--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/classfile/metadataOnStackMark.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,150 @@
+/*
+ * Copyright (c) 2013, 2016, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "classfile/metadataOnStackMark.hpp"
+#include "code/codeCache.hpp"
+#include "compiler/compileBroker.hpp"
+#include "oops/metadata.hpp"
+#include "prims/jvmtiImpl.hpp"
+#include "runtime/synchronizer.hpp"
+#include "runtime/thread.hpp"
+#include "services/threadService.hpp"
+#include "utilities/chunkedList.hpp"
+#if INCLUDE_JVMCI
+#include "jvmci/jvmciRuntime.hpp"
+#endif
+
+MetadataOnStackBuffer* MetadataOnStackMark::_used_buffers = NULL;
+MetadataOnStackBuffer* MetadataOnStackMark::_free_buffers = NULL;
+
+MetadataOnStackBuffer* MetadataOnStackMark::_current_buffer = NULL;
+NOT_PRODUCT(bool MetadataOnStackMark::_is_active = false;)
+
+// Walk metadata on the stack and mark it so that redefinition doesn't delete
+// it.  Class unloading only deletes in-error class files, methods created by
+// the relocator and dummy constant pools.  None of these appear anywhere except
+// in metadata Handles.
+MetadataOnStackMark::MetadataOnStackMark(bool redefinition_walk) {
+  assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
+  assert(_used_buffers == NULL, "sanity check");
+  assert(!_is_active, "MetadataOnStackMarks do not nest");
+  NOT_PRODUCT(_is_active = true;)
+
+  Threads::metadata_handles_do(Metadata::mark_on_stack);
+
+  if (redefinition_walk) {
+    Threads::metadata_do(Metadata::mark_on_stack);
+    CodeCache::metadata_do(Metadata::mark_on_stack);
+    CompileBroker::mark_on_stack();
+    JvmtiCurrentBreakpoints::metadata_do(Metadata::mark_on_stack);
+    ThreadService::metadata_do(Metadata::mark_on_stack);
+#if INCLUDE_JVMCI
+    JVMCIRuntime::metadata_do(Metadata::mark_on_stack);
+#endif
+  }
+}
+
+MetadataOnStackMark::~MetadataOnStackMark() {
+  assert(SafepointSynchronize::is_at_safepoint(), "sanity check");
+  // Unmark everything that was marked.   Can't do the same walk because
+  // redefine classes messes up the code cache so the set of methods
+  // might not be the same.
+  retire_current_buffer();
+
+  MetadataOnStackBuffer* buffer = _used_buffers;
+  while (buffer != NULL) {
+    // Clear on stack state for all metadata.
+    size_t size = buffer->size();
+    for (size_t i  = 0; i < size; i++) {
+      Metadata* md = buffer->at(i);
+      md->set_on_stack(false);
+    }
+
+    MetadataOnStackBuffer* next = buffer->next_used();
+
+    // Move the buffer to the free list.
+    buffer->clear();
+    buffer->set_next_used(NULL);
+    buffer->set_next_free(_free_buffers);
+    _free_buffers = buffer;
+
+    // Step to next used buffer.
+    buffer = next;
+  }
+
+  _used_buffers = NULL;
+
+  NOT_PRODUCT(_is_active = false;)
+}
+
+void MetadataOnStackMark::retire_buffer(MetadataOnStackBuffer* buffer) {
+  if (buffer == NULL) {
+    return;
+  }
+  buffer->set_next_used(_used_buffers);
+  _used_buffers = buffer;
+}
+
+// Current buffer is full or we're ready to walk them, add it to the used list.
+void MetadataOnStackMark::retire_current_buffer() {
+  retire_buffer(_current_buffer);
+  _current_buffer = NULL;
+}
+
+// Get buffer off free list.
+MetadataOnStackBuffer* MetadataOnStackMark::allocate_buffer() {
+  MetadataOnStackBuffer* allocated = _free_buffers;
+
+  if (allocated != NULL) {
+    _free_buffers = allocated->next_free();
+  }
+
+  if (allocated == NULL) {
+    allocated = new MetadataOnStackBuffer();
+  }
+
+  assert(!allocated->is_full(), "Should not be full: " PTR_FORMAT, p2i(allocated));
+
+  return allocated;
+}
+
+// Record which objects are marked so we can unmark the same objects.
+void MetadataOnStackMark::record(Metadata* m) {
+  assert(_is_active, "metadata on stack marking is active");
+
+  MetadataOnStackBuffer* buffer = _current_buffer;
+
+  if (buffer != NULL && buffer->is_full()) {
+    retire_buffer(buffer);
+    buffer = NULL;
+  }
+
+  if (buffer == NULL) {
+    buffer = allocate_buffer();
+    _current_buffer = buffer;
+  }
+
+  buffer->push(m);
+}