--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/oopStorage.hpp Tue Nov 21 09:47:55 2017 -0500
@@ -0,0 +1,734 @@
+/*
+ * 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_OOPSTORAGE_HPP
+#define SHARE_GC_SHARED_OOPSTORAGE_HPP
+
+#include "memory/allocation.hpp"
+#include "metaprogramming/conditional.hpp"
+#include "metaprogramming/isConst.hpp"
+#include "oops/oop.hpp"
+#include "utilities/count_trailing_zeros.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/macros.hpp"
+
+class Mutex;
+class outputStream;
+
+// OopStorage supports management of off-heap references to objects allocated
+// in the Java heap. An OopStorage object provides a set of Java object
+// references (oop values), which clients refer to via oop* handles to the
+// associated OopStorage entries. Clients allocate entries to create a
+// (possibly weak) reference to a Java object, use that reference, and release
+// the reference when no longer needed.
+//
+// The garbage collector must know about all OopStorage objects and their
+// reference strength. OopStorage provides the garbage collector with support
+// for iteration over all the allocated entries.
+//
+// There are several categories of interaction with an OopStorage object.
+//
+// (1) allocation and release of entries, by the mutator or the VM.
+// (2) iteration by the garbage collector, possibly concurrent with mutator.
+// (3) iteration by other, non-GC, tools (only at safepoints).
+// (4) cleanup of unused internal storage, possibly concurrent with mutator.
+//
+// A goal of OopStorage is to make these interactions thread-safe, while
+// minimizing potential lock contention issues within and between these
+// categories. In particular, support for concurrent iteration by the garbage
+// collector, under certain restrictions, is required. Further, it must not
+// block nor be blocked by other operations for long periods.
+//
+// Internally, OopStorage is a set of Block objects, from which entries are
+// allocated and released. A block contains an oop[] and a bitmask indicating
+// which entries are in use (have been allocated and not yet released). New
+// blocks are constructed and added to the storage object when an entry
+// allocation request is made and there are no blocks with unused entries.
+// Blocks may be removed and deleted when empty.
+//
+// There are two important (and somewhat intertwined) protocols governing
+// concurrent access to a storage object. These are the Concurrent Iteration
+// Protocol and the Allocation Protocol. See the ParState class for a
+// discussion of concurrent iteration and the management of thread
+// interactions for this protocol. Similarly, see the allocate() function for
+// a discussion of allocation.
+
+class OopStorage : public CHeapObj<mtGC> {
+public:
+ OopStorage(const char* name, Mutex* allocate_mutex, Mutex* active_mutex);
+ ~OopStorage();
+
+ // These count and usage accessors are racy unless at a safepoint.
+
+ // The number of allocated and not yet released entries.
+ size_t allocation_count() const;
+
+ // The number of blocks of entries. Useful for sizing parallel iteration.
+ size_t block_count() const;
+
+ // The number of blocks with no allocated entries. Useful for sizing
+ // parallel iteration and scheduling block deletion.
+ size_t empty_block_count() const;
+
+ // Total number of blocks * memory allocation per block, plus
+ // bookkeeping overhead, including this storage object.
+ size_t total_memory_usage() const;
+
+ enum EntryStatus {
+ INVALID_ENTRY,
+ UNALLOCATED_ENTRY,
+ ALLOCATED_ENTRY
+ };
+
+ // Locks _allocate_mutex.
+ EntryStatus allocation_status(const oop* ptr) const;
+
+ // Allocates and returns a new entry. Returns NULL if memory allocation
+ // failed. Locks _allocate_mutex.
+ // postcondition: *result == NULL.
+ oop* allocate();
+
+ // Deallocates ptr, after setting its value to NULL. Locks _allocate_mutex.
+ // precondition: ptr is a valid allocated entry.
+ // precondition: *ptr == NULL.
+ void release(const oop* ptr);
+
+ // Releases all the ptrs. Possibly faster than individual calls to
+ // release(oop*). Best if ptrs is sorted by address. Locks
+ // _allocate_mutex.
+ // precondition: All elements of ptrs are valid allocated entries.
