On Wed, 25 May 2022 07:23:36 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
> A part of this issue was contributed with the following changeset: > > commit ea23e7333e03abb4aca3e9f3854bab418a4b70e2 > Author: Daniel D. Daugherty <[dcu...@openjdk.org](mailto:dcu...@openjdk.org)> > Date: Mon Nov 8 14:45:04 2021 +0000 > > 8249004: Reduce ThreadsListHandle overhead in relation to direct > handshakes > Reviewed-by: coleenp, sspitsyn, dholmes, rehn > > The following change in `src/hotspot/share/runtime/thread.cpp` added new > assert: > > bool JavaThread::java_suspend() { > - ThreadsListHandle tlh; > - if (!tlh.includes(this)) { > - log_trace(thread, suspend)("JavaThread:" INTPTR_FORMAT " not on > ThreadsList, no suspension", p2i(this)); > - return false; > - } > + guarantee(Thread::is_JavaThread_protected(this, /* checkTLHOnly */ true), > + "missing ThreadsListHandle in calling context."); > return this->handshake_state()->suspend(); > } > > This new assert misses a check for target thread as being current > `JavaThread`. > > Also, the JVMTI SuspendThread is protected with TLH: > > JvmtiEnv::SuspendThread(jthread thread) { > JavaThread* current = JavaThread::current(); > ThreadsListHandle tlh(current); <= TLS defined here!!! > > oop thread_oop = NULL; > { > JvmtiVTMSTransitionDisabler disabler(true); > > > However, it is possible that a new carrier thread (and an associated > `JavaThread`) can be created after the `TLH` was set and the target virtual > thread can be mounted on new carrier thread. Then target virtual thread will > be associated with newly created `JavaThread` which is unprotected by the TLH. > The right way to be protected from this situation it is to prevent mount > state transitions with `JvmtiVTMSTransitionDisabler` before the TLH is set as > in the change below: > > > @@ -929,13 +929,13 @@ JvmtiEnv::GetAllThreads(jint* threads_count_ptr, > jthread** threads_ptr) { > jvmtiError > JvmtiEnv::SuspendThread(jthread thread) { > JavaThread* current = JavaThread::current(); > - ThreadsListHandle tlh(current); > > jvmtiError err; > JavaThread* java_thread = NULL; > oop thread_oop = NULL; > { > JvmtiVTMSTransitionDisabler disabler(true); > + ThreadsListHandle tlh(current); > > err = get_threadOop_and_JavaThread(tlh.list(), thread, &java_thread, > &thread_oop); > if (err != JVMTI_ERROR_NONE) { > > > > This problem exist in all JVMTI Suspend functions: > `SuspendThread`, `SuspendThreadList` and `SuspendAllVirtualThreads`. This nsk.jvmti test is also failing with the guarantee for current platform thread: `test/hotspot/jtreg/vmTestbase/nsk/jvmti/scenarios/hotswap/HS202/hs202t002` # Internal Error (/scratch/sspitsyn/loom5/open/src/hotspot/share/runtime/thread.cpp:1781), pid=7458, tid=7506 # guarantee(Thread::is_JavaThread_protected_by_TLH( this)) failed: missing ThreadsListHandle in calling context. # # JRE version: Java(TM) SE Runtime Environment (19.0) (fastdebug build 19-internal-2022-05-19-0744187.sspitsyn...) # Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 19-internal-2022-05-19-0744187.sspitsyn..., mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64) # Problematic frame: # V [libjvm.so+0x1a41814] JavaThread::java_suspend()+0xa4 . . . . . . . . . . . . . . . . --------------- T H R E A D --------------- Current thread (0x000014b91001d0f0): JavaThread "Thread-1" [_thread_in_vm, id=7506, stack(0x000014b92bafa000,0x000014b92bbfb000)] Stack: [0x000014b92bafa000,0x000014b92bbfb000], sp=0x000014b92bbf8ef0, free space=1019k Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code) V [libjvm.so+0x1a41814] JavaThread::java_suspend()+0xa4 V [libjvm.so+0x1315a79] JvmtiEnvBase::suspend_thread(oop, JavaThread*, bool, int*)+0x379 V [libjvm.so+0x12fb9ca] JvmtiEnv::SuspendThread(_jobject*)+0x1ba V [libjvm.so+0x12a42df] jvmti_SuspendThread+0x17f C [libhs202t002.so+0xc0a7] callbackMethodExit.part.0+0x107 V [libjvm.so+0x1336887] JvmtiExport::post_method_exit_inner(JavaThread*, methodHandle&, JvmtiThreadState*, bool, frame, jvalue&) [clone .part.0]+0x307 V [libjvm.so+0x133ac71] JvmtiExport::notice_unwind_due_to_exception(JavaThread*, Method*, unsigned char*, oop, bool)+0x531 V [libjvm.so+0xfad21a] InterpreterRuntime::exception_handler_for_exception(JavaThread*, oopDesc*)+0xb9a j nsk.jvmti.scenarios.hotswap.HS202.hs202t002.MyThread.display()V+19 j nsk.jvmti.scenarios.hotswap.HS202.hs202t002.MyThread.playWithThis()V+1 j nsk.jvmti.scenarios.hotswap.HS202.hs202t002.MyThread.run()V+1 v ~StubRoutines::call_stub 0x000014b98fa09d47 V [libjvm.so+0xfba465] JavaCalls::call_helper(JavaValue*, methodHandle const&, JavaCallArguments*, JavaThread*)+0x505 V [libjvm.so+0xfbacf4] JavaCalls::call_virtual(JavaValue*, Klass*, Symbol*, Symbol*, JavaCallArguments*, JavaThread*)+0x4b4 V [libjvm.so+0xfbb167] JavaCalls::call_virtual(JavaValue*, Handle, Klass*, Symbol*, Symbol*, JavaThread*)+0x77 V [libjvm.so+0x113d20b] thread_entry(JavaThread*, JavaThread*)+0x12b V [libjvm.so+0x1a40c6a] JavaThread::thread_main_inner()+0x21a V [libjvm.so+0x1a4e520] Thread::call_run()+0x100 V [libjvm.so+0x16fc3a4] thread_native_entry(Thread*)+0x104 ------------- PR: https://git.openjdk.java.net/jdk/pull/8878
