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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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).

 *

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 * 2 along with this work; if not, write to the Free Software Foundation,

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#ifndef SHARE_GC_SHARED_REFERENCEPROCESSOR_HPP

#define SHARE_GC_SHARED_REFERENCEPROCESSOR_HPP

#include "gc/shared/referenceDiscoverer.hpp"

#include "gc/shared/referencePolicy.hpp"

#include "gc/shared/referenceProcessorStats.hpp"

#include "memory/referenceType.hpp"

#include "oops/instanceRefKlass.hpp"

class AbstractRefProcTaskExecutor;

class GCTimer;

class ReferencePolicy;

class ReferenceProcessorPhaseTimes;

// List of discovered references.

class DiscoveredList {

public:

  DiscoveredList() : _oop_head(NULL), _compressed_head(0), _len(0) { }

  inline oop head() const;

  HeapWord* adr_head() {

    return UseCompressedOops ? (HeapWord*)&_compressed_head :

                               (HeapWord*)&_oop_head;

  }

  inline void set_head(oop o);

  inline bool is_empty() const;

  size_t length()               { return _len; }

  void   set_length(size_t len) { _len = len;  }

  void   inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); }

  void   dec_length(size_t dec) { _len -= dec; }

  inline void clear();

private:

  // Set value depending on UseCompressedOops. This could be a template class

  // but then we have to fix all the instantiations and declarations that use this class.

  oop       _oop_head;

  narrowOop _compressed_head;

  size_t _len;

};

// Iterator for the list of discovered references.

class DiscoveredListIterator {

private:

  DiscoveredList&    _refs_list;

  HeapWord*          _prev_discovered_addr;

  oop                _prev_discovered;

  oop                _current_discovered;

  HeapWord*          _current_discovered_addr;

  oop                _next_discovered;

  HeapWord*          _referent_addr;

  oop                _referent;

  OopClosure*        _keep_alive;

  BoolObjectClosure* _is_alive;

  DEBUG_ONLY(

  oop                _first_seen; // cyclic linked list check

  )

  size_t             _processed;

  size_t             _removed;

public:

  inline DiscoveredListIterator(DiscoveredList&    refs_list,

                                OopClosure*        keep_alive,

                                BoolObjectClosure* is_alive);

  // End Of List.

  inline bool has_next() const { return _current_discovered != NULL; }

  // Get oop to the Reference object.

  inline oop obj() const { return _current_discovered; }

  // Get oop to the referent object.

  inline oop referent() const { return _referent; }

  // Returns true if referent is alive.

  inline bool is_referent_alive() const {

    return _is_alive->do_object_b(_referent);

  }

  // Loads data for the current reference.

  // The "allow_null_referent" argument tells us to allow for the possibility

  // of a NULL referent in the discovered Reference object. This typically

  // happens in the case of concurrent collectors that may have done the

  // discovery concurrently, or interleaved, with mutator execution.

  void load_ptrs(DEBUG_ONLY(bool allow_null_referent));

  // Move to the next discovered reference.

  inline void next() {

    _prev_discovered_addr = _current_discovered_addr;

    _prev_discovered = _current_discovered;

    move_to_next();

  }

  // Remove the current reference from the list

  void remove();

  // Make the referent alive.

  inline void make_referent_alive() {

    if (UseCompressedOops) {

      _keep_alive->do_oop((narrowOop*)_referent_addr);

    } else {

      _keep_alive->do_oop((oop*)_referent_addr);

    }

  }

  // Do enqueuing work, i.e. notifying the GC about the changed discovered pointers.

  void enqueue();

  // Move enqueued references to the reference pending list.

  void complete_enqueue();

  // NULL out referent pointer.

  void clear_referent();

  // Statistics

  inline size_t processed() const { return _processed; }

  inline size_t removed() const { return _removed; }

  inline void move_to_next() {

    if (_current_discovered == _next_discovered) {

      // End of the list.

      _current_discovered = NULL;

    } else {

      _current_discovered = _next_discovered;

    }

    assert(_current_discovered != _first_seen, "cyclic ref_list found");

    _processed++;

  }

};

// The ReferenceProcessor class encapsulates the per-"collector" processing

// of java.lang.Reference objects for GC. The interface is useful for supporting

// a generational abstraction, in particular when there are multiple

// generations that are being independently collected -- possibly

// concurrently and/or incrementally.

// ReferenceProcessor class abstracts away from a generational setting

// by using a closure that determines whether a given reference or referent are

// subject to this ReferenceProcessor's discovery, thus allowing its use in a

// straightforward manner in a general, non-generational, non-contiguous generation

// (or heap) setting.

class ReferenceProcessor : public ReferenceDiscoverer {

  friend class RefProcPhase1Task;

  friend class RefProcPhase2Task;

  friend class RefProcPhase3Task;

  friend class RefProcPhase4Task;

public:

  // Names of sub-phases of reference processing. Indicates the type of the reference

  // processed and the associated phase number at the end.

  enum RefProcSubPhases {

    SoftRefSubPhase1,

    SoftRefSubPhase2,

    WeakRefSubPhase2,

    FinalRefSubPhase2,

    FinalRefSubPhase3,

    PhantomRefSubPhase4,

    RefSubPhaseMax

  };

  // Main phases of reference processing.

  enum RefProcPhases {

    RefPhase1,

    RefPhase2,

    RefPhase3,

    RefPhase4,

    RefPhaseMax

  };

private:

  size_t total_count(DiscoveredList lists[]) const;

  void verify_total_count_zero(DiscoveredList lists[], const char* type) NOT_DEBUG_RETURN;

  // The SoftReference master timestamp clock

  static jlong _soft_ref_timestamp_clock;

  BoolObjectClosure* _is_subject_to_discovery; // determines whether a given oop is subject

                                               // to this ReferenceProcessor's discovery

                                               // (and further processing).

  bool        _discovering_refs;        // true when discovery enabled

  bool        _discovery_is_atomic;     // if discovery is atomic wrt

                                        // other collectors in configuration

  bool        _discovery_is_mt;         // true if reference discovery is MT.

  bool        _enqueuing_is_done;       // true if all weak references enqueued

  bool        _processing_is_mt;        // true during phases when

                                        // reference processing is MT.

  uint        _next_id;                 // round-robin mod _num_queues counter in

                                        // support of work distribution

  bool        _adjust_no_of_processing_threads; // allow dynamic adjustment of processing threads

  // For collectors that do not keep GC liveness information

  // in the object header, this field holds a closure that

  // helps the reference processor determine the reachability

  BoolObjectClosure* _is_alive_non_header;

  // Soft ref clearing policies

  // . the default policy

  static ReferencePolicy*   _default_soft_ref_policy;

  // . the "clear all" policy

  static ReferencePolicy*   _always_clear_soft_ref_policy;

  // . the current policy below is either one of the above

  ReferencePolicy*          _current_soft_ref_policy;

  // The discovered ref lists themselves

  // The active MT'ness degree of the queues below

  uint            _num_queues;

  // The maximum MT'ness degree of the queues below

  uint            _max_num_queues;

  // Master array of discovered oops

  DiscoveredList* _discovered_refs;

  // Arrays of lists of oops, one per thread (pointers into master array above)

  DiscoveredList* _discoveredSoftRefs;

  DiscoveredList* _discoveredWeakRefs;

  DiscoveredList* _discoveredFinalRefs;

  DiscoveredList* _discoveredPhantomRefs;

  // Phase 1: Re-evaluate soft ref policy.

  void process_soft_ref_reconsider(BoolObjectClosure* is_alive,

                                   OopClosure* keep_alive,

                                   VoidClosure* complete_gc,

                                   AbstractRefProcTaskExecutor*  task_executor,

                                   ReferenceProcessorPhaseTimes* phase_times);

  // Phase 2: Drop Soft/Weak/Final references with a NULL or live referent, and clear

  // and enqueue non-Final references.

  void process_soft_weak_final_refs(BoolObjectClosure* is_alive,

                                    OopClosure* keep_alive,

                                    VoidClosure* complete_gc,

                                    AbstractRefProcTaskExecutor*  task_executor,

                                    ReferenceProcessorPhaseTimes* phase_times);

  // Phase 3: Keep alive followers of Final references, and enqueue.

  void process_final_keep_alive(OopClosure* keep_alive,

                                VoidClosure* complete_gc,

                                AbstractRefProcTaskExecutor*  task_executor,

                                ReferenceProcessorPhaseTimes* phase_times);

  // Phase 4: Drop and keep alive live Phantom references, or clear and enqueue if dead.

  void process_phantom_refs(BoolObjectClosure* is_alive,

                            OopClosure* keep_alive,

                            VoidClosure* complete_gc,

                            AbstractRefProcTaskExecutor*  task_executor,

                            ReferenceProcessorPhaseTimes* phase_times);

  // Work methods used by the process_* methods. All methods return the number of

  // removed elements.