+ // precondition: *ptrs[i] == NULL, for i in [0,size).
+ void release(const oop* const* ptrs, size_t size);
+
+ // Applies f to each allocated entry's location. f must be a function or
+ // function object. Assume p is either a const oop* or an oop*, depending
+ // on whether the associated storage is const or non-const, respectively.
+ // Then f(p) must be a valid expression. The result of invoking f(p) must
+ // be implicitly convertible to bool. Iteration terminates and returns
+ // false if any invocation of f returns false. Otherwise, the result of
+ // iteration is true.
+ // precondition: at safepoint.
+ template<typename F> bool iterate_safepoint(F f);
+ template<typename F> bool iterate_safepoint(F f) const;
+
+ // oops_do and weak_oops_do are wrappers around iterate_safepoint, providing
+ // an adaptation layer allowing the use of existing is-alive closures and
+ // OopClosures. Assume p is either const oop* or oop*, depending on whether
+ // the associated storage is const or non-const, respectively. Then
+ //
+ // - closure->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.
+ //
+ // For weak_oops_do, if *p == NULL then neither is_alive nor closure will be
+ // invoked for p. If is_alive->do_object_b(*p) is false, then closure will
+ // not be invoked on p, and *p will be set to NULL.
+
+ template<typename Closure> void oops_do(Closure* closure);
+ template<typename Closure> void oops_do(Closure* closure) const;
+ template<typename Closure> void weak_oops_do(Closure* closure);
+
+ template<typename IsAliveClosure, typename Closure>
+ void weak_oops_do(IsAliveClosure* is_alive, Closure* closure);
+
+#if INCLUDE_ALL_GCS
+ // Parallel iteration is for the exclusive use of the GC.
+ // Other clients must use serial iteration.
+ template<bool concurrent, bool is_const> class ParState;
+#endif // INCLUDE_ALL_GCS
+
+ // Block cleanup functions are for the exclusive use of the GC.
+ // Both stop deleting if there is an in-progress concurrent iteration.
+ // Concurrent deletion locks both the allocate_mutex and the active_mutex.
+ void delete_empty_blocks_safepoint(size_t retain = 1);
+ void delete_empty_blocks_concurrent(size_t retain = 1);
+
+ // Debugging and logging support.
+ const char* name() const;
+ void print_on(outputStream* st) const PRODUCT_RETURN;
+
+ // Provides access to storage internals, for unit testing.
+ class TestAccess;
+
+private:
+ class Block;
+ class BlockList;
+
+ class BlockEntry VALUE_OBJ_CLASS_SPEC {
+ friend class BlockList;
+
+ // Members are mutable, and we deal exclusively with pointers to
+ // const, to make const blocks easier to use; a block being const
+ // doesn't prevent modifying its list state.
+ mutable const Block* _prev;
+ mutable const Block* _next;
+
+ // Noncopyable.
+ BlockEntry(const BlockEntry&);
+ BlockEntry& operator=(const BlockEntry&);
+
+ public:
+ BlockEntry();
+ ~BlockEntry();
+ };
+
+ class BlockList VALUE_OBJ_CLASS_SPEC {
+ const Block* _head;
+ const Block* _tail;
+ const BlockEntry& (*_get_entry)(const Block& block);
+
+ // Noncopyable.
+ BlockList(const BlockList&);
+ BlockList& operator=(const BlockList&);
+
+ public:
+ BlockList(const BlockEntry& (*get_entry)(const Block& block));
+ ~BlockList();
+
+ Block* head();
+ const Block* chead() const;
+ const Block* ctail() const;
+
+ Block* prev(Block& block);
+ Block* next(Block& block);
+
+ const Block* prev(const Block& block) const;
+ const Block* next(const Block& block) const;
+
+ void push_front(const Block& block);
+ void push_back(const Block& block);
+ void unlink(const Block& block);
+ };
+
+ class Block /* No base class, to avoid messing up alignment requirements */ {
+ // _data must be the first non-static data member, for alignment.
+ oop _data[BitsPerWord];
+ static const unsigned _data_pos = 0; // Position of _data.
