RFR: 8331573: Rename CollectedHeap::is_gc_active to be explicitly about STW GCs

[Aleksey Shipilev]

On Thu, 2 May 2024 16:56:11 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> `CollectedHeap::is_gc_active()` is confusing, since its name implies _any_ GC phase is running, while it actually only covers the STW GCs. It would be good to rename it for clarity. The freed-up name, `is_gc_active` could then be repurposed to track any (concurrent or STW) GC phase running. That would be useful to resolve [JDK-8331572](https://bugs.openjdk.org/browse/JDK-8331572).
>> 
>> Doing this rename separately guarantees we have caught and renamed all current uses.
>> 
>> Additional testing:
>>  - [ ] Linux AArch64 server fastdebug, `all`
>
> src/hotspot/share/gc/parallel/psParallelCompact.cpp line 1493:
> 
>> 1491:   PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
>> 1492:   void do_thread(Thread* thread) {
>> 1493:     assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
> 
> Should this be updated to "called outside gc pause" as you did in `G1CollectedHeap::pin_object`? The same comment goes for the other occurrences below.

I deliberately stopped myself from doing this for Parallel GC code, where every GC is STW GC :) I can change to "GC pause" if you want.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19064#discussion_r1587999105