[jdk11u-dev] RFR: 8281615: Deadlock caused by jdwp agent

[Zhengyu Gu]

I would like to backport this patch to jdk11u, because without the fix, jdwp can potential deadlock whole JVM.

Test:
- [x] Testbase_nsk_jdi
- [x] Testbase_nsk_jvmti
- [x] Testbase_nsk_jdwp

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Commit messages:
 - Backport e1060bee2adb9f2e07ca09309d0f89132db30f28

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/843/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=843&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281615
  Stats: 31 lines in 1 file changed: 18 ins; 5 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/843.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/843/head:pull/843

PR: https://git.openjdk.java.net/jdk11u-dev/pull/843