On Wed, 25 Jun 2025 10:15:54 GMT, Alan Bateman <al...@openjdk.org> wrote:
>> ThreadDumper/ThreadSnapshot need to handle a failure to resolve the native
>> VM JavaThread from a java.lang.Thread. This is hard to reproduce but a
>> thread that has since terminated can provoke a crash. Recognise this and
>> return a null ThreadSnapshot.
>
> src/java.base/share/classes/jdk/internal/vm/ThreadDumper.java line 184:
>
>> 182: if (snapshot == null) {
>> 183: return; // Terminated
>> 184: }
>
> Would it be possible to use this instance, otherwise the thread counts will
> be confusing.
>
>
> --- a/src/java.base/share/classes/jdk/internal/vm/ThreadDumper.java
> +++ b/src/java.base/share/classes/jdk/internal/vm/ThreadDumper.java
> @@ -178,8 +178,11 @@ private static void dumpThreads(ThreadContainer
> container, TextWriter writer) {
> }
>
> private static void dumpThread(Thread thread, TextWriter writer) {
> - ThreadSnapshot snapshot = ThreadSnapshot.of(thread);
> Instant now = Instant.now();
> + ThreadSnapshot snapshot = ThreadSnapshot.of(thread);
> + if (snapshot == null) {
> + return; // thread terminated
> + }
> Thread.State state = snapshot.threadState();
> writer.println("#" + thread.threadId() + " "" + snapshot.threadName()
> + "" " + (thread.isVirtual() ? "virtual " : "") + state + "
> " + now);
> @@ -284,8 +287,9 @@ private static void dumpThreads(ThreadContainer
> container, JsonWriter jsonWriter
> Iterator<Thread> threads = container.threads().iterator();
> while (threads.hasNext()) {
> Thread thread = threads.next();
> - dumpThread(thread, jsonWriter);
> - threadCount++;
> + if (dumpThread(thread, jsonWriter)) {
> + threadCount++;
> + }
> }
> jsonWriter.endArray(); // threads
>
> @@ -305,9 +309,12 @@ private static void dumpThreads(ThreadContainer
> container, JsonWriter jsonWriter
> * Write a thread to the given JSON writer.
> * @throws UncheckedIOException if an I/O error occurs
> */
> - private static void dumpThread(Thread thread, JsonWriter jsonWriter) {
> + private static boolean dumpThread(Thread thread, JsonWriter jsonWriter) {
> Instant now = Instant.now();
> ThreadSnapshot snapshot = ThreadSnapshot.of(thread);
> + if (snapshot == null) {
> + return false; // thread terminated
> + }
> Thread.State state = snapshot.threadState();
> StackTraceElement[] stackTrace = snapshot.stackTrace();
>
> @@ -369,6 +376,7 @@ private static void dumpThread(Thread thread, JsonWriter
> jsonWriter) {
> }
>
> jsonWriter.endObject();
> + return true;
> }
Yes, will do that to fix the threadCount...
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/25958#discussion_r2166363495
