timer_routines.c

glibc 2.9,最新版的C语言库函数

/* Handle a timer which is supposed to go off now.  */
static void
thread_expire_timer (struct thread_node *self, struct timer_node *timer)
{
  self->current_timer = timer; /* Lets timer_delete know timer is running. */

  pthread_mutex_unlock (&__timer_mutex);

  switch (__builtin_expect (timer->event.sigev_notify, SIGEV_SIGNAL))
    {
    case SIGEV_NONE:
      break;

    case SIGEV_SIGNAL:
#ifdef __NR_rt_sigqueueinfo
      {
	siginfo_t info;

	/* First, clear the siginfo_t structure, so that we don't pass our
	   stack content to other tasks.  */
	memset (&info, 0, sizeof (siginfo_t));
	/* We must pass the information about the data in a siginfo_t
           value.  */
	info.si_signo = timer->event.sigev_signo;
	info.si_code = SI_TIMER;
	info.si_pid = timer->creator_pid;
	info.si_uid = getuid ();
	info.si_value = timer->event.sigev_value;

	INLINE_SYSCALL (rt_sigqueueinfo, 3, info.si_pid, info.si_signo, &info);
      }
#else
      if (pthread_kill (self->captured, timer->event.sigev_signo) != 0)
	{
	  if (pthread_kill (self->id, timer->event.sigev_signo) != 0)
	    abort ();
        }
#endif
      break;

    case SIGEV_THREAD:
      timer->event.sigev_notify_function (timer->event.sigev_value);
      break;

    default:
      assert (! "unknown event");
      break;
    }

  pthread_mutex_lock (&__timer_mutex);

  self->current_timer = 0;

  pthread_cond_broadcast (&self->cond);
}


/* Thread function; executed by each timer thread. The job of this
   function is to wait on the thread's timer queue and expire the
   timers in chronological order as close to their scheduled time as
   possible.  */
static void
__attribute__ ((noreturn))
thread_func (void *arg)
{
  struct thread_node *self = arg;

  /* Register cleanup handler, in case rogue application terminates
     this thread.  (This cannot happen to __timer_signal_thread, which
     doesn't invoke application callbacks). */

  pthread_cleanup_push (thread_cleanup, self);

  pthread_mutex_lock (&__timer_mutex);

  while (1)
    {
      struct list_links *first;
      struct timer_node *timer = NULL;

      /* While the timer queue is not empty, inspect the first node.  */
      first = list_first (&self->timer_queue);
      if (first != list_null (&self->timer_queue))
	{
	  struct timespec now;

	  timer = timer_links2ptr (first);

	  /* This assumes that the elements of the list of one thread
	     are all for the same clock.  */
	  clock_gettime (timer->clock, &now);

	  while (1)
	    {
	      /* If the timer is due or overdue, remove it from the queue.
		 If it's a periodic timer, re-compute its new time and
		 requeue it.  Either way, perform the timer expiry. */
	      if (timespec_compare (&now, &timer->expirytime) < 0)
		break;

	      list_unlink_ip (first);

	      if (__builtin_expect (timer->value.it_interval.tv_sec, 0) != 0
		  || timer->value.it_interval.tv_nsec != 0)
		{
		  timer->overrun_count = 0;
		  timespec_add (&timer->expirytime, &timer->expirytime,
				&timer->value.it_interval);
		  while (timespec_compare (&timer->expirytime, &now) < 0)
		    {
		      timespec_add (&timer->expirytime, &timer->expirytime,
				    &timer->value.it_interval);
		      if (timer->overrun_count < DELAYTIMER_MAX)
			++timer->overrun_count;
		    }
		  __timer_thread_queue_timer (self, timer);
		}

	      thread_expire_timer (self, timer);

	      first = list_first (&self->timer_queue);
	      if (first == list_null (&self->timer_queue))
		break;

	      timer = timer_links2ptr (first);
	    }
	}

      /* If the queue is not empty, wait until the expiry time of the
	 first node.  Otherwise wait indefinitely.  Insertions at the
	 head of the queue must wake up the thread by broadcasting
	 this condition variable.  */
      if (timer != NULL)
	pthread_cond_timedwait (&self->cond, &__timer_mutex,
				&timer->expirytime);
      else
	pthread_cond_wait (&self->cond, &__timer_mutex);
    }
  /* This macro will never be executed since the while loop loops
     forever - but we have to add it for proper nesting.  */
  pthread_cleanup_pop (1);
}


