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[JDK21] Add support for JVMTI PopFrame #17809

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Jul 25, 2023
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[JDK21] Add support for JVMTI PopFrame #17809

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46 changes: 37 additions & 9 deletions runtime/jvmti/jvmtiStackFrame.c
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Original file line number Diff line number Diff line change
Expand Up @@ -440,17 +440,43 @@ jvmtiPopFrame(jvmtiEnv* env,
ENSURE_CAPABILITY(env, can_pop_frame);

rc = getVMThread(
currentThread, thread, &targetThread, JVMTI_ERROR_OPAQUE_FRAME,
J9JVMTI_GETVMTHREAD_ERROR_ON_NULL_JTHREAD | J9JVMTI_GETVMTHREAD_ERROR_ON_DEAD_THREAD | J9JVMTI_GETVMTHREAD_ERROR_ON_VIRTUALTHREAD);
currentThread, thread, &targetThread, JVMTI_ERROR_NONE,
J9JVMTI_GETVMTHREAD_ERROR_ON_NULL_JTHREAD | J9JVMTI_GETVMTHREAD_ERROR_ON_DEAD_THREAD);
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Is it legal to continue if its a dead thread?

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@babsingh babsingh Jul 21, 2023 •
edited
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No, JVMTI_ERROR_THREAD_NOT_ALIVE will be returned by getVMThread when the J9JVMTI_GETVMTHREAD_ERROR_ON_DEAD_THREAD flag is set.

if (rc == JVMTI_ERROR_NONE) {
/* Does this thread need to be suspended at an event? */
vm->internalVMFunctions->haltThreadForInspection(currentThread, targetThread);
if ((currentThread == targetThread) || !(targetThread->publicFlags & J9_PUBLIC_FLAGS_HALT_THREAD_JAVA_SUSPEND)) {
#if JAVA_SPEC_VERSION >= 21
j9object_t threadObject = NULL;
/* Error if a virtual thread is unmounted since it won't be able to
* pop the current frame.
*/
if (NULL == targetThread) {
rc = JVMTI_ERROR_OPAQUE_FRAME;
goto release;
}
threadObject = (NULL == thread) ? currentThread->threadObject : J9_JNI_UNWRAP_REFERENCE(thread);
#endif /* JAVA_SPEC_VERSION >= 21 */

/* Error if the thread is not suspended and not the current thread. */
if ((currentThread != targetThread)
#if JAVA_SPEC_VERSION >= 21
&& (0 == J9OBJECT_U32_LOAD(currentThread, threadObject, vm->isSuspendedInternalOffset))
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should we be checking current thread or target thread?

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@babsingh babsingh Jul 21, 2023 •
edited
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We need to check if the input/target thread is suspended. If thread != currentThread && thread is not suspended, then JVMTI_ERROR_THREAD_NOT_SUSPENDED is returned.

#else /* JAVA_SPEC_VERSION >= 21 */
&& OMR_ARE_NO_BITS_SET(targetThread->publicFlags, J9_PUBLIC_FLAGS_HALT_THREAD_JAVA_SUSPEND)
#endif /* JAVA_SPEC_VERSION >= 21 */
) {
rc = JVMTI_ERROR_THREAD_NOT_SUSPENDED;
} else {
J9StackWalkState walkState;

walkState.walkThread = targetThread;
J9StackWalkState walkState = {0};
J9VMThread *threadToWalk = targetThread;
#if JAVA_SPEC_VERSION >= 21
J9VMThread stackThread = {0};
J9VMEntryLocalStorage els = {0};
J9VMContinuation *continuation = getJ9VMContinuationToWalk(currentThread, targetThread, threadObject);
if (NULL != continuation) {
vm->internalVMFunctions->copyFieldsFromContinuation(currentThread, &stackThread, &els, continuation);
threadToWalk = &stackThread;
}
#endif /* JAVA_SPEC_VERSION >= 21 */
walkState.walkThread = threadToWalk;
walkState.userData1 = (void *) JVMTI_ERROR_NO_MORE_FRAMES;
walkState.userData2 = (void *) 0;
walkState.frameWalkFunction = popFrameCheckIterator;
Expand All @@ -462,7 +488,9 @@ jvmtiPopFrame(jvmtiEnv* env,
vm->internalVMFunctions->setHaltFlag(targetThread, J9_PUBLIC_FLAGS_POP_FRAMES_INTERRUPT);
}
}
vm->internalVMFunctions->resumeThreadForInspection(currentThread, targetThread);
#if JAVA_SPEC_VERSION >= 21
release:
#endif /* JAVA_SPEC_VERSION >= 21 */
releaseVMThread(currentThread, targetThread, thread);
}
done:
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