8385310: [CRaC] CRaC should fail gracefully on a second checkpoint attempt

src/hotspot/share/include/crlib/crlib_checkpoint_availability.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2026, Azul Systems, Inc. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+#ifndef CRLIB_CHECKPOINT_AVAILABILITY_H
+#define CRLIB_CHECKPOINT_AVAILABILITY_H
+
+#include "crlib.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define CRLIB_EXTENSION_CHECKPOINT_AVAILABILITY_NAME "checkpointable data"
+#define CRLIB_EXTENSION_CHECKPOINTABLE(api) \
+  CRLIB_EXTENSION(api, crlib_checkpoint_availability_t, CRLIB_EXTENSION_CHECKPOINT_CRLIB_CHECKPOINT_AVAILABILITY_NAME)
+
+typedef int crlib_checkpointable_status_t;
+#define CRLIB_CHECKPOINTABLE_NEVER   0   // engine will never accept another checkpoint
+#define CRLIB_CHECKPOINTABLE_NOT_YET 1   // not now; may become ready later
+#define CRLIB_CHECKPOINTABLE_READY   2   // checkpoint can proceed
+
+
+// API for obtaining information about chackpointable status.
+struct crlib_checkpoint_availability {
+  crlib_extension_t header;
+
+  crlib_checkpointable_status_t (*get_checkpointable_status)(crlib_conf_t *);
+};
+typedef const struct crlib_checkpoint_availability crlib_checkpoint_availability_t;
+
+#ifdef __cplusplus
+} // extern "C
+#endif
+
+#endif // CRLIB_CHECKPOINT_AVAILABILITY_H

src/hotspot/share/include/jvm.h

@@ -1181,6 +1181,9 @@ enum cr_fail_type {
 JNIEXPORT jobjectArray JNICALL
 JVM_Checkpoint(JNIEnv *env, jarray fd_arr, jobjectArray obj_arr, jboolean dry_run, jlong jcmd_stream);
 
+JNIEXPORT jint JNICALL
+JVM_GetCheckpointableStatus(JNIEnv *env);
+
 JNIEXPORT void JNICALL
 JVM_StartRecordingDecompilations(JNIEnv *env);
 

src/hotspot/share/prims/jvm.cpp

@@ -3664,6 +3664,10 @@ JVM_ENTRY(jobjectArray, JVM_Checkpoint(JNIEnv *env, jarray fd_arr, jobjectArray
   return (jobjectArray) JNIHandles::make_local(THREAD, ret());
 JVM_END
 
+JVM_ENTRY(jint, JVM_GetCheckpointableStatus(JNIEnv *env))
+  return crac::checkpointable_status();
+JVM_END
+
 JVM_ENTRY(void, JVM_StartRecordingDecompilations(JNIEnv *env))
   CRaCRecompiler::start_recording_decompilations();
 JVM_END

src/hotspot/share/runtime/crac.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2023, 2026, Azul Systems, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -80,6 +80,24 @@ jlong crac::uptime_since_restore() {
   return os::javaTimeNanos() - _restore_start_nanos;
 }
 
+jint crac::checkpointable_status() {
+  if (crac::_engine->prepare_checkpoint_availability_api() == CracEngine::ApiStatus::OK) {
+    crlib_checkpointable_status_t status = crac::_engine->get_checkpointable_status();
+    if (status == CRLIB_CHECKPOINTABLE_NEVER) {
+      if (crac::_generation > 1) {
+        return status;
+      } else {
+        // Engine doesn't support checkpoint after restore,
+        // but it's a first checkpoint. So return READY.
+        return CRLIB_CHECKPOINTABLE_READY;
+      }
+    }
+    return status;
+  }
+
+  return CRLIB_CHECKPOINTABLE_READY;
+}
+
 void VM_Crac::print_resources(const char* msg, ...) {
   if (CRaCPrintResourcesOnCheckpoint) {
     va_list ap;

src/hotspot/share/runtime/crac.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2023, 2026, Azul Systems, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -57,6 +57,7 @@ class crac: AllStatic {
 
   static jlong restore_start_time();
   static jlong uptime_since_restore();
+  static jint checkpointable_status();
 
