User: sparre
Date: 01/10/03 14:43:29
Modified: src/main/org/jboss/system ServiceLibraries.java
Log:
Fixed a possible race between classloader removal and class load.
Revision Changes Path
1.6 +62 -25 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 1.5
retrieving revision 1.6
diff -u -r1.5 -r1.6
--- ServiceLibraries.java 2001/10/03 18:47:10 1.5
+++ ServiceLibraries.java 2001/10/03 21:43:29 1.6
@@ -29,7 +29,7 @@
* @see <related>
* @author <a href="mailto:[EMAIL PROTECTED]";>Marc Fleury</a>
* @author <a href="mailto:[EMAIL PROTECTED]";>Ole Husgaard</a>
- * @version $Revision: 1.5 $ <p>
+ * @version $Revision: 1.6 $ <p>
*
* <b>20010830 marc fleury:</b>
* <ul>initial import
@@ -77,6 +77,16 @@
*/
private Map clToClassSetMap;
+ /**
+ * The version number of the {@link #clToClassSetMap} map.
+ * If a lookup of a class detects a change in this while calling
+ * the classloaders with locks removed, the {@link #clToClassSetMap}
+ * and {@link #classes} fields should <em>only</em> be modified
+ * if the classloader used for loading the class is still in the
+ * {@link #classLoaders] set.
+ */
+ private long clToClassSetMapVersion = 0;
+
/*
* Maps resource names of resources looked up here to the URLs used to
* load them.
@@ -88,6 +98,16 @@
*/
private Map clToResourceSetMap;
+ /**
+ * The version number of the {@link #clToResourceSetMap} map.
+ * If a lookup of a resource detects a change in this while
+ * calling the classloaders with locks removed, the
+ * {@link #clToResourceSetMap} and {@link #resources} fields should
+ * <em>only</em> be modified if the classloader used for loading
+ * the class is still in the {@link #classLoaders] set.
+ */
+ private long clToResourceSetMapVersion = 0;
+
// Constructors --------------------------------------------------
// Public --------------------------------------------------------
@@ -129,19 +149,20 @@
public URL getResource(String name, ClassLoader scl)
{
Set classLoaders2;
- Map resources2;
- Map clToResourceSetMap2;
+ long clToResourceSetMapVersion2;
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.
+ // No, make copies of the classLoader reference to avoid working on
+ // a later version of it.
classLoaders2 = classLoaders;
- resources2 = resources;
- clToResourceSetMap2 = clToResourceSetMap;
+
+ // Save the current version of the resource map, so we
+ // can detect if it has changed.
+ clToResourceSetMapVersion2 = clToResourceSetMapVersion;
}
URL resource = null;
@@ -161,17 +182,25 @@
if (resource != null) {
synchronized (this) {
+ // Did the version change?
+ if (clToResourceSetMapVersion2 != clToResourceSetMapVersion) {
+ // Yes. Is the class loader we used still here?
+ if (!classLoaders.contains(cl)) {
+ // No, it was removed from under us.
+ // Don't change the maps, simply return the resource.
+ return resource;
+ }
+ }
// We can keep track
- resources2.put(name, resource);
+ resources.put(name, resource);
// When we cycle the cl we also need to remove the classes it
loaded
- Set set = (Set)clToResourceSetMap2.get(cl);
+ Set set = (Set)clToResourceSetMap.get(cl);
if (set == null) {
set = new HashSet();
- clToResourceSetMap2.put(cl, set);
+ clToResourceSetMap.put(cl, set);
}
- //set.add(resource);
set.add(name);
return resource;
@@ -223,8 +252,8 @@
classLoaders.remove(cl);
if (clToClassSetMap.containsKey(cl)) {
- // Create a new copy of the map
- clToClassSetMap = new HashMap(clToClassSetMap);
+ // We have a new version of the map
+ ++clToClassSetMapVersion;
Set clClasses = (Set)clToClassSetMap.remove(cl);
@@ -237,7 +266,7 @@
// Same procedure for resources
if (clToResourceSetMap.containsKey(cl)) {
- clToResourceSetMap = new HashMap(clToResourceSetMap);
+ ++clToResourceSetMapVersion;
Set clResources = (Set)clToResourceSetMap.remove(cl);
@@ -265,8 +294,7 @@
{
Class foundClass;
Set classLoaders2;
- Map classes2;
- Map clToClassSetMap2;
+ long clToClassSetMapVersion2;
synchronized (this) {
// Try the local map already
@@ -275,11 +303,13 @@
if (foundClass != null)
return foundClass;
- // Not found, make copies of the references to avoid working on
- // or changing a later version of these.
+ // Not found, make copies of the classLoader reference to avoid
+ // working on a later version of it.
classLoaders2 = classLoaders;
- classes2 = classes;
- clToClassSetMap2 = clToClassSetMap;
+
+ // Save the current version of the class map, so we
+ // can detect if it has changed.
+ clToClassSetMapVersion2 = clToClassSetMapVersion;
}
// If not start asking around to URL classloaders for it
@@ -314,17 +344,24 @@
if (foundClass != null) {
synchronized (this) {
+ // Did the version change?
+ if (clToClassSetMapVersion2 != clToClassSetMapVersion) {
+ // Yes. Is the class loader we used still here?
+ if (!classLoaders.contains(cl)) {
+ // No, it was removed from under us.
+ // Don't change the maps, simply return the class.
+ return foundClass;
+ }
+ }
// We can keep track
- classes2.put(name, foundClass);
+ classes.put(name, foundClass);
// When we cycle the cl we also need to remove the classes it loaded
- Set set = (Set)clToClassSetMap2.get(cl);
+ Set set = (Set)clToClassSetMap.get(cl);
if (set == null) {
set = new HashSet();
- clToClassSetMap2.put(cl, set);
+ clToClassSetMap.put(cl, set);
}
-
- //set.add(foundClass);
set.add(name);
}
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