//my_rwlock/pthread_rwlock_tryrdlock.c
#include	"unpipc.h"
#include	"pthread_rwlock.h"

int
pthread_rwlock_tryrdlock(pthread_rwlock_t *rw)
{
	int		result;

	if (rw->rw_magic != RW_MAGIC)
		return(EINVAL);

	if ( (result = pthread_mutex_lock(&rw->rw_mutex)) != 0)
		return(result);

	if (rw->rw_refcount < 0 || rw->rw_nwaitwriters > 0)
		result = EBUSY;			/*        ,    */
	else
		rw->rw_refcount++;		/*      */

	pthread_mutex_unlock(&rw->rw_mutex);
	return(result);
}
