HADOOP-15512. Clean up Shell from JDK7 workarounds.

Contributed by Zsolt Venczel.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Shell.java

@@ -22,7 +22,6 @@ import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.io.InputStream;
 import java.io.InterruptedIOException;
 import java.nio.charset.Charset;
 import java.util.Arrays;
@@ -1018,17 +1017,7 @@ public abstract class Shell {
       }
       // close the input stream
       try {
-        // JDK 7 tries to automatically drain the input streams for us
-        // when the process exits, but since close is not synchronized,
-        // it creates a race if we close the stream first and the same
-        // fd is recycled.  the stream draining thread will attempt to
-        // drain that fd!!  it may block, OOM, or cause bizarre behavior
-        // see: https://bugs.openjdk.java.net/browse/JDK-8024521
-        //      issue is fixed in build 7u60
-        InputStream stdout = process.getInputStream();
-        synchronized (stdout) {
-          inReader.close();
-        }
+        inReader.close();
       } catch (IOException ioe) {
         LOG.warn("Error while closing the input stream", ioe);
       }
@@ -1037,10 +1026,7 @@ public abstract class Shell {
         joinThread(errThread);
       }
       try {
-        InputStream stderr = process.getErrorStream();
-        synchronized (stderr) {
-          errReader.close();
-        }
+        errReader.close();
       } catch (IOException ioe) {
         LOG.warn("Error while closing the error stream", ioe);
       }