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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.  
  46. #ifdef CONFIG_SYMTAB
  47. #include <symtab.h>
  48. #endif
  49.  
  50. #ifdef CONFIG_FB
  51. #include <genarch/fb/fb.h>
  52. #endif
  53.  
  54. #ifdef CONFIG_SMP
  55.  
  56. /** Initialize spinlock
  57.  *
  58.  * Initialize spinlock.
  59.  *
  60.  * @param sl Pointer to spinlock_t structure.
  61.  */
  62. void spinlock_initialize(spinlock_t *sl, char *name)
  63. {
  64.     atomic_set(&sl->val, 0);
  65. #ifdef CONFIG_DEBUG_SPINLOCK
  66.     sl->name = name;
  67. #endif 
  68. }
  69.  
  70. /** Lock spinlock
  71.  *
  72.  * Lock spinlock.
  73.  * This version has limitted ability to report
  74.  * possible occurence of deadlock.
  75.  *
  76.  * @param sl Pointer to spinlock_t structure.
  77.  */
  78. #ifdef CONFIG_DEBUG_SPINLOCK
  79. void spinlock_lock_debug(spinlock_t *sl)
  80. {
  81.     count_t i = 0;
  82.     bool deadlock_reported = false;
  83. #ifdef CONFIG_SYMTAB
  84.     char *symbol;
  85. #endif
  86.  
  87.     preemption_disable();
  88.     while (test_and_set(&sl->val)) {
  89.  
  90.         /*
  91.          * We need to be careful about printf_lock and fb_lock.
  92.          * Both of them are used to report deadlocks via
  93.          * printf() and fb_putchar().
  94.          *
  95.          * We trust our code that there is no possible deadlock
  96.          * caused by these two locks (except when an exception
  97.          * is triggered for instance by printf() or fb_putchar()).
  98.          * However, we encountered false positives caused by very
  99.          * slow VESA framebuffer interaction (especially when
  100.          * run in a simulator) that caused problems with both
  101.          * printf_lock and fb_lock.
  102.          *
  103.          * Possible deadlocks on both printf_lock and fb_lock
  104.          * are therefore not reported as they would cause an
  105.          * infinite recursion.
  106.          */
  107.         if (sl == &printf_lock)
  108.             continue;
  109. #ifdef CONFIG_FB
  110.         if (sl == &fb_lock)
  111.             continue;
  112. #endif
  113.         if (i++ > DEADLOCK_THRESHOLD) {
  114.             printf("cpu%u: looping on spinlock %" PRIp ":%s, caller=%" PRIp,
  115.                 CPU->id, sl, sl->name, CALLER);
  116. #ifdef CONFIG_SYMTAB
  117.             symbol = get_symtab_entry(CALLER);
  118.             if (symbol)
  119.                 printf("(%s)", symbol);
  120. #endif
  121.             printf("\n");
  122.             i = 0;
  123.             deadlock_reported = true;
  124.         }
  125.     }
  126.  
  127.     if (deadlock_reported)
  128.         printf("cpu%u: not deadlocked\n", CPU->id);
  129.  
  130.     /*
  131.      * Prevent critical section code from bleeding out this way up.
  132.      */
  133.     CS_ENTER_BARRIER();
  134. }
  135. #endif
  136.  
  137. /** Lock spinlock conditionally
  138.  *
  139.  * Lock spinlock conditionally.
  140.  * If the spinlock is not available at the moment,
  141.  * signal failure.
  142.  *
  143.  * @param sl Pointer to spinlock_t structure.
  144.  *
  145.  * @return Zero on failure, non-zero otherwise.
  146.  */
  147. int spinlock_trylock(spinlock_t *sl)
  148. {
  149.     int rc;
  150.    
  151.     preemption_disable();
  152.     rc = !test_and_set(&sl->val);
  153.  
  154.     /*
  155.      * Prevent critical section code from bleeding out this way up.
  156.      */
  157.     CS_ENTER_BARRIER();
  158.  
  159.     if (!rc)
  160.         preemption_enable();
  161.    
  162.     return rc;
  163. }
  164.  
  165. #endif
  166.  
  167. /** @}
  168.  */
  169.