I forgot to mention that you&#39;d have to repeat the find operation once you get the write lock since there is a small window between the unlock and lock where another thread may have created the item.<br><br><br><div class="gmail_quote">
On Thu, Aug 18, 2011 at 6:42 AM, Christopher Rienzo <span dir="ltr">&lt;<a href="mailto:cmrienzo@gmail.com">cmrienzo@gmail.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<p>Unlock the read lock and then lock as a write lock.</p>
<p></p><blockquote type="cite"><div><div></div><div class="h5">On Aug 17, 2011 8:20 PM, &quot;Seven Du&quot; &lt;<a href="mailto:dujinfang@gmail.com" target="_blank">dujinfang@gmail.com</a>&gt; wrote:<br><br><div>
            <div>
                <span>Hi,<br>
                </span></div><div><span><br></span></div><div><span><br></span></div><div><span>Just wondering how to upgrade a read lock to a write lock, say I do a find_or_create_item_in_queue()</span></div><div><span><br>

</span></div><div><span><div><span style="white-space:pre-wrap">	</span>switch_thread_rwlock_rdlock(lock);</div><div><br></div><div><span style="white-space:pre-wrap">	</span>find an item from queue, if not found, create one</div>

<div><br></div><div><div><span style="white-space:pre-wrap">	</span>switch_thread_rwlock_upgrade_to_wrlock(lock);</div></div><div><br></div></span></div><div>
                <span><span style="white-space:pre-wrap">	</span></span><span>write</span></div><div><span><span style="white-space:pre-wrap">	</span></span></div><div><span style="white-space:pre-wrap">	</span>switch_thread_rwlock_unlock(lock);</div>

<div><br></div><div><span>Thanks<br><font color="#888888">-- <br>Seven Du<br><div>About: <a href="http://about.me/dujinfang" target="_blank">http://about.me/dujinfang</a></div><div>Blog: <a href="http://www.dujinfang.com" target="_blank">http://www.dujinfang.com</a></div>

<div>Proj:  <a href="http://www.freeswitch.org.cn" target="_blank">http://www.freeswitch.org.cn</a></div>Sent with <a href="http://www.sparrowmailapp.com" target="_blank">Sparrow</a><br></font></span></div><div></div><div>

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