The global variable is initialized to 0, two threads, one thread increments it by 1 each time, when it is greater than or equal to 100, sends a condition to the other thread. Reset to 0

#include  #include  #include  struct foo{ int f_count; pthread_mutex_t f_lock; pthread_cond_t f_cond; }; /* 初始化互斥量与条件变量 */ struct foo * foo_alloc(){ struct foo *fp; if((fp = malloc(sizeof(struct foo))) != NULL){ fp->f_count = 0; pthread_mutex_init(&fp->f_lock, NULL); pthread_cond_init(&fp->f_cond, NULL); } return fp; } /* 加法 */ void *foo_increase(void *arg){ struct foo *fp; fp = (struct foo*)arg; while(1){ pthread_mutex_lock(&fp->f_lock); fp->f_count++; /* 大于等于100时发送条件 */ if(fp->f_count >= 100){ pthread_cond_signal(&fp->f_cond); } pthread_mutex_unlock(&fp->f_lock); } } /* 重新置０ */ void *foo_print(void *arg){ struct foo *fp; fp = (struct foo*)arg; while(1){ pthread_mutex_lock(&fp->f_lock); while(fp->f_count < 100){ //释放掉锁, 等待条件为真返回, 再次锁住. pthread_cond_wait(&fp->f_cond, &fp->f_lock); } printf("重置 : %d\n", fp->f_count); /* 重新置0 */ fp->f_count = 0; pthread_mutex_unlock(&fp->f_lock); } } int main(void){ struct foo *fp; pthread_t tid_increase1, tid_print; //初始化 fp = foo_alloc(); //加法线程 pthread_create(&tid_increase1, NULL, foo_increase, fp); //重置线程 pthread_create(&tid_print, NULL, foo_print, fp); //防止主线程提前退出 sleep(20); exit(0); }

But why do I print the following result under the reset thread? Shouldn't it be 100?
The reset thread has locked the mutex, but it seems that another thread is still accumulating.

置０前 : 54 置０前 : 92 置０前 : 47 置０前 : 85 置０前 : 51 ．．．