[SPARK-6014] [core][hotfix] Add try-catch block around ShutDownHook

core/src/main/scala/org/apache/spark/storage/DiskBlockManager.scala

@@ -148,7 +148,12 @@ private[spark] class DiskBlockManager(blockManager: BlockManager, conf: SparkCon
   /** Cleanup local dirs and stop shuffle sender. */
   private[spark] def stop() {
     // Remove the shutdown hook.  It causes memory leaks if we leave it around.
-    Utils.removeShutdownHook(shutdownHook)
+    try {
+      Utils.removeShutdownHook(shutdownHook)
+    } catch {
+      case e: Exception => 
+        logError(s"Exception while removing shutdown hook.", e)
+    }
     doStop()
   }
 

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -2170,7 +2170,7 @@ private [util] class SparkShutdownHookManager {
   def runAll(): Unit = synchronized {
     shuttingDown = true
     while (!hooks.isEmpty()) {
-      Utils.logUncaughtExceptions(hooks.poll().run())
+      Try(Utils.logUncaughtExceptions(hooks.poll().run()))
     }
   }
 
@@ -2182,7 +2182,6 @@ private [util] class SparkShutdownHookManager {
   }
 
   def remove(ref: AnyRef): Boolean = synchronized {
-    checkState()
     hooks.remove(ref)
   }