freebsd 에서 fork 후 thread 실행시에 'mutex is on list' 오류 발생에 대해서.

Fatal error 'mutex is on list' at line 540 in file /usr/src/lib/libpthread/thread/thr_mutex.c (errno = 0)

#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
 
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
 
void thr_status()
{
	pthread_attr_t attr;
    int policy;
    printf("Thread Create\n");
    pthread_attr_getdetachstate(&attr, &policy);
    if (policy == PTHREAD_CREATE_JOINABLE)
    {
        printf ("Join able\n");
		pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
    }
    else if (policy == PTHREAD_CREATE_DETACHED)
    {
        printf ("Detache\n");
    }
}
 
void *t_function(void *data)
{
    int id;
    int i = 0;
    id = *((int *)data);
 
	thr_status();
//pthread_detach(pthread_self());
sleep(1);
	thr_status();
 
    while(1)
    {
        printf("%d : %d\n", id, i);
        i++;
        sleep(1);
    }
}
 
int SpawnProcess()
{
    pthread_t p_thread = 0;
    int thr_id = 0;
    int a = 1;
    int status;
 
    int pid=0;
 
/*
	int stacksize = 10;
    pthread_attr_t  attr;
    pthread_attr_init(&attr);
	if (!pthread_attr_setstacksize(&attr, stacksize*1024)) {
	    printf("set stacksize = %dKB\n", stacksize);
    }
    if (!pthread_attr_getstacksize(&attr, &stacksize)) {
        printf("stack size = %d\n", stacksize);
    }
    printf("PTHREAD_THREAD_MAX in limits.h is %u\n", PTHREAD_THREADS_MAX);
*/
 
fprintf(stderr, "before fork \n");
    pid = fork();
    switch(pid)
    {
    case 0:
	// child create thread
fprintf(stderr, "child forked p_thread = (%d), (%p)\n", p_thread, &p_thread);
        // 프로세스 다시 실행시에 여기서 죽어요!!
        thr_id = pthread_create(&p_thread, NULL, t_function, (void *)&a);
        //thr_id = pthread_create(&p_thread, &attr, t_function, (void *)&a);
        pthread_join(p_thread, (void **)&status);
        exit(0);
 
    case -1:
        return 0;
 
    default:
	break;
    }
 
    return 1;
}
 
int WatchChildProcess()
{
    int status;
    pid_t wait_pid;
 
    wait_pid = waitpid(-1, &status, WUNTRACED|WNOHANG);
    if(wait_pid <= 0)
    {
        //sleep(5);
        return 1;
    }
 
    if(wait_pid > 0) /* process killed */
    {
        if (WIFEXITED(status))
        {
            printf("1.Catch the signal. pid=(%d) status=(%d,%d)\n", wait_pid, WIFEXITED(status), WEXITSTATUS(status));
        }
        else if (WIFSIGNALED(status))
        {
            if(WIFEXITED(status) == SIGXFSZ) // file size excess.
            {
 
            }
 
            printf("2.Catch the signal. pid=(%d) status=(%d,%d)\n", wait_pid, status, WIFSIGNALED(status));
        }
 
        /** 
        *   restart child process
        */
        if(!SpawnProcess())
        {
            return 0;
        }
printf("Child Process Spawn Success \n");
    }
 
    return 1;
}
 
int main()
{
    pthread_t p_thread[2];
    int thr_id;
    int status;
    int b = 2;
 
	SpawnProcess();
 
	// parent thread create
    thr_id = pthread_create(&p_thread[1], NULL, t_function, (void *)&b);
 
     // 프로세스 감시
	while(1)
	{
		WatchChildProcess();
		sleep(1);
	}
    pthread_join(p_thread[1], (void **)&status);
 
    return 0;
}