+
+ volatile uintx _allocated_bitmask; // One bit per _data element.
+ const OopStorage* _owner;
+ void* _memory; // Unaligned storage containing block.
+ BlockEntry _active_entry;
+ BlockEntry _allocate_entry;
+
+ Block(const OopStorage* owner, void* memory);
+ ~Block();
+
+ void check_index(unsigned index) const;
+ unsigned get_index(const oop* ptr) const;
+
+ template<typename F, typename BlockPtr>
+ static bool iterate_impl(F f, BlockPtr b);
+
+ // Noncopyable.
+ Block(const Block&);
+ Block& operator=(const Block&);
+
+ public:
+ static const BlockEntry& get_active_entry(const Block& block);
+ static const BlockEntry& get_allocate_entry(const Block& block);
+
+ static size_t allocation_size();
+ static size_t allocation_alignment_shift();
+
+ oop* get_pointer(unsigned index);
+ const oop* get_pointer(unsigned index) const;
+
+ uintx bitmask_for_index(unsigned index) const;
+ uintx bitmask_for_entry(const oop* ptr) const;
+
+ // Allocation bitmask accessors are racy.
+ bool is_full() const;
+ bool is_empty() const;
+ uintx allocated_bitmask() const;
+ uintx cmpxchg_allocated_bitmask(uintx new_value, uintx compare_value);
+
+ bool contains(const oop* ptr) const;
+
+ // Returns NULL if ptr is not in a block or not allocated in that block.
+ static Block* block_for_ptr(const OopStorage* owner, const oop* ptr);
+
+ oop* allocate();
+ static Block* new_block(const OopStorage* owner);
+ static void delete_block(const Block& block);
+
+ template<typename F> bool iterate(F f);
+ template<typename F> bool iterate(F f) const;
+ }; // class Block
+
+ const char* _name;
+ BlockList _active_list;
+ BlockList _allocate_list;
+ Block* volatile _active_head;
+
+ Mutex* _allocate_mutex;
+ Mutex* _active_mutex;
+
+ // Counts are volatile for racy unlocked accesses.
+ volatile size_t _allocation_count;
+ volatile size_t _block_count;
+ volatile size_t _empty_block_count;
+ // mutable because this gets set even for const iteration.
+ mutable bool _concurrent_iteration_active;
+
+ Block* find_block_or_null(const oop* ptr) const;
+ bool is_valid_block_locked_or_safepoint(const Block* block) const;
+ EntryStatus allocation_status_validating_block(const Block* block, const oop* ptr) const;
+ void check_release(const Block* block, const oop* ptr) const NOT_DEBUG_RETURN;
+ void release_from_block(Block& block, uintx release_bitmask);
+ void delete_empty_block(const Block& block);
+
+ static void assert_at_safepoint() NOT_DEBUG_RETURN;
+
+ template<typename F, typename Storage>
+ static bool iterate_impl(F f, Storage* storage);
+
+#if INCLUDE_ALL_GCS
+ // Implementation support for parallel iteration
+ class BasicParState;
+#endif // INCLUDE_ALL_GCS
+
+ // Wrapper for OopClosure-style function, so it can be used with
+ // iterate. Assume p is of type oop*. Then cl->do_oop(p) must be a
+ // valid expression whose value may be ignored.
+ template<typename Closure> class OopFn;
+ template<typename Closure> static OopFn<Closure> oop_fn(Closure* cl);
+
+ // Wrapper for BoolObjectClosure + iteration handler pair, so they
+ // can be used with iterate.
+ template<typename IsAlive, typename F> class IfAliveFn;
+ template<typename IsAlive, typename F>
+ static IfAliveFn<IsAlive, F> if_alive_fn(IsAlive* is_alive, F f);
+
+ // Wrapper for iteration handler, automatically skipping NULL entries.
+ template<typename F> class SkipNullFn;
+ template<typename F> static SkipNullFn<F> skip_null_fn(F f);
+
+ // Wrapper for iteration handler; ignore handler result and return true.