  // (SoftReferences only) Traverse the list and remove any SoftReferences whose

  // referents are not alive, but that should be kept alive for policy reasons.

  // Keep alive the transitive closure of all such referents.

  size_t process_soft_ref_reconsider_work(DiscoveredList&     refs_list,

                                          ReferencePolicy*    policy,

                                          BoolObjectClosure*  is_alive,

                                          OopClosure*         keep_alive,

                                          VoidClosure*        complete_gc);

  // Traverse the list and remove any Refs whose referents are alive,

  // or NULL if discovery is not atomic. Enqueue and clear the reference for

  // others if do_enqueue_and_clear is set.

  size_t process_soft_weak_final_refs_work(DiscoveredList&    refs_list,

                                           BoolObjectClosure* is_alive,

                                           OopClosure*        keep_alive,

                                           bool               do_enqueue_and_clear);

  // Keep alive followers of referents for FinalReferences. Must only be called for

  // those.

  size_t process_final_keep_alive_work(DiscoveredList&    refs_list,

                                       OopClosure*        keep_alive,

                                       VoidClosure*       complete_gc);

  size_t process_phantom_refs_work(DiscoveredList&    refs_list,

                                   BoolObjectClosure* is_alive,

                                   OopClosure*        keep_alive,

                                   VoidClosure*       complete_gc);

public:

  static int number_of_subclasses_of_ref() { return (REF_PHANTOM - REF_OTHER); }

  uint num_queues() const                  { return _num_queues; }

  uint max_num_queues() const              { return _max_num_queues; }

  void set_active_mt_degree(uint v);

  ReferencePolicy* setup_policy(bool always_clear) {

    _current_soft_ref_policy = always_clear ?

      _always_clear_soft_ref_policy : _default_soft_ref_policy;

    _current_soft_ref_policy->setup();   // snapshot the policy threshold

    return _current_soft_ref_policy;

  }

  // "Preclean" all the discovered reference lists by removing references that

  // are active (e.g. due to the mutator calling enqueue()) or with NULL or

  // strongly reachable referents.

  // The first argument is a predicate on an oop that indicates

  // its (strong) reachability and the fourth is a closure that

  // may be used to incrementalize or abort the precleaning process.

  // The caller is responsible for taking care of potential

  // interference with concurrent operations on these lists

  // (or predicates involved) by other threads.

  void preclean_discovered_references(BoolObjectClosure* is_alive,

                                      OopClosure*        keep_alive,

                                      VoidClosure*       complete_gc,

                                      YieldClosure*      yield,

                                      GCTimer*           gc_timer);

private:

  // Returns the name of the discovered reference list

  // occupying the i / _num_queues slot.

  const char* list_name(uint i);

  // "Preclean" the given discovered reference list by removing references with

  // the attributes mentioned in preclean_discovered_references().

  // Supports both normal and fine grain yielding.

  // Returns whether the operation should be aborted.

  bool preclean_discovered_reflist(DiscoveredList&    refs_list,

                                   BoolObjectClosure* is_alive,

                                   OopClosure*        keep_alive,

                                   VoidClosure*       complete_gc,

                                   YieldClosure*      yield);

  // round-robin mod _num_queues (not: _not_ mod _max_num_queues)

  uint next_id() {

    uint id = _next_id;

    assert(!_discovery_is_mt, "Round robin should only be used in serial discovery");

    if (++_next_id == _num_queues) {

      _next_id = 0;

    }

    assert(_next_id < _num_queues, "_next_id %u _num_queues %u _max_num_queues %u", _next_id, _num_queues, _max_num_queues);

    return id;

  }

  DiscoveredList* get_discovered_list(ReferenceType rt);

  inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj,

                                        HeapWord* discovered_addr);

  void clear_discovered_references(DiscoveredList& refs_list);

  void log_reflist(const char* prefix, DiscoveredList list[], uint num_active_queues);

  void log_reflist_counts(DiscoveredList ref_lists[], uint num_active_queues) PRODUCT_RETURN;

  // Balances reference queues.

  void balance_queues(DiscoveredList refs_lists[]);

  bool need_balance_queues(DiscoveredList refs_lists[]);

  // If there is need to balance the given queue, do it.

  void maybe_balance_queues(DiscoveredList refs_lists[]);

  // Update (advance) the soft ref master clock field.

  void update_soft_ref_master_clock();

  bool is_subject_to_discovery(oop const obj) const;

  bool is_mt_processing_set_up(AbstractRefProcTaskExecutor* task_executor) const;

public:

  // Default parameters give you a vanilla reference processor.

