106 lines
2.3 KiB
C
106 lines
2.3 KiB
C
#include <sys/shm.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <pthread.h>
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struct shared_data {
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pthread_mutex_t mutex;
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int counter;
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};
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struct shm_shared_data {
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int shm_id;
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struct shared_data *shared_data;
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};
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void increment_counter(struct shared_data *data) {
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for (int i = 0; i < 100000; i++) {
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if (pthread_mutex_lock(&data->mutex) != 0) {
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perror("pthread_mutex_lock");
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}
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data->counter++;
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if (pthread_mutex_unlock(&data->mutex) != 0) {
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perror("pthread_mutex_unlock");
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}
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}
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}
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struct shm_shared_data shared_data_open() {
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key_t key = ftok("shmfile", 65); // Generate a key for the shared memory segment
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// Create a shared memory segment
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int shm_id = shmget(key, sizeof(struct shared_data), 0666 | IPC_CREAT);
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if (shm_id == -1) {
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perror("shmget");
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exit(EXIT_FAILURE);
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}
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// Attach the shared memory segment to the address space of the process
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struct shared_data *shared_data = shmat(shm_id, NULL, 0);
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if (shared_data == (void*)-1) {
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perror("shmat");
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exit(EXIT_FAILURE);
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}
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struct shm_shared_data shm_shared_data = {
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.shm_id = shm_id,
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.shared_data = shared_data
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};
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return shm_shared_data;
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}
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void shared_data_close(struct shm_shared_data shm_data) {
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// Detach the shared memory segment
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if (shmdt(shm_data.shared_data) == -1) {
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perror("shmdt");
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exit(EXIT_FAILURE);
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}
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}
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void *thread_callback(void *p) {
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struct shm_shared_data shm_data = shared_data_open();
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increment_counter(shm_data.shared_data);
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shared_data_close(shm_data);
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return NULL;
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}
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int main() {
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struct shm_shared_data shm_data = shared_data_open();
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pthread_mutexattr_t mutex_attr;
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pthread_mutexattr_init(&mutex_attr);
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pthread_mutexattr_setpshared(&mutex_attr, PTHREAD_PROCESS_SHARED);
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if (pthread_mutex_init(&shm_data.shared_data->mutex, &mutex_attr) < 0) {
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printf("Failed to initialise mutex\n");
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return -1;
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}
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pthread_t thread1;
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pthread_create(&thread1, NULL, thread_callback, NULL);
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pthread_t thread2;
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pthread_create(&thread2, NULL, thread_callback, NULL);
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pthread_join(thread1, NULL);
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pthread_join(thread2, NULL);
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printf("Counter is %d\n", shm_data.shared_data->counter);
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shared_data_close(shm_data);
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// Remove the shared memory segment
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if (shmctl(shm_data.shm_id, IPC_RMID, NULL) == -1) {
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perror("shmctl");
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exit(EXIT_FAILURE);
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}
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return 0;
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}
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