📄 mutex3.htm
字号:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<meta name="GENERATOR" content="Quadralay WebWorks Publisher Professional Edition 6.0.5">
<meta name="TEMPLATEBASE" content="book_html">
<meta name="LASTUPDATED" content="12/01/03 14:15:00">
<title>7.2 Use of mutexes</title>
<STYLE TYPE="text/css">
<!--
span.Signal { text-transform: uppercase; font-family: Verdana }
-->
</STYLE>
</head>
<body link="#3366CC" vlink="#9999CC" text="#000000" alink="#0000CC" bgcolor="#FFFFFF"
background="images/backgrnd.gif">
<p><img src="images/stlogo.gif" width="106" height="83" align="left"
alt="logo here!"> </p>
<table width="331" border="0" align="right" cellpadding="0" cellspacing="0">
<tr>
<td><a href="os20toc.htm"><img src="images/navtoc.gif" width="84" height="23"
border="0" alt="TOC"> </a></td>
<td><a href="mutex2.htm"><img src="images/navprev.gif" width="80" height="23"
border="0" alt="PREV"> </a></td>
<td><a href="mutex4.htm"><img src="images/navnext.gif" width="83" height="23"
border="0" alt="NEXT"> </a></td>
<td><a href="os20ix.htm"><img src="images/navidx.gif" width="84" height="23"
border="0" alt="INDEX"> </a></td>
</tr>
</table>
<p><br clear="all">
</p>
<hr align="left">
<blockquote>
<h2>
<a name="1106341"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">7.2 Use of mutexes</font>
</h2><hr>
<p>
<a name="1106342"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Mutexes can only be used to protect a resource if all tasks that wish to use the resource also use the same mutex. It cannot protect a resource from a task that does not use the mutex and accesses the resource directly.</font>
</p>
<p>
<a name="1106343"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Mutexes allow at most one task access to the resource at any given time. Areas of code protected using mutexes are sometimes called <strong>critical regions</strong>.</font>
</p>
<p>
<a name="1106345"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The critical region is surrounded with calls to <font size=2 face=Courier><strong>mutex_lock()</strong></font> at the start and <font size=2 face=Courier><strong>mutex_release()</strong></font> at the end. Thus the first task which tries to enter the critical region successfully takes the mutex, and any others are forced to wait. When the task currently in the critical region leaves, it releases the mutex, and allows the first of the waiting tasks into the critical region.</font>
</p>
</blockquote>
<hr>
<table width="331" border="0" align="left" cellpadding="0" cellspacing="0">
<tr>
<td><a href="os20toc.htm"><img src="images/navtoc.gif" width="84" height="23"
border="0" alt="TOC"> </a></td>
<td><a href="mutex2.htm"><img src="images/navprev.gif" width="80" height="23"
border="0" alt="PREV"> </a></td>
<td><a href="mutex4.htm"><img src="images/navnext.gif" width="83" height="23"
border="0" alt="NEXT"> </a></td>
<td><a href="os20ix.htm"><img src="images/navidx.gif" width="84" height="23"
border="0" alt="INDEX"> </a></td>
</tr>
</table>
<font size=1 face="Verdana, Arial, Helvetica, sans-serif"> © 2001, 2002, 2003 STMicroelectronics. All Rights Reserved.<br>
ADCS 7473749B</font>
</body>
</html>
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -