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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 <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.     atomic_set(&sl->val, 0);
  49. #ifdef CONFIG_DEBUG_SPINLOCK
  50.     sl->name = name;
  51. #endif 
  52. }
  53.  
  54. /** Lock spinlock
  55.  *
  56.  * Lock spinlock.
  57.  * This version has limitted ability to report
  58.  * possible occurence of deadlock.
  59.  *
  60.  * @param sl Pointer to spinlock_t structure.
  61.  */
  62. #ifdef CONFIG_DEBUG_SPINLOCK
  63. void spinlock_lock_debug(spinlock_t *sl)
  64. {
  65.     count_t i = 0;
  66.     char *symbol;
  67.     bool deadlock_reported = false;
  68.  
  69.     preemption_disable();
  70.     while (test_and_set(&sl->val)) {
  71.         if (i++ > 300000 && sl!=&printflock) {
  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.             deadlock_reported = true;
  80.         }
  81.     }
  82.  
  83.     if (deadlock_reported)
  84.         printf("cpu%d: not deadlocked\n", CPU->id);
  85.  
  86.     /*
  87.      * Prevent critical section code from bleeding out this way up.
  88.      */
  89.     CS_ENTER_BARRIER();
  90. }
  91. #endif
  92.  
  93. /** Lock spinlock conditionally
  94.  *
  95.  * Lock spinlock conditionally.
  96.  * If the spinlock is not available at the moment,
  97.  * signal failure.
  98.  *
  99.  * @param sl Pointer to spinlock_t structure.
  100.  *
  101.  * @return Zero on failure, non-zero otherwise.
  102.  */
  103. int spinlock_trylock(spinlock_t *sl)
  104. {
  105.     int rc;
  106.    
  107.     preemption_disable();
  108.     rc = !test_and_set(&sl->val);
  109.  
  110.     /*
  111.      * Prevent critical section code from bleeding out this way up.
  112.      */
  113.     CS_ENTER_BARRIER();
  114.  
  115.     if (!rc)
  116.         preemption_enable();
  117.    
  118.     return rc;
  119. }
  120.  
  121. #endif
  122.