8328507: Move StackWatermark code from safepoint cleanup

Reviewed-by: aboldtch, coleenp

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

@@ -347,11 +347,6 @@ protected:
   // collection or expansion activity.
   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const = 0;
 
-  // If a GC uses a stack watermark barrier, the stack processing is lazy, concurrent,
-  // incremental and cooperative. In order for that to work well, mechanisms that stop
-  // another thread might want to ensure its roots are in a sane state.
-  virtual bool uses_stack_watermark_barrier() const { return false; }
-
   // Perform a collection of the heap; intended for use in implementing
   // "System.gc".  This probably implies as full a collection as the
   // "CollectedHeap" supports.

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

@@ -87,6 +87,7 @@
 #include "runtime/java.hpp"
 #include "runtime/orderAccess.hpp"
 #include "runtime/safepointMechanism.hpp"
+#include "runtime/stackWatermarkSet.hpp"
 #include "runtime/vmThread.hpp"
 #include "utilities/events.hpp"
 #include "utilities/powerOfTwo.hpp"
@@ -2302,6 +2303,7 @@ bool ShenandoahHeap::uncommit_bitmap_slice(ShenandoahHeapRegion *r) {
 }
 
 void ShenandoahHeap::safepoint_synchronize_begin() {
+  StackWatermarkSet::safepoint_synchronize_begin();
   SuspendibleThreadSet::synchronize();
 }
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013, 2021, Red Hat, Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -539,11 +539,6 @@ public:
   void sync_pinned_region_status();
   void assert_pinned_region_status() NOT_DEBUG_RETURN;
 
-// ---------- Concurrent Stack Processing support
-//
-public:
-  bool uses_stack_watermark_barrier() const override { return true; }
-
 // ---------- Allocation support
 //
 private:

src/hotspot/share/gc/x/xCollectedHeap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 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
@@ -43,6 +43,7 @@
 #include "memory/universe.hpp"
 #include "oops/stackChunkOop.hpp"
 #include "runtime/continuationJavaClasses.hpp"
+#include "runtime/stackWatermarkSet.hpp"
 #include "utilities/align.hpp"
 
 XCollectedHeap* XCollectedHeap::heap() {
@@ -215,10 +216,6 @@ size_t XCollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
   return _heap.unsafe_max_tlab_alloc();
 }
 
-bool XCollectedHeap::uses_stack_watermark_barrier() const {
-  return true;
-}
-
 MemoryUsage XCollectedHeap::memory_usage() {
   return _heap.serviceability_memory_pool()->get_memory_usage();
 }
@@ -277,6 +274,7 @@ VirtualSpaceSummary XCollectedHeap::create_heap_space_summary() {
 }
 
 void XCollectedHeap::safepoint_synchronize_begin() {
+  StackWatermarkSet::safepoint_synchronize_begin();
   SuspendibleThreadSet::synchronize();
 }
 

src/hotspot/share/gc/x/xCollectedHeap.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 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
@@ -87,8 +87,6 @@ public:
   size_t max_tlab_size() const override;
   size_t unsafe_max_tlab_alloc(Thread* thr) const override;
 
-  bool uses_stack_watermark_barrier() const override;
-
   MemoryUsage memory_usage() override;
   GrowableArray<GCMemoryManager*> memory_managers() override;
   GrowableArray<MemoryPool*> memory_pools() override;

src/hotspot/share/gc/z/zCollectedHeap.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 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
@@ -50,6 +50,7 @@
 #include "oops/stackChunkOop.hpp"
 #include "runtime/continuationJavaClasses.hpp"
 #include "runtime/jniHandles.inline.hpp"
+#include "runtime/stackWatermarkSet.hpp"
 #include "services/memoryUsage.hpp"
 #include "utilities/align.hpp"
 
@@ -240,10 +241,6 @@ size_t ZCollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
   return _heap.unsafe_max_tlab_alloc();
 }
 
-bool ZCollectedHeap::uses_stack_watermark_barrier() const {
-  return true;
-}
-
 MemoryUsage ZCollectedHeap::memory_usage() {
   const size_t initial_size = ZHeap::heap()->initial_capacity();
   const size_t committed    = ZHeap::heap()->capacity();
@@ -338,6 +335,7 @@ bool ZCollectedHeap::contains_null(const oop* p) const {
 }
 
 void ZCollectedHeap::safepoint_synchronize_begin() {
+  StackWatermarkSet::safepoint_synchronize_begin();
   ZGeneration::young()->synchronize_relocation();
   ZGeneration::old()->synchronize_relocation();
   SuspendibleThreadSet::synchronize();

src/hotspot/share/gc/z/zCollectedHeap.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 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
@@ -88,8 +88,6 @@ public:
   size_t max_tlab_size() const override;
   size_t unsafe_max_tlab_alloc(Thread* thr) const override;
 
