From 30d8cd2d962d4dc4d0178f54ff2d0e3ca0ce4e52 Mon Sep 17 00:00:00 2001
From: Jason Feng <fengj@ca.ibm.com>
Date: Tue, 13 Dec 2022 18:01:22 -0500
Subject: [PATCH] Add CRIU helper VM.isJVMInSingleThreadedMode()

Signed-off-by: Jason Feng <fengj@ca.ibm.com>
---
 .../share/classes/com/ibm/oti/vm/VM.java      |  8 +++++++-
 runtime/jcl/common/com_ibm_oti_vm_VM.c        | 19 ++++++++++++++++++-
 runtime/jcl/exports.cmake                     |  1 +
 runtime/jcl/uma/se7_exports.xml               |  3 ++-
 runtime/oti/jclprots.h                        |  7 +++++++
 5 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/jcl/src/java.base/share/classes/com/ibm/oti/vm/VM.java b/jcl/src/java.base/share/classes/com/ibm/oti/vm/VM.java
index 377d2c892ec..2f72b58df30 100644
--- a/jcl/src/java.base/share/classes/com/ibm/oti/vm/VM.java
+++ b/jcl/src/java.base/share/classes/com/ibm/oti/vm/VM.java
@@ -1,4 +1,4 @@
-/*[INCLUDE-IF Sidecar16]*/
+/*[INCLUDE-IF JAVA_SPEC_VERSION >= 8]*/
 
 package com.ibm.oti.vm;
 /*******************************************************************************
@@ -577,4 +577,10 @@ public static int markCurrentThreadAsSystem()
  */
 public static native long getJ9ConstantPoolFromJ9Class(long j9clazz);
 
+/**
+ * Queries whether the JVM is running in single threaded mode.
+ *
+ * @return true if JVM is in single threaded mode, false otherwise
+ */
+public static native boolean isJVMInSingleThreadedMode();
 }
diff --git a/runtime/jcl/common/com_ibm_oti_vm_VM.c b/runtime/jcl/common/com_ibm_oti_vm_VM.c
index c91b95b7c54..6fd628a0060 100644
--- a/runtime/jcl/common/com_ibm_oti_vm_VM.c
+++ b/runtime/jcl/common/com_ibm_oti_vm_VM.c
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 1998, 2021 IBM Corp. and others
+ * Copyright (c) 1998, 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
@@ -173,3 +173,20 @@ Java_com_ibm_oti_vm_VM_getJ9ConstantPoolFromJ9Class(JNIEnv *env, jclass unused,
 	 */
 	return (jlong)(UDATA)clazz->ramConstantPool;
 }
+
+/**
+ * Queries whether the JVM is running in single threaded mode.
+ *
+ * @return JNI_TRUE if JVM is in single threaded mode, JNI_FALSE otherwise
+ */
+jboolean JNICALL
+Java_com_ibm_oti_vm_VM_isJVMInSingleThreadedMode(JNIEnv *env, jclass unused)
+{
+	jboolean result = JNI_FALSE;
+#if defined(J9VM_OPT_CRIU_SUPPORT)
+	if (J9_IS_SINGLE_THREAD_MODE(((J9VMThread*)env)->javaVM)) {
+		result = JNI_TRUE;
+	}
+#endif /* defined(J9VM_OPT_CRIU_SUPPORT) */
+	return result;
+}
diff --git a/runtime/jcl/exports.cmake b/runtime/jcl/exports.cmake
index 75c66077b6b..ab1c685bfc1 100644
--- a/runtime/jcl/exports.cmake
+++ b/runtime/jcl/exports.cmake
@@ -300,6 +300,7 @@ omr_add_exports(jclse
 	Java_com_ibm_oti_vm_VM_markCurrentThreadAsSystemImpl
 	Java_com_ibm_oti_vm_VM_setCommonData
 	Java_com_ibm_oti_vm_VM_getJ9ConstantPoolFromJ9Class
+	Java_com_ibm_oti_vm_VM_isJVMInSingleThreadedMode
 	Java_com_ibm_rmi_io_IIOPInputStream_00024LUDCLStackWalkOptimizer_LUDCLMarkFrame
 	Java_com_ibm_rmi_io_IIOPInputStream_00024LUDCLStackWalkOptimizer_LUDCLUnmarkFrameImpl
 	Java_com_ibm_virtualization_management_internal_GuestOS_retrieveMemoryUsageImpl
diff --git a/runtime/jcl/uma/se7_exports.xml b/runtime/jcl/uma/se7_exports.xml
index 6d8303f8b22..be9bcc368f5 100644
--- a/runtime/jcl/uma/se7_exports.xml
+++ b/runtime/jcl/uma/se7_exports.xml
@@ -1,5 +1,5 @@
 <!-- 
-	Copyright (c) 2007, 2021 IBM Corp. and others
+	Copyright (c) 2007, 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
@@ -74,4 +74,5 @@
 	<export name="Java_com_ibm_java_lang_management_internal_ThreadMXBeanImpl_findNativeThreadIDImpl" />
 	<export name="Java_com_ibm_oti_vm_VM_markCurrentThreadAsSystemImpl" />
 	<export name="Java_com_ibm_oti_vm_VM_getJ9ConstantPoolFromJ9Class" />
+	<export name="Java_com_ibm_oti_vm_VM_isJVMInSingleThreadedMode" />
 </exports>
diff --git a/runtime/oti/jclprots.h b/runtime/oti/jclprots.h
index a558b57af18..f013e0e76fa 100644
--- a/runtime/oti/jclprots.h
+++ b/runtime/oti/jclprots.h
@@ -1258,6 +1258,13 @@ Java_com_ibm_oti_vm_VM_markCurrentThreadAsSystemImpl(JNIEnv *env);
  */
 jlong JNICALL
 Java_com_ibm_oti_vm_VM_getJ9ConstantPoolFromJ9Class(JNIEnv *env, jclass unused, jlong j9clazz);
+/**
+ * Queries whether the JVM is running in single threaded mode.
+ *
+ * @return JNI_TRUE if JVM is in single threaded mode, JNI_FALSE otherwise
+ */
+jboolean JNICALL
+Java_com_ibm_oti_vm_VM_isJVMInSingleThreadedMode(JNIEnv *env, jclass unused);
 
 #if JAVA_SPEC_VERSION >= 16
 jboolean JNICALL