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  1. /*
  2.  * Copyright (C) 2001-2004 Jakub Jermar
  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 <synch/spinlock.h>
  30. #include <arch/atomic.h>
  31. #include <arch/barrier.h>
  32. #include <arch.h>
  33. #include <preemption.h>
  34. #include <print.h>
  35. #include <debug.h>
  36.  
  37. #ifdef __SMP__
  38.  
  39. /** Initialize spinlock
  40.  *
  41.  * Initialize spinlock.
  42.  *
  43.  * @param sl Pointer to spinlock_t structure.
  44.  */
  45. void spinlock_initialize(spinlock_t *sl)
  46. {
  47.     sl->val = 0;
  48. }
  49.  
  50. #ifdef DEBUG_SPINLOCK
  51. /** Lock spinlock
  52.  *
  53.  * Lock spinlock.
  54.  * This version has limitted ability to report
  55.  * possible occurence of deadlock.
  56.  *
  57.  * @param sl Pointer to spinlock_t structure.
  58.  */
  59. void spinlock_lock(spinlock_t *sl)
  60. {
  61.     int i = 0;
  62.     __address caller = ((__u32 *) &sl)[-1];
  63.  
  64.     preemption_disable();
  65.     while (test_and_set(&sl->val)) {
  66.         if (i++ > 300000) {
  67.             printf("cpu%d: looping on spinlock %X, caller=%X\n", CPU->id, sl, caller);
  68.             i = 0;
  69.         }
  70.     }
  71.  
  72.     /*
  73.      * Prevent critical section code from bleeding out this way up.
  74.      */
  75.     CS_ENTER_BARRIER();
  76.  
  77. }
  78.  
  79. #else
  80.  
  81. /** Lock spinlock
  82.  *
  83.  * Lock spinlock.
  84.  *
  85.  * @param sl Pointer to spinlock_t structure.
  86.  */
  87. void spinlock_lock(spinlock_t *sl)
  88. {
  89.     preemption_disable();
  90.  
  91.     /*
  92.      * Each architecture has its own efficient/recommended
  93.      * implementation of spinlock.
  94.      */
  95.     spinlock_arch(&sl->val);
  96.  
  97.     /*
  98.      * Prevent critical section code from bleeding out this way up.
  99.      */
  100.     CS_ENTER_BARRIER();
  101. }
  102. #endif
  103.  
  104. /** Lock spinlock conditionally
  105.  *
  106.  * Lock spinlock conditionally.
  107.  * If the spinlock is not available at the moment,
  108.  * signal failure.
  109.  *
  110.  * @param sl Pointer to spinlock_t structure.
  111.  *
  112.  * @return Zero on failure, non-zero otherwise.
  113.  */
  114. int spinlock_trylock(spinlock_t *sl)
  115. {
  116.     int rc;
  117.    
  118.     preemption_disable();
  119.     rc = !test_and_set(&sl->val);
  120.  
  121.     /*
  122.      * Prevent critical section code from bleeding out this way up.
  123.      */
  124.     CS_ENTER_BARRIER();
  125.  
  126.     if (!rc)
  127.         preemption_enable();
  128.    
  129.     return rc;
  130. }
  131.  
  132. /** Unlock spinlock
  133.  *
  134.  * Unlock spinlock.
  135.  *
  136.  * @param sl Pointer to spinlock_t structure.
  137.  */
  138. void spinlock_unlock(spinlock_t *sl)
  139. {
  140.     ASSERT(sl->val != 0);
  141.  
  142.     /*
  143.      * Prevent critical section code from bleeding out this way down.
  144.      */
  145.     CS_LEAVE_BARRIER();
  146.    
  147.     sl->val = 0;
  148.     preemption_enable();
  149. }
  150.  
  151. #endif
  152.