RFR: 8325871: Move StringTable and SymbolTable rehashing calls

[Erik Österlund]

On Tue, 12 Mar 2024 15:38:01 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> Move the rehashing calls as a test in the concurrent work - ie. trigger concurrent work and check for the need to do rehashing. 
> 
> Tested with tier1-7.

Discussed this a bit with @coleenp and @xmas92. Conclusion is that there was some code before to deal with rehashing in a safepoint happening during concurrent growing in the service thread. Since the safepoint is now explicitly invoked form the service thread, that shouldn't happen any longer, so the related seat belts can be removed. 
And we might want to add double checked locking to StringTable::trigger_concurrent_work which is now called by JavaThreads when interacting with the string table to reduce churn on the lock. 
Otherwise it looks very nice! Simplifying the code and removing things from safepoint cleanup - awesome!

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Changes requested by eosterlund (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18240#pullrequestreview-1939036501