/* Modified condition_wait that checks for cancellation.
Copyright (C) 1995, 1996, 2002 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <hurd/signal.h>
#include <pthread.h>
#include <pt-internal.h>
#include <assert.h> 

/* Just like condition_wait, but cancellable.  Returns true if cancelled.  */
int
hurd_condition_wait (pthread_cond_t *c, pthread_mutex_t *m)
{
  /* This function will be called by hurd_thread_cancel while we are blocked
     in the condition_wait.  We wake up all threads blocked on C,
     so our thread will wake up and notice the cancellation flag.  */
  struct __pthread *self = _pthread_self ();

  void cancel_me (void)
    {
      __pthread_spin_lock (&c->__lock);

      /* If self has been dequeued, self->prevp == 0 */
      if (self->prevp)
	{
	  __pthread_dequeue (self);
	  __pthread_spin_unlock (&c->__lock);
	  __pthread_wakeup (self);
	}
      else
	{
	  /* There is no thread to wakeup */
	  __pthread_spin_unlock (&c->__lock);
	}
    }
  
  struct hurd_sigstate *ss = _hurd_self_sigstate ();

  int cancel;

  assert (ss->intr_port == MACH_PORT_NULL); /* Sanity check for signal bugs. */


  /* Atomically enqueue our cproc on the condition variable's queue of
     waiters, and mark our sigstate to indicate that `cancel_me' must be
     called to wake us up.  We must hold the sigstate lock while acquiring
     the condition variable's lock and tweaking it, so that
     hurd_thread_cancel can never suspend us and then deadlock in
     condition_broadcast waiting for the condition variable's lock.  */

  __pthread_spin_lock (&ss->lock);
  __pthread_spin_lock (&c->__lock);
  cancel = ss->cancel;
  if (cancel)
    /* We were cancelled before doing anything.  Don't block at all.  */
    ss->cancel = 0;
  else
    {
      /* Put us on the queue so that condition_broadcast will know to wake
         us up.  */
      __pthread_enqueue (&c->__queue, self);
      /* Tell hurd_thread_cancel how to unblock us.  */
      ss->cancel_hook = &cancel_me;
    }
  __pthread_spin_unlock (&c->__lock);
  __pthread_spin_unlock (&ss->lock);

  if (cancel)
    {
      /* Cancelled on entry.  Just leave the mutex locked.  */
      m = NULL;
    }
  else
    {
      /* Now unlock the mutex and block until woken.  */
      pthread_mutex_unlock (m);
      __pthread_block (self);
    }

  __pthread_spin_lock (&ss->lock);
  /* Clear the hook, now that we are done blocking.  */
  ss->cancel_hook = NULL;
  /* Check the cancellation flag; we might have unblocked due to
     cancellation rather than a normal condition_signal or
     condition_broadcast (or we might have just happened to get cancelled
     right after waking up).  */
  cancel |= ss->cancel;
  ss->cancel = 0;
  __pthread_spin_unlock (&ss->lock);

  if (m)
    /* Reacquire the mutex and return.  */
    __pthread_mutex_lock (m);

  return cancel;
}