子线程循环 3 次，接着主线程循环 6 次，接着又回到子线程循环 3 次，接着再回到主线程又循环6 次，如此循环50次，试写出代码。

#include <stdio.h>

#include <stdlib.h>

#include <pthread.h>

#include <string.h>

#include <unistd.h>

#define LOOP 50

pthread_mutex_t mylock = PTHREAD_MUTEX_INITIALIZER;

pthread_cond_t mycond = PTHREAD_COND_INITIALIZER;

int num = 0;

int parm_0 = 0;

int parm_1 = 1;

void * th_fun(void * arg)

{

int i, j;

for(i = 0;i < LOOP; i++)

{

pthread_mutex_lock(&mylock);

while(parm_0 != num)

{

pthread_cond_wait(&mycond, &mylock);

}

printf("thread:\n");

for(j = 0;j < 10; j++)

{

printf("%d", j);

}

printf("\n");

num = (num + 1) % 2;

pthread_mutex_unlock(&mylock);

pthread_cond_signal(&mycond);

}

return (void *) 0;

}

int main()

{

int i, k;

pthread_t id;

void *ret;

pthread_create(&id, NULL, th_fun, NULL);

for(i = 0; i < LOOP; i++)

{

pthread_mutex_lock(&mylock);

while(parm_1 != num)

{

pthread_cond_wait(&mycond, &mylock);

}

printf("main:\n");

for(k = 0; k < 3; k++)

{

printf("%d", k + 6);

}

printf("\n");

num = (num + 1) % 2;

pthread_mutex_unlock(&mylock);

pthread_cond_signal(&mycond);

}

pthread_join(id, &ret);

return 0;

}