RFR: 8282427: jdk/jfr/jvm/TestWaste.java is failing with "exit code 139"

[Erik Gahlin]

Could I get a review for a PR that relaxes an assert? When removing the last parent in a frontier, the queue can fill while processing its children, causing _dfs_fallback_idx to equal _next_frontier_idx.

Testing: 5000 * test/jdk/jdk/jfr/jvm/TestWaste.java

Thanks
Erik

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Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/27779/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27779&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8282427
  Stats: 2 lines in 2 files changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27779.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27779/head:pull/27779

PR: https://git.openjdk.org/jdk/pull/27779