8331015: Obsolete -XX:+UseNotificationThread

Reviewed-by: dholmes, kevinw, sspitsyn, coleenp

src/hotspot/share/jfr/recorder/repository/jfrEmergencyDump.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2024, Oracle and/or its affiliates. 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
@@ -497,7 +497,7 @@ static bool prepare_for_emergency_dump(Thread* thread) {
     Service_lock->unlock();
   }
 
-  if (UseNotificationThread && Notification_lock->owned_by_self()) {
+  if (Notification_lock->owned_by_self()) {
     Notification_lock->unlock();
   }
 

src/hotspot/share/runtime/arguments.cpp

@@ -503,7 +503,6 @@ static SpecialFlag const special_jvm_flags[] = {
   { "RequireSharedSpaces",          JDK_Version::jdk(18), JDK_Version::jdk(19), JDK_Version::undefined() },
   { "UseSharedSpaces",              JDK_Version::jdk(18), JDK_Version::jdk(19), JDK_Version::undefined() },
   { "DontYieldALot",                JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
-  { "UseNotificationThread",        JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
   { "LockingMode",                  JDK_Version::jdk(24), JDK_Version::jdk(26), JDK_Version::jdk(27) },
   // --- Deprecated alias flags (see also aliased_jvm_flags) - sorted by obsolete_in then expired_in:
   { "CreateMinidumpOnCrash",        JDK_Version::jdk(9),  JDK_Version::undefined(), JDK_Version::undefined() },
@@ -512,6 +511,7 @@ static SpecialFlag const special_jvm_flags[] = {
 
   { "MetaspaceReclaimPolicy",       JDK_Version::undefined(), JDK_Version::jdk(21), JDK_Version::undefined() },
 
+  { "UseNotificationThread",        JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
   { "PreserveAllAnnotations",       JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
   { "UseEmptySlotsInSupers",        JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },
   { "OldSize",                      JDK_Version::jdk(23), JDK_Version::jdk(24), JDK_Version::jdk(25) },

src/hotspot/share/runtime/globals.hpp

@@ -952,9 +952,6 @@ const int ObjectAlignmentInBytes = 8;
   product(bool, EnableThreadSMRStatistics, trueInDebug, DIAGNOSTIC,         \
              "Enable Thread SMR Statistics")                                \
                                                                             \
-  product(bool, UseNotificationThread, true,                                \
-          "(Deprecated) Use Notification Thread")                           \
-                                                                            \
   product(bool, Inline, true,                                               \
           "Enable inlining")                                                \
                                                                             \

src/hotspot/share/runtime/mutexLocker.cpp

@@ -235,13 +235,8 @@ void mutex_init() {
 
   MUTEX_DEFN(Patching_lock                   , PaddedMutex  , nosafepoint);      // used for safepointing and code patching.
   MUTEX_DEFN(MonitorDeflation_lock           , PaddedMonitor, nosafepoint);      // used for monitor deflation thread operations
-  MUTEX_DEFN(Service_lock                    , PaddedMonitor, service);      // used for service thread operations
-
-  if (UseNotificationThread) {
-    MUTEX_DEFN(Notification_lock             , PaddedMonitor, service);  // used for notification thread operations
-  } else {
-    Notification_lock = Service_lock;
-  }
+  MUTEX_DEFN(Service_lock                    , PaddedMonitor, service);          // used for service thread operations
+  MUTEX_DEFN(Notification_lock               , PaddedMonitor, service);          // used for notification thread operations
 
   MUTEX_DEFN(JmethodIdCreation_lock          , PaddedMutex  , nosafepoint-2); // used for creating jmethodIDs.
   MUTEX_DEFN(InvokeMethodTypeTable_lock      , PaddedMutex  , safepoint);

src/hotspot/share/runtime/serviceThread.cpp

@@ -81,10 +81,7 @@ static void cleanup_oopstorages() {
 
 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
   while (true) {
-    bool sensors_changed = false;
     bool has_jvmti_events = false;
-    bool has_gc_notification_event = false;
-    bool has_dcmd_notification_event = false;
     bool stringtable_work = false;
     bool symboltable_work = false;
     bool finalizerservice_work = false;
@@ -113,10 +110,7 @@ void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
       // only the first recognized bit of work, to avoid frequently true early
       // tests from potentially starving later work.  Hence the use of
       // arithmetic-or to combine results; we don't want short-circuiting.
-      while (((sensors_changed = (!UseNotificationThread && LowMemoryDetector::has_pending_requests())) |
-              (has_jvmti_events = _jvmti_service_queue.has_events()) |
-              (has_gc_notification_event = (!UseNotificationThread && GCNotifier::has_event())) |
-              (has_dcmd_notification_event = (!UseNotificationThread && DCmdFactory::has_pending_jmx_notification())) |
+      while (((has_jvmti_events = _jvmti_service_queue.has_events()) |
               (stringtable_work = StringTable::has_work()) |
               (symboltable_work = SymbolTable::has_work()) |
               (finalizerservice_work = FinalizerService::has_work()) |
@@ -158,20 +152,6 @@ void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
       _jvmti_event = nullptr;  // reset
     }
 
-    if (!UseNotificationThread) {
-      if (sensors_changed) {
-        LowMemoryDetector::process_sensor_changes(jt);
-      }
-
-      if(has_gc_notification_event) {
-        GCNotifier::sendNotification(CHECK);
-      }
-
-      if(has_dcmd_notification_event) {
-        DCmdFactory::send_notification(CHECK);
-      }
-    }
-
     if (resolved_method_table_work) {
       ResolvedMethodTable::do_concurrent_work(jt);
     }

src/hotspot/share/services/lowMemoryDetector.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2024, Oracle and/or its affiliates. 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
@@ -61,8 +61,7 @@
 //
 // May need to deal with hysteresis effect.
 //
-// Memory detection code runs in the Notification thread or
-// ServiceThread depending on UseNotificationThread flag.
+// Memory detection code runs in the Notification thread.
 
 class OopClosure;
 class MemoryPool;

src/hotspot/share/services/management.cpp

@@ -149,9 +149,8 @@ void Management::init() {
 }
 
 void Management::initialize(TRAPS) {
-  if (UseNotificationThread) {
-    NotificationThread::initialize();
-  }
+  NotificationThread::initialize();
+
   if (ManagementServer) {
     ResourceMark rm(THREAD);
     HandleMark hm(THREAD);