수다닷컴

//생각하는 철학자라는 소스인데 (a book on c)
//왜 에러가 나는 걸까요?/* The dining philosopher program. */
#includestdio.h
#includeunistd.h
#includestdlib.h
#includepthread.h /* for calloc() and exit() */
#define N 5 /* number of philosophers */
#define Busy_Eating 1
#define Busy_Thinking 1
#define Left(p) (p) /* chopstick macros */
#define Right(p) (((p) + 1) % N)
typedef int * semaphore;
semaphore chopstick[N]; /* global array */
int fork(void);
semaphore make_semaphore(void);
void philosopher(int me);
void pick_up(int me);
int pipe(int pd[2]);
void put_down(int me);
int read(int fd, void *buf, unsigned len);
void signal(semaphore s);
void sleep(unsigned seconds);
void wait(semaphore s);
int write(int fd, void *buf, unsigned len);
int main(void)
{
int i;
for (i = 0; i N; ++i) { /* put chopsticks on the table */
chopstick[i] = make_semaphore();
signal(chopstick[i]);
}
for (i = 0; i N - 1; ++i) /* create philosophers */
if (fork() == 0)
break;
philosopher(i); /* all executing concurrently */
return 0;
}
/* Acquire chopsticks, input is philosopher number. */
void pick_up(int me)
{
if (me == 0) {
wait(chopstick[Right(me)]);
printf(Philosopher %d picks up right chopstick\n, me);
sleep(1); /* simulate slow picking up to encourage deadlock */
wait(chopstick[Left(me)]);
printf(Philosopher %d picks up left chopstick\n, me);
}
else {
wait(chopstick[Left(me)]);
printf(Philosopher %d picks up left chopstick\n, me);
sleep(1); /* simulate slow picking up to encourage deadlock */
wait(chopstick[Right(me)]);
printf(Philosopher %d picks up right chopstick\n, me);
}
}
/* Relinquish chopsticks, input is the philosopher number. */
void put_down(int me)
{
signal(chopstick[Left(me)]);
signal(chopstick[Right(me)]);
}
/* Philosopher process, input is the philosopher number. */
void philosopher(int me)
{
char *s;
int i = 1;
for ( ; ; ++i) { /* forever */
pick_up(me);
s = i == 1 ? st : i == 2 ? nd : i == 3 ? rd : th;
printf(Philosopher %d eating for the %d%s time\n, me, i, s);
sleep(Busy_Eating);
put_down(me);
printf(Philosopher %d thinking\n, me);
sleep(Busy_Thinking);
}
}
semaphore make_semaphore(void)
{
int *sema;
sema = calloc(2, sizeof(int)); /* permanent storage */
pipe(sema);
return sema;
}
void wait(semaphore s)
{
int junk;
if (read(s[0], &junk, 1) = 0) {
printf(ERROR: wait() failed, check semaphore creation.\n);
exit(1);
}
}
void signal(semaphore s)
{
if (write(s[1], x, 1) = 0) {
printf(ERROR: write() failed, check semaphore creation.\n);
exit(1);
}
}

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