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

[Aleksey Shipilev]

On Thu, 2 May 2024 17:04:44 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 1270:
> 
>> 1268: 
>> 1269:   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
>> 1270:   assert(!heap->is_stw_gc_active(), "not reentrant");
> 
> While reading this I see that all these "not reentrant" asserts seems redundant given that we already do these checks in `IsSTWGCActiveMark`. Brownies points if you get rid of them. ;)

Ah, hm. Indeed! Separate PR? There is some light cleanup in G1 that can be associated with it. This PR would keep with just a mechanical rename.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19064#discussion_r1588015870