   static jlong monotonic_time_offset() {
     return _javaTimeNanos_offset;

src/hotspot/share/runtime/crac_engine.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2025, 2026, Azul Systems, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -606,3 +606,13 @@ CracEngine::ApiStatus CracEngine::prepare_image_score_api() {
 bool CracEngine::set_score(const char* metric, double value) {
   return _image_score_api->set_score(_conf, metric, value);
 }
+
+CracEngine::ApiStatus CracEngine::prepare_checkpoint_availability_api() {
+  prepare_extension_api(_checkpoint_availability_api, CRLIB_EXTENSION_CHECKPOINT_AVAILABILITY_NAME)
+  require_method(get_checkpointable_status)
+  complete_extension_api(_checkpoint_availability_api)
+}
+
+crlib_checkpointable_status_t CracEngine::get_checkpointable_status() {
+  return _checkpoint_availability_api->get_checkpointable_status(_conf);
+}

src/hotspot/share/runtime/crac_engine.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2025, 2026, Azul Systems, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,7 @@
 #define SHARE_RUNTIME_CRAC_ENGINE_HPP
 
 #include "crlib/crlib.h"
+#include "crlib/crlib_checkpoint_availability.h"
 #include "crlib/crlib_description.h"
 #include "crlib/crlib_image_constraints.h"
 #include "crlib/crlib_image_score.h"
@@ -79,6 +80,9 @@ class CracEngine : public CHeapObj<mtInternal> {
   ApiStatus prepare_image_score_api();
   bool set_score(const char* metric, double value);
 
+  ApiStatus prepare_checkpoint_availability_api();
+  crlib_checkpointable_status_t get_checkpointable_status();
+
 private:
   char _name[MAX_ENGINE_LENGTH];
   void *_lib = nullptr;
@@ -90,6 +94,7 @@ class CracEngine : public CHeapObj<mtInternal> {
   crlib_description_t *_description_api = nullptr;
   crlib_image_constraints_t *_image_constraints_api = nullptr;
   crlib_image_score_t *_image_score_api = nullptr;
+  crlib_checkpoint_availability_t *_checkpoint_availability_api = nullptr;
 
   crlib_conf_option_t *_options = nullptr;
 };

src/java.base/linux/native/libcriuengine/criuengine.cpp

@@ -38,6 +38,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#include "crlib/crlib_checkpoint_availability.h"
 #include "crlib/crlib_description.h"
 #include "crlib/crlib_restore_data.h"
 #include "crlib/crlib_user_data.h"
@@ -495,6 +496,18 @@ static char* get_relative_file(const char* rel) {
   return buf;
 }
 
+static crlib_checkpointable_status_t get_checkpointable_status(crlib_conf_t * conf) {
+  if (!conf->direct_map()) {
+    return CRLIB_CHECKPOINTABLE_READY;
+  }
+
+  // With direct_map, restored memory pages are mmap'd directly from the
+  // checkpoint image file rather than copied into anonymous memory. A second
+  // checkpoint would overwrite that same image, corrupting the live mappings
+  // of the running process. CRIU has no safe way to re-checkpoint in this mode.
+  return CRLIB_CHECKPOINTABLE_NEVER;
+}
+
 const char* criuengine::get_criu() {
   char* criu = _criu_location;
   if (criu == nullptr) {
@@ -974,8 +987,17 @@ static crlib_user_data_t user_data_extension = {
   destroy_user_data,
 };
 
+static crlib_checkpoint_availability_t checkpoint_availability_extension = {
+  {
+    CRLIB_EXTENSION_CHECKPOINT_AVAILABILITY_NAME,
+    sizeof(checkpoint_availability_extension)
+  },
+  get_checkpointable_status,
+};
+
 static const crlib_extension_t* extensions[] = {
   &restore_data_extension.header,
+  &checkpoint_availability_extension.header,
   &image_constraints_extension.header,
   &image_score_extension.header,
   &user_data_extension.header,

