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`. The test `serviceability/jvmti/vthread/SelfSuspendDisablerTest` is triggering this guarantee. But it needs this update in the `SuspendThread` in order to do it. # Internal Error (/scratch/sspitsyn/loom5/open/src/hotspot/share/runtime/thread.cpp:1781), pid=31157, tid=31182 # 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, sharing, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64) # Problematic frame: # V [libjvm.so+0x1a41724] JavaThread::java_suspend()+0xa4 . . . . . --------------- S U M M A R Y ------------ Command Line: -Dtest.vm.opts=-XX:+CreateCoredumpOnCrash --enable-preview -Djava.util.concurrent.ForkJoinPool.common.parallelism=1 -XX:-VerifyContinuations -XX:+CheckUnhandledOops -Xcheck:jni -Dmain.wrapper=Virtual -Dtest.tool.vm.opts=-J-XX:+CreateCoredumpOnCrash -J--enable-preview -J-Djava.util.concurrent.ForkJoinPool.common.parallelism=1 -J-XX:-VerifyContinuations -J-XX:+CheckUnhandledOops -J-Xcheck:jni -J-Dmain.wrapper=Virtual -Dtest.compiler.opts= -Dtest.java.opts= -Dtest.jdk=/scratch/sspitsyn/loom5/build/linux-x64-debug/images/jdk -Dcompile.jdk=/scratch/sspitsyn/loom5/build/linux-x64-debug/images/jdk -Dtest.timeout.factor=1.0 -Dtest.nativepath=/scratch/sspitsyn/loom5/build/linux-x64-debug/images/test/hotspot/jtreg/native -Dtest.root=/scratch/sspitsyn/loom5/open/test/hotspot/jtreg -Dtest.name=serviceability/jvmti/vthread/SelfSuspendDisablerTest/SelfSuspendDisablerTest.java -Dtest.file=/scratch/sspitsyn/loom5/open/test/hotspot/jtreg/serviceability/jvmti/vthread/SelfSuspendDisablerT est/SelfSuspendDisablerTest.java -Dtest.src=/scratch/sspitsyn/loom5/open/test/hotspot/jtreg/serviceability/jvmti/vthread/SelfSuspendDisablerTest -Dtest.src.path=/scratch/sspitsyn/loom5/open/test/hotspot/jtreg/serviceability/jvmti/vthread/SelfSuspendDisablerTest:/scratch/sspitsyn/loom5/open/test/lib -Dtest.classes=/scratch/sspitsyn/tst/loom5/JTwork/classes/serviceability/jvmti/vthread/SelfSuspendDisablerTest/SelfSuspendDisablerTest.d -Dtest.class.path=/scratch/sspitsyn/tst/loom5/JTwork/classes/serviceability/jvmti/vthread/SelfSuspendDisablerTest/SelfSuspendDisablerTest.d:/scratch/sspitsyn/tst/loom5/JTwork/classes/test/lib -XX:+CreateCoredumpOnCrash --enable-preview -Djava.util.concurrent.ForkJoinPool.common.parallelism=1 -XX:-VerifyContinuations -XX:+CheckUnhandledOops -Xcheck:jni -Dmain.wrapper=Virtual -Djava.library.path=/scratch/sspitsyn/loom5/build/linux-x64-debug/images/test/hotspot/jtreg/native --enable-preview -agentlib:SelfSuspendDisablerTest com.sun.javatest.regtest.agent.Ma inWrapper /scratch/sspitsyn/tst/loom5/JTwork/serviceability/jvmti/vthread/SelfSuspendDisablerTest/SelfSuspendDisablerTest.d/main.1.jta Host: hotspot-oraclelinux-01, Intel(R) Xeon(R) Platinum 8167M CPU @ 2.00GHz, 32 cores, 235G, Oracle Linux Server release 7.8 Time: Wed May 25 16:23:30 2022 GMT elapsed time: 0.322123 seconds (0d 0h 0m 0s) --------------- T H R E A D --------------- Current thread (0x00007f3440022920): JavaThread "Thread-1" [_thread_in_vm, id=31182, stack(0x00007f348afee000,0x00007f348b0ef000)] Stack: [0x00007f348afee000,0x00007f348b0ef000], sp=0x00007f348b0ed620, free space=1021k Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code) V [libjvm.so+0x1a41724] JavaThread::java_suspend()+0xa4 V [libjvm.so+0x1315989] JvmtiEnvBase::suspend_thread(oop, JavaThread*, bool, int*)+0x379 V [libjvm.so+0x12fba6a] JvmtiEnv::SuspendThread(_jobject*)+0x1ba V [libjvm.so+0x12a42df] jvmti_SuspendThread+0x17f C [libSelfSuspendDisablerTest.so+0x21a8] Java_SelfSuspendDisablerTest_selfSuspend+0x38 j SelfSuspendDisablerTest.selfSuspend()V+0 j SelfSuspendDisablerTest.lambda$main$0()V+0 j SelfSuspendDisablerTest$$Lambda$1+0x0000000801001200.run()V+0 j java.lang.Thread.run()V+13 java.base@19-internal v ~StubRoutines::call_stub 0x00007f34f6db9d47 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+0x1a40b7a] JavaThread::thread_main_inner()+0x21a V [libjvm.so+0x1a4e430] Thread::call_run()+0x100 V [libjvm.so+0x16fc2b4] thread_native_entry(Thread*)+0x104 David, thank you for review and help with analysis of this problem! ------------- PR: https://git.openjdk.java.net/jdk/pull/8878
