PROCESS_SHARED mutexes and rwlocks do not work

#define _XOPEN_SOURCE 600

#include <pthread.h>

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>
#include <errno.h>

#include <libgen.h>

#define SHMEMNAME "lock_test"

struct shmstruct {
	pthread_mutex_t mutex;
	pthread_rwlock_t rwlock;
	int count;
};
struct shmstruct *ptr;
int crash=0;
int sleep_hack=0;

int simple_rwlock()
{
	if (sleep_hack)
		sleep(1);
	fprintf(stderr,"%5d:pthread_rwlock_wrlock\n",getpid());
	pthread_rwlock_wrlock(&ptr->rwlock);
	fprintf(stderr,"%5d:rwlock is now locked\n",getpid());

	sleep(3);
	if (crash){
		char *p=NULL;

		fprintf(stderr,"crashing...%c\n",*p);
	}
	ptr->count++;

	fprintf(stderr,"%5d:pthread_rwlock_unlock:%d\n",getpid(),ptr->count);
	pthread_rwlock_unlock(&ptr->rwlock);

	return 0;
}

int simple_mutex()
{
	fprintf(stderr,"%5d:pthread_mutex_lock\n",getpid());
	pthread_mutex_lock(&ptr->mutex);
	fprintf(stderr,"%5d:mutex is now locked\n",getpid());

	sleep(3);
	if (crash){
		char *p=NULL;

		fprintf(stderr,"crashing...%c\n",*p);
	}
	ptr->count++;

	fprintf(stderr,"%5d:pthread_mutex_unlock:%d\n",getpid(),ptr->count);
	pthread_mutex_unlock(&ptr->mutex);

	return 0;
}

int init_shmem(int fd)
{
	int i;
	pthread_mutexattr_t mattr;
	pthread_rwlockattr_t rwattr;
	
	fprintf(stderr,"initialize shmem with ftruncate\n");
	ftruncate(fd, sizeof(struct shmstruct) );
	pthread_mutexattr_init(&mattr);
	pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
	i=pthread_mutex_init(&ptr->mutex, &mattr);
	fprintf(stderr,"pthread_mutex_init(SHARED) returns: %d\n",i);
	pthread_mutexattr_destroy(&mattr);
	if (i != 0 ){
		errno=i;
		perror("pthread_mutex_init");
		shm_unlink(SHMEMNAME);
		return 1;
	}
	pthread_rwlockattr_init(&rwattr);
	pthread_rwlockattr_setpshared(&rwattr, PTHREAD_PROCESS_SHARED);
	i=pthread_rwlock_init(&ptr->rwlock, &rwattr);
	fprintf(stderr,"pthread_rwlock_init(SHARED) returns: %d\n",i);
	pthread_rwlockattr_destroy(&rwattr);
	if (i != 0 ){
		errno=i;
		perror("pthread_rwlock_init");
		shm_unlink(SHMEMNAME);
		return 1;
	}
	ptr->count=0;
	return 0;
}

int main(int argc, char **argv)
{
	int fd,i,dofork=0,domutex=1,n=1;
	
	i=0;
	if ((fd=shm_open(SHMEMNAME, O_RDWR|O_CREAT|O_EXCL, 
		S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) < 0){

		if (errno==EEXIST){
			if ((fd=shm_open(SHMEMNAME, O_RDWR, 0)) < 0){
				perror("shm_open");
				exit(1);
			}
		} else {
			perror("shm_open");
			exit(1);
		}
	} else
		i=1;
		
	ptr = mmap(NULL, sizeof(struct shmstruct), 
		PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

	if (ptr == MAP_FAILED  ){
		perror("mmap failed");
		return 1;
	}
	if (i)
	 	if (init_shmem(fd))
			exit(1);

	fprintf(stderr,"sizeof(pthread_mutex_t):%d\n",sizeof(pthread_mutex_t));
	fprintf(stderr,"sizeof(pthread_rwlock_t):%d\n",sizeof(pthread_rwlock_t));
	fprintf(stderr,"sizeof(shmstruct):%d\n",sizeof(struct shmstruct));
	
	while ((i=getopt(argc,argv,"icuxrmfn:s"))!= -1){
		switch (i){
		case 'u':
			fprintf(stderr,"pthread_mutex_unlock\n");
			pthread_mutex_unlock(&ptr->mutex);
			exit(0);
			break;
		case 'c':
			crash=1;break;
		case 'i':
			return init_shmem(fd);
			break;
		case 'x':
			fprintf(stderr,"FD: closing(%d)\n",fd);
			close(fd);
			break;
		case 'r':
			domutex=0;
			break;
		case 'm':
			domutex=1;
			break;
		case 'f':
			dofork++;
			break;
		case 'n':
			n=strtol(optarg,NULL,10);
			break;
		case 's':
			sleep_hack=1;
			break;
		}
	}

	fprintf(stderr,"I am   : pid %d\n",getpid());
	while (dofork >0 ){
	
		switch ((i=fork()) ){
			case -1:
				perror("fork");
				exit(1);
			case 0:
				break;
			default:
				fprintf(stderr,"created: pid %d\n",i);
				dofork=0;
		}
		dofork--;
	}

	while (n > 0){	
		if (domutex)
			simple_mutex();
		else
			simple_rwlock();
		n--;
	}
	return 0;
}