Function search

examples/libc/ex3.c:77–162

/* This is the search routine that is executed in each thread */

void *search(void *arg)
{
  int num = (int) arg;
  int i, j, ntries;
  pthread_t tid;

  /* get the calling thread ID */
  tid = pthread_self();

  /* use the thread ID to set the seed for the random number generator */
  /* Since srand and rand are not thread-safe, serialize with lock */

  /* Try to lock the mutex lock --
     if locked, check to see if the thread has been cancelled
     if not locked then continue */
  while (pthread_mutex_trylock(&lock) == EBUSY)
    pthread_testcancel();

  srand((int)tid);
  i = rand() & 0xFFFFFF;
  pthread_mutex_unlock(&lock);
  ntries = 0;

  /* Set the cancellation parameters --
     - Enable thread cancellation
     - Defer the action of the cancellation */

  pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
  pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);

  while (started < NUM_THREADS)
    sched_yield ();

  /* Push the cleanup routine (print_it) onto the thread
     cleanup stack.  This routine will be called when the
     thread is cancelled.  Also note that the pthread_cleanup_push
     call must have a matching pthread_cleanup_pop call.  The
     push and pop calls MUST be at the same lexical level
     within the code */

  /* Pass address of `ntries' since the current value of `ntries' is not
     the one we want to use in the cleanup function */

  pthread_cleanup_push(print_it, (void *)&ntries);

  /* Loop forever */
  while (1) {
    i = (i + 1) & 0xFFFFFF;
    ntries++;

    /* Does the random number match the target number? */
    if (num == i) {
      /* Try to lock the mutex lock --
         if locked, check to see if the thread has been cancelled
         if not locked then continue */
      while (pthread_mutex_trylock(&lock) == EBUSY)
        pthread_testcancel();