static/freebsd/man3/pthread_rwlock_wrlock.3 3.html


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<table class="head">
  <tr>
    <td class="head-ltitle">PTHREAD_RWLOCK_WRLOCK(3)</td>
    <td class="head-vol">Library Functions Manual</td>
    <td class="head-rtitle">PTHREAD_RWLOCK_WRLOCK(3)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">pthread_rwlock_wrlock</code>,
    <code class="Nm">pthread_rwlock_trywrlock</code> &#x2014;
    <span class="Nd">acquire a read/write lock for writing</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="LIBRARY"><a class="permalink" href="#LIBRARY">LIBRARY</a></h1>
<p class="Pp"><span class="Lb">POSIX Threads Library (libpthread,
    -lpthread)</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
    &lt;<a class="In">pthread.h</a>&gt;</code></p>
<p class="Pp"><var class="Ft">int</var>
  <br/>
  <code class="Fn">pthread_rwlock_wrlock</code>(<var class="Fa" style="white-space: nowrap;">pthread_rwlock_t
    *lock</var>);</p>
<p class="Pp"><var class="Ft">int</var>
  <br/>
  <code class="Fn">pthread_rwlock_trywrlock</code>(<var class="Fa" style="white-space: nowrap;">pthread_rwlock_t
    *lock</var>);</p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The
    <a class="permalink" href="#pthread_rwlock_wrlock"><code class="Fn" id="pthread_rwlock_wrlock">pthread_rwlock_wrlock</code></a>()
    function blocks until a write lock can be acquired against
    <var class="Fa">lock</var>. The
    <a class="permalink" href="#pthread_rwlock_trywrlock"><code class="Fn" id="pthread_rwlock_trywrlock">pthread_rwlock_trywrlock</code></a>()
    function performs the same action, but does not block if the lock cannot be
    immediately obtained.</p>
<p class="Pp">The results are undefined if the calling thread already holds the
    lock at the time the call is made.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="IMPLEMENTATION_NOTES"><a class="permalink" href="#IMPLEMENTATION_NOTES">IMPLEMENTATION
  NOTES</a></h1>
<p class="Pp">To prevent writer starvation, writers are favored over
  readers.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="RETURN_VALUES"><a class="permalink" href="#RETURN_VALUES">RETURN
  VALUES</a></h1>
<p class="Pp">If successful, the <code class="Fn">pthread_rwlock_wrlock</code>()
    and <code class="Fn">pthread_rwlock_trywrlock</code>() functions will return
    zero. Otherwise an error number will be returned to indicate the error.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="ERRORS"><a class="permalink" href="#ERRORS">ERRORS</a></h1>
<p class="Pp">The <code class="Fn">pthread_rwlock_trywrlock</code>() function
    will fail if:</p>
<dl class="Bl-tag">
  <dt id="EBUSY">[<a class="permalink" href="#EBUSY"><code class="Er">EBUSY</code></a>]</dt>
  <dd>The calling thread is not able to acquire the lock without blocking.</dd>
</dl>
<p class="Pp">The <code class="Fn">pthread_rwlock_wrlock</code>() and
    <code class="Fn">pthread_rwlock_trywrlock</code>() functions may fail
  if:</p>
<dl class="Bl-tag">
  <dt id="EDEADLK">[<a class="permalink" href="#EDEADLK"><code class="Er">EDEADLK</code></a>]</dt>
  <dd>The calling thread already owns the read/write lock (for reading or
      writing).</dd>
  <dt id="EINVAL">[<a class="permalink" href="#EINVAL"><code class="Er">EINVAL</code></a>]</dt>
  <dd>The value specified by <var class="Fa">lock</var> is invalid.</dd>
  <dt id="ENOMEM">[<a class="permalink" href="#ENOMEM"><code class="Er">ENOMEM</code></a>]</dt>
  <dd>Insufficient memory exists to initialize the lock (applies to statically
      initialized locks only).</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
  ALSO</a></h1>
<p class="Pp"><a class="Xr">pthread_rwlock_init(3)</a>,
    <a class="Xr">pthread_rwlock_rdlock(3)</a>,
    <a class="Xr">pthread_rwlock_tryrdlock(3)</a>,
    <a class="Xr">pthread_rwlock_unlock(3)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="STANDARDS"><a class="permalink" href="#STANDARDS">STANDARDS</a></h1>
<p class="Pp">The <code class="Fn">pthread_rwlock_wrlock</code>() and
    <code class="Fn">pthread_rwlock_trywrlock</code>() functions are expected to
    conform to <span class="St">Version&#x00A0;2 of the Single UNIX
    Specification (&#x201C;SUSv2&#x201D;)</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Fn">pthread_rwlock_wrlock</code>() function first
    appeared in <span class="Ux">FreeBSD 3.0</span>.</p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">August 4, 1998</td>
    <td class="foot-os">FreeBSD 15.0</td>
  </tr>
</table>