多线程造成死锁的两种情况

* * 程序中使用一个以上的互斥量造成程序死锁 */ #include<stdio.h> #include<stdlib.h> #include<pthread.h> //定义两个互斥锁并初始化 pthread_mutex_t ALock = PTHREAD_MUTEX_INITIALIZER; pthread_mutex_t BLock = PTHREAD_MUTEX_INITIALIZER; /* * 功能：线程1函数 */ void* thread1_func(void *arg) { //sleep(1); pthread_mutex_lock(&ALock); sleep(2); printf("thread 1 lock ALock, wanting get BLock...\n"); pthread_mutex_lock(&BLock); printf("thread 1 get BLock\n"); pthread_mutex_unlock(&BLock); pthread_mutex_unlock(&ALock); pthread_exit(NULL); } /* * 功能：线程而2函数 */ void* thread2_func(void *arg) { sleep(1); pthread_mutex_lock(&BLock); printf("thread 2 lock BLock, wating get ALock...\n"); pthread_mutex_lock(&ALock); printf("thread 2 get ALock\n"); pthread_mutex_unlock(&ALock); pthread_mutex_unlock(&BLock); pthread_exit(NULL); } int main(void) { pthread_t thid1, thid2; pthread_create(&thid1, NULL, thread1_func, NULL); pthread_create(&thid2, NULL, thread2_func, NULL); pthread_join(thid1, NULL); pthread_join(thid2, NULL); printf("main thread exit\n"); exit(0); } #include<stdio.h> #include<stdlib.h> #include<pthread.h> //在同一个线程对同一个互斥量加锁两次会出现死锁 pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;//定义一个互斥量，并对其进行初始化 int a = 6; /*void* thread_func(void *arg) { pthread_mutex_lock(&lock); pthread_mutex_lock(&lock); printf("thread a = %d\n", a); pthread_mutex_unlock(&lock); pthread_exit(NULL); }*/ int main(void) { pthread_mutex_lock(&lock); pthread_mutex_lock(&lock);//对一个互斥量加锁两次，出现死锁 printf("%d\n", a);//永远不会执行到这里 pthread_mutex_unlock(&lock); exit(EXIT_SUCCESS); /* int err; pthread_t thid; err = pthread_create(&thid, NULL, thread_func, NULL); if(err != 0) { printf("pthread_create failed\n"); exit(EXIT_FAILURE); } pthread_join(thid, NULL); printf("main thread a = %d\n",a); exit(EXIT_SUCCESS);*/ }