAccesstoPlate, &V, 1); //V(plate)
printf("Father put the plates back.\n");
}
else // get an apple
{
sleep(2); //get an apple,sleep 2 seconds
semop( getAccesstoPlate, &P, 1); //P(plate)
printf("Father get access to the plates.\n");
printPlates("father:");
for(i=0; i<3; i++)
{
if( 0 == plate[i]) //find an empty plate, and put the furit in
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