8299673: Simplify object pinning interactions with string deduplication

Co-authored-by: Stefan Karlsson <stefank@openjdk.org>
Co-authored-by: Axel Boldt-Christmas <aboldtch@openjdk.org>
Reviewed-by: kbarrett, stefank, dholmes

Author: 3 people

src/hotspot/share/gc/epsilon/epsilonHeap.hpp

@@ -110,8 +110,7 @@ class EpsilonHeap : public CollectedHeap {
   void object_iterate(ObjectClosure* cl) override;
 
   // Object pinning support: every object is implicitly pinned
-  bool supports_object_pinning() const           override { return true; }
-  oop pin_object(JavaThread* thread, oop obj)    override { return obj; }
+  void pin_object(JavaThread* thread, oop obj) override { }
   void unpin_object(JavaThread* thread, oop obj) override { }
 
   // No support for block parsing.

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -79,7 +79,7 @@
 #include "gc/shared/gcBehaviours.hpp"
 #include "gc/shared/gcHeapSummary.hpp"
 #include "gc/shared/gcId.hpp"
-#include "gc/shared/gcLocker.hpp"
+#include "gc/shared/gcLocker.inline.hpp"
 #include "gc/shared/gcTimer.hpp"
 #include "gc/shared/gcTraceTime.inline.hpp"
 #include "gc/shared/generationSpec.hpp"
@@ -2399,6 +2399,14 @@ bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
   return false; // keep some compilers happy
 }
 
+void G1CollectedHeap::pin_object(JavaThread* thread, oop obj) {
+  GCLocker::lock_critical(thread);
+}
+
+void G1CollectedHeap::unpin_object(JavaThread* thread, oop obj) {
+  GCLocker::unlock_critical(thread);
+}
+
 void G1CollectedHeap::print_heap_regions() const {
   LogTarget(Trace, gc, heap, region) lt;
   if (lt.is_enabled()) {

src/hotspot/share/gc/g1/g1CollectedHeap.hpp

@@ -1312,6 +1312,9 @@ class G1CollectedHeap : public CollectedHeap {
   G1HeapSummary create_g1_heap_summary();
   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
 
+  void pin_object(JavaThread* thread, oop obj) override;
+  void unpin_object(JavaThread* thread, oop obj) override;
+
   // Printing
 private:
   void print_heap_regions() const;

src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2023, 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
@@ -35,7 +35,7 @@
 #include "gc/parallel/psScavenge.hpp"
 #include "gc/parallel/psVMOperations.hpp"
 #include "gc/shared/gcHeapSummary.hpp"
-#include "gc/shared/gcLocker.hpp"
+#include "gc/shared/gcLocker.inline.hpp"
 #include "gc/shared/gcWhen.hpp"
 #include "gc/shared/genArguments.hpp"
 #include "gc/shared/gcInitLogger.hpp"
@@ -860,3 +860,11 @@ GrowableArray<MemoryPool*> ParallelScavengeHeap::memory_pools() {
   memory_pools.append(_old_pool);
   return memory_pools;
 }
+
+void ParallelScavengeHeap::pin_object(JavaThread* thread, oop obj) {
+  GCLocker::lock_critical(thread);
+}
+
+void ParallelScavengeHeap::unpin_object(JavaThread* thread, oop obj) {
+  GCLocker::unlock_critical(thread);
+}

src/hotspot/share/gc/parallel/parallelScavengeHeap.hpp

@@ -273,6 +273,9 @@ class ParallelScavengeHeap : public CollectedHeap {
   bool can_load_archived_objects() const override { return UseCompressedOops; }
   HeapWord* allocate_loaded_archive_space(size_t size) override;
   void complete_loaded_archive_space(MemRegion archive_space) override;
+
+  void pin_object(JavaThread* thread, oop obj) override;
+  void unpin_object(JavaThread* thread, oop obj) override;
 };
 
