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add user app for philosopher with semaphore, pthread, etc.

main
chyyuu 8 years ago
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commit
b12791a169
1 changed files with 63 additions and 0 deletions
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      related_info/lab7/semaphore_condition/philosophers-with-semaphore.c

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related_info/lab7/semaphore_condition/philosophers-with-semaphore.c View File

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/* Philosophers.c - Demonstrate the semaphore solution to the dining
philosophers problem. The Room semaphore is neede to prevent all
philosophers from entering the room and grabbing their left most fork
at the same time, which would lead to deadlock. The Room sempahore
can be enabled by specifying a command line argument. */
#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
typedef enum { False=0, True=1 } bool ;
#define N 5 /* Number of times each philosopher tries to eat */
#define P 3 /* Number of philosophers */
sem_t Room;
sem_t Fork[P];
bool Switch ;
void *tphilosopher(void *ptr) {
int i, k = *((int *) ptr);
for(i = 1; i <= N; i++) {
printf("%*cThink %d %d\n", k*4, ' ', k, i);
if(Switch) {
sem_wait(&Room) ;
}
sem_wait(&Fork[k]) ;
sem_wait(&Fork[(k+1) % P]) ;
printf("%*cEat %d %d\n", k*4, ' ', k, i);
sem_post(&Fork[k]) ;
sem_post(&Fork[(k+1) % P]) ;
if(Switch) {
sem_post(&Room) ;
}
}
pthread_exit(0);
}
int main(int argc, char * argv[]) {
int i, targ[P];
pthread_t thread[P];
sem_init(&Room, 0, P-1);
Switch = (argc > 1); /* Room semaphore on/off */
printf("Switch=%s\n",(Switch?"true":"false"));
for(i=0;i<P;i++) {
sem_init(&Fork[i], 0, 1);
}
for(i=0;i<P;i++) {
targ[i] = i;
pthread_create(&thread[i], NULL, &tphilosopher,(void *) &targ[i]);
}
for(i=0;i<P;i++) {
pthread_join(thread[i], NULL);
}
for(i=0;i<P;i++) {
sem_destroy(&Fork[i]);
}
sem_destroy(&Room);
return 0;
}
/* Please note that the checks on the return value of the system calls
have been omitted to avoid cluttering the code. However, system calls
can and will fail, in which case the results are unpredictable. */

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