From: Lukas Jiriste <ljiriste@student.42prague.com>
Date: Thu, 23 May 2024 07:52:46 +0000 (+0200)
Subject: Add semaphore to each philo
X-Git-Url: https://git.ljiriste.work/?a=commitdiff_plain;h=20b3bffac789da5e1eb381a452ad6b333c311626;p=42%2Fphilosophers.git

Add semaphore to each philo

To react fast to starving philosopher, there has to be another thread
checking the state of the philo. Because of this there has to be
a mechanism to prevent data race. Because mutexes are forbidden
it has to be a semaphore.
This commit contains the semaphore and some code that dictates
its usage.
---

diff --git a/philo_bonus/philo.c b/philo_bonus/philo.c
index 5acbb9e..9550f0c 100644
--- a/philo_bonus/philo.c
+++ b/philo_bonus/philo.c
@@ -6,19 +6,34 @@
 /*   By: ljiriste <marvin@42.fr>                    +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2024/05/09 08:45:21 by ljiriste          #+#    #+#             */
-/*   Updated: 2024/05/12 21:52:05 by ljiriste         ###   ########.fr       */
+/*   Updated: 2024/05/23 09:50:14 by ljiriste         ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
 #include "philo.h"
 #include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
 
-static void	open_semaphores(sem_t *semaphores[sem_num])
+static void	open_semaphores(t_philo *philo)
 {
-	semaphores[forks] = sem_open(FORKS_SEM, 0);
-	semaphores[fed] = sem_open(WELL_FED_SEM, 0);
-	semaphores[death] = sem_open(DEATH_SEM, 0);
-	semaphores[term] = sem_open(TERM_SEM, 0);
+	char	*sem_name;
+
+	philo->semaphores[forks] = sem_open(FORKS_SEM, 0);
+	philo->semaphores[fed] = sem_open(WELL_FED_SEM, 0);
+	philo->semaphores[death] = sem_open(DEATH_SEM, 0);
+	philo->semaphores[term] = sem_open(TERM_SEM, 0);
+	sem_name = create_philo_sem_name(philo->id);
+	philo->philo_sem = sem_open(sem_name, O_CREAT | O_EXCL, S_IRUSR | S_IWUSR, 1);
+	free(sem_name);
+	if (philo->philo_sem == SEM_FAILED)
+	{
+		sem_wait(philo->semaphores[term]);
+		printf("An error has occured.\n");
+		sem_wait(philo->semaphores[death]);
+		exit(2);
+	}
+	return ;
 }
 
 static void	philo_think(t_philo *philo)
@@ -29,17 +44,14 @@ static void	philo_think(t_philo *philo)
 
 static void	philo_eat(t_philo *philo)
 {
-	useconds_t	time_now;
-
 	sem_wait(philo->semaphores[forks]);
 	print_timestamp(philo, "has taken a fork");
 	sem_wait(philo->semaphores[forks]);
 	print_timestamp(philo, "has taken a fork");
-	time_now = usecs_since_start(philo->settings.start);
-	if (time_now - philo->last_eaten > philo->settings.time_to_die)
-		die(philo);
-	philo->last_eaten = time_now;
+	sem_wait(philo->philo_sem);
+	philo->last_eaten = usecs_since_start(philo->settings.start);
 	++philo->num_eaten;
+	sem_post(philo->philo_sem);
 	print_timestamp(philo, "is eating");
 	if (philo->settings.should_check_hunger &&
 		philo->num_eaten == philo->settings.min_eat_num)
@@ -59,11 +71,16 @@ static void	philo_sleep(t_philo *philo)
 
 void	be_a_philosopher(t_philo *philo)
 {
-	open_semaphores(philo->semaphores);
-	while (1)
+	pid_t	hunger_watcher_pid;
+
+	open_semaphores(philo);
+	hunger_watcher_pid = create_hunger_watcher(philo);
+	while (is_alive(philo))
 	{
 		philo_think(philo);
 		philo_eat(philo);
 		philo_sleep(philo);
 	}
+	destroy_hunger_watcher(hunger_watcher_pid);
+	exit(0);
 }
diff --git a/philo_bonus/philo.h b/philo_bonus/philo.h
index 7f1e43e..8b3a1d6 100644
--- a/philo_bonus/philo.h
+++ b/philo_bonus/philo.h
@@ -60,6 +60,7 @@ typedef struct s_philosopher
 	unsigned int	id;
 	useconds_t		last_eaten;
 	sem_t			*semaphores[sem_num];
+	sem_t			*philo_sem;
 	t_settings		settings;
 }					t_philo;