From 52b7b40034ddbb21d06b11ddc4eb6d766b0f616d Mon Sep 17 00:00:00 2001
From: "Justin Clark-Casey (justincc)" <jjustincc@googlemail.com>
Date: Wed, 19 Mar 2014 00:48:13 +0000
Subject: [PATCH] Simplify DoubleQueue to eliminate redundant sempahore work.

Exclusion is already guaranteed by the lock on m_syncRoot.
Semaphore could not allow more than one thread in these sections anyway since the underlying SDK structures are not thread-safe.
---
 OpenSim/Framework/Util.cs | 34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)

diff --git a/OpenSim/Framework/Util.cs b/OpenSim/Framework/Util.cs
index efaed6220c..f6e76dc8f9 100644
--- a/OpenSim/Framework/Util.cs
+++ b/OpenSim/Framework/Util.cs
@@ -2296,11 +2296,6 @@ namespace OpenSim.Framework
         private Queue<T> m_highQueue = new Queue<T>();
 
         private object m_syncRoot = new object();
-        private Semaphore m_s = new Semaphore(0, 1);
-
-        public DoubleQueue()
-        {
-        }
 
         public virtual int Count
         {
@@ -2329,11 +2324,7 @@ namespace OpenSim.Framework
         private void Enqueue(Queue<T> q, T data)
         {
             lock (m_syncRoot)
-            {
                 q.Enqueue(data);
-                m_s.WaitOne(0);
-                m_s.Release();
-            }
         }
 
         public virtual T Dequeue()
@@ -2363,42 +2354,31 @@ namespace OpenSim.Framework
 
         public bool Dequeue(TimeSpan wait, ref T res)
         {
-            if (!m_s.WaitOne(wait))
+            if (!Monitor.TryEnter(m_syncRoot, wait))
                 return false;
 
-            lock (m_syncRoot)
+            try
             {
                 if (m_highQueue.Count > 0)
                     res = m_highQueue.Dequeue();
                 else if (m_lowQueue.Count > 0)
                     res = m_lowQueue.Dequeue();
 
-                if (m_highQueue.Count == 0 && m_lowQueue.Count == 0)
-                    return true;
-
-                try
-                {
-                    m_s.Release();
-                }
-                catch
-                {
-                }
-
                 return true;
             }
+            finally
+            {
+                Monitor.Exit(m_syncRoot);
+            }
         }
 
         public virtual void Clear()
         {
-
             lock (m_syncRoot)
             {
-                // Make sure sem count is 0
-                m_s.WaitOne(0);
-
                 m_lowQueue.Clear();
                 m_highQueue.Clear();
             }
         }
     }
-}
+}
\ No newline at end of file