User: sparre
Date: 01/10/03 11:47:10
Modified: src/main/org/jboss/system ServiceLibraries.java
Log:
Changed synchronization to avoid deadlock with SUNs java.lang.ClassLoader
implementation.
Revision Changes Path
1.5 +158 -148 jboss/src/main/org/jboss/system/ServiceLibraries.java
Index: ServiceLibraries.java
===================================================================
RCS file: /cvsroot/jboss/jboss/src/main/org/jboss/system/ServiceLibraries.java,v
retrieving revision 1.4
retrieving revision 1.5
diff -u -r1.4 -r1.5
--- ServiceLibraries.java 2001/09/26 21:47:05 1.4
+++ ServiceLibraries.java 2001/10/03 18:47:10 1.5
@@ -8,7 +8,6 @@
import java.io.File;
import java.net.URL;
-import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
@@ -29,7 +28,8 @@
*
* @see <related>
* @author <a href="mailto:[EMAIL PROTECTED]";>Marc Fleury</a>
- * @version $Revision: 1.4 $ <p>
+ * @author <a href="mailto:[EMAIL PROTECTED]";>Ole Husgaard</a>
+ * @version $Revision: 1.5 $ <p>
*
* <b>20010830 marc fleury:</b>
* <ul>initial import
@@ -38,6 +38,11 @@
* <b>20010908 david jencks:</b>
* <ul>Modified to make undeploy work better.
* <li>
+ * <b>20011003 Ole Husgaard:</b>
+ * <ul>Changed synchronization to avoid deadlock with SUNs
+ * java.lang.Classloader implementation. Kudos to Dr. Christoph Jung
+ * and Sacha Labourey for identifying this problem.
+ * <li>
* </ul>
*
*/
@@ -51,19 +56,38 @@
// Static --------------------------------------------------------
private static ServiceLibraries libraries;
+
// Constants -----------------------------------------------------
// Attributes ----------------------------------------------------
- // The classloaders
+ /**
+ * The classloaders we use for loading classes here.
+ */
private Set classLoaders;
- // The classes kept in this library
- private Map classes, resources,
- // A given classloader loads a set of class
- clToClassSetMap, clToResourceSetMap;
+ /*
+ * Maps class names of the classes loaded here to the classes.
+ */
+ private Map classes;
+
+ /*
+ * Maps class loaders to the set of classes they loaded here.
+ */
+ private Map clToClassSetMap;
+ /*
+ * Maps resource names of resources looked up here to the URLs used to
+ * load them.
+ */
+ private Map resources;
+
+ /*
+ * Maps class loaders to the set of resource names they looked up here.
+ */
+ private Map clToResourceSetMap;
+
// Constructors --------------------------------------------------
// Public --------------------------------------------------------
@@ -76,9 +100,7 @@
public static ServiceLibraries getLibraries()
{
if (libraries == null)
- {
libraries = new ServiceLibraries();
- }
return libraries;
}
@@ -86,7 +108,7 @@
// ServiceClassLoaderMBean implementation ------------------------
/**
- * Gets the Name attribute of the ServiceLibraries object
+ * Gets the Name attribute of the ServiceLibraries object.
*
* @return The Name value
*/
@@ -97,58 +119,56 @@
/**
- * Gets the Resource attribute of the ServiceLibraries object
+ * Find a resource in the ServiceLibraries object.
*
- * @param name Description of Parameter
- * @param scl Description of Parameter
- * @return The Resource value
+ * @param name The name of the resource
+ * @param scl The asking class loader
+ * @return An URL for reading the resource, or <code>null</code> if the
+ * resource could not be found.
*/
public URL getResource(String name, ClassLoader scl)
{
-
- // Is it in the global map?
- if (resources.containsKey(name))
- {
-
- return (URL)resources.get(name);
+ Set classLoaders2;
+ Map resources2;
+ Map clToResourceSetMap2;
+
+ synchronized (this) {
+ // Is it in the global map?
+ if (resources.containsKey(name))
+ return (URL)resources.get(name);
+
+ // No, make copies of the references to avoid working on or changing
+ // a later version of these.
