The source code for din_philo.c is shown below:
1 /*
2 * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All Rights Reserved.
3 * @(#)din_philo.c 1.4 (Oracle) 10/03/26
4 */
5
6 #include <pthread.h>
7 #include <stdio.h>
8 #include <unistd.h>
9 #include <stdlib.h>
10 #include <errno.h>
11 #include <assert.h>
12
13 #define PHILOS 5
14 #define DELAY 5000
15 #define FOOD 100
16
17 void *philosopher (void *id);
18 void grab_chopstick (int,
19 int,
20 char *);
21 void down_chopsticks (int,
22 int);
23 int food_on_table ();
24
25 pthread_mutex_t chopstick[PHILOS];
26 pthread_t philo[PHILOS];
27 pthread_mutex_t food_lock;
28 int sleep_seconds = 0;
29
30
31 int
32 main (int argn,
33 char **argv)
34 {
35 int i;
36
37 if (argn == 2)
38 sleep_seconds = atoi (argv[1]);
39
40 pthread_mutex_init (&food_lock, NULL);
41 for (i = 0; i < PHILOS; i++)
42 pthread_mutex_init (&chopstick[i], NULL);
43 for (i = 0; i < PHILOS; i++)
44 pthread_create (&philo[i], NULL, philosopher, (void *)i);
45 for (i = 0; i < PHILOS; i++)
46 pthread_join (philo[i], NULL);
47 return 0;
48 }
49
50 void *
51 philosopher (void *num)
52 {
53 int id;
54 int i, left_chopstick, right_chopstick, f;
55
56 id = (int)num;
57 printf ("Philosopher %d is done thinking and now ready to eat.\n", id);
58 right_chopstick = id;
59 left_chopstick = id + 1;
60
61 /* Wrap around the chopsticks. */
62 if (left_chopstick == PHILOS)
63 left_chopstick = 0;
64
65 while (f = food_on_table ()) {
66
67 /* Thanks to philosophers #1 who would like to take a nap
68 * before picking up the chopsticks, the other philosophers
69 * may be able to eat their dishes and not deadlock.
70 */
71 if (id == 1)
72 sleep (sleep_seconds);
73
74 grab_chopstick (id, right_chopstick, "right ");
75 grab_chopstick (id, left_chopstick, "left");
76
77 printf ("Philosopher %d: eating.\n", id);
78 usleep (DELAY * (FOOD - f + 1));
79 down_chopsticks (left_chopstick, right_chopstick);
80 }
81
82 printf ("Philosopher %d is done eating.\n", id);
83 return (NULL);
84 }
85
86 int
87 food_on_table ()
88 {
89 static int food = FOOD;
90 int myfood;
91
92 pthread_mutex_lock (&food_lock);
93 if (food > 0) {
94 food--;
95 }
96 myfood = food;
97 pthread_mutex_unlock (&food_lock);
98 return myfood;
99 }
100
101 void
102 grab_chopstick (int phil,
103 int c,
104 char *hand)
105 {
106 pthread_mutex_lock (&chopstick[c]);
107 printf ("Philosopher %d: got %s chopstick %d\n", phil, hand, c);
108 }
109
110 void
111 down_chopsticks (int c1,
112 int c2)
113 {
114 pthread_mutex_unlock (&chopstick[c1]);
115 pthread_mutex_unlock (&chopstick[c2]);
116 }