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  1. /*
  2.  * Copyright (c) 2007 Michal Kebrt
  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 arm32
  30.  * @{
  31.  */
  32. /** @file
  33.  *  @brief Atomic operations.
  34.  */
  35.  
  36. #ifndef KERN_arm32_ATOMIC_H_
  37. #define KERN_arm32_ATOMIC_H_
  38.  
  39. /** Atomic addition.
  40.  *
  41.  * @param val Where to add.
  42.  * @param i   Value to be added.
  43.  *
  44.  * @return Value after addition.
  45.  *
  46.  */
  47. static inline long atomic_add(atomic_t *val, int i)
  48. {
  49.     int ret;
  50.     volatile long *mem = &(val->count);
  51.    
  52.     asm volatile (
  53.         "1:\n"
  54.             "ldr r2, [%[mem]]\n"
  55.             "add r3, r2, %[i]\n"
  56.             "str r3, %[ret]\n"
  57.             "swp r3, r3, [%[mem]]\n"
  58.             "cmp r3, r2\n"
  59.             "bne 1b\n"
  60.         : [ret] "=m" (ret)
  61.         : [mem] "r" (mem), [i] "r" (i)
  62.         : "r3", "r2"
  63.     );
  64.    
  65.     return ret;
  66. }
  67.  
  68. /** Atomic increment.
  69.  *
  70.  * @param val Variable to be incremented.
  71.  */
  72. static inline void atomic_inc(atomic_t *val)
  73. {
  74.     atomic_add(val, 1);
  75. }
  76.  
  77. /** Atomic decrement.
  78.  *
  79.  * @param val Variable to be decremented.
  80.  */
  81. static inline void atomic_dec(atomic_t *val) {
  82.     atomic_add(val, -1);
  83. }
  84.  
  85. /** Atomic pre-increment.
  86.  *
  87.  * @param val Variable to be incremented.
  88.  * @return    Value after incrementation.
  89.  */
  90. static inline long atomic_preinc(atomic_t *val)
  91. {
  92.     return atomic_add(val, 1);
  93. }
  94.  
  95. /** Atomic pre-decrement.
  96.  *
  97.  * @param val Variable to be decremented.
  98.  * @return    Value after decrementation.
  99.  */
  100. static inline long atomic_predec(atomic_t *val)
  101. {
  102.     return atomic_add(val, -1);
  103. }
  104.  
  105. /** Atomic post-increment.
  106.  *
  107.  * @param val Variable to be incremented.
  108.  * @return    Value before incrementation.
  109.  */
  110. static inline long atomic_postinc(atomic_t *val)
  111. {
  112.     return atomic_add(val, 1) - 1;
  113. }
  114.  
  115. /** Atomic post-decrement.
  116.  *
  117.  * @param val Variable to be decremented.
  118.  * @return    Value before decrementation.
  119.  */
  120. static inline long atomic_postdec(atomic_t *val)
  121. {
  122.     return atomic_add(val, -1) + 1;
  123. }
  124.  
  125. #endif
  126.  
  127. /** @}
  128.  */
  129.