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#include <stdio.h>
#include <stdlib.h>
int flag = 1;
void * thr_fn(void * arg) {
while (flag){
printf("******\n");
sleep(10);
}
printf("sleep test thread exit\n");
}
int main() {
pthread_t thread;
if (0 != pthread_create(&thread, NULL, thr_fn, NULL)) {
printf("error when create pthread,%d\n", errno);
return 1;
}
char c ;
while ((c = getchar()) != 'q');
printf("Now terminate the thread!\n");
flag = 0;
printf("Wait for thread to exit\n");
pthread_join(thread, NULL);
printf("Bye\n");
return 0;
}
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输入q后，需要等线程从sleep中醒来（由挂起状态变为运行状态），即最坏情况要等10s，线程才会被join。采用sleep的缺点：不能及时唤醒线程。
采用pthread_cond_timedwait函数，条件到了，线程即会被join，可及时唤醒线程。实现的如下：
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#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
static pthread_t thread;
static pthread_cond_t cond;
static pthread_mutex_t mutex;
static int flag = 1;
void * thr_fn(void * arg)
{
struct timeval now;
struct timespec outtime;
pthread_mutex_lock(&mutex);
while (flag) {
printf("*****\n");
gettimeofday(&now, NULL);
outtime.tv_sec = now.tv_sec + 5;
outtime.tv_nsec = now.tv_usec * 1000;
pthread_cond_timedwait(&cond, &mutex, &outtime);
}
pthread_mutex_unlock(&mutex);
printf("cond thread exit\n");
}
int main(void)
{
pthread_mutex_init(&mutex, NULL);
pthread_cond_init(&cond, NULL);
if (0 != pthread_create(&thread, NULL, thr_fn, NULL)) {
printf("error when create pthread,%d\n", errno);
return 1;
}
char c ;
while ((c = getchar()) != 'q');
printf("Now terminate the thread!\n");
pthread_mutex_lock(&mutex);
flag = 0;
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
printf("Wait for thread to exit\n");
pthread_join(thread, NULL);
printf("Bye\n");
return 0;
}
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pthread_cond_timedwait()函数阻塞住调用该函数的线程，等待由cond指定的条件被触发（pthread_cond_broadcast() or pthread_cond_signal()）。
当pthread_cond_timedwait()被调用时，调用线程必须已经锁住了mutex。函数pthread_cond_timedwait()会对mutex进行【解锁和执行对条件的等待】（原子操作）。
