text: /*	$OpenBSD: mutex.h,v 1.6 2009/04/27 21:48:56 kettenis Exp $	*/
  /*
   * Copyright (c) 2004 Artur Grabowski <art@openbsd.org>
   * All rights reserved. 
   *
   * Redistribution and use in source and binary forms, with or without 
   * modification, are permitted provided that the following conditions 
   * are met: 
   *
   * 1. Redistributions of source code must retain the above copyright 
   *    notice, this list of conditions and the following disclaimer. 
   * 2. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission. 
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
   * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
   * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL  DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
   * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
   */
  /*
   * Portions copyright (c) 2010, Intel Corporation
   */
  
  #ifndef __MUTEX_H__
  #define __MUTEX_H__
  
  /*
   * A mutex is:
   *  - owned by a cpu.
   *  - non-recursive.
   *  - spinning.
   *  - not providing mutual exclusion between processes, only cpus.
   *  - providing interrupt blocking when necessary.
   *
   * Different mutexes can be nested, but not interleaved. This is ok:
   * "mtx_enter(foo); mtx_enter(bar); mtx_leave(bar); mtx_leave(foo);"
   * This is _not_ ok:
   * "mtx_enter(foo); mtx_enter(bar); mtx_leave(foo); mtx_leave(bar);"
   */
  
  struct mutex {
  	__volatile__ uint32_t mtx_lock;
  };
  
  /*
   * Some architectures need to do magic for the ipl, so they need a macro.
   */
  void mtx_init(struct mutex *);
  void mtx_enter(struct mutex *);
  void mtx_leave(struct mutex *);
  
  #endif  /* __MUTEX_H__ */
  