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<H1><A NAME="SECTION009600000000000000000">
7.6 <tt class="module">mutex</tt> --
Mutual exclusion support</A>
</H1>
<P>
<P>
The <tt class="module">mutex</tt> defines a class that allows mutual-exclusion
via acquiring and releasing locks. It does not require (or imply)
threading or multi-tasking, though it could be useful for
those purposes.
<P>
The <tt class="module">mutex</tt> module defines the following class:
<P>
<dl><dt><b><a name='l2h-1671'><tt class='class'>mutex</tt></a></b> ()
<dd>
Create a new (unlocked) mutex.
<P>
A mutex has two pieces of state -- a ``locked'' bit and a queue.
When the mutex is not locked, the queue is empty.
Otherwise, the queue contains 0 or more
<code>(<var>function</var>, <var>argument</var>)</code> pairs
representing functions (or methods) waiting to acquire the lock.
When the mutex is unlocked while the queue is not empty,
the first queue entry is removed and its
<code><var>function</var>(<var>argument</var>)</code> pair called,
implying it now has the lock.
<P>
Of course, no multi-threading is implied - hence the funny interface
for lock, where a function is called once the lock is acquired.
</dl>
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