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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. #include <symtab.h>
  37.  
  38. #ifdef CONFIG_SMP
  39.  
  40. /** Initialize spinlock
  41.  *
  42.  * Initialize spinlock.
  43.  *
  44.  * @param sl Pointer to spinlock_t structure.
  45.  */
  46. void spinlock_initialize(spinlock_t *sl, char *name)
  47. {
  48.     sl->val = 0;
  49. #ifdef CONFIG_DEBUG_SPINLOCK
  50.     sl->name = name;
  51. #endif 
  52. }
  53.  
  54. #ifdef CONFIG_DEBUG_SPINLOCK
  55. /** Lock spinlock
  56.  *
  57.  * Lock spinlock.
  58.  * This version has limitted ability to report
  59.  * possible occurence of deadlock.
  60.  *
  61.  * @param sl Pointer to spinlock_t structure.
  62.  */
  63. void spinlock_lock(spinlock_t *sl)
  64. {
  65.     int i = 0;
  66.     __address caller = ((__address *) &sl)[-1];
  67.     char *symbol;
  68.  
  69.     preemption_disable();
  70.     while (test_and_set(&sl->val)) {
  71.         if (i++ > 300000) {
  72.             printf("cpu%d: looping on spinlock %p:%s, caller=%p",
  73.                    CPU->id, sl, sl->name, caller);
  74.             symbol = get_symtab_entry(caller);
  75.             if (symbol)
  76.                 printf("(%s)", symbol);
  77.             printf("\n");
  78.             i = 0;
  79.         }
  80.     }
  81.  
  82.     /*
  83.      * Prevent critical section code from bleeding out this way up.
  84.      */
  85.     CS_ENTER_BARRIER();
  86.  
  87. }
  88.  
  89. #else
  90.  
  91. /** Lock spinlock
  92.  *
  93.  * Lock spinlock.
  94.  *
  95.  * @param sl Pointer to spinlock_t structure.
  96.  */
  97. void spinlock_lock(spinlock_t *sl)
  98. {
  99.     preemption_disable();
  100.  
  101.     /*
  102.      * Each architecture has its own efficient/recommended
  103.      * implementation of spinlock.
  104.      */
  105.     spinlock_arch(&sl->val);
  106.  
  107.     /*
  108.      * Prevent critical section code from bleeding out this way up.
  109.      */
  110.     CS_ENTER_BARRIER();
  111. }
  112. #endif
  113.  
  114. /** Lock spinlock conditionally
  115.  *
  116.  * Lock spinlock conditionally.
  117.  * If the spinlock is not available at the moment,
  118.  * signal failure.
  119.  *
  120.  * @param sl Pointer to spinlock_t structure.
  121.  *
  122.  * @return Zero on failure, non-zero otherwise.
  123.  */
  124. int spinlock_trylock(spinlock_t *sl)
  125. {
  126.     int rc;
  127.    
  128.     preemption_disable();
  129.     rc = !test_and_set(&sl->val);
  130.  
  131.     /*
  132.      * Prevent critical section code from bleeding out this way up.
  133.      */
  134.     CS_ENTER_BARRIER();
  135.  
  136.     if (!rc)
  137.         preemption_enable();
  138.    
  139.     return rc;
  140. }
  141.  
  142. /** Unlock spinlock
  143.  *
  144.  * Unlock spinlock.
  145.  *
  146.  * @param sl Pointer to spinlock_t structure.
  147.  */
  148. void spinlock_unlock(spinlock_t *sl)
  149. {
  150.     ASSERT(sl->val != 0);
  151.  
  152.     /*
  153.      * Prevent critical section code from bleeding out this way down.
  154.      */
  155.     CS_LEAVE_BARRIER();
  156.    
  157.     sl->val = 0;
  158.     preemption_enable();
  159. }
  160.  
  161. #endif
  162.