8266795: Remove dead code LowMemoryDetectorDisabler

Reviewed-by: dholmes

src/hotspot/share/services/lowMemoryDetector.cpp

@@ -39,7 +39,6 @@
 #include "services/management.hpp"
 
 volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
-volatile jint LowMemoryDetector::_disabled_count = 0;
 
 bool LowMemoryDetector::has_pending_requests() {
   assert(Notification_lock->owned_by_self(), "Must own Notification_lock");

src/hotspot/share/services/lowMemoryDetector.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2021, 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
@@ -211,19 +211,13 @@ public:
 };
 
 class LowMemoryDetector : public AllStatic {
-  friend class LowMemoryDetectorDisabler;
   friend class ServiceThread;
   friend class NotificationThread;
 private:
   // true if any collected heap has low memory detection enabled
   static volatile bool _enabled_for_collected_pools;
-  // > 0 if temporary disabed
-  static volatile jint _disabled_count;
 
   static bool has_pending_requests();
-  static bool temporary_disabled() { return _disabled_count > 0; }
-  static void disable() { Atomic::inc(&_disabled_count); }
-  static void enable() { Atomic::dec(&_disabled_count); }
   static void process_sensor_changes(TRAPS);
 
 public:
@@ -244,19 +238,13 @@ public:
     }
   }
 
-  // indicates if low memory detection is enabled for any collected
-  // memory pools
-  static inline bool is_enabled_for_collected_pools() {
-    return !temporary_disabled() && _enabled_for_collected_pools;
-  }
-
   // recompute enabled flag
   static void recompute_enabled_for_collected_pools();
 
   // low memory detection for collected memory pools.
   static inline void detect_low_memory_for_collected_pools() {
     // no-op if low memory detection not enabled
-    if (!is_enabled_for_collected_pools()) {
+    if (!_enabled_for_collected_pools) {
       return;
     }
     int num_memory_pools = MemoryService::num_memory_pools();
@@ -276,17 +264,4 @@ public:
   }
 };
 
-class LowMemoryDetectorDisabler: public StackObj {
-public:
-  LowMemoryDetectorDisabler()
-  {
-    LowMemoryDetector::disable();
-  }
-  ~LowMemoryDetectorDisabler()
-  {
-    assert(LowMemoryDetector::temporary_disabled(), "should be disabled!");
-    LowMemoryDetector::enable();
-  }
-};
-
 #endif // SHARE_SERVICES_LOWMEMORYDETECTOR_HPP