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  47. <a name="g_t_005f_005fmalloc_005flock"></a>
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  54. <h3 class="section">2.26 <code>__malloc_lock</code>, <code>__malloc_unlock</code>&mdash;lock malloc pool</h3>
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  57. <p><strong>Synopsis</strong>
  58. </p><div class="example">
  59. <pre class="example">#include &lt;malloc.h&gt;
  60. void __malloc_lock (struct _reent *<var>reent</var>);
  61. void __malloc_unlock (struct _reent *<var>reent</var>);
  62. </pre></div>
  63. <p><strong>Description</strong><br>
  64. The <code>malloc</code> family of routines call these functions when they need to lock
  65. the memory pool. The version of these routines supplied in the library use
  66. the lock API defined in sys/lock.h. If multiple threads of execution can
  67. call <code>malloc</code>, or if <code>malloc</code> can be called reentrantly, then you need to
  68. define your own versions of these functions in order to safely lock the
  69. memory pool during a call. If you do not, the memory pool may become
  70. corrupted.
  71. </p>
  72. <p>A call to <code>malloc</code> may call <code>__malloc_lock</code> recursively; that is,
  73. the sequence of calls may go <code>__malloc_lock</code>, <code>__malloc_lock</code>,
  74. <code>__malloc_unlock</code>, <code>__malloc_unlock</code>. Any implementation of these
  75. routines must be careful to avoid causing a thread to wait for a lock
  76. that it already holds.
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