74 lines
1.7 KiB
C
74 lines
1.7 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <sys/shm.h>
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#include <unistd.h>
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#define NUM_PROCS 4
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#define SHM_SIZE 1024
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#define PATHNAME "."
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#define PROJ_ID 65
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int create_mem_segment(int **shm_array) {
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int shmid;
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key_t key = ftok(PATHNAME, PROJ_ID);
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// Create a new shared segment
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if ((shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0666)) < 0) {
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perror("[!] Shmget failed");
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exit(EXIT_FAILURE);
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}
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// Attach (system chooses a suitable address)
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if ((*shm_array = (int *)shmat(shmid, NULL, 0)) == (int *)-1) {
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perror("[!] Shmat failed");
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exit(EXIT_FAILURE);
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}
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return shmid;
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}
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int compare(const void *a, const void *b) { return (*(int *)a - *(int *)b); }
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int main() {
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int *shm_array;
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int delay = 5;
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// Creation and attaching into a new shared segment
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int shmid = create_mem_segment(&shm_array);
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printf("[SCHEDULER] Shared segment created at %p (%d)\n", (void *)shm_array,
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shmid);
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// Wait until init has finished writing into the segment
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printf("[SCHEDULER] Sleeping for %d seconds before reading\n", delay);
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sleep(delay);
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// Copying array to a local variable
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int priorities[NUM_PROCS];
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for (int i = 0; i < NUM_PROCS; i++) {
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priorities[i] = shm_array[i];
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}
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// TODO: "After scheduler prints the data, init should detach from shared
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// memory" -> Some mechanism to indicate when init has detached must be put in
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// place
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// Detaching and deleting the segment
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shmdt(shm_array);
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shmctl(shmid, IPC_RMID, NULL);
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// Sorting and printing the priorities
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qsort(&priorities, NUM_PROCS, sizeof(int), compare);
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printf("[SCHEDULER] Priorities: ");
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for (int i = 0; i < NUM_PROCS; i++) {
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printf("%d ", priorities[i]);
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}
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printf("\n");
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return 0;
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}
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