RFR: 8366154: Validate thread type requirements in debug commands [v2]

[Kevin Walls]

On Tue, 9 Sep 2025 09:27:22 GMT, Kerem Kat <krk at openjdk.org> wrote:

>> Have used these occasionally and am surprised to realize psf and others show frames from the VM operation's caller thread.
>> 
>> 
>> The duplication around the active() checks is odd.  If we are adding:
>> 
>> bool onThread()
>> If no current thread, print warning and return false.  Callers will return immediately.
>> 
>> Could we add e.g.:
>> 
>> bool hasActiveThread()
>> If no current thread, print warning and return false.  Callers will return immediately.
>> If no active thread, print warning and return false.  Callers will return immediately.
>> Callers can go on to use  JavaThread* p = JavaThread::active(); without checking (as we currently do).
>> (We are presumably in a debugger session, speed is not the priority, repeating some checks or fetching of active() is not tragic, but this file has less duplication.)
>
> Thank you for the description for `hasActiveThread`. Is it much different than the `onJavaThread` in the first revision?

OK, I see now that I'm suggesting more like what you had originally, that you go back to what David disliked. 8-)

I would have gone for having this check in the helper method (even if it means multiple Thread::current calls) over duplication inserted into three command implementations.  Seems like a way to fix their assumptions also.

Just want to check with David if he might agree that keeping the individual commands simpler is worth permitting the additional helper method.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27033#discussion_r2332935293