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+/* linux-dp.c --- dining philosophers, on LinuxThreads
+ Jim Blandy <jimb@cygnus.com> --- March 1999 */
+
+/* It's okay to edit this file and shift line numbers around. The
+ tests use gdb_get_line_number to find source locations, so they
+ don't depend on having certain line numbers in certain places. */
+
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <pthread.h>
+#include <sys/time.h>
+#include <sys/types.h>
+
+/* The number of philosophers at the table. */
+int num_philosophers;
+
+/* Mutex ordering -
+ If you want to lock a mutex M, all the mutexes you have locked
+ already must appear before M on this list.
+
+ fork_mutex[0]
+ fork_mutex[1]
+ ...
+ fork_mutex[num_philosophers - 1]
+ stdout_mutex
+ random_mutex
+*/
+
+/* You must hold this mutex while writing to stdout. */
+pthread_mutex_t stdout_mutex;
+
+/* You must hold this mutex while calling any of the random number
+ generation routines. */
+pthread_mutex_t random_mutex;
+
+/* array of mutexes, one for each fork; fork_mutex[i] is to the left
+ of philosopher i. A philosopher is holding fork i iff his/her
+ thread has locked fork_mutex[i]. */
+pthread_mutex_t *fork_mutex;
+
+/* array of threads, one representing each philosopher. */
+pthread_t *philosophers;
+
+void *
+xmalloc (size_t n)
+{
+ void *p = malloc (n);
+
+ if (! p)
+ {
+ fprintf (stderr, "out of memory\n");
+ exit (2);
+ }
+
+ return p;
+}
+
+void
+shared_printf (char *format, ...)
+{
+ va_list ap;
+
+ va_start (ap, format);
+ pthread_mutex_lock (&stdout_mutex);
+ vprintf (format, ap);
+ pthread_mutex_unlock (&stdout_mutex);
+ va_end (ap);
+}
+
+int
+shared_random ()
+{
+ static unsigned int seed;
+ int result;
+
+ pthread_mutex_lock (&random_mutex);
+ result = rand_r (&seed);
+ pthread_mutex_unlock (&random_mutex);
+ return result;
+}
+
+void
+my_usleep (long usecs)
+{
+ struct timeval timeout;
+
+ timeout.tv_sec = usecs / 1000000;
+ timeout.tv_usec = usecs % 1000000;
+
+ select (0, 0, 0, 0, &timeout);
+}
+
+void
+random_delay ()
+{
+ my_usleep ((shared_random () % 2000) * 100);
+}
+
+void
+print_philosopher (int n, char left, char right)
+{
+ int i;
+
+ shared_printf ("%*s%c %d %c\n", (n * 4) + 2, "", left, n, right);
+}
+
+void *
+philosopher (void *data)
+{
+ int n = * (int *) data;
+
+ print_philosopher (n, '_', '_');
+
+#if 1
+ if (n == num_philosophers - 1)
+ for (;;)
+ {
+ /* The last philosopher is different. He goes for his right
+ fork first, so there is no cycle in the mutex graph. */
+
+ /* Grab the right fork. */
+ pthread_mutex_lock (&fork_mutex[(n + 1) % num_philosophers]);
+ print_philosopher (n, '_', '!');
+ random_delay ();
+
+ /* Then grab the left fork. */
+ pthread_mutex_lock (&fork_mutex[n]);
+ print_philosopher (n, '!', '!');
+ random_delay ();
+
+ print_philosopher (n, '_', '_');
+ pthread_mutex_unlock (&fork_mutex[n]);
+ pthread_mutex_unlock (&fork_mutex[(n + 1) % num_philosophers]);
+ random_delay ();
+ }
+ else
+#endif
+ for (;;)
+ {
+ /* Grab the left fork. */
+ pthread_mutex_lock (&fork_mutex[n]);
+ print_philosopher (n, '!', '_');
+ random_delay ();
+
+ /* Then grab the right fork. */
+ pthread_mutex_lock (&fork_mutex[(n + 1) % num_philosophers]);
+ print_philosopher (n, '!', '!');
+ random_delay ();
+
+ print_philosopher (n, '_', '_');
+ pthread_mutex_unlock (&fork_mutex[n]);
+ pthread_mutex_unlock (&fork_mutex[(n + 1) % num_philosophers]);
+ random_delay ();
+ }
+}
+
+int
+main (int argc, char **argv)
+{
+ num_philosophers = 5;
+
+ /* Set up the mutexes. */
+ {
+ pthread_mutexattr_t ma;
+ int i;
+
+ pthread_mutexattr_init (&ma);
+ pthread_mutex_init (&stdout_mutex, &ma);
+ pthread_mutex_init (&random_mutex, &ma);
+ fork_mutex = xmalloc (num_philosophers * sizeof (fork_mutex[0]));
+ for (i = 0; i < num_philosophers; i++)
+ pthread_mutex_init (&fork_mutex[i], &ma);
+ pthread_mutexattr_destroy (&ma);
+ }
+
+ /* Set off the threads. */
+ {
+ int i;
+ int *numbers = xmalloc (num_philosophers * sizeof (*numbers));
+ pthread_attr_t ta;
+
+ philosophers = xmalloc (num_philosophers * sizeof (*philosophers));
+
+ pthread_attr_init (&ta);
+
+ for (i = 0; i < num_philosophers; i++)
+ {
+ numbers[i] = i;
+ /* linuxthreads.exp: create philosopher */
+ pthread_create (&philosophers[i], &ta, philosopher, &numbers[i]);
+ }
+
+ pthread_attr_destroy (&ta);
+ }
+
+ /* linuxthreads.exp: info threads 2 */
+ sleep (1000000);
+
+ /* Drink yourself into oblivion. */
+ for (;;)
+ sleep (1000000);
+
+ return 0;
+}