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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.  /** @addtogroup sync
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief   Spinlocks.
  36.  */
  37.  
  38. #include <synch/spinlock.h>
  39. #include <atomic.h>
  40. #include <arch/barrier.h>
  41. #include <arch.h>
  42. #include <preemption.h>
  43. #include <print.h>
  44. #include <debug.h>
  45. #include <symtab.h>
  46.  
  47. #ifdef CONFIG_FB
  48. #include <genarch/fb/fb.h>
  49. #endif
  50.  
  51. #ifdef CONFIG_SMP
  52.  
  53. /** Initialize spinlock
  54.  *
  55.  * Initialize spinlock.
  56.  *
  57.  * @param sl Pointer to spinlock_t structure.
  58.  */
  59. void spinlock_initialize(spinlock_t *sl, char *name)
  60. {
  61.     atomic_set(&sl->val, 0);
  62. #ifdef CONFIG_DEBUG_SPINLOCK
  63.     sl->name = name;
  64. #endif 
  65. }
  66.  
  67. /** Lock spinlock
  68.  *
  69.  * Lock spinlock.
  70.  * This version has limitted ability to report
  71.  * possible occurence of deadlock.
  72.  *
  73.  * @param sl Pointer to spinlock_t structure.
  74.  */
  75. #ifdef CONFIG_DEBUG_SPINLOCK
  76. #define DEADLOCK_THRESHOLD  100000000
  77. void spinlock_lock_debug(spinlock_t *sl)
  78. {
  79.     count_t i = 0;
  80.     char *symbol;
  81.     bool deadlock_reported = false;
  82.  
  83.     preemption_disable();
  84.     while (test_and_set(&sl->val)) {
  85.  
  86.         /*
  87.          * We need to be careful about printflock and fb_lock.
  88.          * Both of them are used to report deadlocks via
  89.          * printf() and fb_putchar().
  90.          *
  91.          * We trust our code that there is no possible deadlock
  92.          * caused by these two locks (except when an exception
  93.          * is triggered for instance by printf() or fb_putchar()).
  94.          * However, we encountered false positives caused by very
  95.          * slow VESA framebuffer interaction (especially when
  96.          * run in a simulator) that caused problems with both
  97.          * printflock and fb_lock.
  98.          *
  99.          * Possible deadlocks on both printflock and fb_lock
  100.          * are therefore not reported as they would cause an
  101.          * infinite recursion.
  102.          */
  103.         if (sl == &printflock)
  104.             continue;
  105. #ifdef CONFIG_FB
  106.         if (sl == &fb_lock)
  107.             continue;
  108. #endif
  109.         if (i++ > DEADLOCK_THRESHOLD) {
  110.             printf("cpu%d: looping on spinlock %.*p:%s, caller=%.*p",
  111.                    CPU->id, sizeof(__address) * 2, sl, sl->name, sizeof(__address) * 2, CALLER);
  112.             symbol = get_symtab_entry(CALLER);
  113.             if (symbol)
  114.                 printf("(%s)", symbol);
  115.             printf("\n");
  116.             i = 0;
  117.             deadlock_reported = true;
  118.         }
  119.     }
  120.  
  121.     if (deadlock_reported)
  122.         printf("cpu%d: not deadlocked\n", CPU->id);
  123.  
  124.     /*
  125.      * Prevent critical section code from bleeding out this way up.
  126.      */
  127.     CS_ENTER_BARRIER();
  128. }
  129. #endif
  130.  
  131. /** Lock spinlock conditionally
  132.  *
  133.  * Lock spinlock conditionally.
  134.  * If the spinlock is not available at the moment,
  135.  * signal failure.
  136.  *
  137.  * @param sl Pointer to spinlock_t structure.
  138.  *
  139.  * @return Zero on failure, non-zero otherwise.
  140.  */
  141. int spinlock_trylock(spinlock_t *sl)
  142. {
  143.     int rc;
  144.    
  145.     preemption_disable();
  146.     rc = !test_and_set(&sl->val);
  147.  
  148.     /*
  149.      * Prevent critical section code from bleeding out this way up.
  150.      */
  151.     CS_ENTER_BARRIER();
  152.  
  153.     if (!rc)
  154.         preemption_enable();
  155.    
  156.     return rc;
  157. }
  158.  
  159. #endif
  160.  
  161.  /** @}
  162.  */
  163.  
  164.