On Fri, 18 Nov 2022 03:42:39 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
>> Enabling the `notify_jvmti_events` is an optimization to avoid having this >> notification overhead with JVMTI virtual thread mount state transitions when >> it is not needed. >> We need to enable it only once and never disable it if enabled. >> The first attempt to enable it is at startup if there was any agent loaded >> with command line options. >> In such a case, the get_jvmti_interface() is called in a context of >> `AgentOnLoad()` in unattached thread. >> It only sets the `java_lang_VirtualThread::set_notify_jvmti_events(true)` >> The `init_static_notify_jvmti_events()` is called from the >> `javaClasses_init()`. >> The agents that are loaded into running VM are initialized with the >> `AgentOnAttach()`. >> In this case, we can't rely on the `javaClasses_init()` and so, have to >> explicitly call the `init_static_notify_jvmti_events()`. >> I feels like this can be simplified. I keep thinking about the best way to >> do it. >> Probably, the pair <set_notify_jvmti_events, >> init_static_notify_jvmti_events> can be replaced with just function. The >> problem is that we can't use the `ThreadInVMfromNative` helper for >> unattached thread. > > If `notify_jvmti_events()` is false, then you call > `set_notify_jvmti_events(true)`, which means you will never enter the `if` > block again. However, if the thread is not attached, you do not call > `init_static_notify_jvmti_events()`. What happens if later there is an > attached thread that triggers this code? Is seem when that happens you should > call `init_static_notify_jvmti_events()`, but won't because > `notify_jvmti_events()` is true. I think you need a flag that tells you if `init_static_notify_jvmti_events()` has been called. ------------- PR: https://git.openjdk.org/jdk/pull/11204