+ classLoaders2 = classLoaders;
+ resources2 = resources;
+ clToResourceSetMap2 = clToResourceSetMap;
}
URL resource = null;
// First ask for the class to the asking class loader
if (scl instanceof URLClassLoader)
- {
resource = ((URLClassLoader)scl).getResourceLocally(name);
- }
if (resource == null)
{
// If not start asking around to URL classloaders for it
- int i = 1;
- synchronized (classLoaders)
- {
- Iterator allLoaders = classLoaders.iterator();
- while (allLoaders.hasNext())
- {
- URLClassLoader cl = (URLClassLoader)allLoaders.next();
+ for (Iterator iter = classLoaders2.iterator(); iter.hasNext();) {
+ URLClassLoader cl = (URLClassLoader)iter.next();
- if (!cl.equals(scl))
- {
+ if (!cl.equals(scl)) { // already tried this one
+ resource = cl.getResourceLocally(name);
- resource = cl.getResourceLocally(name);
-
- if (resource != null)
- {
-
+ if (resource != null) {
+ synchronized (this) {
// We can keep track
- resources.put(name, resource);
+ resources2.put(name, resource);
// When we cycle the cl we also need to remove the classes it
loaded
- Set set = (Set)clToResourceSetMap.get(cl);
- if (set == null)
- {
+ Set set = (Set)clToResourceSetMap2.get(cl);
+ if (set == null) {
set = new HashSet();
- clToResourceSetMap.put(cl, set);
+ clToResourceSetMap2.put(cl, set);
}
//set.add(resource);
@@ -156,102 +176,110 @@
return resource;
}
- //Just cycle through the class loaders until you find it
- }
+ } // if we found it
}
- //allLoaders
- }
- //Synchronization
- }
- // If we reach here, all of the classloaders currently in the VM don't know
about the resource
+ } // for all ClassLoaders
+ } // If we reach here, all of the classloaders currently in the VM don't know
about the resource
+
return resource;
}
/**
- * Adds a feature to the ClassLoader attribute of the ServiceLibraries object
+ * Add a ClassLoader to the ServiceLibraries object.
*
- * @param cl The feature to be added to the ClassLoader attribute
+ * @param cl The class loader to be added.
*/
- public void addClassLoader(URLClassLoader cl)
+ public synchronized void addClassLoader(URLClassLoader cl)
{
- synchronized (classLoaders)
- {
-
- // we allow for duplicate class loader definitions in the services.xml
files
- // we should however only keep the first classloader declared
+ // we allow for duplicate class loader definitions in the services.xml files
+ // we should however only keep the first classloader declared
- if (!classLoaders.contains(cl))
- {
- classLoaders.add(cl);
- System.out.println("Libraries adding URLClassLoader " + cl.hashCode() +
" key URL " + ((URLClassLoader)cl).getKeyURL().toString());
- }
- else
- {
- System.out.println("Libraries skipping duplicate URLClassLoader for key
URL " + ((URLClassLoader)cl).getKeyURL().toString());
- }
- }
+ if (!classLoaders.contains(cl)) {
+ // We create a new copy of the classLoaders set.
+ classLoaders = new HashSet(classLoaders);
+
+ classLoaders.add(cl);
+
+ System.out.println("Libraries adding URLClassLoader " + cl.hashCode() + "
key URL " + ((URLClassLoader)cl).getKeyURL().toString());
+ } else
+ System.out.println("Libraries skipping duplicate URLClassLoader for key
URL " + ((URLClassLoader)cl).getKeyURL().toString());
}
/**
- * #Description of the Method
+ * Remove a ClassLoader from the ServiceLibraries object.
*
- * @param cl Description of Parameter
+ * @param cl The ClassLoader to be removed.
*/
- public void removeClassLoader(URLClassLoader cl)
+ public synchronized void removeClassLoader(URLClassLoader cl)
{
- synchronized (classLoaders)
- {
- System.out.println("removing classloader " + cl);
+ System.out.println("removing classloader " + cl);
- classLoaders.remove(cl);
+ if (!classLoaders.contains(cl))
+ return; // nothing to remove
+ // We create a new copy of the classLoaders set.
+ classLoaders = new HashSet(classLoaders);
+ classLoaders.remove(cl);
+
+ if (clToClassSetMap.containsKey(cl)) {
+ // Create a new copy of the map
+ clToClassSetMap = new HashMap(clToClassSetMap);
+
Set clClasses = (Set)clToClassSetMap.remove(cl);
- if (clClasses != null)
- {
- Iterator iterator = clClasses.iterator();
- while (iterator.hasNext())
- {
- Object o = iterator.next();
- Object o1 = classes.remove(o);
- System.out.println("removing class " + o + ", removed: " + o1);
- }
+
+ for (Iterator iter = clClasses.iterator(); iter.hasNext();) {
+ Object o = iter.next();
+ Object o1 = classes.remove(o);
+ System.out.println("removing class " + o + ", removed: " + o1);
}
+ }
+
+ // Same procedure for resources
+ if (clToResourceSetMap.containsKey(cl)) {
+ clToResourceSetMap = new HashMap(clToResourceSetMap);
Set clResources = (Set)clToResourceSetMap.remove(cl);
- if (clResources != null)
- {
- Iterator iterator2 = clResources.iterator();
- while (iterator2.hasNext())
- {
- Object o = iterator2.next();
- Object o1 = resources.remove(o);
- System.out.println("removing resource " + o + ", removed: " + o1);
- }
+
+ for (Iterator iter = clResources.iterator(); iter.hasNext();) {
+ Object o = iter.next();
+ Object o1 = resources.remove(o);
+ System.out.println("removing resource " + o + ", removed: " + o1);
}
}
- ;
}
/**
- * #Description of the Method
+ * Load a class in the ServiceLibraries object.