src/java.base/share/classes/jdk/internal/crac/mirror/CheckpointableStatus.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2026, Azul Systems, Inc. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.internal.crac.mirror;
+
+public enum CheckpointableStatus {
+    NEVER_AFTER_RESTORE, READY_LATER, READY;
+
+    public static CheckpointableStatus fromCode(int code) {
+        CheckpointableStatus[] values = values();
+        if (code < 0 || code >= values.length) {
+            throw new IllegalArgumentException("Unknown CheckpointableStatus code: " + code);
+        }
+        return values[code];
+    }
+}

src/java.base/share/classes/jdk/internal/crac/mirror/Core.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2025, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2017, 2026, Azul Systems, Inc. All rights reserved.
  * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -57,6 +57,7 @@ public class Core {
 
     private static final long JCMD_STREAM_NULL = 0;
     private static native Object[] checkpointRestore0(int[] fdArr, Object[] objArr, boolean dryRun, long jcmdStream);
+    private static native int getCheckpointableStatus0();
     private static final Object checkpointRestoreLock = new Object();
     private static boolean checkpointInProgress = false;
 
@@ -272,6 +273,26 @@ public static void checkpointRestore() throws
     private static void checkpointRestore(long jcmdStream) throws
             CheckpointException,
             RestoreException {
+        int status_code = getCheckpointableStatus0();
+        switch (CheckpointableStatus.fromCode(status_code)) {
+            case NEVER_AFTER_RESTORE -> {
+                CheckpointException ex = new CheckpointException();
+                ex.addSuppressed(new IllegalStateException("Current engine doesn't support second checkpoint after restore."));
+                throw ex;
+            }
+            case READY_LATER -> {
+                CheckpointException ex = new CheckpointException();
+                ex.addSuppressed(new IllegalStateException("CRaC cannot commit checkpoint right now, try later."));
+                throw ex;
+            }
+            case READY -> {
+                // fall through to checkpoint logic below
+            }
+            default -> {
+                System.err.printf("Engine returned unknown checkpointable status code: %d. Proceeding with checkpoint.%n", status_code);
+            }
+        }
+
         final List<String> newArguments;
 
         // checkpointRestoreLock protects against the simultaneous

src/java.base/share/native/libjava/CracCore.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2025, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2017, 2026, Azul Systems, Inc. All rights reserved.
  * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -39,6 +39,11 @@ Java_jdk_internal_crac_mirror_Core_checkpointRestore0(JNIEnv *env, jclass ignore
     return JVM_Checkpoint(env, fdArr, objArr, dry_run, jcmd_stream);
 }
 
+JNIEXPORT jint JNICALL
+Java_jdk_internal_crac_mirror_Core_getCheckpointableStatus0(JNIEnv *env, jclass ignore) {
+    return JVM_GetCheckpointableStatus(env);
+}
+
 JNIEXPORT void JNICALL
 Java_jdk_internal_crac_mirror_Core_startRecordingDecompilations0(JNIEnv *env, jclass ignore) {
     JVM_StartRecordingDecompilations(env);

src/java.base/share/native/libsimengine/simengine.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
+ * Copyright (c) 2021, 2026, Azul Systems, Inc. All rights reserved.
  * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -36,6 +36,7 @@
 #endif // LINUX
 
 #include "crcommon.hpp"
+#include "crlib/crlib_checkpoint_availability.h"
 #include "crlib/crlib_restore_data.h"
 #include "crlib/crlib_description.h"
 #include "jni.h"
@@ -288,8 +289,21 @@ static crlib_description_t description_extension = {
   configuration_options,
 };
 
+static crlib_checkpointable_status_t get_checkpointable_status(crlib_conf_t *) {
+  return CRLIB_CHECKPOINTABLE_READY;
+}
+
+static crlib_checkpoint_availability checkpoint_availability_extension = {
+  {
+    CRLIB_EXTENSION_CHECKPOINT_AVAILABILITY_NAME,
+    sizeof(checkpoint_availability_extension)
+  },
+  get_checkpointable_status,
+};
+
 static const crlib_extension_t *extensions[] = {
   &restore_data_extension.header,
+  &checkpoint_availability_extension.header,
   &image_constraints_extension.header,
   &image_score_extension.header,
   &description_extension.header,