gnu/dist/gdb6/gdb/testsuite/gdb.threads/linux-dp.c

   1 /* linux-dp.c --- dining philosophers, on LinuxThreads
   2    Jim Blandy <jimb@cygnus.com> --- March 1999  */
   3
   4 /* It's okay to edit this file and shift line numbers around.  The
   5    tests use gdb_get_line_number to find source locations, so they
   6    don't depend on having certain line numbers in certain places.  */
   7
   8 #include <stdarg.h>
   9 #include <stdlib.h>
  10 #include <stdio.h>
  11 #include <pthread.h>
  12 #include <sys/time.h>
  13 #include <sys/types.h>
  14
  15 /* The number of philosophers at the table.  */
  16 int num_philosophers;
  17
  18 /* Mutex ordering -
  19    If you want to lock a mutex M, all the mutexes you have locked
  20    already must appear before M on this list.
  21
  22    fork_mutex[0]
  23    fork_mutex[1]
  24    ...
  25    fork_mutex[num_philosophers - 1]
  26    stdout_mutex
  27    random_mutex
  28 */
  29
  30 /* You must hold this mutex while writing to stdout.  */
  31 pthread_mutex_t stdout_mutex;
  32
  33 /* You must hold this mutex while calling any of the random number
  34    generation routines.  */
  35 pthread_mutex_t random_mutex;
  36
  37 /* array of mutexes, one for each fork; fork_mutex[i] is to the left
  38    of philosopher i.  A philosopher is holding fork i iff his/her
  39    thread has locked fork_mutex[i].  */
  40 pthread_mutex_t *fork_mutex;
  41
  42 /* array of threads, one representing each philosopher.  */
  43 pthread_t *philosophers;
  44
  45 void *
  46 xmalloc (size_t n)
  47 {
  48   void *p = malloc (n);
  49
  50   if (! p)
  51     {
  52       fprintf (stderr, "out of memory\n");
  53       exit (2);
  54     }
  55
  56   return p;
  57 }
  58
  59 void
  60 shared_printf (char *format, ...)
  61 {
  62   va_list ap;
  63
  64   va_start (ap, format);
  65   pthread_mutex_lock (&stdout_mutex);
  66   vprintf (format, ap);
  67   pthread_mutex_unlock (&stdout_mutex);
  68   va_end (ap);
  69 }
  70
  71 int
  72 shared_random ()
  73 {
  74   static unsigned int seed;
  75   int result;
  76
  77   pthread_mutex_lock (&random_mutex);
  78   result = rand_r (&seed);
  79   pthread_mutex_unlock (&random_mutex);
  80   return result;
  81 }
  82
  83 void
  84 my_usleep (long usecs)
  85 {
  86   struct timeval timeout;
  87
  88   timeout.tv_sec = usecs / 1000000;
  89   timeout.tv_usec = usecs % 1000000;
  90
  91   select (0, 0, 0, 0, &timeout);
  92 }
  93
  94 void
  95 random_delay ()
  96 {
  97   my_usleep ((shared_random () % 2000) * 100);
  98 }
  99
 100 void
 101 print_philosopher (int n, char left, char right)
 102 {
 103   int i;
 104
 105   shared_printf ("%*s%c %d %c\n", (n * 4) + 2, "", left, n, right);
 106 }
 107
 108 void *
 109 philosopher (void *data)
 110 {
 111   int n = * (int *) data;
 112
 113   print_philosopher (n, '_', '_');
 114
 115 #if 1
 116   if (n == num_philosophers - 1)
 117     for (;;)
 118       {
 119         /* The last philosopher is different.  He goes for his right
 120            fork first, so there is no cycle in the mutex graph.  */
 121
 122         /* Grab the right fork.  */
 123         pthread_mutex_lock (&fork_mutex[(n + 1) % num_philosophers]);
 124         print_philosopher (n, '_', '!');
 125         random_delay ();
 126
 127         /* Then grab the left fork. */
 128         pthread_mutex_lock (&fork_mutex[n]);
 129         print_philosopher (n, '!', '!');
 130         random_delay ();
 131
 132         print_philosopher (n, '_', '_');
 133         pthread_mutex_unlock (&fork_mutex[n]);
 134         pthread_mutex_unlock (&fork_mutex[(n + 1) % num_philosophers]);
 135         random_delay ();
 136       }
 137   else
 138 #endif
 139     for (;;)
 140       {
 141         /* Grab the left fork. */
 142         pthread_mutex_lock (&fork_mutex[n]);
 143         print_philosopher (n, '!', '_');
 144         random_delay ();
 145
 146         /* Then grab the right fork.  */
 147         pthread_mutex_lock (&fork_mutex[(n + 1) % num_philosophers]);
 148         print_philosopher (n, '!', '!');
 149         random_delay ();
 150
 151         print_philosopher (n, '_', '_');
 152         pthread_mutex_unlock (&fork_mutex[n]);
 153         pthread_mutex_unlock (&fork_mutex[(n + 1) % num_philosophers]);
 154         random_delay ();
 155       }
 156
 157   return (void *) 0;
 158 }
 159
 160 int
 161 main (int argc, char **argv)
 162 {
 163   num_philosophers = 5;
 164
 165   /* Set up the mutexes.  */
 166   {
 167     pthread_mutexattr_t ma;
 168     int i;
 169
 170     pthread_mutexattr_init (&ma);
 171     pthread_mutex_init (&stdout_mutex, &ma);
 172     pthread_mutex_init (&random_mutex, &ma);
 173     fork_mutex = xmalloc (num_philosophers * sizeof (fork_mutex[0]));
 174     for (i = 0; i < num_philosophers; i++)
 175       pthread_mutex_init (&fork_mutex[i], &ma);
 176     pthread_mutexattr_destroy (&ma);
 177   }
 178
 179   /* Set off the threads.  */
 180   {
 181     int i;
 182     int *numbers = xmalloc (num_philosophers * sizeof (*numbers));
 183     pthread_attr_t ta;
 184
 185     philosophers = xmalloc (num_philosophers * sizeof (*philosophers));
 186
 187     pthread_attr_init (&ta);
 188
 189     for (i = 0; i < num_philosophers; i++)
 190       {
 191         numbers[i] = i;
 192         /* linuxthreads.exp: create philosopher */
 193         pthread_create (&philosophers[i], &ta, philosopher, &numbers[i]);
 194       }
 195
 196     pthread_attr_destroy (&ta);
 197   }
 198
 199   /* linuxthreads.exp: info threads 2 */
 200   sleep (1000000);
 201
 202   /* Drink yourself into oblivion.  */
 203   for (;;)
 204     sleep (1000000);
 205
 206   return 0;
 207 }