On Fri, 11 Sep 2020 18:26:03 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
>> This is a specific of "CheckUnhandledOops" >> I've written in bug comment "Another possible fix would be to disable >> corruption of NULL unhandled oops. They couldn't >> be changed really." >> We discussed it with Coleen and seems that moving NULL oops out of possible >> safepoint or handling them seems easier >> option than changing UnhandledOops.cpp to don't corrupt NULL. It is here: >> https://github.com/openjdk/jdk/blob/77bdc3065057b07a676b010562c89bb0f21512b7/src/hotspot/share/runtime/unhandledOops.cpp#L113 > > ThreadService::get_current_contended_monitor calls > Thread::check_for_dangling_thread_pointer calls > ThreadsSMRSupport::is_a_protected_JavaThread_with_lock((JavaThread *) thread), > The potential safepoint is here, where CheckUnhandledOops puts junk in any > oop on the stack. > > inline bool ThreadsSMRSupport::is_a_protected_JavaThread_with_lock(JavaThread > *thread) { > MutexLocker ml(Threads_lock->owned_by_self() ? NULL : Threads_lock); > return is_a_protected_JavaThread(thread); > } Thanks Coleen. I'm still not sure that CheckUnhandledOops should be touching NULL oops but ... Leonid the workaround seems okay. ------------- PR: https://git.openjdk.java.net/jdk/pull/123
