Running the following program:

import jdk.jfr.Recording;
import jdk.jfr.Configuration;
public class P {
  public static void main(String... args) throws Exception {
    Configuration c = Configuration.getConfiguration("default");
    try (Recording r = new Recording(c)) {
       r.start();
       Thread.sleep(10_000);
    }
    System.out.println("Recording finished");
    Thread.sleep(1000_000);
  }
}

With the following line added to RequestEngine.java:

     private static long run_requests(Collection<RequestHook> entries, long eventTimestamp) {
         long last = lastTimeMillis;
+ System.out.println("Time: " + last);
         // The interval for periodic events is typically at least 1 s, so
         // System.currentTimeMillis() is sufficient. JVM.counterTime() lacks

results in:

Time: 1676829368686
Time: 1676829368699
Time: 1676829368711
Time: 1676829368722
Time: 1676829368735
Time: 1676829368747
Time: 1676829368760
Time: 1676829368773
...

The "JFR Periodic Task" thread runs back-to-back, with about 13 ms between each each turn. One would expect the thread to be stopped or at least sleep/wait when a recording is finished. Furthermore, flush calls are made into JVM.after native JFR has been destroyed.

I think this can explain som strange things we have seen, crashes or timeouts.