 // Class that can be used to print information about the

src/hotspot/share/gc/serial/serialHeap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2023, 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
@@ -26,6 +26,7 @@
 #include "gc/serial/defNewGeneration.inline.hpp"
 #include "gc/serial/serialHeap.hpp"
 #include "gc/serial/tenuredGeneration.inline.hpp"
+#include "gc/shared/gcLocker.inline.hpp"
 #include "gc/shared/genMemoryPools.hpp"
 #include "gc/shared/strongRootsScope.hpp"
 #include "gc/shared/suspendibleThreadSet.hpp"
@@ -123,3 +124,11 @@ void SerialHeap::complete_loaded_archive_space(MemRegion archive_space) {
   assert(old_gen()->used_region().contains(archive_space), "Archive space not contained in old gen");
   old_gen()->complete_loaded_archive_space(archive_space);
 }
+
+void SerialHeap::pin_object(JavaThread* thread, oop obj) {
+  GCLocker::lock_critical(thread);
+}
+
+void SerialHeap::unpin_object(JavaThread* thread, oop obj) {
+  GCLocker::unlock_critical(thread);
+}

src/hotspot/share/gc/serial/serialHeap.hpp

@@ -108,6 +108,9 @@ class SerialHeap : public GenCollectedHeap {
   bool can_load_archived_objects() const override { return UseCompressedOops; }
   HeapWord* allocate_loaded_archive_space(size_t size) override;
   void complete_loaded_archive_space(MemRegion archive_space) override;
+
+  void pin_object(JavaThread* thread, oop obj) override;
+  void unpin_object(JavaThread* thread, oop obj) override;
 };
 
 #endif // SHARE_GC_SERIAL_SERIALHEAP_HPP

src/hotspot/share/gc/shared/collectedHeap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2023, 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
@@ -635,19 +635,6 @@ void CollectedHeap::reset_promotion_should_fail() {
 
 #endif  // #ifndef PRODUCT
 
-bool CollectedHeap::supports_object_pinning() const {
-  return false;
-}
-
-oop CollectedHeap::pin_object(JavaThread* thread, oop obj) {
-  ShouldNotReachHere();
-  return NULL;
-}
-
-void CollectedHeap::unpin_object(JavaThread* thread, oop obj) {
-  ShouldNotReachHere();
-}
-
 bool CollectedHeap::is_archived_object(oop object) const {
   return false;
 }

src/hotspot/share/gc/shared/collectedHeap.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2023, 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
@@ -501,11 +501,11 @@ class CollectedHeap : public CHeapObj<mtGC> {
   virtual WorkerThreads* safepoint_workers() { return NULL; }
 
   // Support for object pinning. This is used by JNI Get*Critical()
-  // and Release*Critical() family of functions. If supported, the GC
-  // must guarantee that pinned objects never move.
-  virtual bool supports_object_pinning() const;
-  virtual oop pin_object(JavaThread* thread, oop obj);
-  virtual void unpin_object(JavaThread* thread, oop obj);
+  // and Release*Critical() family of functions. The GC must guarantee
+  // that pinned objects never move and don't get reclaimed as garbage.
+  // These functions are potentially safepointing.
+  virtual void pin_object(JavaThread* thread, oop obj) = 0;
+  virtual void unpin_object(JavaThread* thread, oop obj) = 0;
 
   // Is the given object inside a CDS archive area?
   virtual bool is_archived_object(oop object) const;

src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp

@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013, 2022, Red Hat, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -1916,9 +1917,8 @@ void ShenandoahHeap::unregister_nmethod(nmethod* nm) {
   ShenandoahCodeRoots::unregister_nmethod(nm);
 }
 
-oop ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
+void ShenandoahHeap::pin_object(JavaThread* thr, oop o) {
   heap_region_containing(o)->record_pin();
-  return o;
 }
 
 void ShenandoahHeap::unpin_object(JavaThread* thr, oop o) {