RFR: 8330846: Add stacks of mounted virtual threads to the HotSpot thread dump [v7]

[Thomas Stuefe]

On Tue, 4 Jun 2024 05:30:36 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> src/hotspot/share/runtime/javaThread.cpp line 1832:
>> 
>>> 1830:         st->print("\t");
>>> 1831:         indentation--;
>>> 1832:       }
>> 
>> Suggestion:
>> 
>> while (indentation-- > 0) {
>>   st->print("\t");
>> }
>> 
>> Though not sure using `\t` is the best way to indent this as stream indentation is based on spaces.
>
> Actually I'm not sure what this indentation actually does at this location and its affect on other user's of this API. I would have expected the caller to set up the necessary indentation in the stream that gets passed in. I see you inc the indentation but then use the current indentation to insert multiple tabs - which should not be necessary if the stream indentation works correctly. ???

Note that We are in the process of adding better and saner auto-indentation to outputStream. See https://github.com/openjdk/jdk/pull/19461 . I don't think that PR is going to take long.

If you don't want to wait, please:
- As David wrote, use spaces, not tabs
- Today's pattern for using outputStream indentation is:
  - set up indentation, preferably with streamIndentor, not manually with inc/dec
  - then, before printing each line, call stream->indent()
 
This pattern would also help us to later identify and remove this manual indentation pattern if auto-indent becomes a thing.

But really, waiting for https://github.com/openjdk/jdk/pull/19461 would be preferable. Then, all you have to do is place a streamIndentor around stack printing. Sub-function printing is then indented automatically.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19482#discussion_r1625622263