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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>pthread_setcancelstate</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="pthread_setcancelstate"></a> <a name="tag_03_568"></a><!-- pthread_setcancelstate --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_568_01"></a>NAME</h4><blockquote>pthread_setcancelstate, pthread_setcanceltype, pthread_testcancel - set cancelability state</blockquote><h4><a name="tag_03_568_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><div class="box"><code><tt><sup>[<a href="javascript:open_code('THR')">THR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> #include <<a href="../basedefs/pthread.h.html">pthread.h</a>><br><br> int pthread_setcancelstate(int</tt> <i>state</i><tt>, int *</tt><i>oldstate</i><tt>);<br> int pthread_setcanceltype(int</tt> <i>type</i><tt>, int *</tt><i>oldtype</i><tt>);<br> void pthread_testcancel(void); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_568_03"></a>DESCRIPTION</h4><blockquote><p>The <i>pthread_setcancelstate</i>() function shall atomically both set the calling thread's cancelability state to the indicated<i>state</i> and return the previous cancelability state at the location referenced by <i>oldstate</i>. Legal values for<i>state</i> are PTHREAD_CANCEL_ENABLE and PTHREAD_CANCEL_DISABLE.</p><p>The <i>pthread_setcanceltype</i>() function shall atomically both set the calling thread's cancelability type to the indicated<i>type</i> and return the previous cancelability type at the location referenced by <i>oldtype</i>. Legal values for <i>type</i>are PTHREAD_CANCEL_DEFERRED and PTHREAD_CANCEL_ASYNCHRONOUS.</p><p>The cancelability state and type of any newly created threads, including the thread in which <i>main</i>() was first invoked,shall be PTHREAD_CANCEL_ENABLE and PTHREAD_CANCEL_DEFERRED respectively.</p><p>The <i>pthread_testcancel</i>() function shall create a cancellation point in the calling thread. The<i>pthread_testcancel</i>() function shall have no effect if cancelability is disabled.</p></blockquote><h4><a name="tag_03_568_04"></a>RETURN VALUE</h4><blockquote><p>If successful, the <i>pthread_setcancelstate</i>() and <i>pthread_setcanceltype</i>() functions shall return zero; otherwise, anerror number shall be returned to indicate the error.</p></blockquote><h4><a name="tag_03_568_05"></a>ERRORS</h4><blockquote><p>The <i>pthread_setcancelstate</i>() function may fail if:</p><dl compact><dt>[EINVAL]</dt><dd>The specified state is not PTHREAD_CANCEL_ENABLE or PTHREAD_CANCEL_DISABLE.</dd></dl><p>The <i>pthread_setcanceltype</i>() function may fail if:</p><dl compact><dt>[EINVAL]</dt><dd>The specified type is not PTHREAD_CANCEL_DEFERRED or PTHREAD_CANCEL_ASYNCHRONOUS.</dd></dl><p>These functions shall not return an error code of [EINTR].</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_568_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_568_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_568_08"></a>RATIONALE</h4><blockquote><p>The <i>pthread_setcancelstate</i>() and <i>pthread_setcanceltype</i>() functions control the points at which a thread may beasynchronously canceled. For cancellation control to be usable in modular fashion, some rules need to be followed.</p><p>An object can be considered to be a generalization of a procedure. It is a set of procedures and global variables written as aunit and called by clients not known by the object. Objects may depend on other objects.</p><p>First, cancelability should only be disabled on entry to an object, never explicitly enabled. On exit from an object, thecancelability state should always be restored to its value on entry to the object.</p><p>This follows from a modularity argument: if the client of an object (or the client of an object that uses that object) hasdisabled cancelability, it is because the client does not want to be concerned about cleaning up if the thread is canceled whileexecuting some sequence of actions. If an object is called in such a state and it enables cancelability and a cancellation requestis pending for that thread, then the thread is canceled, contrary to the wish of the client that disabled.</p><p>Second, the cancelability type may be explicitly set to either <i>deferred</i> or <i>asynchronous</i> upon entry to an object.But as with the cancelability state, on exit from an object the cancelability type should always be restored to its value on entryto the object.</p><p>Finally, only functions that are cancel-safe may be called from a thread that is asynchronously cancelable.</p></blockquote><h4><a name="tag_03_568_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_568_10"></a>SEE ALSO</h4><blockquote><p><a href="pthread_cancel.html"><i>pthread_cancel</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <ahref="../basedefs/pthread.h.html"><i><pthread.h></i></a></p></blockquote><h4><a name="tag_03_568_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 5. Included for alignment with the POSIX Threads Extension.</p></blockquote><h4><a name="tag_03_568_12"></a>Issue 6</h4><blockquote><p>The <i>pthread_setcancelstate</i>(), <i>pthread_setcanceltype</i>(), and <i>pthread_testcancel</i>() functions are marked aspart of the Threads option.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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