8197992: Move the OopStorage::ParState type out of inline.hpp

Reviewed-by: tschatzl, kbarrett

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

@@ -0,0 +1,198 @@
+/*
+ * Copyright (c) 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
+ * 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_GC_SHARED_OOPSTORAGEPARSTATE_HPP
+#define SHARE_GC_SHARED_OOPSTORAGEPARSTATE_HPP
+
+#include "gc/shared/oopStorage.hpp"
+#include "memory/allocation.hpp"
+#include "utilities/macros.hpp"
+
+#if INCLUDE_ALL_GCS
+
+//////////////////////////////////////////////////////////////////////////////
+// Support for parallel and optionally concurrent state iteration.
+//
+// Parallel iteration is for the exclusive use of the GC.  Other iteration
+// clients must use serial iteration.
+//
+// Concurrent Iteration
+//
+// Iteration involves the _active_list, which contains all of the blocks owned
+// by a storage object.  This is a doubly-linked list, linked through
+// dedicated fields in the blocks.
+//
+// At most one concurrent ParState can exist at a time for a given storage
+// object.
+//
+// A concurrent ParState sets the associated storage's
+// _concurrent_iteration_active flag true when the state is constructed, and
+// sets it false when the state is destroyed.  These assignments are made with
+// _active_mutex locked.  Meanwhile, empty block deletion is not done while
+// _concurrent_iteration_active is true.  The flag check and the dependent
+// removal of a block from the _active_list is performed with _active_mutex
+// locked.  This prevents concurrent iteration and empty block deletion from
+// interfering with with each other.
+//
+// Both allocate() and delete_empty_blocks_concurrent() lock the
+// _allocate_mutex while performing their respective list manipulations,
+// preventing them from interfering with each other.
+//
+// When allocate() creates a new block, it is added to the front of the
+// _active_list.  Then _active_head is set to the new block.  When concurrent
+// iteration is started (by a parallel worker thread calling the state's
+// iterate() function), the current _active_head is used as the initial block
+// for the iteration, with iteration proceeding down the list headed by that
+// block.
+//
+// As a result, the list over which concurrent iteration operates is stable.
+// However, once the iteration is started, later allocations may add blocks to
+// the front of the list that won't be examined by the iteration.  And while
+// the list is stable, concurrent allocate() and release() operations may
+// change the set of allocated entries in a block at any time during the
+// iteration.
+//
+// As a result, a concurrent iteration handler must accept that some
+// allocations and releases that occur after the iteration started will not be
+// seen by the iteration.  Further, some may overlap examination by the
+// iteration.  To help with this, allocate() and release() have an invariant
+// that an entry's value must be NULL when it is not in use.
+//
+// An in-progress delete_empty_blocks_concurrent() operation can contend with
+// the start of a concurrent iteration over the _active_mutex.  Since both are
+// under GC control, that potential contention can be eliminated by never
+// scheduling both operations to run at the same time.
+//
+// ParState<concurrent, is_const>
+//   concurrent must be true if iteration is concurrent with the
+//   mutator, false if iteration is at a safepoint.
+//
+//   is_const must be true if the iteration is over a constant storage
+//   object, false if the iteration may modify the storage object.
+//
+// ParState([const] OopStorage* storage)
+//   Construct an object for managing an iteration over storage.  For a
+//   concurrent ParState, empty block deletion for the associated storage
+//   is inhibited for the life of the ParState.  There can be no more
+//   than one live concurrent ParState at a time for a given storage object.
+//
+// template<typename F> void iterate(F f)
+//   Repeatedly claims a block from the associated storage that has
+//   not been processed by this iteration (possibly by other threads),
+//   and applies f to each entry in the claimed block. Assume p is of
+//   type const oop* or oop*, according to is_const. Then f(p) must be
+//   a valid expression whose value is ignored.  Concurrent uses must
+//   be prepared for an entry's value to change at any time, due to
+//   mutator activity.
+//
+// template<typename Closure> void oops_do(Closure* cl)
+//   Wrapper around iterate, providing an adaptation layer allowing
+//   the use of OopClosures and similar objects for iteration.  Assume
+//   p is of type const oop* or oop*, according to is_const.  Then
+//   cl->do_oop(p) must be a valid expression whose value is ignored.
+//   Concurrent uses must be prepared for the entry's value to change
+//   at any time, due to mutator activity.
+//
+// Optional operations, provided only if !concurrent && !is_const.
+// These are not provided when is_const, because the storage object
+// may be modified by the iteration infrastructure, even if the
+// provided closure doesn't modify the storage object.  These are not
+// provided when concurrent because any pre-filtering behavior by the
+// iteration infrastructure is inappropriate for concurrent iteration;
+// modifications of the storage by the mutator could result in the
+// pre-filtering being applied (successfully or not) to objects that
+// are unrelated to what the closure finds in the entry.
+//
+// template<typename Closure> void weak_oops_do(Closure* cl)
+// template<typename IsAliveClosure, typename Closure>
+// void weak_oops_do(IsAliveClosure* is_alive, Closure* cl)
+//   Wrappers around iterate, providing an adaptation layer allowing
+//   the use of is-alive closures and OopClosures for iteration.
+//   Assume p is of type oop*.  Then
+//
+//   - cl->do_oop(p) must be a valid expression whose value is ignored.
+//
+//   - is_alive->do_object_b(*p) must be a valid expression whose value
+//   is convertible to bool.
+//
+//   If *p == NULL then neither is_alive nor cl will be invoked for p.
+//   If is_alive->do_object_b(*p) is false, then cl will not be
+//   invoked on p.
+
+class OopStorage::BasicParState VALUE_OBJ_CLASS_SPEC {
+  OopStorage* _storage;
+  void* volatile _next_block;
+  bool _concurrent;
+
+  // Noncopyable.
+  BasicParState(const BasicParState&);
+  BasicParState& operator=(const BasicParState&);
+
+  void update_iteration_state(bool value);
+  void ensure_iteration_started();
+  Block* claim_next_block();
+
+  // Wrapper for iteration handler; ignore handler result and return true.
+  template<typename F> class AlwaysTrueFn;
+
+public:
+  BasicParState(OopStorage* storage, bool concurrent);
+  ~BasicParState();
+
+  template<bool is_const, typename F> void iterate(F f);
+};
+
+template<bool concurrent, bool is_const>
+class OopStorage::ParState VALUE_OBJ_CLASS_SPEC {
+  BasicParState _basic_state;
+
+public:
+  ParState(const OopStorage* storage) :
+    // For simplicity, always recorded as non-const.
+    _basic_state(const_cast<OopStorage*>(storage), concurrent)
+  {}
+
+  template<typename F> void iterate(F f);
+  template<typename Closure> void oops_do(Closure* cl);
+};
+
+template<>
+class OopStorage::ParState<false, false> VALUE_OBJ_CLASS_SPEC {
+  BasicParState _basic_state;
+
+public:
+  ParState(OopStorage* storage) :
+    _basic_state(storage, false)
+  {}
+
+  template<typename F> void iterate(F f);
+  template<typename Closure> void oops_do(Closure* cl);
+  template<typename Closure> void weak_oops_do(Closure* cl);
+  template<typename IsAliveClosure, typename Closure>
+  void weak_oops_do(IsAliveClosure* is_alive, Closure* cl);
+};
+
+#endif // INCLUDE_ALL_GCS
+
+#endif // SHARE_GC_SHARED_OOPSTORAGEPARSTATE_HPP