[GR-67221] Avoid dereferencing possibly dead weakref in thread disposal

PullRequest: graal/21357

Author: msimacek

truffle/src/com.oracle.truffle.polyglot/src/com/oracle/truffle/polyglot/PolyglotContextImpl.java

@@ -83,6 +83,7 @@
 import java.util.function.Supplier;
 import java.util.logging.Level;
 
+import org.graalvm.collections.Pair;
 import org.graalvm.options.OptionValues;
 import org.graalvm.polyglot.Context;
 import org.graalvm.polyglot.PolyglotException;
@@ -928,7 +929,7 @@ void resume(Future<Void> pauseFuture) {
     @TruffleBoundary
     Object[] enterThreadChanged(boolean enterReverted, boolean pollSafepoint, boolean mustSucceed, PolyglotThreadTask polyglotThreadFirstEnter,
                     boolean leaveAndEnter) {
-        List<Map.Entry<Thread, PolyglotThreadInfo>> deadThreads = null;
+        List<Pair<Thread, PolyglotThreadInfo>> deadThreads = null;
         PolyglotThreadInfo enteredThread = null;
         boolean localEnterReverted = enterReverted;
         Object[] prev = null;
@@ -1121,21 +1122,21 @@ Object[] enterThreadChanged(boolean enterReverted, boolean pollSafepoint, boolea
         }
     }
 
-    private void finalizeAndDisposeThreads(List<Map.Entry<Thread, PolyglotThreadInfo>> deadThreads) {
+    private void finalizeAndDisposeThreads(List<Pair<Thread, PolyglotThreadInfo>> deadThreads) {
         assert !Thread.holdsLock(this);
         Throwable ex = null;
-        for (Map.Entry<Thread, PolyglotThreadInfo> removedThreadInfoEntryToRemove : deadThreads) {
-            ex = notifyThreadFinalizing(removedThreadInfoEntryToRemove.getValue(), ex, false);
+        for (Pair<Thread, PolyglotThreadInfo> removedThreadInfoEntryToRemove : deadThreads) {
+            ex = notifyThreadFinalizing(removedThreadInfoEntryToRemove.getRight(), ex, false);
         }
 
-        for (Map.Entry<Thread, PolyglotThreadInfo> threadInfoEntryToRemove : deadThreads) {
-            ex = notifyThreadDisposing(threadInfoEntryToRemove.getValue(), ex);
+        for (Pair<Thread, PolyglotThreadInfo> threadInfoEntryToRemove : deadThreads) {
+            ex = notifyThreadDisposing(threadInfoEntryToRemove.getRight(), ex);
         }
 
         synchronized (this) {
-            for (Map.Entry<Thread, PolyglotThreadInfo> threadInfoEntryToRemove : deadThreads) {
-                threadInfoEntryToRemove.getValue().setContextThreadLocals(DISPOSED_CONTEXT_THREAD_LOCALS);
-                threads.remove(threadInfoEntryToRemove.getKey());
+            for (Pair<Thread, PolyglotThreadInfo> threadInfoEntryToRemove : deadThreads) {
+                threadInfoEntryToRemove.getRight().setContextThreadLocals(DISPOSED_CONTEXT_THREAD_LOCALS);
+                threads.remove(threadInfoEntryToRemove.getLeft());
             }
         }
 
@@ -1144,20 +1145,22 @@ private void finalizeAndDisposeThreads(List<Map.Entry<Thread, PolyglotThreadInfo
         }
     }
 
-    private List<Map.Entry<Thread, PolyglotThreadInfo>> collectDeadThreads() {
+    private List<Pair<Thread, PolyglotThreadInfo>> collectDeadThreads() {
         assert Thread.holdsLock(this);
-        List<Map.Entry<Thread, PolyglotThreadInfo>> deadThreads = null;
+        List<Pair<Thread, PolyglotThreadInfo>> deadThreads = null;
         /*
          * A thread is added to the threads map only by the thread itself, so when the thread is in
          * the map, and it is not alive, then it surely won't be used ever again.
          */
         for (Map.Entry<Thread, PolyglotThreadInfo> threadInfoEntry : threads.entrySet()) {
-            if (!threadInfoEntry.getKey().isAlive() && !threadInfoEntry.getValue().isFinalizingDeadThread()) {
+            Thread thread = threadInfoEntry.getKey();
+            PolyglotThreadInfo threadInfo = threadInfoEntry.getValue();
+            if (thread != null && threadInfo != null && !thread.isAlive() && !threadInfo.isFinalizingDeadThread()) {
                 if (deadThreads == null) {
                     deadThreads = new ArrayList<>();
                 }
-                deadThreads.add(threadInfoEntry);
-                threadInfoEntry.getValue().setFinalizingDeadThread();
+                deadThreads.add(Pair.create(thread, threadInfo));
+                threadInfo.setFinalizingDeadThread();
             }
         }
         return deadThreads;