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simple dining philosophers code (Linux only)

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This commit is contained in:
Remzi H. Arpaci-Dusseau
2019-04-16 16:17:36 -05:00
parent fed11531f7
commit 2621d03f99
6 changed files with 385 additions and 0 deletions
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9
threads-sema/Makefile Normal file
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FLAGS = -Wall -pthread -I../include
all:
gcc $(FLAGS) -o dining_philosophers_deadlock dining_philosophers_deadlock.c
gcc $(FLAGS) -o dining_philosophers_deadlock_print dining_philosophers_deadlock_print.c
gcc $(FLAGS) -o dining_philosophers_no_deadlock dining_philosophers_no_deadlock.c
gcc $(FLAGS) -o dining_philosophers_no_deadlock_print dining_philosophers_no_deadlock_print.c

12
threads-sema/README.md Normal file
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# Dining Philosophers
The dining philosophers example from the text is found herein, in a few
different forms:
- `dining_philosophers.c`: code with deadlock
- `dining_philosophers_print.c`: code with deadlock, and some useful printing
- `dining_philosophers_no_deadlock.c`: code without deadlock
- `dining_philosophers_no_deadlock_print.c`: code without deadlock, and some useful printing
Run `make` to build all of them with the highly primitive `Makefile`.

78
threads-sema/dining_philosophers_deadlock.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include "common.h"
#include "common_threads.h"
typedef struct {
int num_loops;
int thread_id;
} arg_t;
sem_t forks[5];
int left(int p) {
return p;
}
int right(int p) {
return (p + 1) % 5;
}
void get_forks(int p) {
Sem_wait(&forks[left(p)]);
Sem_wait(&forks[right(p)]);
}
void put_forks(int p) {
Sem_post(&forks[left(p)]);
Sem_post(&forks[right(p)]);
}
void think() {
return;
}
void eat() {
return;
}
void *philosopher(void *arg) {
arg_t *args = (arg_t *) arg;
int i;
for (i = 0; i < args->num_loops; i++) {
think();
get_forks(args->thread_id);
eat();
put_forks(args->thread_id);
}
return NULL;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "usage: dining_philosophers_deadlock <num_loops>\n");
exit(1);
}
printf("dining: started\n");
int i;
for (i = 0; i < 5; i++)
Sem_init(&forks[i], 1);
pthread_t p[5];
arg_t a[5];
for (i = 0; i < 5; i++) {
a[i].num_loops = atoi(argv[1]);
a[i].thread_id = i;
Pthread_create(&p[i], NULL, philosopher, &a[i]);
}
for (i = 0; i < 5; i++)
Pthread_join(p[i], NULL);
printf("dining: finished\n");
return 0;
}

98
threads-sema/dining_philosophers_deadlock_print.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include "common.h"
#include "common_threads.h"
typedef struct {
int num_loops;
int thread_id;
} arg_t;
sem_t forks[5];
sem_t print_lock;
void space(int s) {
Sem_wait(&print_lock);
int i;
for (i = 0; i < s * 10; i++)
printf(" ");
}
void space_end() {
Sem_post(&print_lock);
}
int left(int p) {
return p;
}
int right(int p) {
return (p + 1) % 5;
}
void get_forks(int p) {
space(p); printf("%d: try %d\n", p, left(p)); space_end();
Sem_wait(&forks[left(p)]);
space(p); printf("%d: try %d\n", p, right(p)); space_end();
Sem_wait(&forks[right(p)]);
}
void put_forks(int p) {
Sem_post(&forks[left(p)]);
Sem_post(&forks[right(p)]);
}
void think() {
return;
}
void eat() {
return;
}
void *philosopher(void *arg) {
arg_t *args = (arg_t *) arg;
space(args->thread_id); printf("%d: start\n", args->thread_id); space_end();
int i;
for (i = 0; i < args->num_loops; i++) {
space(args->thread_id); printf("%d: think\n", args->thread_id); space_end();
think();
get_forks(args->thread_id);
space(args->thread_id); printf("%d: eat\n", args->thread_id); space_end();
eat();
put_forks(args->thread_id);
space(args->thread_id); printf("%d: done\n", args->thread_id); space_end();
}
return NULL;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "usage: dining_philosophers <num_loops>\n");
exit(1);
}
printf("dining: started\n");
int i;
for (i = 0; i < 5; i++)
Sem_init(&forks[i], 1);
Sem_init(&print_lock, 1);
pthread_t p[5];
arg_t a[5];
for (i = 0; i < 5; i++) {
a[i].num_loops = atoi(argv[1]);
a[i].thread_id = i;
Pthread_create(&p[i], NULL, philosopher, &a[i]);
}
for (i = 0; i < 5; i++)
Pthread_join(p[i], NULL);
printf("dining: finished\n");
return 0;
}

