RFR: 8304147: JVM crash during shutdown when dumping dynamic archive [v3]

[David Holmes]

> `DynamicArchive::prepare_for_dump_at_exit()` could be called concurrently on the two VM exit paths, leading either to assertion failures in debug builds, or a crash in product build when the actual dump occurred. The basic fix was to move the `DynamicArchive::prepare_for_dump_at_exit()` functionality into `before_exit` (java.cpp) where it can only be executed by one thread - thus avoiding the race (Phase 1).
> 
> Once that is done we can move the actual dump operation to be co-located with the `prepare_for_dump_at_exit()` (Phase 2) and then consolidate that code by refactoring it into a new `DynamicArchive::dump_at_exit()` method (Phase 3), and then removing the leftover methods that are no longer needed (Phase 4).
> 
> Each phase can be seen in distinct commits if you prefer to see the steps involved.
> 
> Testing:
>  - new ExitRace test
>  - all dynamicArchive tests
>  - tiers 1-4
> 
> Thanks.

David Holmes has updated the pull request incrementally with one additional commit since the last revision:

  Address Coleen's comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13134/files
  - new: https://git.openjdk.org/jdk/pull/13134/files/518f5409..f037df96

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13134&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13134&range=01-02

  Stats: 7 lines in 1 file changed: 1 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/13134.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13134/head:pull/13134

PR: https://git.openjdk.org/jdk/pull/13134