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Patch MXBean to support virtual threads
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Use carrierThreadObject instead of threadObject for Java 19.

For thread with a virtual thread mount that is waiting on a lock,
we should return the virtualthreadobject as lock object/owner.

Signed-off-by: Gengchen Tuo <gengchen.tuo@ibm.com>
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@thallium
thallium committed Oct 21, 2022
1 parent 2b8eca6 commit ce4d4a3
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Showing 2 changed files with 70 additions and 26 deletions.
75 changes: 51 additions & 24 deletions runtime/jcl/common/mgmtthread.c
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Original file line number Diff line number Diff line change
Expand Up @@ -227,15 +227,17 @@ Java_com_ibm_java_lang_management_internal_ThreadMXBeanImpl_getAllThreadIdsImpl(
/* Grab any thread (mainThread will do) */
currentThread = javaVM->mainThread;
/* Loop over all vmThreads until we get back to the starting thread: Count phase */
threadCount = 0;
do {
{
if ((currentThread->threadObject != NULL) && (J9VMJAVALANGTHREAD_THREADREF((J9VMThread *)env,currentThread->threadObject) != NULL)) {
/* CMVC 182865 - exclude threads which have not initialized their ID */
jlong threadID = getThreadID((J9VMThread *)env, (j9object_t)currentThread->threadObject);
if (((jlong)0) != threadID) {
threadIDs[threadCount++] = threadID;
}
#if JAVA_SPEC_VERSION >= 19
j9object_t threadObject = currentThread->carrierThreadObject;
#else /* JAVA_SPEC_VERSION >= 19 */
j9object_t threadObject = currentThread->threadObject;
#endif /* JAVA_SPEC_VERSION >= 19 */
if ((NULL != threadObject) && (NULL != J9VMJAVALANGTHREAD_THREADREF((J9VMThread *)env, threadObject))) {
/* CMVC 182865 - exclude threads which have not initialized their ID */
jlong threadID = getThreadID((J9VMThread *)env, threadObject);
if (((jlong)0) != threadID) {
threadIDs[threadCount++] = threadID;
}
}
} while ((currentThread = currentThread->linkNext) != javaVM->mainThread);
Expand Down Expand Up @@ -937,24 +939,27 @@ getThread(JNIEnv *env, jlong threadID)
currentThread = javaVM->mainThread;
/* Loop over all vmThreads until we get back to the starting thread: look for matching threadID */
while (TRUE) {
if ((currentThread->threadObject != NULL) && (getThreadID((J9VMThread *)env, (j9object_t)currentThread->threadObject) == threadID)) {
{
/*
* We've found our matching thread, so we're done.
* But first we have to check if the thread is alive
* i.e. The j.l.Thread object's thread ref != 0
*/
if (J9VMJAVALANGTHREAD_THREADREF((J9VMThread *)env,currentThread->threadObject) == NULL) {
currentThread = NULL;
}
return currentThread;
#if JAVA_SPEC_VERSION >= 19
j9object_t threadObject = currentThread->carrierThreadObject;
#else /* JAVA_SPEC_VERSION >= 19 */
j9object_t threadObject = currentThread->threadObject;
#endif /* JAVA_SPEC_VERSION >= 19 */
if ((NULL != threadObject) && (threadID == getThreadID((J9VMThread *)env, threadObject))) {
/*
* We've found our matching thread, so we're done.
* But first we have to check if the thread is alive
* i.e. The j.l.Thread object's thread ref != 0
*/
if (NULL == J9VMJAVALANGTHREAD_THREADREF((J9VMThread *)env, threadObject)) {
currentThread = NULL;
}
return currentThread;
}

if ((currentThread = currentThread->linkNext) == javaVM->mainThread) {
/* Back at starting thread with no match, so return NULL */
return NULL;
}
}
}
}

Expand Down Expand Up @@ -1317,15 +1322,25 @@ getThreadInfo(J9VMThread *currentThread, J9VMThread *targetThread, ThreadInfo *i
j9object_t monitorOwnerObject = NULL;
IDATA exc = 0; /* exception index */

