--- a/jdk/src/share/classes/java/lang/ref/Reference.java Wed Jan 29 22:18:46 2014 -0800
+++ b/jdk/src/share/classes/java/lang/ref/Reference.java Thu Jan 30 15:36:04 2014 +0100
@@ -111,7 +111,7 @@
* therefore critical that any code holding this lock complete as quickly
* as possible, allocate no new objects, and avoid calling user code.
*/
- static private class Lock { };
+ static private class Lock { }
private static Lock lock = new Lock();
@@ -126,6 +126,22 @@
*/
private static class ReferenceHandler extends Thread {
+ private static void ensureClassInitialized(Class<?> clazz) {
+ try {
+ Class.forName(clazz.getName(), true, clazz.getClassLoader());
+ } catch (ClassNotFoundException e) {
+ throw (Error) new NoClassDefFoundError(e.getMessage()).initCause(e);
+ }
+ }
+
+ static {
+ // pre-load and initialize InterruptedException and Cleaner classes
+ // so that we don't get into trouble later in the run loop if there's
+ // memory shortage while loading/initializing them lazily.
+ ensureClassInitialized(InterruptedException.class);
+ ensureClassInitialized(Cleaner.class);
+ }
+
ReferenceHandler(ThreadGroup g, String name) {
super(g, name);
}
@@ -133,37 +149,40 @@
public void run() {
for (;;) {
Reference<Object> r;
- synchronized (lock) {
- if (pending != null) {
- r = pending;
- pending = r.discovered;
- r.discovered = null;
- } else {
- // The waiting on the lock may cause an OOME because it may try to allocate
- // exception objects, so also catch OOME here to avoid silent exit of the
- // reference handler thread.
- //
- // Explicitly define the order of the two exceptions we catch here
- // when waiting for the lock.
- //
- // We do not want to try to potentially load the InterruptedException class
- // (which would be done if this was its first use, and InterruptedException
- // were checked first) in this situation.
- //
- // This may lead to the VM not ever trying to load the InterruptedException
- // class again.
- try {
- try {
- lock.wait();
- } catch (OutOfMemoryError x) { }
- } catch (InterruptedException x) { }
- continue;
+ Cleaner c;
+ try {
+ synchronized (lock) {
+ if (pending != null) {
+ r = pending;
+ // 'instanceof' might throw OutOfMemoryError sometimes
+ // so do this before un-linking 'r' from the 'pending' chain...
+ c = r instanceof Cleaner ? (Cleaner) r : null;
+ // unlink 'r' from 'pending' chain
+ pending = r.discovered;
+ r.discovered = null;
+ } else {
+ // The waiting on the lock may cause an OutOfMemoryError
+ // because it may try to allocate exception objects.
+ lock.wait();
+ continue;
+ }
}
+ } catch (OutOfMemoryError x) {
+ // Give other threads CPU time so they hopefully drop some live references
+ // and GC reclaims some space.
+ // Also prevent CPU intensive spinning in case 'r instanceof Cleaner' above
+ // persistently throws OOME for some time...
+ Thread.yield();
+ // retry
+ continue;
+ } catch (InterruptedException x) {
+ // retry
+ continue;
}
// Fast path for cleaners
- if (r instanceof Cleaner) {
- ((Cleaner)r).clean();
+ if (c != null) {
+ c.clean();
continue;
}