Initial commit.
This commit is contained in:
commit
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/ipc.h>
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#include <sys/shm.h>
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#include <sys/stat.h>
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#include "semp.h"
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/**************************************************************************
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* Authors: Gary Fleming, Amber McCloughan
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* Class: CIS452 - Operating Systems Concepts
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* Professor: Dr. Greg Wolffe
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* Date: 3/14/2019
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*
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* Program that synchronizes shared memory between two processes.
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* Both processes swap memory back and forth, but a semaphore prevents
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* them from clobbering data.
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*
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* You must pass an argument to the program, which is the number of
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* times you want each process to swap the memory back and forth.
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***************************************************************************/
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// Size of shared memory segment.
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#define SIZE 16
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/**
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* Main function of the reader program. Takes in
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* an argument, which is the number of times each
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* process will loop.
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*
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* @param argc, number of arguments.
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* @param argv, the actual arguments.
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*/
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int main(int argc, char *argv[])
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{
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// Status for waiting on child.
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int status;
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/* The i for the for loop, the # of times looped, temp variable
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for swapping memory, and shared memory pointer.
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*/
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long int i, loop, temp, *shmPtr;
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// Shared memory ID.
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int shmId;
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// PID for forking.
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pid_t pid;
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// Getting loop # from program arguments.
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loop = atoi(argv[1]); // get value of loop variable (from command-line argument)
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// Getting shared memory segment.
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if ((shmId = shmget(IPC_PRIVATE, SIZE, IPC_CREAT | S_IRUSR | S_IWUSR)) < 0)
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{
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perror("i can't get no..\n");
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exit(1);
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}
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// Attaching shared memory segment.
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if ((shmPtr = shmat(shmId, 0, 0)) == (void *)-1)
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{
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perror("can't attach\n");
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exit(1);
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}
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// Initializing values for shared memory.
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shmPtr[0] = 0;
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shmPtr[1] = 1;
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// Creating semaphore.
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int semId = semp_init(1);
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// Forking
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if (!(pid = fork()))
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{ // Child
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for (i = 0; i < loop; i++)
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{
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// Wait
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semp_wait(semId);
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temp = shmPtr[0]; // swap the contents of shmPtr[0] and shmPtr[1]
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shmPtr[0] = shmPtr[1];
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shmPtr[1] = temp;
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// Signal
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semp_signal(semId);
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}
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// Detaching shared memory.
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if (shmdt(shmPtr) < 0)
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{
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perror("just can't let go\n");
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exit(1);
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}
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// Child exits.
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exit(0);
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}
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else
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{ // Parent
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for (i = 0; i < loop; i++)
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{
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// Wait
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semp_wait(semId);
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temp = shmPtr[1]; // swap the contents of shmPtr[1] and shmPtr[0]
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shmPtr[1] = shmPtr[0];
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shmPtr[0] = temp;
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// Signal
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semp_signal(semId);
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}
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}
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// Waiting on child to exit.
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wait(&status);
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// Printing out the values. Should be 0 1.
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printf("values: %li\t%li\n", shmPtr[0], shmPtr[1]);
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// Detaching shared memory.
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if (shmdt(shmPtr) < 0)
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{
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perror("just can't let go\n");
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exit(1);
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}
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// Flagging shared memory for deletion.
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if (shmctl(shmId, IPC_RMID, 0) < 0)
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{
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perror("can't deallocate\n");
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exit(1);
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}
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// Deleting semaphore.
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semp_destroy(semId);
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// Goodbye.
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return 0;
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}
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/ipc.h>
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#include <sys/shm.h>
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#include <sys/stat.h>
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#include <sys/sem.h>
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/**************************************************************************
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* Authors: Gary Fleming, Amber McCloughan
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* Class: CIS452 - Operating Systems Concepts
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* Professor: Dr. Greg Wolffe
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* Date: 3/14/2019
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*
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* Program that synchronizes shared memory between two processes.
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* Both processes swap memory back and forth, but a semaphore prevents
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* them from clobbering data.
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*
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* You must pass an argument to the program, which is the number of
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* times you want each process to swap the memory back and forth.
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***************************************************************************/
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// Size of shared memory segment.
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#define SIZE 16
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/**
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* Main function of the reader program. Takes in
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* an argument, which is the number of times each
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* process will loop.
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*
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* @param argc, number of arguments.
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* @param argv, the actual arguments.
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*/
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int main(int argc, char *argv[])
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{
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// Status for waiting on the child.
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int status;
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/* The i for the for loop, the # of times looped, temp variable
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for swapping memory, and shared memory pointers.
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*/
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long int i, loop, temp, *shmPtr;
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// Shared memory ID.
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int shmId;
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// PID for forking.
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pid_t pid;
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// Getting loop # from program arguments.
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loop = atoi(argv[1]); // get value of loop variable (from command-line argument)
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// Getting the shared memory segment.
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if ((shmId = shmget(IPC_PRIVATE, SIZE, IPC_CREAT | S_IRUSR | S_IWUSR)) < 0)
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{
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perror("i can't get no..\n");
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exit(1);
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}
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// Attaching shared memory segment.
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if ((shmPtr = shmat(shmId, 0, 0)) == (void *)-1)
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{
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perror("can't attach\n");
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exit(1);
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}
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// Initializing values for shared memory.
