8255243: Reinforce escape barrier interactions with ZGC conc stack processing

Co-authored-by: Richard Reingruber <rrich@openjdk.org>
Reviewed-by: rrich, sspitsyn

src/hotspot/share/runtime/keepStackGCProcessed.hpp

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, 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.
+ *
+ */
+
+#ifndef SHARE_RUNTIME_KEEPSTACKGCPROCESSED_HPP
+#define SHARE_RUNTIME_KEEPSTACKGCPROCESSED_HPP
+
+#include "memory/allocation.hpp"
+#include "runtime/stackWatermark.hpp"
+#include "runtime/stackWatermarkKind.hpp"
+#include "runtime/stackWatermarkSet.hpp"
+
+// Use this class to mark a remote thread you are currently interested
+// in examining the entire stack, without it slipping into an unprocessed
+// state at safepoint polls.
+class KeepStackGCProcessedMark : public StackObj {
+  friend class StackWatermark;
+  bool _active;
+  JavaThread* _jt;
+
+  void finish_processing();
+
+public:
+  KeepStackGCProcessedMark(JavaThread* jt);
+  ~KeepStackGCProcessedMark();
+};
+
+
+#endif // SHARE_RUNTIME_KEEPSTACKGCPROCESSED_HPP