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