83
threads-sema/dining_philosophers_no_deadlock.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include "common.h"
#include "common_threads.h"
typedef struct {
int num_loops;
int thread_id;
} arg_t;
sem_t forks[5];
int left(int p) {
return p;
}
int right(int p) {
return (p + 1) % 5;
}
void get_forks(int p) {
if (p == 4) {
Sem_wait(&forks[right(p)]);
Sem_wait(&forks[left(p)]);
} else {
Sem_wait(&forks[left(p)]);
Sem_wait(&forks[right(p)]);
}
}
void put_forks(int p) {
Sem_post(&forks[left(p)]);
Sem_post(&forks[right(p)]);
}
void think() {
return;
}
void eat() {
return;
}
void *philosopher(void *arg) {
arg_t *args = (arg_t *) arg;
int i;
for (i = 0; i < args->num_loops; i++) {
think();
get_forks(args->thread_id);
eat();
put_forks(args->thread_id);
}
return NULL;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "usage: dining_philosophers <num_loops>\n");
exit(1);
}
printf("dining: started\n");
int i;
for (i = 0; i < 5; i++)
Sem_init(&forks[i], 1);
pthread_t p[5];
arg_t a[5];
for (i = 0; i < 5; i++) {
a[i].num_loops = atoi(argv[1]);
a[i].thread_id = i;
Pthread_create(&p[i], NULL, philosopher, &a[i]);
}
for (i = 0; i < 5; i++)
Pthread_join(p[i], NULL);
printf("dining: finished\n");
return 0;
}

105
threads-sema/dining_philosophers_no_deadlock_print.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include "common.h"
#include "common_threads.h"
typedef struct {
int num_loops;
int thread_id;
} arg_t;
sem_t forks[5];
sem_t print_lock;
void space(int s) {
Sem_wait(&print_lock);
int i;
for (i = 0; i < s * 10; i++)
printf(" ");
}
void space_end() {
Sem_post(&print_lock);
}
int left(int p) {
return p;
}
int right(int p) {
return (p + 1) % 5;
}
void get_forks(int p) {
if (p == 4) {
space(p); printf("4 try %d\n", right(p)); space_end();
Sem_wait(&forks[right(p)]);
space(p); printf("4 try %d\n", left(p)); space_end();
Sem_wait(&forks[left(p)]);
} else {
space(p); printf("try %d\n", left(p)); space_end();
Sem_wait(&forks[left(p)]);
space(p); printf("try %d\n", right(p)); space_end();
Sem_wait(&forks[right(p)]);
}
}
void put_forks(int p) {
Sem_post(&forks[left(p)]);
Sem_post(&forks[right(p)]);
}
void think() {
return;
}
void eat() {
return;
}
void *philosopher(void *arg) {
arg_t *args = (arg_t *) arg;
space(args->thread_id); printf("%d: start\n", args->thread_id); space_end();
int i;
for (i = 0; i < args->num_loops; i++) {
space(args->thread_id); printf("%d: think\n", args->thread_id); space_end();
think();
get_forks(args->thread_id);
space(args->thread_id); printf("%d: eat\n", args->thread_id); space_end();
eat();
put_forks(args->thread_id);
space(args->thread_id); printf("%d: done\n", args->thread_id); space_end();
}
return NULL;
}
int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "usage: dining_philosophers <num_loops>\n");
exit(1);
}
printf("dining: started\n");
int i;
for (i = 0; i < 5; i++)
Sem_init(&forks[i], 1);
Sem_init(&print_lock, 1);
pthread_t p[5];
arg_t a[5];
for (i = 0; i < 5; i++) {
a[i].num_loops = atoi(argv[1]);
a[i].thread_id = i;
Pthread_create(&p[i], NULL, philosopher, &a[i]);
}
for (i = 0; i < 5; i++)
Pthread_join(p[i], NULL);
printf("dining: finished\n");
return 0;
}