📄 conc_pr8.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="08/22/03 10:12:45">
<title>7.7 Semaphores</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="c2isetto.htm"><img src="images/navtoc.gif" width="84" height="23"
border="0" alt="TOC"> </a></td>
<td><a href="conc_pr7.htm"><img src="images/navprev.gif" width="80" height="23"
border="0" alt="PREV"> </a></td>
<td><a href="conc_pr9.htm"><img src="images/navnext.gif" width="83" height="23"
border="0" alt="NEXT"> </a></td>
<td><a href="c2isetix.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="1205811"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">7.7 Semaphores</font>
</h2><hr>
<p>
<a name="1205812"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Semaphores provide a means of controlling the execution of concurrent processes. An n-valued semaphore ensures that from the set of processes that are waiting on that semaphore, at most n can run concurrently. If a process has a critical piece of code which must only execute when the semaphore allows it to, then the code waits on the semaphore before commencing, and signals to the semaphore when it has finished.</font>
</p>
<p>
<a name="1205813"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The ST20-C2 provides an efficient implementation of an n-valued semaphore for processes. <strong>signal</strong> and <strong>wait</strong> instructions, shown in <a href="conc_pr8.htm#1205834"><font color="#0000ff" face="Verdana, Arial, Helvetica, sans-serif"><i>Table
⌨️ 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 + -