Merge pull request #18251 from babsingh/fix_getthreadobjectforcontinu…

…ation Retain Continuation.vthread until the J9VMContinuation is freed
eclipse-openj9 · Oct 13, 2023 · 3ad3c3b · 3ad3c3b
2 parents 91e0706 + e64ca00
commit 3ad3c3b
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Showing 5 changed files with 25 additions and 7 deletions.
diff --git a/runtime/j9vm/javanextvmi.cpp b/runtime/j9vm/javanextvmi.cpp
@@ -296,14 +296,15 @@ exitVThreadTransitionCritical(J9VMThread *currentThread, j9object_t vthread)
 }
 
 static void
-unsetParentVthread(J9VMThread *currentThread, jobject thread)
+setContinuationStateToLastUnmount(J9VMThread *currentThread, jobject thread)
 {
 	enterVThreadTransitionCritical(currentThread, thread);
 	/* Re-fetch reference as enterVThreadTransitionCritical may release VMAccess. */
 	j9object_t threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
 	j9object_t continuationObj = J9VMJAVALANGVIRTUALTHREAD_CONT(currentThread, threadObj);
-	/* Add reverse link from Continuation object to VirtualThread object, this let JVMTI code. */
-	J9VMJDKINTERNALVMCONTINUATION_SET_VTHREAD(currentThread, continuationObj, NULL);
+	ContinuationState volatile *continuationStatePtr = VM_ContinuationHelpers::getContinuationStateAddress(currentThread, continuationObj);
+	/* Used in JVMTI to not suspend the virtual thread once it enters the last unmount phase. */
+	VM_ContinuationHelpers::setLastUnmount(continuationStatePtr);
 	exitVThreadTransitionCritical(currentThread, threadObj);
 }
 
@@ -501,7 +502,7 @@ JVM_VirtualThreadUnmountBegin(JNIEnv *env, jobject thread, jboolean lastUnmount)
 
 	if (lastUnmount) {
 		TRIGGER_J9HOOK_VM_VIRTUAL_THREAD_END(vm->hookInterface, currentThread);
-		unsetParentVthread((J9VMThread *)env, thread);
+		setContinuationStateToLastUnmount((J9VMThread *)env, thread);
 	}
 	virtualThreadUnmountBegin(env, thread);
 
@@ -661,7 +662,7 @@ JVM_VirtualThreadEnd(JNIEnv *env, jobject vthread)
 	vmFuncs->internalEnterVMFromJNI(currentThread);
 
 	TRIGGER_J9HOOK_VM_VIRTUAL_THREAD_END(vm->hookInterface, currentThread);
-	unsetParentVthread((J9VMThread *)env, vthread);
+	setContinuationStateToLastUnmount((J9VMThread *)env, vthread);
 	virtualThreadUnmountBegin(env, vthread);
 
 	vmFuncs->internalExitVMToJNI(currentThread);

diff --git a/runtime/jvmti/jvmtiThread.c b/runtime/jvmti/jvmtiThread.c
@@ -1324,8 +1324,11 @@ jvmtiGetCurrentThread(jvmtiEnv *env,
 static jvmtiIterationControl
 jvmtiSuspendResumeCallBack(J9VMThread *vmThread, J9MM_IterateObjectDescriptor *object, void *userData)
 {
-	j9object_t vthread = J9VMJDKINTERNALVMCONTINUATION_VTHREAD(vmThread, object->object);
-	if (NULL != vthread) {
+	j9object_t continuationObj = object->object;
+	j9object_t vthread = J9VMJDKINTERNALVMCONTINUATION_VTHREAD(vmThread, continuationObj);
+	ContinuationState continuationState = J9VMJDKINTERNALVMCONTINUATION_STATE(vmThread, continuationObj);;
+
+	if ((NULL != vthread) && J9_ARE_NO_BITS_SET(continuationState, J9_GC_CONTINUATION_STATE_LAST_UNMOUNT)) {
 		jvmtiVThreadCallBackData *data = (jvmtiVThreadCallBackData*)userData;
 		BOOLEAN is_excepted = FALSE;
 		for (jint i = 0; i < data->except_count; ++i) {

diff --git a/runtime/oti/ContinuationHelpers.hpp b/runtime/oti/ContinuationHelpers.hpp
@@ -108,6 +108,18 @@ class VM_ContinuationHelpers {
 		*continuationStatePtr |= J9_GC_CONTINUATION_STATE_STARTED;
 	}
 
+	static VMINLINE bool
+	isLastUnmount(ContinuationState continuationState)
+	{
+		return J9_ARE_ALL_BITS_SET(continuationState, J9_GC_CONTINUATION_STATE_LAST_UNMOUNT);
+	}
+
+	static VMINLINE void
+	setLastUnmount(ContinuationState volatile *continuationStatePtr)
+	{
+		*continuationStatePtr |= J9_GC_CONTINUATION_STATE_LAST_UNMOUNT;
+	}
+
 	static VMINLINE bool
 	isFinished(ContinuationState continuationState)
 	{

diff --git a/runtime/oti/j9consts.h b/runtime/oti/j9consts.h
@@ -501,6 +501,7 @@ extern "C" {
 #define J9_GC_CONTINUATION_STATE_PENDING_TO_BE_MOUNTED 0x4
 #define J9_GC_CONTINUATION_STATE_CONCURRENT_SCAN_LOCAL 0x8
 #define J9_GC_CONTINUATION_STATE_CONCURRENT_SCAN_GLOBAL 0x10
+#define J9_GC_CONTINUATION_STATE_LAST_UNMOUNT 0x20
 #define J9_GC_CONTINUATION_STATE_CONCURRENT_SCAN_ANY (J9_GC_CONTINUATION_STATE_CONCURRENT_SCAN_LOCAL | J9_GC_CONTINUATION_STATE_CONCURRENT_SCAN_GLOBAL)
 #define J9_GC_CONTINUATION_STATE_CARRIERID_MASK (~(uintptr_t)0xff)
 

diff --git a/runtime/vm/ContinuationHelpers.cpp b/runtime/vm/ContinuationHelpers.cpp
@@ -343,6 +343,7 @@ freeContinuation(J9VMThread *currentThread, j9object_t continuationObject, BOOLE
 
 		/* Update Continuation object's vmRef field. */
 		J9VMJDKINTERNALVMCONTINUATION_SET_VMREF(currentThread, continuationObject, NULL);
+		J9VMJDKINTERNALVMCONTINUATION_SET_VTHREAD(currentThread, continuationObject, NULL);
 
 		recycleContinuation(currentThread->javaVM, currentThread, continuation, skipLocalCache);
 	}