As noted in [JDK-8352088](https://bugs.openjdk.org/browse/JDK-8352088), JVMTI `GetThreadGroupChildren` does an upcall to java. This results in a`ClassPrepare` event the first time it does this, and these events can cause problems (deadlocks) for the debugger or debug agent. The [JDK-8352088](https://bugs.openjdk.org/browse/JDK-8352088) was fixed to get rid of class loading during Java upcall from `GetThreadGroupChildren`. However, some other events can be generated as well. It is more safe to disable all JVMTI events during debugger-related upcalls originated by JVMTI. The `ClassPrepare` events are important for the debug agent. So, an assert was added into `ClassPrepare` event generation to make sure there are no attempts to post this event during upcalls. Some specific implementation details can be added to the first PR comment.
Testing: - Verified with the test `jdk/com/sun/jdi/EarlyThreadGroupChildrenTest.java` that was added with the fix of [JDK-8352088](https://bugs.openjdk.org/browse/JDK-8352088): - the assert described above is fired if the fix of JDK-8352088 is removed - the test is passed without if the fix of JDK-8352088 is removed and the assert is removed - Ran mach5 tiers 1-6 ------------- Commit messages: - 8352773: JVMTI should disable events during java upcalls Changes: https://git.openjdk.org/jdk/pull/24539/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24539&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8352773 Stats: 32 lines in 6 files changed: 30 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/24539.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/24539/head:pull/24539 PR: https://git.openjdk.org/jdk/pull/24539
