lzh/MentOS
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Clean up the semget example. Clean up the return values of semop function.

Browse Source
This commit is contained in:
Enrico Fraccaroli (Galfurian)
2023-05-19 14:24:04 -04:00
parent 9f63a93d63
commit 3e03f1e6fd
5 changed files with 245 additions and 152 deletions
Download Patch File Download Diff File Expand all files Collapse all files
programs/tests/t_semget.c
+95 -59
View File
@@ -25,97 +25,133 @@ void semid_print(struct semid_ds *temp)
int main()
{
struct sembuf op;
struct sembuf father[2];
struct sembuf op_child;
struct sembuf op_father[3];
union semun arg;
long ret, id;
long ret, semid;
key_t key;
// Checking if ftok works.
// ========================================================================
// Generating a key using ftok
key = ftok("/home/user/test7.txt", 5);
printf("Key : %d\n", key);
if (key < 0) {
perror("Failed to generate key using ftok.");
return 1;
}
printf("Generated key using ftok (key = %d)\n", key);
// ========================================================================
// Create the first semaphore.
id = semget(2, 1, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
printf("Id: %d\n", id);
//long id2 = semget(IPC_PRIVATE, 1, IPC_CREAT);
//long id2 = semget(2, 2, IPC_EXCL); //need to return -1 bc already exists
//long id3 = semget(2, 2, 0); //need to return 3 (semid of the first)
//long id4 = semget(100, 2, IPC_CREAT | IPC_EXCL); //need to return 101 (new semaphore)
semid = semget(key, 1, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
if (semid < 0) {
perror("Failed to create semaphore set.");
return 1;
}
printf("[father] Created semaphore set (id : %d)\n", semid);
// ========================================================================
// Set the value of the semaphore in the structure.
arg.val = 0;
arg.val = 1;
// Setting the semaphore value.
printf("Set Value (%d): %d\n", id, arg.val);
ret = semctl(id, 0, SETVAL, &arg);
if (ret == -1) {
ret = semctl(semid, 0, SETVAL, &arg);
if (ret < 0) {
perror("Failed to set value of semaphore.");
return 1;
}
printf("[father] Set semaphore value (id : %d, value : %d == 1)\n", semid, arg.val);
// ========================================================================
// Check if we successfully set the value of the semaphore.
ret = semctl(id, 0, GETVAL, &arg);
printf("Check Value before(%d): %d\n", id, ret);
ret = semctl(semid, 0, GETVAL, NULL);
if (ret < 0) {
perror("Failed to get the value of semaphore set.");
return 1;
}
printf("[father] Get semaphore value (id : %d, value : %d == 1)\n", semid, ret);
// ========================================================================
// Create child process.
if (!fork()) {
// Make the child process sleep.
sleep(2);
// Initialize the operation structure.
op.sem_num = 0; // Operate on semaphore 0.
op.sem_op = 1; // Increment value by 1.
op.sem_flg = 0; // No flags.
op_child.sem_num = 0; // Operate on semaphore 0.
op_child.sem_op = 1; // Increment value by 1.
op_child.sem_flg = 0; // No flags.
// This should allow the father process to decrement the semaphore by 2.
// Semaphore has value 1.
sleep(3);
if (semop(semid, &op_child, 1) < 0) {
perror("Failed to perform first child operation.");
return 1;
}
printf("[child] Succesfully performed opeation (id : %d)\n", semid);
// Perform the operation.
semop(id, &op, 1);
sleep(5);
semop(id, &op, 1);
// Remove the semaphore.
//semctl(id, 0, IPC_RMID, NULL);
// Check if we successfully set the value of the semaphore.
ret = semctl(semid, 0, GETVAL, NULL);
if (ret < 0) {
perror("Failed to get the value of semaphore set.");
return 1;
}
printf("[child] Get semaphore value (id : %d, value : %d == 0)\n", semid, ret);
// Semaphore has value 2, now the father can continue.
sleep(3);
if (semop(semid, &op_child, 1) < 0) {
perror("Failed to perform second child operation.");
return 1;
}
printf("[child] Succesfully performed opeation (id : %d)\n", semid);
// Check if we successfully set the value of the semaphore.
ret = semctl(semid, 0, GETVAL, NULL);
if (ret < 0) {
perror("Failed to get the value of semaphore set.");
return 1;
}
printf("[child] Get semaphore value (id : %d, value : %d == 0)\n", semid, ret);
printf("[child] Exit, now.\n", semid, ret);
// Exit with the child process.
return 0;
}
// ========================================================================
// Initialize the operation structure.
father[0].sem_num = 0; // Operate on semaphore 0.
father[0].sem_op = -1; // Decrement value by 1.
father[0].sem_flg = 0; // No flags.
father[1].sem_num = 0; // Operate on semaphore 0.
father[1].sem_op = -1; // Decrement value by 1.
father[1].sem_flg = 0; // No flags.
op_father[0].sem_num = 0; // Operate on semaphore 0.
op_father[0].sem_op = -1; // Decrement value by 1.
op_father[0].sem_flg = 0; // No flags.
op_father[1].sem_num = 0; // Operate on semaphore 0.
op_father[1].sem_op = -1; // Decrement value by 1.
op_father[1].sem_flg = 0; // No flags.
op_father[2].sem_num = 0; // Operate on semaphore 0.
op_father[2].sem_op = -1; // Decrement value by 1.
op_father[2].sem_flg = 0; // No flags.
// We set the semaphore at the beginning at 1, and the child process will
// increment the semaphore by 1, allowing us to decrement the semaphore by
// 2.
// Perform the operation.
if (semop(id, father, 2) < 0) {
perror("ERROR\n");
// ========================================================================
// Perform the operations.
if (semop(semid, op_father, 3) < 0) {
perror("Failed to perform father operation.");
return 1;
}
sleep(2);
printf("[father] Performed semaphore operations (id : %d)\n", semid);
// Check if we successfully set the value of the semaphore.
ret = semctl(id, 0, GETVAL, &arg);
printf("Check Value after(%d): %d\n", id, ret);
ret = semctl(semid, 0, GETVAL, NULL);
if (ret < 0) {
perror("Failed to get the value of semaphore set.");
return 1;
}
printf("[father] Get semaphore value (id : %d, value : %d == 0)\n", semid, ret);
/*if ((semid = semctl(id, 0, IPC_RMID, 0)) == -1){
printf("%d\n", errno);
}else{
printf("found %d\n", semid);
}*/
//long id2 = semget(IPC_PRIVATE, 2, 0);
//long id3 = semget(IPC_PRIVATE, 2, 0);
//printf("id %d id2 %d id3 %d id4 %d\n", id, id2, id3, id4);
/*if (i == -1){
printf("Error with IPC_KEY\n");
return -1;
}*/
// Delete the semaphore set.
ret = semctl(semid, 0, IPC_RMID, 0);
if (ret < 0) {
perror("Failed to remove semaphore set.");
}
printf("[father] Correctly removed semaphore set.\n");
return 0;
}