On Tue, 30 Apr 2024 01:49:31 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
>> src/hotspot/share/prims/jvmtiThreadState.cpp line 366: >> >>> 364: attempts--; >>> 365: } >>> 366: DEBUG_ONLY(if (attempts == 0) break;) >> >> Previously `_VTMS_transition_count` considered all threads at the same time. >> Now you are iterating through the threads and looking at a flag in each one. >> Is it guaranteed that once the `_VTMS_transition_mark` flag has been >> verified not to be set in a thread it won't get set while still iterating in >> the threads loop? > > Thank you for the comment. It is thinking in a right direction. > Each `JavaThread` set the `VTM_transition_mark` only once and then checks for > disable counters: > - `_VTMS_transition_disable_for_all_count` > - `java_lang_Thread::VTMS_transition_disable_count(vth())` > > If any of the disable counters is not zero then each `JavaThread` clears the > optimistically set mark and continues under protection of the > `JvmtiVTMSTransition_lock`. I'm not sure this answered Chris' query properly. Or I'm reading Chris' query wrong. Perhaps this is not what Chris had in mind, but I'm wondering what happens in some Thread-A when it is checked and passed by but then Thread-A sets the flag in itself after the for-loop has passed it by. Does that Thread-A flag value get lost? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/18937#discussion_r1597266296