/* Enqueue a timer in wakeup order in the thread's timer queue.
   Returns 1 if the timer was inserted at the head of the queue,
   causing the queue's next wakeup time to change. */

int
__timer_thread_queue_timer (struct thread_node *thread,
			    struct timer_node *insert)
{
  struct list_links *iter;
  int athead = 1;

  for (iter = list_first (&thread->timer_queue);
       iter != list_null (&thread->timer_queue);
        iter = list_next (iter))
    {
      struct timer_node *timer = timer_links2ptr (iter);

      if (timespec_compare (&insert->expirytime, &timer->expirytime) < 0)
	  break;
      athead = 0;
    }

  list_insbefore (iter, &insert->links);
  return athead;
}


/* Start a thread and associate it with the given thread node.  Global
   lock must be held by caller.  */
int
__timer_thread_start (struct thread_node *thread)
{
  int retval = 1;

  assert (!thread->exists);
  thread->exists = 1;

  if (pthread_create (&thread->id, &thread->attr,
		      (void *(*) (void *)) thread_func, thread) != 0)
    {
      thread->exists = 0;
      retval = -1;
    }

  return retval;
}


void
__timer_thread_wakeup (struct thread_node *thread)
{
  pthread_cond_broadcast (&thread->cond);
}


/* Compare two pthread_attr_t thread attributes for exact equality.
   Returns 1 if they are equal, otherwise zero if they are not equal
   or contain illegal values.  This version is NPTL-specific for
   performance reason.  One could use the access functions to get the
   values of all the fields of the attribute structure.  */
static int
thread_attr_compare (const pthread_attr_t *left, const pthread_attr_t *right)
{
  struct pthread_attr *ileft = (struct pthread_attr *) left;
  struct pthread_attr *iright = (struct pthread_attr *) right;

  return (ileft->flags == iright->flags
	  && ileft->schedpolicy == iright->schedpolicy
	  && (ileft->schedparam.sched_priority
	      == iright->schedparam.sched_priority)
	  && ileft->guardsize == iright->guardsize
	  && ileft->stackaddr == iright->stackaddr
	  && ileft->stacksize == iright->stacksize
	  && ((ileft->cpuset == NULL && iright->cpuset == NULL)
	      || (ileft->cpuset != NULL && iright->cpuset != NULL
		  && ileft->cpusetsize == iright->cpusetsize
		  && memcmp (ileft->cpuset, iright->cpuset,
			     ileft->cpusetsize) == 0)));
}


/* Search the list of active threads and find one which has matching
   attributes.  Global mutex lock must be held by caller.  */
struct thread_node *
__timer_thread_find_matching (const pthread_attr_t *desired_attr,
			      clockid_t desired_clock_id)
{
  struct list_links *iter = list_first (&thread_active_list);

  while (iter != list_null (&thread_active_list))
    {
      struct thread_node *candidate = thread_links2ptr (iter);

      if (thread_attr_compare (desired_attr, &candidate->attr)
	  && desired_clock_id == candidate->clock_id)
	return candidate;

      iter = list_next (iter);
    }

  return NULL;
}


/* Grab a free timer structure from the global free list.  The global
   lock must be held by the caller.  */
struct timer_node *
__timer_alloc (void)
{
  struct list_links *node = list_first (&timer_free_list);

  if (node != list_null (&timer_free_list))
    {
      struct timer_node *timer = timer_links2ptr (node);
      list_unlink_ip (node);
      timer->inuse = TIMER_INUSE;
      timer->refcount = 1;
      return timer;
    }

  return NULL;
}


/* Return a timer structure to the global free list.  The global lock
   must be held by the caller.  */
void
__timer_dealloc (struct timer_node *timer)
{
  assert (timer->refcount == 0);
  timer->thread = NULL;	/* Break association between timer and thread.  */
  timer->inuse = TIMER_FREE;
  list_append (&timer_free_list, &timer->links);
}


/* Thread cancellation handler which unlocks a mutex.  */
void
__timer_mutex_cancel_handler (void *arg)
{
  pthread_mutex_unlock (arg);
}