Automatic merge of jdk:master into master

Author: duke

src/hotspot/share/runtime/globals.hpp

@@ -1191,10 +1191,6 @@ const intx ObjectAlignmentInBytes = 8;
   develop(bool, VerifyJNIFields, trueInDebug,                               \
           "Verify jfieldIDs for instance fields")                           \
                                                                             \
-  notproduct(bool, VerifyJNIEnvThread, false,                               \
-          "Verify JNIEnv.thread == Thread::current() when entering VM "     \
-          "from JNI")                                                       \
-                                                                            \
   develop(bool, VerifyFPU, false,                                           \
           "Verify FPU state (check for NaN's, etc.)")                       \
                                                                             \

src/hotspot/share/runtime/interfaceSupport.inline.hpp

@@ -340,6 +340,11 @@ class VMNativeEntryWrapper {
 #define JRT_END }
 
 // Definitions for JNI
+//
+// As the JNIEnv can be passed from external native code we validate
+// it in debug builds, primarily for our own testing. In general JNI
+// does not attempt to detect programming errors and a bad JNIEnv may
+// not even be readable.
 
 #define JNI_ENTRY(result_type, header)                               \
     JNI_ENTRY_NO_PRESERVE(result_type, header)                       \
@@ -349,7 +354,7 @@ class VMNativeEntryWrapper {
 extern "C" {                                                         \
   result_type JNICALL header {                                       \
     JavaThread* thread=JavaThread::thread_from_jni_environment(env); \
-    assert( !VerifyJNIEnvThread || (thread == Thread::current()), "JNIEnv is only valid in same thread"); \
+    assert(thread == Thread::current(), "JNIEnv is only valid in same thread"); \
     MACOS_AARCH64_ONLY(ThreadWXEnable __wx(WXWrite, thread));        \
     ThreadInVMfromNative __tiv(thread);                              \
     debug_only(VMNativeEntryWrapper __vew;)                          \
@@ -360,7 +365,7 @@ extern "C" {                                                         \
 extern "C" {                                                         \
   result_type JNICALL header {                                       \
     JavaThread* thread=JavaThread::thread_from_jni_environment(env); \
-    assert( !VerifyJNIEnvThread || (thread == Thread::current()), "JNIEnv is only valid in same thread"); \
+    assert(thread == Thread::current(), "JNIEnv is only valid in same thread"); \
     VM_LEAF_BASE(result_type, header)
 
 

src/hotspot/share/runtime/thread.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -1312,16 +1312,21 @@ class JavaThread: public Thread {
   // Returns the jni environment for this thread
   JNIEnv* jni_environment()                      { return &_jni_environment; }
 
+  // Returns the current thread as indicated by the given JNIEnv.
+  // We don't assert it is Thread::current here as that is done at the
+  // external JNI entry points where the JNIEnv is passed into the VM.
   static JavaThread* thread_from_jni_environment(JNIEnv* env) {
-    JavaThread *thread_from_jni_env = (JavaThread*)((intptr_t)env - in_bytes(jni_environment_offset()));
-    // Only return NULL if thread is off the thread list; starting to
-    // exit should not return NULL.
-    if (thread_from_jni_env->is_terminated()) {
-      thread_from_jni_env->block_if_vm_exited();
-      return NULL;
-    } else {
-      return thread_from_jni_env;
+    JavaThread* current = (JavaThread*)((intptr_t)env - in_bytes(jni_environment_offset()));
+    // We can't get here in a thread that has completed its execution and so
+    // "is_terminated", but a thread is also considered terminated if the VM
+    // has exited, so we have to check this and block in case this is a daemon
+    // thread returning to the VM (the JNI DirectBuffer entry points rely on
+    // this).
+    if (current->is_terminated()) {
+      current->block_if_vm_exited();
+      ShouldNotReachHere();
     }
+    return current;
   }
 
   // JNI critical regions. These can nest.