On Wed, 14 Aug 2024 19:34:26 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. src/hotspot/share/runtime/javaCalls.cpp line 358: > 356: #endif > 357: > 358: CompilationPolicy::compile_if_required(method, CHECK); I'd like to understand what is going to happen at the line 358. Are we going to compile method with -Xcomp even though the `interp_only` mode is required? If so, do we waist cycles in doing this? This question is not to Leonid. Maybe @dean-long could answer this, please? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20587#discussion_r1722514173
