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  1. /*
  2.  * Copyright (C) 2005 Martin Decky
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. #include <arch/mm/asid.h>
  30. #include <synch/spinlock.h>
  31. #include <arch.h>
  32. #include <debug.h>
  33.  
  34. #define ASIDS   256
  35.  
  36. static spinlock_t asid_usage_lock;
  37. static count_t asid_usage[ASIDS];   /**< Usage tracking array for ASIDs */
  38.  
  39. /** Get ASID
  40.  *
  41.  * Get the least used ASID.
  42.  *
  43.  * @return ASID
  44.  */
  45. asid_t asid_get(void)
  46. {
  47.     pri_t pri;
  48.     int i, j;
  49.     count_t min;
  50.    
  51.     min = (unsigned) -1;
  52.    
  53.     pri = cpu_priority_high();
  54.     spinlock_lock(&asid_usage_lock);
  55.    
  56.     for (i=0, j = 0; (i<ASIDS); i++) {
  57.         if (asid_usage[i] < min) {
  58.             j = i;
  59.             min = asid_usage[i];
  60.             if (!min)
  61.                 break;
  62.         }
  63.     }
  64.  
  65.     asid_usage[i]++;
  66.  
  67.     spinlock_unlock(&asid_usage_lock);
  68.     cpu_priority_restore(pri);
  69.  
  70.     return i;
  71. }
  72.  
  73. /** Release ASID
  74.  *
  75.  * Release ASID by decrementing its usage count.
  76.  *
  77.  * @param asid ASID.
  78.  */
  79. void asid_put(asid_t asid)
  80. {
  81.     pri_t pri;
  82.  
  83.     pri = cpu_priority_high();
  84.     spinlock_lock(&asid_usage_lock);
  85.  
  86.     ASSERT(asid_usage[asid] > 0);
  87.     asid_usage[asid]--;
  88.  
  89.     spinlock_unlock(&asid_usage_lock);
  90.     cpu_priority_restore(pri);
  91. }
  92.