text: /*	$OpenBSD: lock.h,v 1.1 2004/06/25 11:03:28 art Exp $	*/
  /*	$NetBSD: lock.h,v 1.1.2.2 2000/05/03 14:40:55 sommerfeld Exp $	*/
  
  /*-
   * Copyright (c) 2000 The NetBSD Foundation, Inc.
   * All rights reserved.
   *
   * This code is derived from software contributed to The NetBSD Foundation
   * by Jason R. Thorpe.
   *
   * 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. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the NetBSD
   *	Foundation, Inc. and its contributors.
   * 4. Neither the name of The NetBSD Foundation nor the names of its
   *    contributors may be used to endorse or promote products derived
   *    from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   * ``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 FOUNDATION OR CONTRIBUTORS
   * 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.
   */
  
  /*
   * Machine-dependent spin lock operations.
   */
  
  #ifndef _AMD64_LOCK_H_
  #define	_AMD64_LOCK_H_
  
  typedef	__volatile int		__cpu_simple_lock_t;
  
  #define	__SIMPLELOCK_LOCKED	1
  #define	__SIMPLELOCK_UNLOCKED	0
  
  /*
   * compiler barrier: prevent reordering of instructions.
   * XXX something similar will move to <sys/cdefs.h>
   * or thereabouts.
   * This prevents the compiler from reordering code around
   * this "instruction", acting as a sequence point for code generation.
   */
  
  #define __lockbarrier() __asm __volatile("": : :"memory")
  
  #ifdef LOCKDEBUG
  
  extern void __cpu_simple_lock_init(__cpu_simple_lock_t *);
  extern void __cpu_simple_lock(__cpu_simple_lock_t *);
  extern int __cpu_simple_lock_try(__cpu_simple_lock_t *);
  extern void __cpu_simple_unlock(__cpu_simple_lock_t *);
  
  #else
  
  #include <machine/atomic.h>
  
  static __inline void __cpu_simple_lock_init(__cpu_simple_lock_t *)
  	__attribute__((__unused__));
  static __inline void __cpu_simple_lock(__cpu_simple_lock_t *)
  	__attribute__((__unused__));
  static __inline int __cpu_simple_lock_try(__cpu_simple_lock_t *)
  	__attribute__((__unused__));
  static __inline void __cpu_simple_unlock(__cpu_simple_lock_t *)
  	__attribute__((__unused__));
  
  static __inline void
  __cpu_simple_lock_init(__cpu_simple_lock_t *lockp)
  {
  	*lockp = __SIMPLELOCK_UNLOCKED;
  	__lockbarrier();
  }
  
  static __inline void
  __cpu_simple_lock(__cpu_simple_lock_t *lockp)
  {
  	while (x86_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
  	    == __SIMPLELOCK_LOCKED) {
  		continue;	/* spin */
  	}
  	__lockbarrier();
  }
  
  static __inline int
  __cpu_simple_lock_try(__cpu_simple_lock_t *lockp)
  {
  	int r = (x86_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
  	    == __SIMPLELOCK_UNLOCKED);
  
  	__lockbarrier();
  
  	return (r);
  }
  
  static __inline void
  __cpu_simple_unlock(__cpu_simple_lock_t *lockp)
  {
  	__lockbarrier();
  	*lockp = __SIMPLELOCK_UNLOCKED;
  }
  
  #endif /* !LOCKDEBUG */
  
  #endif /* _AMD64_LOCK_H_ */
  