| 1 | #include <unistd.h> |
| 2 | #include <stdio.h> |
| 3 | #include <semaphore.h> |
| 4 | |
| 5 | static int db = 42; |
| 6 | static int NbL = 0; |
| 7 | sem_t mutex; |
| 8 | sem_t redact; |
| 9 | |
| 10 | static void *lecteur(void *arg) |
| 11 | { |
| 12 | while (1) { |
| 13 | sem_wait(&mutex); |
| 14 | if (NbL == 0) |
| 15 | sem_wait(&redact); |
| 16 | NbL++; |
| 17 | sem_post(&mutex); |
| 18 | // lecture de la base |
| 19 | sleep(1); |
| 20 | printf("lecteur bd=%d\n", db); |
| 21 | // fin de l’accès à la base |
| 22 | sem_wait(&mutex); |
| 23 | NbL--; |
| 24 | if (NbL == 0) |
| 25 | sem_post(&redact); |
| 26 | sem_post(&mutex); |
| 27 | } |
| 28 | return NULL; |
| 29 | } |
| 30 | |
| 31 | static void *redacteur(void *arg) |
| 32 | { |
| 33 | while (1) { |
| 34 | sem_wait(&redact); |
| 35 | // modifier les données de la base |
| 36 | db++; |
| 37 | printf("redacteur bd=%d\n", db); |
| 38 | sleep(2); |
| 39 | sem_post(&redact); |
| 40 | } |
| 41 | return NULL; |
| 42 | } |
| 43 | |
| 44 | int main() |
| 45 | { |
| 46 | |
| 47 | } |