<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>mp:with-lock</title><link rel="stylesheet" href="ecl.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="The ECL manual"><link rel="up" href="ch19s02.html" title="4.2. MP Reference"><link rel="prev" href="re27.html" title="mp:process-run-function"><link rel="next" href="ch20.html" title="Chapter 5. Memory Management"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><code class="function">mp:with-lock</code></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re27.html">Prev</a> </td><th width="60%" align="center">4.2. MP Reference</th><td width="20%" align="right"> <a accesskey="n" href="ch20.html">Next</a></td></tr></table><hr></div><div class="refentry" title="mp:with-lock"><a name="ref.mp.with-lock"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p><code class="function">mp:with-lock</code> — Synchronize a piece of code between different tasks.</p></div><div class="refsynopsisdiv" title="Macro"><h2>Macro</h2><div class="funcsynopsis"><p><code class="funcdef">(mp::with-lock</code> (<var class="pdparam">lock</var>)) ⇒ <var class="pdparam">&body</var>) ⇒ <var class="pdparam">body</var>)</p></div></div><div class="refsect1" title="Description"><a name="id661511"></a><h2>Description</h2><p>It grabs a lock, executes a piece of lisp code and releases the lock at
the end. The inner forms are protected so that when any condition is
signalled the lock is released.</p></div><div class="refsect1" title="Example"><a name="id661523"></a><h2>Example</h2><p>Ensure each task increments the counter properly. The lock is
required because INCF is not an atomic operation.</p><pre class="programlisting">
(defvar *counter* 0)
(defvar *counter-lock* (mp:make-lock :name 'counter))
(flet ((task (name)
(loop while (<= *counter* 10)
do (progn
(sleep 1)
(with-lock (*counter-lock*)
(format t "~%;;; ~A counts ~D" name *counter*)
(terpri)
(incf *counter*))))))
(mp:process-run-function 'ana #'task 'ana)
(mp:process-run-function 'jose #'task 'jose))
</pre></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re27.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch19s02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch20.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><code class="function">mp:process-run-function</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 5. Memory Management</td></tr></table></div></body></html>
