sys/sys/spinlock.h

   1 /*
   2  * Copyright (c) 2005 Jeffrey M. Hsu.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Jeffrey M. Hsu.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of The DragonFly Project nor the names of its
  16  *    contributors may be used to endorse or promote products derived
  17  *    from this software without specific, prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  22  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  23  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  24  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  25  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  26  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  27  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #ifndef _SYS_SPINLOCK_H_
  34 #define _SYS_SPINLOCK_H_
  35
  36 /*
  37  * Note that the spinlock structure is retained whether we are SMP or not,
  38  * so structures using embedded spinlocks do not change size for SMP vs UP
  39  * builds.
  40  *
  41  * DragonFly spinlocks use a basic count/flag system.  It has been shown to
  42  * be the quickest way of doing things over time.  Shared spinlocks are
  43  * supported (and even relatively optimal).
  44  *
  45  * There is no description field.  The wait description is pulled from
  46  * __func__ if the lock cannot be instantly obtained.
  47  */
  48 struct spinlock {
  49         int counta;
  50         int countb;
  51 };
  52
  53 #define SPINLOCK_INITIALIZER(head, d)   { 0, 0 }
  54
  55 #define SPINLOCK_SHARED                 0x80000000
  56 #define SPINLOCK_EXCLWAIT               0x00100000 /* high bits counter */
  57 #define SPINLOCK_EXCLWAIT_MASK          0x7FF00000
  58 #define SPINLOCK_EXCLWAIT_SHIFT         20
  59
  60 #endif
  61