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Old 04-28-2009, 10:24 AM   #1
LinuxInfo
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Registered: Sep 2008
Posts: 21

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Need some help in modifying a program.


Respected sir,

I have a producer-consumer programs that uses two semaphores to to control the shared resoures. I want to modify these two programs in such a way that it uses only single semaphore. I need to use an integer instead of array in Union.

Here are the programs:

=================
PRODUCER
=================

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ipc.h>

#include <sys/sem.h>
#define PUB7645 "./PubFile"

union semun {
int val;
struct semid_ds *buf;
ushort *array;
};
int
main() {
int i=0, intValue, semID;
key_t key;
FILE *fptr;

union semun arg;
static ushort startVal[2] = {1, 0};
static struct sembuf acquire = {0, -1, SEM_UNDO},
release = {1, 1, SEM_UNDO};
key = ftok(".", 's');

if ((semID = semget(key, 2, IPC_CREAT | 0666)) == -1) {
perror("Sem Creation:");
exit(2);
}

arg.array = startVal;
if (semctl(semID, 2, SETALL, arg) == -1 ) {
perror("semctl: SETALL");
exit(3);
}
for( ; ; ) {
srand(getpid()+i);
intValue =rand()*49/RAND_MAX + 1;

if (semop(semID, &acquire, 1) == -1) {
perror("Producer waiting");
exit(4);
}

if ((fptr = fopen(PUB7645, "w")) == NULL) {
perror(PUB7645);
exit(1);
}
fprintf(fptr, "%d\n", intValue);
fclose(fptr);

if (semop(semID, &release, 1) == -1) {
perror("new");
exit(5);
}
i++;
}
}
=================
Consumer:
=================

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ipc.h>

#include <sys/sem.h>
#define PUB7645 "./PubFile"

union semun {
int val;
struct semid_ds *buf;
ushort *array;
};
int main() {
int i=0, intValue, semID;
key_t key;
FILE *fptr;

union semun arg;
static struct sembuf acquire = {1, -1, SEM_UNDO},
release = {0, 1, SEM_UNDO};

key = ftok(".", 's');

if ((semID = semget(key, 2, IPC_CREAT | 0666)) == -1) {
perror("Sem Creation:");
exit(2);
}
for(i=1; i<=5 ; i++) {

if (semop(semID, &acquire, 1) == -1) {
perror(“Consumer waiting");
exit(4);
}

if ((fptr = fopen(PUB7645, "r")) == NULL) {
perror(PUB7645);
exit(1);
}

fscanf(fptr, "%d", &intValue);
fclose(fptr);
if (semop(semID, &release, 1) == -1) {
perror(“Release");
exit(4);
}

printf("%d\t", intValue);
}
printf("\nI am process %d. I got five numbers ", getpid());
printf("from a producer as above.\n");
}

Thanks.
 
Old 04-28-2009, 02:52 PM   #2
Mara
Moderator
 
Registered: Feb 2002
Location: Grenoble
Distribution: Debian
Posts: 9,671

Rep: Reputation: 218Reputation: 218Reputation: 218
It looks like a homework question, so I intend to give general guidelines. However, in this case the solution seems obvious to me, as the semaphores are always used together. It should be really simple to change. If you have a specific problem with some details/functions, write about it.
 
Old 04-28-2009, 03:59 PM   #3
johnsfine
LQ Guru
 
Registered: Dec 2007
Distribution: Centos
Posts: 5,286

Rep: Reputation: 1191Reputation: 1191Reputation: 1191Reputation: 1191Reputation: 1191Reputation: 1191Reputation: 1191Reputation: 1191Reputation: 1191
I'm curious. Are you at U Regina? Or does your instructor just use material from there?

Either way, try reading the very clear explanation of your current topic at:

http://www.cs.uregina.ca/Links/class...semaphore.html
 
Old 04-28-2009, 04:49 PM   #4
unSpawn
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Registered: May 2001
Posts: 29,390
Blog Entries: 55

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@LinuxInfo: at this point you have managed to post 4 assignment questions:
http://www.linuxquestions.org/questi...ogram.-704904/
http://www.linuxquestions.org/questi...m.....-707332/
http://www.linuxquestions.org/questi...ogram.-717216/
and this thread.

As johnsfine and others have indicated posting homework is not appreciated if you don't put in any effort yourself.
You may consider this a friendly nudge but beware of the consequences if you don't care and persist in your ways.
 
  


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