8345493: JFR: JVM.flush hangs intermittently

Reviewed-by: egahlin
Backport-of: 4257215

Author: Markus Grönlund

src/jdk.jfr/share/classes/jdk/jfr/internal/PlatformRecorder.java

@@ -679,4 +679,8 @@ public synchronized void migrate(SafePath repo) throws IOException {
     public RepositoryChunk getCurrentChunk() {
         return currentChunk;
     }
+
+    public synchronized void flush() {
+        MetadataRepository.getInstance().flush();
+    }
 }

src/jdk.jfr/share/classes/jdk/jfr/internal/periodic/FlushTask.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -26,6 +26,8 @@
 
 import jdk.jfr.internal.JVM;
 import jdk.jfr.internal.MetadataRepository;
+import jdk.jfr.internal.PlatformRecorder;
+import jdk.jfr.internal.PrivateAccess;
 import jdk.jfr.internal.util.Utils;
 
 /**
@@ -44,7 +46,8 @@ public FlushTask() {
 
     @Override
     public void execute(long timestamp, PeriodicType periodicType) {
-        MetadataRepository.getInstance().flush();
+        PlatformRecorder recorder = PrivateAccess.getInstance().getPlatformRecorder();
+        recorder.flush();
         Utils.notifyFlush();
     }