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

Add some more comments. Implement sempahore search function. Check correctness of the current semaphore code, and it works as expected.

Browse Source
This commit is contained in:
Enrico Fraccaroli
2023-04-21 17:55:19 +02:00
parent bfe30f797a
commit 8ad4e45b50
4 changed files with 156 additions and 128 deletions
Download Patch File Download Diff File Expand all files Collapse all files
programs/tests/t_semget.c
+61 -36
View File
@@ -6,7 +6,6 @@
#include "stdlib.h"
#include "sys/unistd.h"
/*
Testing Semaphores.
This program creates a son and then performs a blocking operation on a semaphore. The son sleeps for
@@ -14,68 +13,95 @@ five seconds and then it wakes up his father and then it deletes the semaphore.
*/
void semid_print(struct semid_ds *temp){
void semid_print(struct semid_ds *temp)
{
printf("pid, IPC_KEY, Semid, semop, change: %d, %d, %d, %d, %d\n", temp->owner, temp->key, temp->semid, temp->sem_otime, temp->sem_ctime);
for(int i=0; i<(temp->sem_nsems); i++){
printf("%d semaphore:\n", i+1);
for (int i = 0; i < (temp->sem_nsems); i++) {
printf("%d semaphore:\n", i + 1);
printf("value: %d, pid %d, process waiting %d\n", temp->sems[i].sem_val, temp->sems[i].sem_pid, temp->sems[i].sem_zcnt);
}
}
int main()
{
{
struct sembuf op;
union semun arg;
arg.val = 1;
//key_t i = ftok("/test1.txt", 5); //checking ftok
long id = semget(2,1,IPC_CREAT); //first semaphores
long ret, id;
key_t key;
// Checking if ftok works.
key = ftok("/home/user/test7.txt", 5);
printf("Key : %d\n", key);
// Create the first semaphore.
id = semget(2, 1, IPC_CREAT);
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)
long value;
printf("ID: %d\n", id);
if ((value = semctl(id, 0, SETVAL, &arg)) == -1){
printf("ERRORE\n");
}else{
//semid_print(arg.v);
printf("valore sem 0: %d \n", semctl(id, 0, GETVAL, &arg));
// Set the value of the semaphore in the structure.
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) {
perror("Failed to set value of semaphore.");
return 1;
}
// Check if we successfully set the value of the semaphore.
ret = semctl(id, 0, GETVAL, &arg);
printf("Check Value (%d): %d\n", id, ret);
if (!fork()){
// Create child process.
if (!fork()) {
// Make the child process sleep.
sleep(5);
struct sembuf op2;
op2.sem_num = 0;
op2.sem_op = 150;
op2.sem_flg = 0;
semop(id, &op2, 1);
// 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.
// This should allow the father process to decrement the semaphore by 2.
// Perform the operation.
semop(id, &op, 1);
// Remove the semaphore.
semctl(id, 0, IPC_RMID, NULL);
exit(0);
// Exit with the child process.
return 0;
}
struct sembuf op;
op.sem_num = 0;
op.sem_op = -1;
op.sem_flg = 0;
if (semop(id, &op, 2) < 0){
// Initialize the operation structure.
op.sem_num = 0; // Operate on semaphore 0.
op.sem_op = -2; // Decrement value by 2.
op.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, &op, 1) < 0) {
printf("ERRORE\n");
}
printf("valore sem 0: %d \n", semctl(id, 0, GETVAL, &arg));
// Check if we successfully set the value of the semaphore.
ret = semctl(id, 0, GETVAL, &arg);
printf("Check Value (%d): %d\n", id, 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);
@@ -83,7 +109,6 @@ int main()
printf("Error with IPC_KEY\n");
return -1;
}*/
return 0;
}