Linux C thread-04.證明pthread_mutex_t可以同時用在多個thread之間的互鎖功能，但是可能會有同一筆資料重覆運算浪費CPU

 

#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <stdio.h>
#include <sys/time.h>
#include <string.h>
#define MAX 20
pthread_t thread[4];
pthread_mutex_t mut;
int number;
int i;
void *thread1(void *p)
{
printf ("thread1 : I'm thread 1\n");
for (i = 0; i < MAX; i++)
{
printf("thread1 : %d\n",i);
pthread_mutex_lock(&mut);
if(i<MAX)
{
number++;
printf("thread1 : number = %d\n",number);
}
pthread_mutex_unlock(&mut);
sleep(1);
}
printf("thread1 :主函數在等我完成任務嗎？\n");
pthread_exit(NULL);
}
void *thread2(void *p)
{
printf("thread2 : I'm thread 2\n");
for (i = 0; i < MAX; i++)
{
printf("thread2 : %d\n",i);
pthread_mutex_lock(&mut);
if(i<MAX)
{
number++;
printf("thread2 : number = %d\n",number);
}
pthread_mutex_unlock(&mut);
sleep(1);
}
printf("thread2 :主函數在等我完成任務嗎？\n");
pthread_exit(NULL);
}
void *thread3(void *p)
{
printf("thread3 : I'm thread 3\n");
for (i = 0; i < MAX; i++)
{
printf("thread3 : %d\n",i);
pthread_mutex_lock(&mut);
if(i<MAX)
{
number++;
printf("thread3 : number = %d\n",number);
}
pthread_mutex_unlock(&mut);
sleep(1);
}
printf("thread3 :主函數在等我完成任務嗎？\n");
pthread_exit(NULL);
}
void *thread4(void *p)
{
printf("thread4 : I'm thread 4\n");
for (i = 0; i < MAX; i++)
{
printf("thread4 : %d\n",i);
pthread_mutex_lock(&mut);
if(i<MAX)
{
number++;
printf("thread4 : number = %d\n",number);
}
pthread_mutex_unlock(&mut);
sleep(1);
}
printf("thread4 :主函數在等我完成任務嗎？\n");
pthread_exit(NULL);
}
void thread_create(void)
{
int temp;
memset(&thread, 0, sizeof(thread));          //comment1
/*創建線程*/
if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0)       //comment2
{
printf("線程1創建失敗!\n");
}
else
{
printf("線程1被創建\n");
}
if((temp = pthread_create(&thread[1], NULL, thread2, NULL)) != 0)  //comment3
{
printf("線程2創建失敗");
}
else
{
printf("線程2被創建\n");
}
if((temp = pthread_create(&thread[2], NULL, thread3, NULL)) != 0)  //comment3
{
printf("線程3創建失敗");
}
else
{
printf("線程3被創建\n");
}
if((temp = pthread_create(&thread[3], NULL, thread4, NULL)) != 0)  //comment3
{
printf("線程4創建失敗");
}
else
{
printf("線程4被創建\n");
}
}
void thread_wait(void)
{
/*等待線程結束*/
if(thread[0] !=0)
{//comment4
pthread_join(thread[0],NULL);
printf("線程1已經結束\n");
}
if(thread[1] !=0)
{                //comment5
pthread_join(thread[1],NULL);
printf("線程2已經結束\n");
}
if(thread[2] !=0)
{                //comment5
pthread_join(thread[2],NULL);
printf("線程3已經結束\n");
}
if(thread[3] !=0)
{                //comment5
pthread_join(thread[3],NULL);
printf("線程4已經結束\n");
}
}
int main()
{
number=0;
/*用��認屬性初始化互斥鎖*/
pthread_mutex_init(&mut,NULL);
printf("我��主函數哦，我正在創建線程，呵呵\n");
thread_create();
printf("我��主函數哦，我正在等待線程完成任務��，呵呵\n");
thread_wait();
return 0;
}