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<a name="g_t_005f_005fmalloc_005flock_002c-_005f_005fmalloc_005funlock_002d_002d_002dlock-malloc-pool"></a>
<h3 class="section">2.26 <code>__malloc_lock</code>, <code>__malloc_unlock</code>&mdash;lock malloc pool</h3>
<a name="index-_005f_005fmalloc_005flock"></a>
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<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;malloc.h&gt;
void __malloc_lock (struct _reent *<var>reent</var>);
void __malloc_unlock (struct _reent *<var>reent</var>);

</pre></div>
<p><strong>Description</strong><br>
The <code>malloc</code> family of routines call these functions when they need to lock
the memory pool.  The version of these routines supplied in the library use
the lock API defined in sys/lock.h.  If multiple threads of execution can
call <code>malloc</code>, or if <code>malloc</code> can be called reentrantly, then you need to
define your own versions of these functions in order to safely lock the
memory pool during a call.  If you do not, the memory pool may become
corrupted.
</p>
<p>A call to <code>malloc</code> may call <code>__malloc_lock</code> recursively; that is,
the sequence of calls may go <code>__malloc_lock</code>, <code>__malloc_lock</code>,
<code>__malloc_unlock</code>, <code>__malloc_unlock</code>.  Any implementation of these
routines must be careful to avoid causing a thread to wait for a lock
that it already holds.
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