*
- * @param name Description of Parameter
- * @param resolve Description of Parameter
- * @param scl Description of Parameter
- * @return Description of the Returned Value
- * @exception ClassNotFoundException Description of Exception
+ * @param name The name of the class
+ * @param resolve If <code>true</code>, the class will be resolved
+ * @param scl The asking class loader
+ * @return The loaded class.
+ * resource could not be found.
+ * @throws ClassNotFoundException If the class could not be found.
*/
public Class loadClass(String name, boolean resolve, ClassLoader scl)
throws ClassNotFoundException
{
- // Try the local map already
- Class foundClass = (Class)classes.get(name);
+ Class foundClass;
+ Set classLoaders2;
+ Map classes2;
+ Map clToClassSetMap2;
+
+ synchronized (this) {
+ // Try the local map already
+ foundClass = (Class)classes.get(name);
- if (foundClass != null)
- {
- return foundClass;
+ if (foundClass != null)
+ return foundClass;
+
+ // Not found, make copies of the references to avoid working on
+ // or changing a later version of these.
+ classLoaders2 = classLoaders;
+ classes2 = classes;
+ clToClassSetMap2 = clToClassSetMap;
}
// If not start asking around to URL classloaders for it
@@ -259,66 +287,49 @@
// who will find it?
URLClassLoader cl = null;
- if (scl instanceof URLClassLoader)
- {
+ if (scl instanceof URLClassLoader) {
// First ask the asking classloader chances are the dependent class is in
there
- try
- {
-
+ try {
foundClass = ((URLClassLoader)scl).loadClassLocally(name, resolve);
//If we get here we know the scl is the right one
cl = (URLClassLoader)scl;
- }
- catch (ClassNotFoundException ignored)
- {
+ } catch (ClassNotFoundException ignored) {
}
}
-
- synchronized (classLoaders)
- {
- Iterator allLoaders = classLoaders.iterator();
- while (allLoaders.hasNext() && (foundClass == null))
- {
- // next!
- cl = (URLClassLoader)allLoaders.next();
-
- if (!scl.equals(cl))
- {
- try
- {
-
- foundClass = cl.loadClassLocally(name, resolve);
- }
- catch (ClassNotFoundException ignored2)
- {
- //try next loader
- }
+ Iterator allLoaders = classLoaders2.iterator();
+ while (allLoaders.hasNext() && (foundClass == null)) {
+ // next!
+ cl = (URLClassLoader)allLoaders.next();
+
+ if (!scl.equals(cl)) {
+ try {
+ foundClass = cl.loadClassLocally(name, resolve);
+ } catch (ClassNotFoundException ignored2) {
+ //try next loader
}
}
- //allLoaders
+ } //allLoaders
- if (foundClass != null)
- {
+ if (foundClass != null) {
+ synchronized (this) {
// We can keep track
- classes.put(name, foundClass);
+ classes2.put(name, foundClass);
// When we cycle the cl we also need to remove the classes it loaded
- Set set = (Set)clToClassSetMap.get(cl);
- if (set == null)
- {
+ Set set = (Set)clToClassSetMap2.get(cl);
+ if (set == null) {
set = new HashSet();
- clToClassSetMap.put(cl, set);
+ clToClassSetMap2.put(cl, set);
}
//set.add(foundClass);
set.add(name);
-
- return foundClass;
}
+
+ return foundClass;
}
- //Synchronization
// If we reach here, all of the classloaders currently in the VM don't know
about the class
throw new ClassNotFoundException(name);
@@ -338,14 +349,13 @@
public ObjectName preRegister(MBeanServer server, ObjectName name)
throws java.lang.Exception
{
-
//this.server = server;
- classLoaders = Collections.synchronizedSet(new HashSet());
- classes = Collections.synchronizedMap(new HashMap());
- resources = Collections.synchronizedMap(new HashMap());
- clToResourceSetMap = Collections.synchronizedMap(new HashMap());
- clToClassSetMap = Collections.synchronizedMap(new HashMap());
+ classLoaders = new HashSet();
+ classes = new HashMap();
+ resources = new HashMap();
+ clToResourceSetMap = new HashMap();
+ clToClassSetMap = new HashMap();
System.out.println("[GPA] Microkernel ClassLoaders and Libraries
initialized");
return name == null ? new ObjectName(OBJECT_NAME) : name;
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