On Tue, 20 Aug 2024 17:38:01 GMT, Leonid Mesnik <lmes...@openjdk.org> wrote:
>> The summary of the problem. Test is intermittently failing because can't get >> expected field watch event. >> The test is failing to get event in the 'setfmodw001b' thread with Xcomp >> only. >> I verified that frame with the method 'run' of setfmodw001b is compiled when >> line >> 118: setfmodw001.setWatch(4); >> is executed, however the thread is in interp_only mode. The watch events are >> supported by interpreter only and just ignored by compiled code. >> >> The reason of failure is race beteween setting interp_only mode in line >> >> https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/vmTestbase/nsk/jvmti/SetFieldModificationWatch/setfmodw001.java#L75 >> >> and calling method call_helper while >> the method run() >> https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/vmTestbase/nsk/jvmti/SetFieldModificationWatch/setfmodw001.java#L116 >> >> in newly created thread 'setfmodw001b' is invoked. >> >> The javaCalls:call are used to invoke methods from hotspot, so it might be >> rare issues. But still, synchronization might be improved. >> The >> void JavaCalls::call_helper(JavaValue* result, const methodHandle& method, >> JavaCallArguments* args, TRAPS) >> >> checks if interp_only mode is set and use 'Method::from_interpreted_entry()' >> if not. However the interp_only might be set later before compiled method is >> called (or enter first safe point?). This might happens in safepoint during >> transition via handshake. >> So the running thread is in interp_only mode however the run() method is >> compiled and executed already and never going to be deoptimized. >> >> The additional setWatch calls don't try to deptimize method that are already >> in interp_only mode. >> >> BTW, the when JVMCI is enabled and verified adapter exists it is also will >> be loaded even in interp_only mode set. There is not race here, just >> ignoring of interp_only mode. >> >> I run failing test with Xcomp ~1000 times and tiers1-5. > > Leonid Mesnik has updated the pull request incrementally with one additional > commit since the last revision: > > fixed identation. Marked as reviewed by sspitsyn (Reviewer). ------------- PR Review: https://git.openjdk.org/jdk/pull/20587#pullrequestreview-2248773043
