CODE USING C LANGUAGE

Project Objectives:

The purpose of this project is to give students an opportunity to experiment with process synchronization mechanisms.

Project Description:

Project Description:

In this assignment, a memory location is shared by four processes. Each process independently tries to increase the content of the shared memory location from 1 to a certain value by increments of one. Process 1 has a target of 100000, Process 2s target is 200000, Process 3 has a target of 300000, and the goal of 4 is 500000. When the program terminates, therefore, the shared memory variable will have a total of 1100000 (i.e. this value will be output by whichever of the four processes finishes last).

In this project, you are to modify the assignment1 to protect the critical section using semaphores.

After all the children have finished, the parent process should release the shared memory and semaphores and then terminate. Use the "wait" function so that the parent knows precisely when each of the children finishes. The parent should print the process ID of each child as the child finishes execution. Then it should release shared memory, semaphores, and print "End of Simulation".

Sample output

From Process 1: counter = 330547.

From Process 2: counter = 447860.

From Process 3: counter = 600059.

From Process 4: counter = 1100000

Child with ID 2412 has just exited.

Child with ID 2411 has just exited.

Child with ID 2413 has just exited.

Child with ID 2414 has just exited.

// GLOBAL

int sem_id;// semaphore id

// semaphore buffers

static struct sembuf OP = {0,-1,0};

static struct sembuf OV = {0,1,0};

struct sembuf *P =&OP;

struct sembuf *V =&OV;

// semapore union used to generate semaphore

typedef union{

int val;

struct semid_ds *buf;

ushort *array;

} semunion;

// POP (wait()) function for semaphore to protect critical section

int POP()

{

int status;

status = semop(sem_id, P,1);

return status;

}

// VOP (signal()) function for semaphore to release protection

int VOP()

{

int status;

status = semop(sem_id, V,1);

return status;

In the main()

int value, value1;

semunion semctl_arg;

semctl_arg.val = 1;

/* Create semaphores */

sem_id = semget(SEMKEY, NSEMS, IPC_CREAT | 0666);

if(sem_id < 0) printf("Error in creating the semaphore./n");

/* Initialize semaphore */

value1 =semctl(sem_id, semnum, SETVAL, semctl_arg);

value =semctl(sem_id, semnum, GETVAL, semctl_arg);

if (value < 1) printf("Eror detected in SETVAL. ");

/* De-allocate semaphore */

semctl_arg.val = 0;

status =semctl(sem_id, 0, IPC_RMID, semctl_arg);

if( status < 0) printf("Error in removing the semaphore. ");

Hints:

Build your project in an incremental fashion. Attempt to meet each objective before moving on to the next.