8205417: Obsolete UnlinkSymbolsALot debugging option

Obsolete and remove support for UnlinkSymbolsALot

Reviewed-by: hseigel, dholmes

src/hotspot/share/runtime/arguments.cpp

@@ -539,7 +539,6 @@ static SpecialFlag const special_jvm_flags[] = {
   { "PrintSafepointStatisticsTimeout", JDK_Version::jdk(11), JDK_Version::jdk(12), JDK_Version::jdk(13) },
   { "PrintSafepointStatisticsCount",JDK_Version::jdk(11), JDK_Version::jdk(12), JDK_Version::jdk(13) },
   { "AggressiveOpts",               JDK_Version::jdk(11), JDK_Version::jdk(12), JDK_Version::jdk(13) },
-  { "UnlinkSymbolsALot",            JDK_Version::jdk(11), JDK_Version::jdk(12), JDK_Version::jdk(13) },
 
   // --- Deprecated alias flags (see also aliased_jvm_flags) - sorted by obsolete_in then expired_in:
   { "DefaultMaxRAMFraction",        JDK_Version::jdk(8),  JDK_Version::undefined(), JDK_Version::undefined() },
@@ -572,6 +571,7 @@ static SpecialFlag const special_jvm_flags[] = {
   { "NativeMonitorTimeout",          JDK_Version::undefined(), JDK_Version::jdk(11), JDK_Version::jdk(12) },
   { "NativeMonitorSpinLimit",        JDK_Version::undefined(), JDK_Version::jdk(11), JDK_Version::jdk(12) },
   { "NativeMonitorFlags",            JDK_Version::undefined(), JDK_Version::jdk(11), JDK_Version::jdk(12) },
+  { "UnlinkSymbolsALot",             JDK_Version::jdk(11),     JDK_Version::jdk(12), JDK_Version::jdk(13) },
   { "AllowNonVirtualCalls",          JDK_Version::jdk(11),     JDK_Version::jdk(12), JDK_Version::jdk(13) },
 
 #ifdef TEST_VERIFY_SPECIAL_JVM_FLAGS

src/hotspot/share/runtime/globals.hpp

@@ -486,9 +486,6 @@ define_pd_global(uint64_t,MaxRAM,                    1ULL*G);
   notproduct(bool, ZombieALot, false,                                       \
           "Create zombies (non-entrant) at exit from the runtime system")   \
                                                                             \
-  product(bool, UnlinkSymbolsALot, false,                                   \
-          "Unlink unreferenced symbols from the symbol table at safepoints")\
-                                                                            \
   notproduct(bool, WalkStackALot, false,                                    \
           "Trace stack (no print) at every exit from the runtime system")   \
                                                                             \

src/hotspot/share/runtime/interfaceSupport.cpp

@@ -66,9 +66,6 @@ VMEntryWrapper::~VMEntryWrapper() {
   if (ZombieALot) {
     InterfaceSupport::zombieAll();
   }
-  if (UnlinkSymbolsALot) {
-    InterfaceSupport::unlinkSymbols();
-  }
   // do verification AFTER potential deoptimization
   if (VerifyStack) {
     InterfaceSupport::verify_stack();
@@ -208,11 +205,6 @@ void InterfaceSupport::zombieAll() {
   zombieAllCounter++;
 }
 
-void InterfaceSupport::unlinkSymbols() {
-  VM_UnlinkSymbols op;
-  VMThread::execute(&op);
-}
-
 void InterfaceSupport::deoptimizeAll() {
   // This method is called by all threads when a thread make
   // transition to VM state (for example, runtime calls).

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2018, 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
@@ -60,7 +60,6 @@ class InterfaceSupport: AllStatic {
   static void walk_stack();
 
   static void zombieAll();
-  static void unlinkSymbols();
   static void deoptimizeAll();
   static void stress_derived_pointers();
   static void verify_stack();

src/hotspot/share/runtime/vm_operations.cpp

@@ -192,12 +192,6 @@ void VM_ZombieAll::doit() {
 
 #endif // !PRODUCT
 
-void VM_UnlinkSymbols::doit() {
-  JavaThread *thread = (JavaThread *)calling_thread();
-  assert(thread->is_Java_thread(), "must be a Java thread");
-  SymbolTable::unlink();
-}
-
 void VM_Verify::doit() {
   Universe::heap()->prepare_for_verify();
   Universe::verify();

src/hotspot/share/runtime/vm_operations.hpp

@@ -52,7 +52,6 @@
   template(DeoptimizeFrame)                       \
   template(DeoptimizeAll)                         \
   template(ZombieAll)                             \
-  template(UnlinkSymbols)                         \
   template(Verify)                                \
   template(PrintJNI)                              \
   template(HeapDumper)                            \
@@ -353,14 +352,6 @@ class VM_ZombieAll: public VM_Operation {
 };
 #endif // PRODUCT
 
-class VM_UnlinkSymbols: public VM_Operation {
- public:
-  VM_UnlinkSymbols() {}
-  VMOp_Type type() const                         { return VMOp_UnlinkSymbols; }
-  void doit();
-  bool allow_nested_vm_operations() const        { return true; }
-};
-
 class VM_Verify: public VM_Operation {
  public:
   VMOp_Type type() const { return VMOp_Verify; }