UP button does not wok in action bar

Question

i've started learning android programming from this source : http://developer.android.com/training/index.html

and i'm in Adding the action bar > Adding action buttons section

i use Eclipse for coding and may be there are some difference with tutorial

for now my problem is that the UP button that i added to action bar for my second activity to navigate to Main Activity does not work

it appears on the screen but when i tap on it, nothing happened

i think the problem is in my android manifest file so i put it here to guide me

Tnx in advance

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="21" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.test.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.test.DisplayMessageActivity"
            android:label="@string/title_activity_display_message" >             

            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.test.MainActivity" />
        </activity>
    </application>

</manifest>

program is simple, in the main activity (MainActivity) user enter a text in the text field and send it to second activity (DispalyMessageActivity) by pressing send button and showing it in second activity (DispalyMessageActivity)