RFR: 8376568: Change Thread::getStackTrace to use handshake op for all cases [v3]

[Alan Bateman]

On Tue, 3 Feb 2026 11:04:46 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> The proposal is that ThreadSnapshot.of(Thread) can be called with any platform or virtual Thread in any state. With the update, it eagerly tests with isAlive so will filter out NEW and already TERMINATED threads. If/when we change Thread.getStackTrace to use ThreadSnapshot then the isAlive check can be dropped from Thread.getStackTrace. The underlying implementation in get_thread_snapshot does not need to deal with the NEW state.
>> 
>> There is no need for ThreadDumper to do any additional filtering. The thread streams that it consumes filter out Threads that are not alive.
>
>> There is no need for ThreadDumper to do any additional filtering. The thread streams that it consumes filter out Threads that are not alive.
> 
> Okay that is not at all obvious. But in that case you are never passing a NEW thread to `ThreadSnapshot.of()`. But if that is to be the primary API for getting stacktraces then having it filter on isAlive is reasonable.

The thread stream is documented to be a stream of "live" threads and the implementations filter out unstarted or already terminated threads.

If I read your latest message correctly then I think you are agreement with the current chnage to test isAlive at the "front door". It means get_thread_snapshot is never called with an unstarted/NEW Thread.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29461#discussion_r2759456977