-  bool uses_stack_watermark_barrier() const override;
-
   MemoryUsage memory_usage() override;
   GrowableArray<GCMemoryManager*> memory_managers() override;
   GrowableArray<MemoryPool*> memory_pools() override;

src/hotspot/share/runtime/safepoint.cpp

@@ -510,7 +510,6 @@ void SafepointSynchronize::end() {
 class ParallelCleanupTask : public WorkerTask {
 private:
   SubTasksDone _subtasks;
-  bool _do_lazy_roots;
 
   class Tracer {
   private:
@@ -531,35 +530,15 @@ private:
 public:
   ParallelCleanupTask() :
     WorkerTask("Parallel Safepoint Cleanup"),
-    _subtasks(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS),
-    _do_lazy_roots(!VMThread::vm_operation()->skip_thread_oop_barriers() &&
-                   Universe::heap()->uses_stack_watermark_barrier()) {}
+    _subtasks(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS) {}
 
   uint expected_num_workers() const {
     uint workers = 0;
 
-    if (_do_lazy_roots) {
-      workers++;
-    }
-
     return MAX2<uint>(1, workers);
   }
 
   void work(uint worker_id) {
-    if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_LAZY_ROOT_PROCESSING)) {
-      if (_do_lazy_roots) {
-        Tracer t("lazy partial thread root processing");
-        class LazyRootClosure : public ThreadClosure {
-        public:
-          void do_thread(Thread* thread) {
-            StackWatermarkSet::start_processing(JavaThread::cast(thread), StackWatermarkKind::gc);
-          }
-        };
-        LazyRootClosure cl;
-        Threads::java_threads_do(&cl);
-      }
-    }
-
     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) {
       // Don't bother reporting event or time for this very short operation.
       // To have any utility we'd also want to report whether needed.

src/hotspot/share/runtime/safepoint.hpp

@@ -70,7 +70,6 @@ class SafepointSynchronize : AllStatic {
 
   // The enums are listed in the order of the tasks when done serially.
   enum SafepointCleanupTasks {
-    SAFEPOINT_CLEANUP_LAZY_ROOT_PROCESSING,
     SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP,
     // Leave this one last.
     SAFEPOINT_CLEANUP_NUM_TASKS

src/hotspot/share/runtime/stackWatermarkSet.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 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
@@ -31,6 +31,9 @@
 #include "runtime/safepointMechanism.inline.hpp"
 #include "runtime/stackWatermark.inline.hpp"
 #include "runtime/stackWatermarkSet.inline.hpp"
+#include "runtime/threadSMR.hpp"
+#include "runtime/vmOperation.hpp"
+#include "runtime/vmThread.hpp"
 #include "utilities/debug.hpp"
 #include "utilities/globalDefinitions.hpp"
 #include "utilities/preserveException.hpp"
@@ -118,7 +121,6 @@ void StackWatermarkSet::on_safepoint(JavaThread* jt) {
 
 void StackWatermarkSet::start_processing(JavaThread* jt, StackWatermarkKind kind) {
   verify_processing_context();
-  assert(!jt->is_terminated(), "Poll after termination is a bug");
   StackWatermark* watermark = get(jt, kind);
   if (watermark != nullptr) {
     watermark->start_processing();
@@ -158,3 +160,13 @@ uintptr_t StackWatermarkSet::lowest_watermark(JavaThread* jt) {
     return watermark;
   }
 }
+
+void StackWatermarkSet::safepoint_synchronize_begin() {
+  if (VMThread::vm_operation()->skip_thread_oop_barriers()) {
+    return;
+  }
+
+  for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
+    StackWatermarkSet::start_processing(thread, StackWatermarkKind::gc);
+  }
+}

src/hotspot/share/runtime/stackWatermarkSet.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 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
@@ -88,6 +88,10 @@ public:
   // The lowest watermark among the watermarks in the set (the first encountered
   // watermark in the set as you unwind frames)
   static uintptr_t lowest_watermark(JavaThread* jt);
+
+  // We are synchronizing a safepoint, so we might want to ensure processing has at least
+  // started, as safepoint operations sometimes assume that is the case
+  static void safepoint_synchronize_begin();
 };
 
 #endif // SHARE_RUNTIME_STACKWATERMARKSET_HPP