Message10684

I can confirm that the following patch also appears to fix the issue.

diff --git a/src/org/python/modules/_io/Closer.java b/src/org/python/modules/_io/Closer.java
index 3aec84f..d4a8a8e 100644
--- a/src/org/python/modules/_io/Closer.java
+++ b/src/org/python/modules/_io/Closer.java
@@ -3,6 +3,7 @@ package org.python.modules._io;

 import java.lang.ref.WeakReference;
 import java.util.concurrent.Callable;
+import java.util.concurrent.atomic.AtomicBoolean;

 import org.python.core.PyObject;
 import org.python.core.PySystemState;
@@ -32,9 +33,12 @@ class Closer<C extends PyIOBase> implements Callable<Void> {
     /** Interpreter state that will call {@link #call()} on shutdown. */
     protected PySystemState sys;

+    private AtomicBoolean dismissed;
+
     public Closer(C toClose, PySystemState sys) {
         this.client = new WeakReference<C>(toClose);
         this.sys = sys;
+        this.dismissed = new AtomicBoolean(false);
         sys.registerCloser(this);
     }

@@ -42,10 +46,9 @@ class Closer<C extends PyIOBase> implements Callable<Void> {
      * Tell the Closer that its services are no longer required. This unhooks it from the shutdown
      * list. Repeated calls are allowed but only the first has any effect.
      */
-    public synchronized void dismiss() {
-        if (sys != null) {
+    public void dismiss() {
+        if (dismissed.compareAndSet(false, true)) {
             sys.unregisterCloser(this);
-            sys = null;
         }
     }

@@ -55,9 +58,8 @@ class Closer<C extends PyIOBase> implements Callable<Void> {
      */
     @Override
     public synchronized Void call() {
-        if (sys != null) {
+        if (dismissed.compareAndSet(false, true)) {
             // This will prevent repeated work and dismiss() manipulating the list of closers
-            sys = null;
             // Call close on the client (if it still exists)
             C toClose = client.get();
             if (toClose != null) {
@@ -66,4 +68,4 @@ class Closer<C extends PyIOBase> implements Callable<Void> {
         }
         return null;
     }
-}
\ No newline at end of file
+}