/* Changing pager attributes synchronously
   Copyright (C) 1994 Free Software Foundation

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

   This program 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
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */

#include "priv.h"
#include <assert.h>

/* Change the attributes of the memory object underlying pager P.
   Args MAY_CACHE and COPY_STRATEGY are as for 
   memory_object_change_atributes.  Wait for the kernel to report completion
   off WAIT is set.*/
void
pager_change_attributes (struct pager *p,
 			 boolean_t may_cache,
 			 memory_object_copy_strategy_t copy_strategy,
			 int wait)
{
  struct attribute_request *ar = 0;
  
  mutex_lock (&p->interlock);

  p->may_cache = may_cache;
  p->copy_strategy = copy_strategy;
  
  if (p->pager_state == NOTINIT)
    {
      mutex_unlock (&p->interlock);
      return;
    }

  if (wait)
    {
      for (ar = p->attribute_requests; ar; ar = ar->next)
	if (ar->may_cache == may_cache 
	    && ar->copy_strategy == copy_strategy)
	  {
	    ar->attrs_pending++;
	    ar->threads_waiting++;
	    break;
	  }
      if (!ar)
	{
	  ar = malloc (sizeof (struct attribute_request));
	  ar->may_cache = may_cache;
	  ar->copy_strategy = copy_strategy;
	  ar->attrs_pending = 1;
	  ar->threads_waiting = 1;
	  ar->next = p->attribute_requests;
	  if (ar->next)
	    ar->next->prevp = &ar->next;
	  ar->prevp = &p->attribute_requests;
	  p->attribute_requests = ar;
	}
    }      

  memory_object_change_attributes (p->memobjcntl, may_cache, copy_strategy,
				   wait ? p->port.port_right : MACH_PORT_NULL);
  
  if (wait)
    {
      while (ar->attrs_pending)
	condition_wait (&p->wakeup, &p->interlock);
      if (!--ar->threads_waiting)
	{
	  *ar->prevp = ar->next;
	  free (ar);
	}
    }
  
  mutex_unlock (&p->interlock);
}