+ template<typename F> class AlwaysTrueFn;
+};
+
+inline OopStorage::Block* OopStorage::BlockList::head() {
+ return const_cast<Block*>(_head);
+}
+
+inline const OopStorage::Block* OopStorage::BlockList::chead() const {
+ return _head;
+}
+
+inline const OopStorage::Block* OopStorage::BlockList::ctail() const {
+ return _tail;
+}
+
+inline OopStorage::Block* OopStorage::BlockList::prev(Block& block) {
+ return const_cast<Block*>(_get_entry(block)._prev);
+}
+
+inline OopStorage::Block* OopStorage::BlockList::next(Block& block) {
+ return const_cast<Block*>(_get_entry(block)._next);
+}
+
+inline const OopStorage::Block* OopStorage::BlockList::prev(const Block& block) const {
+ return _get_entry(block)._prev;
+}
+
+inline const OopStorage::Block* OopStorage::BlockList::next(const Block& block) const {
+ return _get_entry(block)._next;
+}
+
+template<typename Closure>
+class OopStorage::OopFn VALUE_OBJ_CLASS_SPEC {
+public:
+ explicit OopFn(Closure* cl) : _cl(cl) {}
+
+ template<typename OopPtr> // [const] oop*
+ bool operator()(OopPtr ptr) const {
+ _cl->do_oop(ptr);
+ return true;
+ }
+
+private:
+ Closure* _cl;
+};
+
+template<typename Closure>
+inline OopStorage::OopFn<Closure> OopStorage::oop_fn(Closure* cl) {
+ return OopFn<Closure>(cl);
+}
+
+template<typename IsAlive, typename F>
+class OopStorage::IfAliveFn VALUE_OBJ_CLASS_SPEC {
+public:
+ IfAliveFn(IsAlive* is_alive, F f) : _is_alive(is_alive), _f(f) {}
+
+ bool operator()(oop* ptr) const {
+ bool result = true;
+ oop v = *ptr;
+ if (v != NULL) {
+ if (_is_alive->do_object_b(v)) {
+ result = _f(ptr);
+ } else {
+ *ptr = NULL; // Clear dead value.
+ }
+ }
+ return result;
+ }
+
+private:
+ IsAlive* _is_alive;
+ F _f;
+};
+
+template<typename IsAlive, typename F>
+inline OopStorage::IfAliveFn<IsAlive, F> OopStorage::if_alive_fn(IsAlive* is_alive, F f) {
+ return IfAliveFn<IsAlive, F>(is_alive, f);
+}
+
+template<typename F>
+class OopStorage::SkipNullFn VALUE_OBJ_CLASS_SPEC {
+public:
+ SkipNullFn(F f) : _f(f) {}
+
+ template<typename OopPtr> // [const] oop*
+ bool operator()(OopPtr ptr) const {
+ return (*ptr != NULL) ? _f(ptr) : true;
+ }
+
+private:
+ F _f;
+};
+
+template<typename F>
+inline OopStorage::SkipNullFn<F> OopStorage::skip_null_fn(F f) {
+ return SkipNullFn<F>(f);
+}
+
+template<typename F>
+class OopStorage::AlwaysTrueFn VALUE_OBJ_CLASS_SPEC {
+ F _f;
+
+public:
+ AlwaysTrueFn(F f) : _f(f) {}
+
+ template<typename OopPtr> // [const] oop*
+ bool operator()(OopPtr ptr) const { _f(ptr); return true; }
+};
+
+// Inline Block accesses for use in iteration inner loop.
+
+inline void OopStorage::Block::check_index(unsigned index) const {
+ assert(index < ARRAY_SIZE(_data), "Index out of bounds: %u", index);
+}
+
+inline oop* OopStorage::Block::get_pointer(unsigned index) {
+ check_index(index);
+ return &_data[index];
+}
+
+inline const oop* OopStorage::Block::get_pointer(unsigned index) const {
+ check_index(index);
+ return &_data[index];
+}
+
+inline uintx OopStorage::Block::allocated_bitmask() const {
+ return _allocated_bitmask;
+}
+
+inline uintx OopStorage::Block::bitmask_for_index(unsigned index) const {
+ check_index(index);
+ return uintx(1) << index;
+}
+
+// Provide const or non-const iteration, depending on whether BlockPtr
+// is const Block* or Block*, respectively.
