Merge pull request #18439 from babsingh/main1

Spin during VirtualThread MountBegin and UnmountBegin
eclipse-openj9 · Nov 13, 2023 · bc535a4 · bc535a4
2 parents f9dffe6 + feac356
commit bc535a4
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Showing 3 changed files with 52 additions and 21 deletions.
diff --git a/runtime/j9vm/javanextvmi.cpp b/runtime/j9vm/javanextvmi.cpp
@@ -40,6 +40,8 @@ extern "C" {
 
 #if JAVA_SPEC_VERSION >= 19
 extern J9JavaVM *BFUjavaVM;
+
+extern IDATA (*f_threadSleep)(I_64 millis);
 #endif /* JAVA_SPEC_VERSION >= 19 */
 
 /* Define for debug
@@ -328,6 +330,27 @@ virtualThreadMountBegin(JNIEnv *env, jobject thread)
 	}
 
 	enterVThreadTransitionCritical(currentThread, thread);
+
+	/* Virtual thread is being mounted but it has been suspended. Spin until the
+	 * virtual thread is resumed. The virtual thread should not be mounted until
+	 * it is resumed.
+	 */
+	J9JavaVM *vm = currentThread->javaVM;
+	J9InternalVMFunctions *vmFuncs = vm->internalVMFunctions;
+	threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
+	while (0 != J9OBJECT_U32_LOAD(currentThread, threadObj, vm->isSuspendedInternalOffset)) {
+		exitVThreadTransitionCritical(currentThread, threadObj);
+		vmFuncs->internalReleaseVMAccess(currentThread);
+		/* Spin is used instead of the halt flag; otherwise, the carrier thread will
+		 * show as suspended.
+		 *
+		 * TODO: Dynamically increase the sleep time to a bounded maximum.
+		 */
+		f_threadSleep(10);
+		vmFuncs->internalAcquireVMAccess(currentThread);
+		enterVThreadTransitionCritical(currentThread, thread);
+		threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
+	}
 }
 
 /* Caller must have VMAccess. */
@@ -354,15 +377,6 @@ virtualThreadMountEnd(JNIEnv *env, jobject thread)
 				J9VMJDKINTERNALVMCONTINUATION_VMREF(currentThread, continuationObj));
 	}
 
-	/* Virtual thread is being mounted but it has been suspended. Thus,
-	 * set J9_PUBLIC_FLAGS_HALT_THREAD_JAVA_SUSPEND flag. At this
-	 * point, virtual thread object is stored in targetThread->threadObject.
-	 */
-	if (0 != J9OBJECT_U32_LOAD(currentThread, threadObj, vm->isSuspendedInternalOffset)) {
-		Assert_SC_true(threadObj == currentThread->threadObject);
-		vm->internalVMFunctions->setHaltFlag(currentThread, J9_PUBLIC_FLAGS_HALT_THREAD_JAVA_SUSPEND);
-	}
-
 	/* Allow thread to be inspected again. */
 	exitVThreadTransitionCritical(currentThread, threadObj);
 
@@ -396,6 +410,28 @@ virtualThreadUnmountBegin(JNIEnv *env, jobject thread)
 
 	enterVThreadTransitionCritical(currentThread, thread);
 	VM_VMHelpers::virtualThreadHideFrames(currentThread, JNI_TRUE);
+
+	J9InternalVMFunctions *vmFuncs = vm->internalVMFunctions;
+	j9object_t carrierThreadObject = currentThread->carrierThreadObject;
+	threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
+	/* Virtual thread is being umounted. If its carrier thread is suspended, spin until
+	 * the carrier thread is resumed. The carrier thread should not be mounted until it
+	 * is resumed.
+	 */
+	while (0 != J9OBJECT_U32_LOAD(currentThread, carrierThreadObject, vm->isSuspendedInternalOffset)) {
+		exitVThreadTransitionCritical(currentThread, threadObj);
+		vmFuncs->internalReleaseVMAccess(currentThread);
+		/* Spin is used instead of the halt flag; otherwise, the virtual thread will
+		 * show as suspended.
+		 *
+		 * TODO: Dynamically increase the sleep time to a bounded maximum.
+		 */
+		f_threadSleep(10);
+		vmFuncs->internalAcquireVMAccess(currentThread);
+		enterVThreadTransitionCritical(currentThread, thread);
+		carrierThreadObject = currentThread->carrierThreadObject;
+		threadObj = J9_JNI_UNWRAP_REFERENCE(thread);
+	}
 }
 
 /* Caller must have VMAccess. */
@@ -429,15 +465,6 @@ virtualThreadUnmountEnd(JNIEnv *env, jobject thread)
 		vmFuncs->freeTLS(currentThread, threadObj);
 	}
 
