181 lines
6.5 KiB
HTML
181 lines
6.5 KiB
HTML
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<title>pthread_rwlock_trywrlock</title>
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<basefont size="3"> <a name="pthread_rwlock_trywrlock"></a> <a name="tag_03_560"></a><!-- pthread_rwlock_trywrlock -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_560_01"></a>NAME</h4>
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<blockquote>pthread_rwlock_trywrlock, pthread_rwlock_wrlock - lock a read-write lock object for writing</blockquote>
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<h4><a name="tag_03_560_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('THR')">THR</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/pthread.h.html">pthread.h</a>><br>
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<br>
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int pthread_rwlock_trywrlock(pthread_rwlock_t</tt> <i>*rwlock</i><tt>);<br>
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int pthread_rwlock_wrlock(pthread_rwlock_t</tt> <i>*rwlock</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border=
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"0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_560_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>pthread_rwlock_trywrlock</i>() function shall apply a write lock like the <i>pthread_rwlock_wrlock</i>() function, with
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the exception that the function shall fail if any thread currently holds <i>rwlock</i> (for reading or writing).</p>
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<p>The <i>pthread_rwlock_wrlock</i>() function shall apply a write lock to the read-write lock referenced by <i>rwlock</i>. The
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calling thread acquires the write lock if no other thread (reader or writer) holds the read-write lock <i>rwlock</i>. Otherwise,
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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 the
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read-write lock (whether a read or write lock).</p>
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<p>Implementations may favor writers over readers to avoid writer starvation.</p>
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<p>Results are undefined if any of these functions are called with an uninitialized read-write lock.</p>
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<p>If a signal is delivered to a thread waiting for a read-write lock for writing, upon return from the signal handler the thread
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resumes waiting for the read-write lock for writing as if it was not interrupted.</p>
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</blockquote>
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<h4><a name="tag_03_560_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>The <i>pthread_rwlock_trywrlock</i>() function shall return zero if the lock for writing on the read-write lock object
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referenced by <i>rwlock</i> is acquired. Otherwise, an error number shall be returned to indicate the error.</p>
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<p>If successful, the <i>pthread_rwlock_wrlock</i>() function shall return zero; otherwise, an error number shall be returned to
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indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_560_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>pthread_rwlock_trywrlock</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EBUSY]</dt>
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<dd>The read-write lock could not be acquired for writing because it was already locked for reading or writing.</dd>
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</dl>
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<p>The <i>pthread_rwlock_trywrlock</i>() and <i>pthread_rwlock_wrlock</i>() functions may fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The value specified by <i>rwlock</i> does not refer to an initialized read-write lock object.</dd>
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</dl>
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<p>The <i>pthread_rwlock_wrlock</i>() function may fail if:</p>
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<dl compact>
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<dt>[EDEADLK]</dt>
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<dd>The current thread already owns the read-write lock for writing or reading.</dd>
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</dl>
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<p>These functions shall not return an error code of [EINTR].</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_560_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_560_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Applications using these functions may be subject to priority inversion, as discussed in the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap03.html#tag_03_285">Section 3.285, Priority Inversion</a>.</p>
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</blockquote>
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<h4><a name="tag_03_560_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_560_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_560_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="pthread_rwlock_destroy.html"><i>pthread_rwlock_destroy</i>()</a> , <a href=
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"pthread_rwlock_rdlock.html"><i>pthread_rwlock_rdlock</i>()</a> , <a href=
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"pthread_rwlock_timedrdlock.html"><i>pthread_rwlock_timedrdlock</i>()</a> , <a href=
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"pthread_rwlock_timedwrlock.html"><i>pthread_rwlock_timedwrlock</i>()</a> , <a href=
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"pthread_rwlock_tryrdlock.html"><i>pthread_rwlock_tryrdlock</i>()</a> , <a href=
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"pthread_rwlock_unlock.html"><i>pthread_rwlock_unlock</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a
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href="../basedefs/pthread.h.html"><i><pthread.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_560_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5.</p>
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</blockquote>
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<h4><a name="tag_03_560_12"></a>Issue 6</h4>
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<blockquote>
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<p>The following changes are made for alignment with IEEE Std 1003.1j-2000:</p>
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<ul>
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<li>
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<p>The margin code in the SYNOPSIS is changed to THR to indicate that the functionality is now part of the Threads option
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(previously it was part of the Read-Write Locks option in IEEE Std 1003.1j-2000 and also part of the XSI extension).</p>
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</li>
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<li>
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<p>The [EDEADLK] error is deleted as a <i>pthread_rwlock_trywrlock</i>() error.</p>
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</li>
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<li>
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<p>The SEE ALSO section is updated.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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