From 9af8a68cdd137731a2412110db39df01e6f12617 Mon Sep 17 00:00:00 2001
From: Charles Oliver Nutter <headius@headius.com>
Date: Thu, 9 May 2024 15:10:24 -0500
Subject: [PATCH] Synchronize state in AbstractVariable and Argv

These fields are changed together but without any synchronization
or atomicity. Simplest fix for now is to synchronize the methods
and mark them as volatile.

Fixes #8178
---
 .../org/jruby/embed/variable/AbstractVariable.java | 14 +++++++-------
 .../main/java/org/jruby/embed/variable/Argv.java   |  8 ++++----
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java b/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java
index 46177487d74..386df1e93ac 100644
--- a/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java
+++ b/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java
@@ -49,10 +49,10 @@ abstract class AbstractVariable implements BiVariable {
      */
     protected final IRubyObject receiver;
     protected final String name;
-    protected Object javaObject = null;
-    protected Class javaType = null;
-    protected IRubyObject rubyObject = null;
-    protected boolean fromRuby;
+    protected volatile Object javaObject;
+    protected volatile Class javaType;
+    protected volatile IRubyObject rubyObject;
+    protected volatile boolean fromRuby;
 
     /**
      * Constructor used when this variable is originaed from Java.
@@ -94,7 +94,7 @@ static RubyObject getTopSelf(final IRubyObject receiver) {
         return (RubyObject) receiver.getRuntime().getTopSelf();
     }
 
-    protected void updateByJavaObject(final Ruby runtime, Object... values) {
+    protected synchronized void updateByJavaObject(final Ruby runtime, Object... values) {
         assert values != null;
         javaObject = values[0];
         if (javaObject == null) {
@@ -108,7 +108,7 @@ protected void updateByJavaObject(final Ruby runtime, Object... values) {
         fromRuby = false;
     }
 
-    protected void updateRubyObject(final IRubyObject rubyObject) {
+    protected synchronized void updateRubyObject(final IRubyObject rubyObject) {
         if ( rubyObject == null ) return;
         this.rubyObject = rubyObject;
         this.javaType = null;
@@ -134,7 +134,7 @@ public String getName() {
         return name;
     }
 
-    public Object getJavaObject() {
+    public synchronized Object getJavaObject() {
         if (rubyObject == null) return javaObject;
 
         if (javaType != null) { // Java originated variables
diff --git a/core/src/main/java/org/jruby/embed/variable/Argv.java b/core/src/main/java/org/jruby/embed/variable/Argv.java
index ad8559f10c2..0040990cbbe 100644
--- a/core/src/main/java/org/jruby/embed/variable/Argv.java
+++ b/core/src/main/java/org/jruby/embed/variable/Argv.java
@@ -114,7 +114,7 @@ public static boolean isValidName(Object name) {
      * invoked during EvalUnit#run() is executed.
      */
     @Override
-    public void inject() {
+    public synchronized void inject() {
         final Ruby runtime = getRuntime();
 
         final RubyArray argv = RubyArray.newArray(runtime);
@@ -141,7 +141,7 @@ else if ( javaObject instanceof String[] ) {
      * this variable in top self.
      */
     @Override
-    public void remove() {
+    public synchronized void remove() {
         this.javaObject = new ArrayList();
         inject();
     }
@@ -173,7 +173,7 @@ private static void updateARGV(final IRubyObject receiver, final BiVariableMap v
     }
 
     // ARGV appears to require special treatment, leaving javaType intact
-    protected void updateRubyObject(final IRubyObject rubyObject) {
+    protected synchronized void updateRubyObject(final IRubyObject rubyObject) {
         if ( rubyObject == null ) return;
         this.rubyObject = rubyObject;
     }
@@ -193,7 +193,7 @@ public static void retrieveByKey(RubyObject receiver, BiVariableMap vars, String
 
     @Override
     @SuppressWarnings("unchecked")
-    public Object getJavaObject() {
+    public synchronized Object getJavaObject() {
         if ( rubyObject == null || ! fromRuby ) return javaObject;
 
         final RubyArray ary = (RubyArray) rubyObject;