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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_rwlock_trywrlock</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="pthread_rwlock_trywrlock"></a> <a name="tag_03_560"></a><!-- pthread_rwlock_trywrlock --> <!--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_560_01"></a>NAME</h4><blockquote>pthread_rwlock_trywrlock, pthread_rwlock_wrlock - lock a read-write lock object for writing</blockquote><h4><a name="tag_03_560_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_rwlock_trywrlock(pthread_rwlock_t</tt> <i>*rwlock</i><tt>);<br> int pthread_rwlock_wrlock(pthread_rwlock_t</tt> <i>*rwlock</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_560_03"></a>DESCRIPTION</h4><blockquote><p>The <i>pthread_rwlock_trywrlock</i>() function shall apply a write lock like the <i>pthread_rwlock_wrlock</i>() function, withthe exception that the function shall fail if any thread currently holds <i>rwlock</i> (for reading or writing).</p><p>The <i>pthread_rwlock_wrlock</i>() function shall apply a write lock to the read-write lock referenced by <i>rwlock</i>. Thecalling thread acquires the write lock if no other thread (reader or writer) holds the read-write lock <i>rwlock</i>. Otherwise,the thread shall block until it can acquire the lock. The calling thread may deadlock if at the time the call is made it holds theread-write lock (whether a read or write lock).</p><p>Implementations may favor writers over readers to avoid writer starvation.</p><p>Results are undefined if any of these functions are called with an uninitialized read-write lock.</p><p>If a signal is delivered to a thread waiting for a read-write lock for writing, upon return from the signal handler the threadresumes waiting for the read-write lock for writing as if it was not interrupted.</p></blockquote><h4><a name="tag_03_560_04"></a>RETURN VALUE</h4><blockquote><p>The <i>pthread_rwlock_trywrlock</i>() function shall return zero if the lock for writing on the read-write lock objectreferenced by <i>rwlock</i> is acquired. Otherwise, an error number shall be returned to indicate the error.</p><p>If successful, the <i>pthread_rwlock_wrlock</i>() function shall return zero; otherwise, an error number shall be returned toindicate the error.</p></blockquote><h4><a name="tag_03_560_05"></a>ERRORS</h4><blockquote><p>The <i>pthread_rwlock_trywrlock</i>() function shall fail if:</p><dl compact><dt>[EBUSY]</dt><dd>The read-write lock could not be acquired for writing because it was already locked for reading or writing.</dd></dl><p>The <i>pthread_rwlock_trywrlock</i>() and <i>pthread_rwlock_wrlock</i>() functions may fail if:</p><dl compact><dt>[EINVAL]</dt><dd>The value specified by <i>rwlock</i> does not refer to an initialized read-write lock object.</dd></dl><p>The <i>pthread_rwlock_wrlock</i>() function may fail if:</p><dl compact><dt>[EDEADLK]</dt><dd>The current thread already owns the read-write lock for writing or reading.</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_560_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_560_07"></a>APPLICATION USAGE</h4><blockquote><p>Applications using these functions may be subject to priority inversion, as discussed in the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap03.html#tag_03_285">Section 3.285, Priority Inversion</a>.</p></blockquote><h4><a name="tag_03_560_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_560_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_560_10"></a>SEE ALSO</h4><blockquote><p><a href="pthread_rwlock_destroy.html"><i>pthread_rwlock_destroy</i>()</a> , <a href="pthread_rwlock_rdlock.html"><i>pthread_rwlock_rdlock</i>()</a> , <a href="pthread_rwlock_timedrdlock.html"><i>pthread_rwlock_timedrdlock</i>()</a> , <a href="pthread_rwlock_timedwrlock.html"><i>pthread_rwlock_timedwrlock</i>()</a> , <a href="pthread_rwlock_tryrdlock.html"><i>pthread_rwlock_tryrdlock</i>()</a> , <a href="pthread_rwlock_unlock.html"><i>pthread_rwlock_unlock</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_560_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 5.</p></blockquote><h4><a name="tag_03_560_12"></a>Issue 6</h4><blockquote><p>The following changes are made for alignment with IEEE Std 1003.1j-2000:</p><ul><li><p>The margin code in the SYNOPSIS is changed to THR to indicate that the functionality is now part of the Threads option(previously it was part of the Read-Write Locks option in IEEE Std 1003.1j-2000 and also part of the XSI extension).</p></li><li><p>The [EDEADLK] error is deleted as a <i>pthread_rwlock_trywrlock</i>() error.</p></li><li><p>The SEE ALSO section is updated.</p></li></ul></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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