-	j9object_t carrierThreadObject = currentThread->carrierThreadObject;
-	/* The J9_PUBLIC_FLAGS_HALT_THREAD_JAVA_SUSPEND will be set for the virtual
-	 * thread's carrier thread if it was suspended while the virtual thread was mounted.
-	 */
-	if (0 != J9OBJECT_U32_LOAD(currentThread, carrierThreadObject, vm->isSuspendedInternalOffset)) {
-		Assert_SC_true((currentThread->threadObject == carrierThreadObject) && (NULL == currentThread->currentContinuation));
-		vmFuncs->setHaltFlag(currentThread, J9_PUBLIC_FLAGS_HALT_THREAD_JAVA_SUSPEND);
-	}
-
 	/* Allow thread to be inspected again. */
 	exitVThreadTransitionCritical(currentThread, threadObj);
 }

diff --git a/runtime/j9vm/jvm.c b/runtime/j9vm/jvm.c
@@ -212,6 +212,7 @@ typedef IDATA (*MonitorDestroy)(omrthread_monitor_t monitor);
 typedef IDATA (* ThreadLibControl)(const char * key, UDATA value);
 typedef IDATA (*SetCategory)(omrthread_t thread, UDATA category, UDATA type);
 typedef IDATA (*LibEnableCPUMonitor)(omrthread_t thread);
+typedef IDATA (*ThreadSleep)(I_64 millis);
 
 typedef I_32 (*PortInitLibrary)(J9PortLibrary *portLib, J9PortLibraryVersion *version, UDATA size);
 typedef UDATA (*PortGetSize)(struct J9PortLibraryVersion *version);
@@ -260,6 +261,7 @@ static pNewStringPlatform globalNewStringPlatform;
 static p_a2e_vsprintf global_a2e_vsprintf;
 #endif
 
+ThreadSleep f_threadSleep;
 static ThreadGlobal f_threadGlobal;
 static ThreadAttachEx f_threadAttachEx;
 static ThreadDetach f_threadDetach;
@@ -1015,8 +1017,9 @@ preloadLibraries(void)
 	f_threadLibControl = (ThreadLibControl) GetProcAddress (threadDLL, (LPCSTR) "omrthread_lib_control");
 	f_setCategory = (SetCategory) GetProcAddress (threadDLL, (LPCSTR) "omrthread_set_category");
 	f_libEnableCPUMonitor = (LibEnableCPUMonitor) GetProcAddress (threadDLL, (LPCSTR) "omrthread_lib_enable_cpu_monitor");
+	f_threadSleep = (ThreadSleep) GetProcAddress (threadDLL, (LPCSTR) "omrthread_sleep");
 	if (!f_threadGlobal || !f_threadAttachEx || !f_threadDetach || !f_monitorEnter || !f_monitorExit || !f_monitorInit
-		|| !f_monitorDestroy || !f_threadLibControl || !f_setCategory || !f_libEnableCPUMonitor
+		|| !f_monitorDestroy || !f_threadLibControl || !f_setCategory || !f_libEnableCPUMonitor || !f_threadSleep
 	) {
 		FreeLibrary(vmDLL);
 		FreeLibrary(threadDLL);
@@ -1442,8 +1445,9 @@ preloadLibraries(void)
 	f_threadLibControl = (ThreadLibControl) dlsym (threadDLL, "omrthread_lib_control");
 	f_setCategory = (SetCategory) dlsym (threadDLL, "omrthread_set_category");
 	f_libEnableCPUMonitor = (LibEnableCPUMonitor) dlsym (threadDLL, "omrthread_lib_enable_cpu_monitor");
+	f_threadSleep = (ThreadSleep) dlsym (threadDLL, "omrthread_sleep");
 	if (!f_threadGlobal || !f_threadAttachEx || !f_threadDetach || !f_monitorEnter || !f_monitorExit || !f_monitorInit
-		|| !f_monitorDestroy || !f_threadLibControl || !f_setCategory || !f_libEnableCPUMonitor
+		|| !f_monitorDestroy || !f_threadLibControl || !f_setCategory || !f_libEnableCPUMonitor || !f_threadSleep
 	) {
 		dlclose(vmDLL);
 #ifdef J9ZOS390

diff --git a/runtime/jvmti/jvmtiThread.c b/runtime/jvmti/jvmtiThread.c
@@ -1326,7 +1326,7 @@ jvmtiSuspendResumeCallBack(J9VMThread *vmThread, J9MM_IterateObjectDescriptor *o
 {
 	j9object_t continuationObj = object->object;
 	j9object_t vthread = J9VMJDKINTERNALVMCONTINUATION_VTHREAD(vmThread, continuationObj);
-	ContinuationState continuationState = J9VMJDKINTERNALVMCONTINUATION_STATE(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;