[jdk15u-dev] RFR: 8273790: Potential cyclic dependencies between Gregorian and CalendarSystem

[Yuri Nesterenko]

Clean backport of a potential deadlock fix. The test works fine: does pass after the fix, timeouts before.

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Commit messages:
 - Backport ddc262746aea99050b9a6484f51c7ddb8f4bc991

Changes: https://git.openjdk.java.net/jdk15u-dev/pull/127/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk15u-dev&pr=127&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273790
  Stats: 183 lines in 2 files changed: 179 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk15u-dev/pull/127.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk15u-dev pull/127/head:pull/127

PR: https://git.openjdk.java.net/jdk15u-dev/pull/127