#include "apue.h"#include <pthread.h>#include <time.h>#include <sys/time.h>extern int makethread(void *(*)(void *), void *);struct to_info {	void	(*to_fn)(void *);	/* function */	void	*to_arg;			/* argument */	struct timespec to_wait;	/* time to wait */};#define SECTONSEC  1000000000	/* seconds to nanoseconds */#define USECTONSEC 1000			/* microseconds to nanoseconds */void *timeout_helper(void *arg){	struct to_info	*tip;	tip = (struct to_info *)arg;	nanosleep(&tip->to_wait, NULL);	(*tip->to_fn)(tip->to_arg);	return(0);}voidtimeout(const struct timespec *when, void (*func)(void *), void *arg){	struct timespec	now;	struct timeval	tv;	struct to_info	*tip;	int				err;	gettimeofday(&tv, NULL);	now.tv_sec = tv.tv_sec;	now.tv_nsec = tv.tv_usec * USECTONSEC;	if ((when->tv_sec > now.tv_sec) ||	  (when->tv_sec == now.tv_sec && when->tv_nsec > now.tv_nsec)) {		tip = malloc(sizeof(struct to_info));		if (tip != NULL) {			tip->to_fn = func;			tip->to_arg = arg;			tip->to_wait.tv_sec = when->tv_sec - now.tv_sec;			if (when->tv_nsec >= now.tv_nsec) {				tip->to_wait.tv_nsec = when->tv_nsec - now.tv_nsec;			} else {				tip->to_wait.tv_sec--;				tip->to_wait.tv_nsec = SECTONSEC - now.tv_nsec +				  when->tv_nsec;			}			err = makethread(timeout_helper, (void *)tip);			if (err == 0)				return;		}	}	/*	 * We get here if (a) when <= now, or (b) malloc fails, or	 * (c) we can't make a thread, so we just call the function now.	 */	(*func)(arg);}pthread_mutexattr_t attr;pthread_mutex_t mutex;voidretry(void *arg){	pthread_mutex_lock(&mutex);	/* perform retry steps ... */	pthread_mutex_unlock(&mutex);}intmain(void){	int				err, condition, arg;	struct timespec	when;	if ((err = pthread_mutexattr_init(&attr)) != 0)		err_exit(err, "pthread_mutexattr_init failed");	if ((err = pthread_mutexattr_settype(&attr,	  PTHREAD_MUTEX_RECURSIVE)) != 0)		err_exit(err, "can't set recursive type");	if ((err = pthread_mutex_init(&mutex, &attr)) != 0)		err_exit(err, "can't create recursive mutex");	/* ... */	pthread_mutex_lock(&mutex);	/* ... */	if (condition) {		/* calculate target time "when" */		timeout(&when, retry, (void *)arg);	}	/* ... */	pthread_mutex_unlock(&mutex);	/* ... */	exit(0);}