### Eclipse Workspace Patch 1.0
#P log4j2
Index: api/src/main/java/org/apache/logging/log4j/spi/DefaultThreadContextMap.java
===================================================================
--- api/src/main/java/org/apache/logging/log4j/spi/DefaultThreadContextMap.java	(revision 1439358)
+++ api/src/main/java/org/apache/logging/log4j/spi/DefaultThreadContextMap.java	(working copy)
@@ -16,9 +16,12 @@
  */
 package org.apache.logging.log4j.spi;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
+import org.apache.logging.log4j.ThreadContext;
+
 /**
  *
  */
@@ -52,12 +55,15 @@
         if (!useMap) {
             return;
         }
-        Map<String, String> map = localMap.get();
-        if (map == null) {
-            map = new HashMap<String, String>();
-            localMap.set(map);
-        }
-        map.put(key, value);
+       final Map<String, String> map = localMap.get(); 
+        Map<String, String> copy = null; // copy on write
+        if (map == null) { 
+            copy = new HashMap<String, String>(); 
+        } else { 
+            copy = new HashMap<String, String>(map); 
+        } 
+        copy.put(key, value); 
+        localMap.set(copy); 
     }
 
     /**
@@ -79,8 +85,11 @@
      */
     public void remove(final String key) {
         final Map<String, String> map = localMap.get();
+        Map<String, String> copy = null;
         if (map != null) {
-            map.remove(key);
+            copy = new HashMap<String, String>(map); // copy on write
+            copy.remove(key);
+            localMap.set(copy);
         }
     }
 
@@ -109,6 +118,16 @@
         final Map<String, String> map = localMap.get();
         return map == null ? new HashMap<String, String>() : new HashMap<String, String>(map);
     }
+    /**
+     * Get an immutable copy of the current thread's context Map.
+     * @return An immutable copy of the ThreadContext Map.
+     */
+    public Map<String, String> getImmutableContext() {
+        final Map<String, String> map = localMap.get();
+        
+        // no need to make a deep copy here, improves performance a lot
+        return map == null ? ThreadContext.EMPTY_MAP : Collections.unmodifiableMap(map);
+    }
 
     /**
      * Return the context Map.