On Wed, 9 Apr 2025 20:38:08 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
>> 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 > > src/hotspot/share/prims/jvmtiEnvBase.cpp line 867: > >> 865: // This call collects the strong and weak groups >> 866: JavaThread* THREAD = current_thread; >> 867: JvmtiJavaUpcallMark jjum(current_thread); > > Add comment like you did above for the JvmtiEnv::InterruptThread case. Okay, thanks! Added now. > src/hotspot/share/prims/jvmtiExport.cpp line 1419: > >> 1417: // ClassPrepare events are important for JDWP agent but not >> expected during such upcalls. >> 1418: // Catch if this invariant is not broken. >> 1419: assert(!thread->is_in_java_upcall(), "unexpected ClassPrepare >> event during JVMTI upcall"); > > I think we should do this for ClassLoad also. Okay, thanks! Updated now. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/24539#discussion_r2036227345 PR Review Comment: https://git.openjdk.org/jdk/pull/24539#discussion_r2036227287
