Dotaz: IPC a semafory

[tristan]

Dobry den,

potreboval by som poradit s nastavovanim semaforov. Co mi nejde do hlavy je, preco tento kod:

	/* Semaphores */
	union semun semUnion;
	
	/* Creating semaphore 1 */
	if ((sem1ID=semget(keySem1,2,IPC_CREAT|0666)) == -1) {
		perror("zadanie: semaphore1: ");
	        exit (6);
	}
	/* Setting semaphore 1 */
	/* Allowing proc_t writing */
	semUnion.val=1;
	if ((semctl(sem1ID,0,SETVAL,semUnion)) == -1) {
		perror("zadanie: semaphore1: ");
		exit (7);
	}
	/* Denying proc_s reading */
	semUnion.val=0;
	if ((semctl(sem1ID,1,SETVAL,semUnion)) == -1) {
		perror("zadanie: semaphore1: ");
		exit (7);
	}
	
	/* Creating semaphore 2 */
	if ((sem2ID=semget(keySem2,2,IPC_CREAT|0666)) == -1) {
		perror("zadanie: semaphore2: ");
		exit (6);
	}
	/* Setting semaphore 2 */
	/* Allowing proc_s writing */
	semUnion.val=1;
	if ((semctl(sem2ID,0,SETVAL,semUnion)) == -1) {
		perror("zadanie: semaphore1: ");
		exit (7);
	}
	/* Denying proc_d reading */
	semUnion.val=0;
	if ((semctl(sem2ID,1,SETVAL,semUnion)) == -1) {
		perror("zadanie: semaphore2: ");
		exit (7);
	}
	
	fprintf(stdout,"zadanie: sem1[0]: %d\n",semctl(sem1ID,0,GETVAL,semUnion));
 	fprintf(stdout,"zadanie: sem1[1]: %d\n",semctl(sem1ID,1,GETVAL,semUnion));
	fprintf(stdout,"zadanie: sem2[0]: %d\n",semctl(sem2ID,0,GETVAL,semUnion));
        fprintf(stdout,"zadanie: sem2[1]: %d\n",semctl(sem2ID,1,GETVAL,semUnion));

dava takyto vypis:

zadanie: sem1[0]: 1
zadanie: sem1[1]: 0
zadanie: sem2[0]: 0
zadanie: sem2[1]: 0

Dakujem za napady.

Odpovědi

[tristan]

Prave som zistil, ze na Debiane 3.1 to pracuje spravne, ale na Gentoo to pokulhava a nechapem preco:(