线程死锁例子

Posted 2020-10-04 夜空释

/*  头文件 */  
#include <stdio.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <pthread.h>  
#include <signal.h>  
  
pthread_mutex_t mutex_one,mutex_two;  
pthread_mutex_t mutex;  
pthread_cond_t cond;  
  
void *thread_routine_one(void *arg)  
{  
    pthread_cond_wait(&cond,&mutex);//确保two线程先运行  
  
    printf("thread_routine_one: lock mutex_one!\n");  
    pthread_mutex_lock(&mutex_one);  
  
    printf("thread_routine_one: lock mutex_two!\n");  
    pthread_mutex_lock(&mutex_two);//获取two锁，这个要等待two线程对two锁的释放  
  
    sleep(1);  
    printf("thread_routine_one: unlock mutex_two!\n");  
    pthread_mutex_unlock(&mutex_two);  
  
    printf("thread_routine_one: unlock mutex_one!\n");  
    pthread_mutex_unlock(&mutex_one);  
  
    return NULL;  
}  
  
void *thread_routine_two(void *arg)  
{  
    printf("thread_routine_two: lock mutex_two!\n");  
    pthread_mutex_lock(&mutex_two);//获取two锁  
    pthread_cond_signal(&cond);//让one线程运行  
    sleep(1);//休眠，让one可以先运行获取one锁  
  
    printf("thread_routine_two: lock mutex_one!\n");  
  
    pthread_mutex_lock(&mutex_one);//获取one锁，这个同样必须等待one线程多one锁的释放  
  
    /**这时出现死锁现象了，在two线程要等待one线程对one锁的释放，同时two锁没有释放 
     * 然而在one线程需要等待two线程对two锁的释放，然后才会对one锁的释放！出现相互等待的过程**/  
  
    printf("thread_routine_two: unlock mutex_one!\n");  
    pthread_mutex_unlock(&mutex_one);  
  
    printf("thread_routine_two: unlock mutex_two!\n");  
    pthread_mutex_unlock(&mutex_two);  
  
    return NULL;  
}  
  
void main()  
{  
    pthread_t pthread_one,pthread_two;  
  
    pthread_mutex_init(&mutex_one,NULL);  
    pthread_mutex_init(&mutex_two,NULL);  
    pthread_mutex_init(&mutex,NULL);  
    pthread_cond_init(&cond,NULL);  
  
    pthread_create(&pthread_one,NULL,thread_routine_one,NULL);  
    pthread_create(&pthread_two,NULL,thread_routine_two,NULL);  
  
    while(1)  
        sleep(1);  
}  

 线程程A已经拥有至少一个资源，此时又去申请其他资源，而该资源又正在被B线程使用，而同时B线程也在等待A线程的资源释放后才会释放自己的资源，便会造成死锁。此时请求进程阻塞，但对自己已经获得的资源保持不放，