From f5623b460224ce363316c63f5d28947215078fc5 Mon Sep 17 00:00:00 2001 From: Zheng Tan Date: Tue, 3 May 2016 12:22:52 -0700 Subject: [SPARK-15059][CORE] Remove fine-grained lock in ChildFirstURLClassLoader to avoid dead lock ## What changes were proposed in this pull request? In some cases, fine-grained lock have race condition with class-loader lock and have caused dead lock issue. It is safe to drop this fine grained lock and load all classes by single class-loader lock. Author: Zheng Tan Closes #12857 from tankkyo/master. --- .../apache/spark/util/MutableURLClassLoader.scala | 31 ++++------------------ 1 file changed, 5 insertions(+), 26 deletions(-) diff --git a/core/src/main/scala/org/apache/spark/util/MutableURLClassLoader.scala b/core/src/main/scala/org/apache/spark/util/MutableURLClassLoader.scala index 0a3180da87..034826c57e 100644 --- a/core/src/main/scala/org/apache/spark/util/MutableURLClassLoader.scala +++ b/core/src/main/scala/org/apache/spark/util/MutableURLClassLoader.scala @@ -19,7 +19,6 @@ package org.apache.spark.util import java.net.{URL, URLClassLoader} import java.util.Enumeration -import java.util.concurrent.ConcurrentHashMap import scala.collection.JavaConverters._ @@ -48,32 +47,12 @@ private[spark] class ChildFirstURLClassLoader(urls: Array[URL], parent: ClassLoa private val parentClassLoader = new ParentClassLoader(parent) - /** - * Used to implement fine-grained class loading locks similar to what is done by Java 7. This - * prevents deadlock issues when using non-hierarchical class loaders. - * - * Note that due to some issues with implementing class loaders in - * Scala, Java 7's `ClassLoader.registerAsParallelCapable` method is not called. - */ - private val locks = new ConcurrentHashMap[String, Object]() - override def loadClass(name: String, resolve: Boolean): Class[_] = { - var lock = locks.get(name) - if (lock == null) { - val newLock = new Object() - lock = locks.putIfAbsent(name, newLock) - if (lock == null) { - lock = newLock - } - } - - lock.synchronized { - try { - super.loadClass(name, resolve) - } catch { - case e: ClassNotFoundException => - parentClassLoader.loadClass(name, resolve) - } + try { + super.loadClass(name, resolve) + } catch { + case e: ClassNotFoundException => + parentClassLoader.loadClass(name, resolve) } } -- cgit v1.2.3