RFR: 8253262: Allocate in DumpRegion is not thread safe

Thu Sep 17 04:58:54 UTC 2020

At CDS dump, the symbols are allocated from _dump_region (DumpRegion) which is global, and not thread safe when
executed in JavaThread. Add a lock DumpRegoin_lock to guard symbol allocation from it.

Tests: tier1-4

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Commit messages:
 - 8253262: Allocate in DumpRegion is not thread safe

Changes: https://git.openjdk.java.net/jdk/pull/216/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=216&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253262
  Stats: 12 lines in 3 files changed: 5 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/216.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/216/head:pull/216

PR: https://git.openjdk.java.net/jdk/pull/216