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