RFR: 8074101: Add verification that all tasks are actually claimed during roots processing [v5]

[Thomas Schatzl]

On Wed, 13 Jan 2021 11:19:12 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> The first commit removes some obsolete enum items, while the second commit adds the verification logic. Commit 2 introduces some "empty" task claims for the verification logic, explicitly marked in the comments.
>> 
>> Test: hotspot_gc
>
> Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review

Lgmt.

src/hotspot/share/gc/shared/workgroup.cpp line 377:

> 375:   // all non-skipped tasks are claimed
> 376:   for (uint i = 0; i < _n_tasks; ++i) {
> 377:     if (_tasks[i] == 0) {

pre-existing: This could be fixed in a separate CR: _tasks could be an array of bool instead of (u)int. Using an int is a historic artifact of not having a good Atomics library.

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2046