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shmPtr[0] = 0;
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shmPtr[1] = 1;
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// Getting semaphore.
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int semId = semget(IPC_PRIVATE, 1, 00600);
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// Initializing semaphore to 1.
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semctl(semId, 0, SETVAL, 1);
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// Operation for locking the semaphore (subtract 1)
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struct sembuf lock = {0, -1, SEM_UNDO};
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// Operating for unlocking the semaphore (add 1)
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struct sembuf unlock = {0, 1, SEM_UNDO};
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// Forking
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if (!(pid = fork()))
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{ // Child
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for (i = 0; i < loop; i++)
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{
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// Wait
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semop(semId, &lock, 1);
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temp = shmPtr[0]; // swap the contents of shmPtr[0] and shmPtr[1]
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shmPtr[0] = shmPtr[1];
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shmPtr[1] = temp;
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// Signal
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semop(semId, &unlock, 1);
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}
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// Detaching shared memory.
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if (shmdt(shmPtr) < 0)
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{
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perror("just can't let go\n");
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exit(1);
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}
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// Child exits.
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exit(0);
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}
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else
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{ // Parent
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for (i = 0; i < loop; i++)
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{
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// Wait
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semop(semId, &lock, 1);
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temp = shmPtr[1]; // swap the contents of shmPtr[1] and shmPtr[0]
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shmPtr[1] = shmPtr[0];
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shmPtr[0] = temp;
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// Signal
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semop(semId, &unlock, 1);
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}
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}
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// Waiting on the child to exit.
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wait(&status);
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// Printing out the values. Should be 0 1.
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printf("values: %li\t%li\n", shmPtr[0], shmPtr[1]);
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// Detaching shared memory.
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if (shmdt(shmPtr) < 0)
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{
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perror("just can't let go\n");
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exit(1);
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}
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// Flagging shared memory for deletion.
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if (shmctl(shmId, IPC_RMID, 0) < 0)
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{
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perror("can't deallocate\n");
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exit(1);
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}
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// Deleting semaphore.
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semctl(semId, 0, IPC_RMID);
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// Goodbye.
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return 0;
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}
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@ -0,0 +1,72 @@
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#include "semp.h"
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#include <sys/sem.h>
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/**************************************************************************
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* Authors: Gary Fleming, Amber McCloughan
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* Class: CIS452 - Operating Systems Concepts
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* Professor: Dr. Greg Wolffe
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* Date: 3/14/2019
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*
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* Library of functions for synchronization
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* using semaphores. Includes the classic
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* wait() and signal() functions, as well as
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* functions for initializing and deleting
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* semaphores.
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*
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* @see semp.h for function definitions.
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***************************************************************************/
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/**
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* Initialize a semaphore. The ID for using the other
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* functions is returned by the function.
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*
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* @param value, the value to initialize the semaphore to.
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* @return semId, the ID of the semaphore.
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*/
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int semp_init(int value)
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{
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int semId = semget(IPC_PRIVATE, 1, 00600);
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semctl(semId, 0, SETVAL, value);
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return semId;
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}
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/**
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* Attempts to wait on the semaphore. Subtracts 1 from
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* the internal value of the semaphore.
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*
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* @param semId, the ID of the semaphore.
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* @return 0 if there were no errors.
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*/
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int semp_wait(int semId)
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{
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struct sembuf lock = {0, -1, SEM_UNDO};
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semop(semId, &lock, 1);
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return 0;
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}
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/**
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* Signals the semaphore. Adds 1 to the internal value
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* of the semaphore.
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*
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* @param semId, the ID of the semaphore.
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* @return 0 if there were no errors.
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*/
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int semp_signal(int semId)
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{
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struct sembuf unlock = {0, 1, SEM_UNDO};
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semop(semId, &unlock, 1);
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return 0;
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}
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/**
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* Deletes the semaphore.
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*
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* @param semId, the ID of the semaphore.
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* @return 0 if there were no errors.
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*/
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int semp_destroy(int semId)
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{
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semctl(semId, 0, IPC_RMID);
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return 0;
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}
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@ -0,0 +1,50 @@
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#ifndef LAB_SEMP_H
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#define LAB_SEMP_H
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/**************************************************************************
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* Authors: Gary Fleming, Amber McCloughan
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* Class: CIS452 - Operating Systems Concepts
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* Professor: Dr. Greg Wolffe
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* Date: 3/14/2019
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*
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* Library of functions for synchronization
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* using semaphores. Includes the classic
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* wait() and signal() functions, as well as
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* functions for initializing and deleting
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* semaphores.
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*
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* @see semp.c for function implementations.
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***************************************************************************/
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/**
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* Initialize a semaphore. The ID for using the other
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* functions should be returned by the function.
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*
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* @param value, the value to initialize the semaphore to.
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*/
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int semp_init(int value);
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/**
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* Attempts to wait on the semaphore. Subtracts 1 from
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* the internal value of the semaphore.
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*
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* @param semId, the ID of the semaphore.
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*/
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int semp_wait(int semId);
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/**
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* Signals the semaphore. Adds 1 to the internal value
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* of the semaphore.
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*
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* @param semId, the ID of the semaphore.
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*/
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int semp_signal(int semId);
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/**
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* Deletes the semaphore.
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*
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* @param semId, the ID of the semaphore.
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*/
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int semp_destroy(int semId);
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#endif
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