Florian Fischer
63b8d9420a
Remove the double semaphore cleanup in the child and the parent. Set nops to 1 since there is only one operation not two. Use a blocking semaphore operation in the parent to wait for the child increasing the semaphore value.
111 lines
3.7 KiB
C
111 lines
3.7 KiB
C
/// @file t_semflg.c
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/// @brief Tests some of the IPC flags.
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/// @copyright (c) 2014-2024 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#include "sys/unistd.h"
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#include "sys/errno.h"
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#include "sys/sem.h"
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#include "sys/ipc.h"
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#include "stdlib.h"
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#include "fcntl.h"
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#include "stdio.h"
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int main(int argc, char *argv[])
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{
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struct sembuf op[1];
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union semun arg;
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long ret, semid;
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// ========================================================================
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// Create the first semaphore.
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semid = semget(IPC_PRIVATE, 1, IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
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if (semid < 0) {
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perror("Failed to create semaphore set");
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return 1;
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}
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printf("[father] Created semaphore set (semid : %d)\n", semid);
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// ========================================================================
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// Set the value of the semaphore in the structure.
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arg.val = 1;
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// Setting the semaphore value.
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ret = semctl(semid, 0, SETVAL, &arg);
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if (ret < 0) {
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perror("Failed to set value of semaphore");
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return 1;
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}
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printf("[father] Set semaphore value (id : %d, value : %d == 1)\n", semid, arg.val);
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// ========================================================================
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// Check if we successfully set the value of the semaphore.
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ret = semctl(semid, 0, GETVAL, NULL);
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if (ret < 0) {
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perror("Failed to get the value of semaphore set");
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return 1;
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}
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printf("[father] Get semaphore value (id : %d, value : %d == 1)\n", semid, ret);
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// ========================================================================
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// Create child process.
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if (!fork()) {
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struct sembuf op_child;
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// Initialize the operation structure.
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op_child.sem_num = 0; // Operate on semaphore 0.
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op_child.sem_op = 1; // Increment value by 1.
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op_child.sem_flg = 0; // No flags.
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sleep(3);
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// ====================================================================
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// Increment semaphore value.
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if (semop(semid, &op_child, 1) < 0) {
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perror("Failed to perform first child operation");
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return 1;
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}
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printf("[child] Succesfully performed opeation (id : %d)\n", semid);
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// ====================================================================
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// Check if we successfully set the value of the semaphore.
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ret = semctl(semid, 0, GETVAL, NULL);
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if (ret < 0) {
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perror("Failed to get the value of semaphore set");
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return 1;
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}
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printf("[child] Get semaphore value (id : %d, value : %d == 1)\n", semid, ret);
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printf("[child] Exit, now.\n", semid, ret);
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return 0;
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}
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op[0].sem_num = 0;
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op[0].sem_op = -2;
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op[0].sem_flg = 0;
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// ========================================================================
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// Perform the operation.
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if (semop(semid, op, 1) < 0) {
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perror("Failed to perform operation");
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return 1;
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}
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printf("[father] Performed semaphore operations (id : %d)\n", semid);
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// ========================================================================
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// Check if we successfully set the value of the semaphore.
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ret = semctl(semid, 0, GETVAL, NULL);
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if (ret < 0) {
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perror("Failed to get the value of semaphore set");
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return 1;
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}
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printf("[father] Get semaphore value (id : %d, value : %d == 1)\n", semid, ret);
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// ========================================================================
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// Delete the semaphore set.
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ret = semctl(semid, 0, IPC_RMID, 0);
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if (ret < 0) {
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perror("Failed to remove semaphore set");
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}
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printf("[father] Correctly removed semaphore set.\n");
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return 0;
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}
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