Linux多线程──主线程和子线程分别循环一定次数

vd17j9ak27

　　

子线程循环

10

次，接着主线程循环

100

次，接着又回到子线程循环

10

次，接着再回到主线程又循环

100

次，如此循环

50

次，试写出代码。

　　

要注意条件变量的自动复位问题。参看这篇文章：Linux 的多线程编程的高效开发经验

　　

代码：

　　

#include <pthread.h>
#include <stdio.h>
// 互斥锁，条件变量
pthread_mutex_t mutex;
pthread_cond_t cond;
// 循环次数
int main_count = 0;
int subthread_count = 0;
// 线程等待标志
bool main_thread_wait_flag = false;
bool subthread_wait_flag = false;
void main_thread_func();
void *subthread_func(void *arg);
int main(int argc, char **argv)
{
pthread_t tid;
pthread_mutex_init(&mutex, NULL);
pthread_cond_init(&cond, NULL);
pthread_create(&tid, NULL, subthread_func, NULL);
main_thread_func();
pthread_join(tid, NULL);
return 0;
}
void main_thread_func()
{
while (true)
{
pthread_mutex_lock(&mutex);
main_thread_wait_flag = true;
pthread_cond_wait(&cond, &mutex);
main_thread_wait_flag = false;
pthread_mutex_unlock(&mutex);
for (int i = 1; i <= 100; ++i)
{
fprintf(stdout, "main thread: %d\n", i);
}
while (true)
{
pthread_mutex_lock(&mutex);
if (true == subthread_wait_flag)
{
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
break;
}
pthread_mutex_unlock(&mutex);
}
++main_count;
if (main_count >= 50)
{
fprintf(stdout, "main thread loop 50 times\n");
break;
}
}
}
void *subthread_func(void *arg)
{
while (true)
{
for (int i = 1; i <= 10; ++i)
{
fprintf(stdout, "subthread: %d\n", i);
}
while (true)
{
pthread_mutex_lock(&mutex);
if (true == main_thread_wait_flag)
{
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
break;
}
pthread_mutex_unlock(&mutex);
}
pthread_mutex_lock(&mutex);
subthread_wait_flag = true;
pthread_cond_wait(&cond, &mutex);
subthread_wait_flag = false;
pthread_mutex_unlock(&mutex);
++subthread_count;
if (subthread_count >= 50)
{
fprintf(stdout, "subthread loop 50 times\n");
break;
}
}
return (void *)0;
}