+template<typename F, typename BlockPtr> // BlockPtr := [const] Block*
+inline bool OopStorage::Block::iterate_impl(F f, BlockPtr block) {
+ uintx bitmask = block->allocated_bitmask();
+ while (bitmask != 0) {
+ unsigned index = count_trailing_zeros(bitmask);
+ bitmask ^= block->bitmask_for_index(index);
+ if (!f(block->get_pointer(index))) {
+ return false;
+ }
+ }
+ return true;
+}
+
+template<typename F>
+inline bool OopStorage::Block::iterate(F f) {
+ return iterate_impl(f, this);
+}
+
+template<typename F>
+inline bool OopStorage::Block::iterate(F f) const {
+ return iterate_impl(f, this);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+// Support for serial iteration, always at a safepoint.
+
+// Provide const or non-const iteration, depending on whether Storage is
+// const OopStorage* or OopStorage*, respectively.
+template<typename F, typename Storage> // Storage := [const] OopStorage
+inline bool OopStorage::iterate_impl(F f, Storage* storage) {
+ assert_at_safepoint();
+ // Propagate const/non-const iteration to the block layer, by using
+ // const or non-const blocks as corresponding to Storage.
+ typedef typename Conditional<IsConst<Storage>::value, const Block*, Block*>::type BlockPtr;
+ for (BlockPtr block = storage->_active_head;
+ block != NULL;
+ block = storage->_active_list.next(*block)) {
+ if (!block->iterate(f)) {
+ return false;
+ }
+ }
+ return true;
+}
+
+template<typename F>
+inline bool OopStorage::iterate_safepoint(F f) {
+ return iterate_impl(f, this);
+}
+
+template<typename F>
+inline bool OopStorage::iterate_safepoint(F f) const {
+ return iterate_impl(f, this);
+}
+
+template<typename Closure>
+inline void OopStorage::oops_do(Closure* cl) {
+ iterate_safepoint(oop_fn(cl));
+}
+
+template<typename Closure>
+inline void OopStorage::oops_do(Closure* cl) const {
+ iterate_safepoint(oop_fn(cl));
+}
+
+template<typename Closure>
+inline void OopStorage::weak_oops_do(Closure* cl) {
+ iterate_safepoint(skip_null_fn(oop_fn(cl)));
+}
+
+template<typename IsAliveClosure, typename Closure>
+inline void OopStorage::weak_oops_do(IsAliveClosure* is_alive, Closure* cl) {
+ iterate_safepoint(if_alive_fn(is_alive, oop_fn(cl)));
+}
+
+#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 {
+public:
+ BasicParState(OopStorage* storage, bool concurrent);
+ ~BasicParState();
+
+ template<bool is_const, typename F> void iterate(F f) {
+ // Wrap f in ATF so we can use Block::iterate.
+ AlwaysTrueFn<F> atf_f(f);
+ ensure_iteration_started();
+ typename Conditional<is_const, const Block*, Block*>::type block;
+ while ((block = claim_next_block()) != NULL) {
+ block->iterate(atf_f);
+ }
+ }
+
+private:
+ 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();
+};
+
+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) {
+ _basic_state.template iterate<is_const>(f);
+ }
+
+ template<typename Closure>
+ void oops_do(Closure* cl) {
+ this->iterate(oop_fn(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) {
+ _basic_state.template iterate<false>(f);
+ }
+
+ template<typename Closure>
+ void oops_do(Closure* cl) {
+ this->iterate(oop_fn(cl));
+ }
+
+ template<typename Closure>
+ void weak_oops_do(Closure* cl) {
+ this->iterate(skip_null_fn(oop_fn(cl)));
+ }
+
+ template<typename IsAliveClosure, typename Closure>
+ void weak_oops_do(IsAliveClosure* is_alive, Closure* cl) {
+ this->iterate(if_alive_fn(is_alive, oop_fn(cl)));
+ }
+};
+
+#endif // INCLUDE_ALL_GCS
+
+#endif // include guard