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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) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>pthread_rwlock_unlock</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="pthread_rwlock_unlock"></a> <a name="tag_03_561"></a><!-- pthread_rwlock_unlock --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_561_01"></a>NAME</h4><blockquote>pthread_rwlock_unlock - unlock a read-write lock object</blockquote><h4><a name="tag_03_561_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_unlock(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_561_03"></a>DESCRIPTION</h4><blockquote><p>The <i>pthread_rwlock_unlock</i>() function shall release a lock held on the read-write lock object referenced by <i>rwlock</i>.Results are undefined if the read-write lock <i>rwlock</i> is not held by the calling thread.</p><p>If this function is called to release a read lock from the read-write lock object and there are other read locks currently heldon this read-write lock object, the read-write lock object remains in the read locked state. If this function releases the lastread lock for this read-write lock object, the read-write lock object shall be put in the unlocked state with no owners.</p><p>If this function is called to release a write lock for this read-write lock object, the read-write lock object shall be put inthe unlocked state.</p><p>If there are threads blocked on the lock when it becomes available, the scheduling policy shall determine which thread(s) shallacquire the lock. <sup>[<a href="javascript:open_code('TPS')">TPS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> If the Thread Execution Scheduling option is supported, when threads executing with thescheduling policies SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC are waiting on the lock, they shall acquire the lock in priority orderwhen the lock becomes available. For equal priority threads, write locks shall take precedence over read locks. <img src="../images/opt-end.gif" alt="[Option End]" border="0"> If the Thread Execution Scheduling option is not supported, it isimplementation-defined whether write locks take precedence over read locks.</p><p>Results are undefined if any of these functions are called with an uninitialized read-write lock.</p></blockquote><h4><a name="tag_03_561_04"></a>RETURN VALUE</h4><blockquote><p>If successful, the <i>pthread_rwlock_unlock</i>() function shall return zero; otherwise, an error number shall be returned toindicate the error.</p></blockquote><h4><a name="tag_03_561_05"></a>ERRORS</h4><blockquote><p>The <i>pthread_rwlock_unlock</i>() function 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><dt>[EPERM]</dt><dd>The current thread does not hold a lock on the read-write lock.</dd></dl><p>The <i>pthread_rwlock_unlock</i>() function 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_561_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_561_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_561_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_561_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_561_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_trywrlock.html"><i>pthread_rwlock_trywrlock</i>()</a>, <a href="pthread_rwlock_wrlock.html"><i>pthread_rwlock_wrlock</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_561_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 5.</p></blockquote><h4><a name="tag_03_561_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 DESCRIPTION is updated as follows:</p><ul><li><p>The conditions under which writers have precedence over readers are specified.</p></li><li><p>The concept of read-write lock owner is deleted.</p></li></ul></li><li><p>The SEE ALSO section is updated.</p></li></ul></blockquote><div class="box"><em>End of informative text.</em></div><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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