#if JAVA_SPEC_VERSION >= 19
J9VMThread stackThread = {0};
J9VMEntryLocalStorage els = {0};
J9VMContinuation *continuation = targetThread->currentContinuation;
j9object_t threadObject = currentThread->carrierThreadObject;
#else /* JAVA_SPEC_VERSION >= 19 */
j9object_t threadObject = currentThread->threadObject;
#endif /* JAVA_SPEC_VERSION >= 19 */

Trc_JCL_threadmxbean_getThreadInfo_Entry(currentThread, targetThread);

info->thread =
vmfns->j9jni_createLocalRef((JNIEnv *)currentThread, (j9object_t)targetThread->threadObject);
info->thread = vmfns->j9jni_createLocalRef((JNIEnv *)currentThread, threadObject);

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@pshipton

pshipton Oct 24, 2022

Member

The original code used targetThread->threadObject and this modifies it to currentThread->threadObject.

#14538 (comment)

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@pshipton

pshipton Oct 24, 2022

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Not just here, but other other two places that were modified as well were originally targetThread->threadObject

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@babsingh

babsingh Oct 24, 2022

Contributor

I will make the correction since there was a typo in my feedback #15956 (comment) while copy-pasting. fyi @thallium @fengxue-IS

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@thallium

thallium Oct 24, 2022

Author Contributor

Thank you
/* Set the native thread ID available through the thread library. */
info->nativeTID = (jlong) omrthread_get_osId(targetThread->osThread);
info->vmstate = getVMThreadObjectState(targetThread, &monitorObject, &monitorOwner, NULL);
if (targetThread->threadObject) {
info->jclThreadState = getJclThreadState(info->vmstate, J9VMJAVALANGTHREAD_STARTED(currentThread, targetThread->threadObject));
if (NULL != threadObject) {
info->jclThreadState = getJclThreadState(
info->vmstate,
J9VMJAVALANGTHREAD_STARTED(currentThread, threadObject));
} else {
info->jclThreadState = getJclThreadState(info->vmstate, JNI_TRUE);
}
Expand All @@ -1344,6 +1359,18 @@ getThreadInfo(J9VMThread *currentThread, J9VMThread *targetThread, ThreadInfo *i

/* this may block on vm->managementDataLock */
getContentionStats(currentThread, targetThread, info);
#if JAVA_SPEC_VERSION >= 19
/* getStackFramePCs needs to run on the carrier thread's stack to produce the right output.
* For threads with a continuation mounted, copy the carrier thread's stack data from the
* continuation to a stack allocated J9VMThread structure. To avoid potential dependencies
* on targetThread pointer's address, the stack allocated thread is only used for getStackFramePCs.
*/
if (NULL != continuation) {
memcpy(&stackThread, targetThread, sizeof(J9VMThread));
vm->internalVMFunctions->copyFieldsFromContinuation(currentThread, &stackThread, &els, continuation);
targetThread = &stackThread;
}
#endif /* JAVA_SPEC_VERSION >= 19 */

exc = getStackFramePCs(currentThread, targetThread, info);
if (exc > 0) {
Expand Down
21 changes: 19 additions & 2 deletions runtime/util/thrinfo.c
View file
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*******************************************************************************
* Copyright (c) 1991, 2020 IBM Corp. and others
* Copyright (c) 1991, 2022 IBM Corp. and others
*
* This program and the accompanying materials are made available under
* the terms of the Eclipse Public License 2.0 which accompanies this
Expand Down Expand Up @@ -287,7 +287,24 @@ getVMThreadStateHelper(J9VMThread *targetThread,
*/
}
}


#if JAVA_SPEC_VERSION >= 19
/* For a J9VMThread with a mounted virtual thread that is waiting on a
* lock, the virtual thread object should be returned as the lock object
* and the corresponding J9VMThread should be returned as the lock
* owner.
*
* ThreadMXBean documentation states that it does not support VirtualThread
* and behaviour on locks, related to VirtualThread, has not been defined.
* This code matches the RI's ThreadMXBean API behaviour.
*/
if (((J9VMTHREAD_STATE_WAITING == vmstate) || (J9VMTHREAD_STATE_WAITING_TIMED == vmstate))
&& (NULL != targetThread->currentContinuation)
) {
lockObject = targetThread->threadObject;
lockOwner = targetThread;
}
#endif /* JAVA_SPEC_VERSION >= 19 */
} else {
/*
* Can't wait on an uninflated object monitor, so the thread
Expand Down

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