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Re-fetch objects after VM access is released and reacquired #18420

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merged 1 commit into from
Nov 9, 2023
Merged

Re-fetch objects after VM access is released and reacquired #18420

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15 changes: 11 additions & 4 deletions runtime/jvmti/jvmtiHelpers.c
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Original file line number Diff line number Diff line change
Expand Up @@ -143,10 +143,13 @@ getVMThread(J9VMThread *currentThread, jthread thread, J9VMThread **vmThreadPtr,
#if JAVA_SPEC_VERSION >= 19
isVirtualThread = IS_JAVA_LANG_VIRTUALTHREAD(currentThread, threadObject);
if (isVirtualThread) {
jint vthreadState = 0;
j9object_t carrierThread = NULL;
vm->internalVMFunctions->acquireVThreadInspector(currentThread, thread, TRUE);

jint vthreadState = J9VMJAVALANGVIRTUALTHREAD_STATE(currentThread, threadObject);
j9object_t carrierThread = (j9object_t)J9VMJAVALANGVIRTUALTHREAD_CARRIERTHREAD(currentThread, threadObject);
/* Re-fetch threadObject since acquireVThreadInspector can release and reacquire VM access. */
threadObject = J9_JNI_UNWRAP_REFERENCE(thread);
vthreadState = J9VMJAVALANGVIRTUALTHREAD_STATE(currentThread, threadObject);
carrierThread = (j9object_t)J9VMJAVALANGVIRTUALTHREAD_CARRIERTHREAD(currentThread, threadObject);
if (NULL != carrierThread) {
targetThread = J9VMJAVALANGTHREAD_THREADREF(currentThread, carrierThread);
}
Expand Down Expand Up @@ -1659,7 +1662,7 @@ setEventNotificationMode(J9JVMTIEnv * j9env, J9VMThread * currentThread, jint mo
if (event_thread == NULL) {
eventMap = &(j9env->globalEventEnable);
} else {
j9object_t threadObject = J9_JNI_UNWRAP_REFERENCE(event_thread);
j9object_t threadObject = NULL;
J9VMThread *vmThreadForTLS = NULL;
rc = getVMThread(
currentThread, event_thread, &targetThread, JVMTI_ERROR_NONE,
Expand All @@ -1668,6 +1671,10 @@ setEventNotificationMode(J9JVMTIEnv * j9env, J9VMThread * currentThread, jint mo
goto done;
}
vmThreadForTLS = targetThread;
/* Fetch threadObject after getVMThread because getVMThread can release and
* reacquire VM access.
*/
threadObject = J9_JNI_UNWRAP_REFERENCE(event_thread);
#if JAVA_SPEC_VERSION >= 19
rc = allocateTLS(vm, threadObject);
if (JVMTI_ERROR_NONE != rc) {
Expand Down
7 changes: 4 additions & 3 deletions runtime/vm/ContinuationHelpers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -531,17 +531,18 @@ acquireVThreadInspector(J9VMThread *currentThread, jobject thread, BOOLEAN spin)
J9JavaVM *vm = currentThread->javaVM;
J9InternalVMFunctions *vmFuncs = vm->internalVMFunctions;
MM_ObjectAccessBarrierAPI objectAccessBarrier = MM_ObjectAccessBarrierAPI(currentThread);
j9object_t threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
I_64 vthreadInspectorCount;
j9object_t threadObj = NULL;
I_64 vthreadInspectorCount = 0;
retry:
/* Consistently re-fetch threadObj for all the cases below. */
threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
vthreadInspectorCount = J9OBJECT_I64_LOAD(currentThread, threadObj, vm->virtualThreadInspectorCountOffset);
if (vthreadInspectorCount < 0) {
/* Thread is in transition, wait. */
vmFuncs->internalExitVMToJNI(currentThread);
VM_AtomicSupport::yieldCPU();
/* After wait, the thread may suspend here. */
vmFuncs->internalEnterVMFromJNI(currentThread);
threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
if (spin) {
goto retry;
} else {
Expand Down