I am practicing multi-threading.

I create two posix threads that display a text to the screen (infinite loop), but it seem only the first thread run. I modify the program without looping, first thread prints, following is second thread. It seems that my thread are not parallel, first thread has to finish before thread two start. How can I make them parallel?

Thanks,

hdr.h

#ifndef HDR_HDR_H_
#define HDR_HDR_H_
#define HDR_HDR_H_
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#endif /* HDR_HDR_H_ */

multithread01.c

#include "../hdr/myfunc.h"
pthread_mutex_t lock;

int main(int argc, char **argv)
{
    pthread_t tid01;
    pthread_t tid02;
    void * status01;
    void * status02;

    pthread_create(&tid01, NULL, PrintOut01(), NULL);
    pthread_create(&tid02, NULL, PrintOut02(), NULL);

    pthread_join(&tid01, &status01);
    pthread_join(&tid02, &status02);

    return 0;

}

myfunc.h

#ifndef HDR_MYFUNC_H_
#define HDR_MYFUNC_H_
#include "../hdr/hdr.h"
void * PrintOut01 (void);
void * PrintOut02 (void);
#endif /* HDR_MYFUNC_H_ */

myfunc.c

#include "../hdr/hdr.h"

extern pthread_mutex_t lock;

void * PrintOut01 ()
{
    while (1)
    {
        pthread_mutex_lock(&lock);
        printf ("This is thread 01\n");
        pthread_mutex_unlock(&lock);
    }
}

void * PrintOut02 ()
{
    while (1)
    {
        pthread_mutex_lock(&lock);
        printf ("This is thread 02\n");
        pthread_mutex_unlock(&lock);
    }
}