  ReferenceProcessor(BoolObjectClosure* is_subject_to_discovery,

                     bool mt_processing = false, uint mt_processing_degree = 1,

                     bool mt_discovery  = false, uint mt_discovery_degree  = 1,

                     bool atomic_discovery = true,

                     BoolObjectClosure* is_alive_non_header = NULL,

                     bool adjust_no_of_processing_threads = false);

  // RefDiscoveryPolicy values

  enum DiscoveryPolicy {

    ReferenceBasedDiscovery = 0,

    ReferentBasedDiscovery  = 1,

    DiscoveryPolicyMin      = ReferenceBasedDiscovery,

    DiscoveryPolicyMax      = ReferentBasedDiscovery

  };

  static void init_statics();

  // get and set "is_alive_non_header" field

  BoolObjectClosure* is_alive_non_header() {

    return _is_alive_non_header;

  }

  void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) {

    _is_alive_non_header = is_alive_non_header;

  }

  BoolObjectClosure* is_subject_to_discovery_closure() const { return _is_subject_to_discovery; }

  void set_is_subject_to_discovery_closure(BoolObjectClosure* cl) { _is_subject_to_discovery = cl; }

  // start and stop weak ref discovery

  void enable_discovery(bool check_no_refs = true);

  void disable_discovery()  { _discovering_refs = false; }

  bool discovery_enabled()  { return _discovering_refs;  }

  // whether discovery is atomic wrt other collectors

  bool discovery_is_atomic() const { return _discovery_is_atomic; }

  void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; }

  // whether discovery is done by multiple threads same-old-timeously

  bool discovery_is_mt() const { return _discovery_is_mt; }

  void set_mt_discovery(bool mt) { _discovery_is_mt = mt; }

  // Whether we are in a phase when _processing_ is MT.

  bool processing_is_mt() const { return _processing_is_mt; }

  void set_mt_processing(bool mt) { _processing_is_mt = mt; }

  // whether all enqueueing of weak references is complete

  bool enqueuing_is_done()  { return _enqueuing_is_done; }

  void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; }

  // iterate over oops

  void weak_oops_do(OopClosure* f);       // weak roots

  void verify_list(DiscoveredList& ref_list);

  // Discover a Reference object, using appropriate discovery criteria

  virtual bool discover_reference(oop obj, ReferenceType rt);

  // Has discovered references that need handling

  bool has_discovered_references();

  // Process references found during GC (called by the garbage collector)

  ReferenceProcessorStats

  process_discovered_references(BoolObjectClosure*            is_alive,

                                OopClosure*                   keep_alive,

                                VoidClosure*                  complete_gc,

                                AbstractRefProcTaskExecutor*  task_executor,

                                ReferenceProcessorPhaseTimes* phase_times);

  // If a discovery is in process that is being superceded, abandon it: all

  // the discovered lists will be empty, and all the objects on them will

  // have NULL discovered fields.  Must be called only at a safepoint.

  void abandon_partial_discovery();

  size_t total_reference_count(ReferenceType rt) const;

  // debugging

  void verify_no_references_recorded() PRODUCT_RETURN;

  void verify_referent(oop obj)        PRODUCT_RETURN;

  bool adjust_no_of_processing_threads() const { return _adjust_no_of_processing_threads; }

};

// A subject-to-discovery closure that uses a single memory span to determine the area that

// is subject to discovery. Useful for collectors which have contiguous generations.

class SpanSubjectToDiscoveryClosure : public BoolObjectClosure {

  MemRegion _span;

public:

  SpanSubjectToDiscoveryClosure() : BoolObjectClosure(), _span() { }

  SpanSubjectToDiscoveryClosure(MemRegion span) : BoolObjectClosure(), _span(span) { }

  MemRegion span() const { return _span; }

  void set_span(MemRegion mr) {

    _span = mr;

  }

  virtual bool do_object_b(oop obj) {

    return _span.contains(obj);

  }

};

// A utility class to disable reference discovery in

// the scope which contains it, for given ReferenceProcessor.

class NoRefDiscovery: StackObj {

 private:

  ReferenceProcessor* _rp;

  bool _was_discovering_refs;

 public: