2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
6 Source code repo: http://github.com/khizmax/libcds/
7 Download: http://sourceforge.net/projects/libcds/files/
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31 #ifndef CDSLIB_INTRUSIVE_TREIBER_STACK_H
32 #define CDSLIB_INTRUSIVE_TREIBER_STACK_H
34 #include <type_traits>
35 #include <mutex> // unique_lock
36 #include <cds/intrusive/details/single_link_struct.h>
37 #include <cds/algo/elimination.h>
38 #include <cds/opt/buffer.h>
39 #include <cds/sync/spinlock.h>
40 #include <cds/details/type_padding.h>
42 namespace cds { namespace intrusive {
44 /// TreiberStack related definitions
45 /** @ingroup cds_intrusive_helper
47 namespace treiber_stack {
52 - GC - garbage collector used
53 - Tag - a \ref cds_intrusive_hook_tag "tag"
55 template <class GC, typename Tag = opt::none >
56 using node = cds::intrusive::single_link::node< GC, Tag >;
61 - opt::gc - garbage collector used.
62 - opt::tag - a \ref cds_intrusive_hook_tag "tag"
64 template < typename... Options >
65 using base_hook = cds::intrusive::single_link::base_hook< Options...>;
69 \p MemberOffset specifies offset in bytes of \ref node member into your structure.
70 Use \p offsetof macro to define \p MemberOffset
73 - opt::gc - garbage collector used.
74 - opt::tag - a \ref cds_intrusive_hook_tag "tag"
76 template < size_t MemberOffset, typename... Options >
77 using member_hook = cds::intrusive::single_link::member_hook< MemberOffset, Options... >;
81 \p NodeTraits defines type traits for node.
82 See \ref node_traits for \p NodeTraits interface description
85 - opt::gc - garbage collector used.
86 - opt::tag - a \ref cds_intrusive_hook_tag "tag"
88 template <typename NodeTraits, typename... Options >
89 using traits_hook = cds::intrusive::single_link::traits_hook< NodeTraits, Options... >;
92 /// Operation id for the \ref cds_elimination_description "elimination back-off"
94 op_push, ///< push op id
98 /// Operation descriptor for the \ref cds_elimination_description "elimination back-off"
100 struct operation: public cds::algo::elimination::operation_desc
102 operation_id idOp; ///< Op id
103 T * pVal; ///< for push: pointer to argument; for pop: accepts a return value
104 atomics::atomic<unsigned int> nStatus; ///< Internal elimination status
108 , nStatus( 0 /*op_free*/ )
113 /// Stack internal statistics. May be useful for debugging or profiling
115 Template argument \p Counter defines type of counter.
116 Default is cds::atomicity::event_counter.
117 You may use stronger type of counter like as cds::atomicity::item_counter,
118 or even an integral type, for example, \p int
120 template <typename Counter = cds::atomicity::event_counter >
123 typedef Counter counter_type ; ///< Counter type
125 counter_type m_PushCount ; ///< Push call count
126 counter_type m_PopCount ; ///< Pop call count
127 counter_type m_PushRace ; ///< Count of push race conditions encountered
128 counter_type m_PopRace ; ///< Count of pop race conditions encountered
129 counter_type m_ActivePushCollision ; ///< Count of active push collision for elimination back-off
130 counter_type m_ActivePopCollision ; ///< Count of active pop collision for elimination back-off
131 counter_type m_PassivePushCollision ; ///< Count of passive push collision for elimination back-off
132 counter_type m_PassivePopCollision ; ///< Count of passive pop collision for elimination back-off
133 counter_type m_EliminationFailed ; ///< Count of unsuccessful elimination back-off
136 void onPush() { ++m_PushCount; }
137 void onPop() { ++m_PopCount; }
138 void onPushRace() { ++m_PushRace; }
139 void onPopRace() { ++m_PopRace; }
140 void onActiveCollision( operation_id opId )
142 if ( opId == treiber_stack::op_push )
143 ++m_ActivePushCollision;
145 ++m_ActivePopCollision;
147 void onPassiveCollision( operation_id opId )
149 if ( opId == treiber_stack::op_push )
150 ++m_PassivePushCollision;
152 ++m_PassivePopCollision;
154 void onEliminationFailed()
156 ++m_EliminationFailed;
161 /// Empty (no overhead) stack statistics. Support interface like treiber_stack::stat
169 void onActiveCollision( operation_id ) {}
170 void onPassiveCollision( operation_id ) {}
171 void onEliminationFailed() {}
175 /// TreiberStack default type traits
178 /// Back-off strategy
179 typedef cds::backoff::Default back_off;
181 /// Hook, possible types are \p treiber_stack::base_hook, \p treiber_stack::member_hook, \p treiber_stack::traits_hook
182 typedef treiber_stack::base_hook<> hook;
184 /// The functor used for dispose removed items. Default is \p opt::v::empty_disposer. This option is used only in \p TreiberStack::clear() function
185 typedef opt::v::empty_disposer disposer;
187 /// Item counting feature; by default, disabled. Use \p cds::atomicity::item_counter to enable item counting
188 typedef cds::atomicity::empty_item_counter item_counter;
190 /// C++ memory ordering model
192 Can be \p opt::v::relaxed_ordering (relaxed memory model, the default)
193 or \p opt::v::sequential_consistent (sequentially consisnent memory model).
195 typedef opt::v::relaxed_ordering memory_model;
197 /// Internal statistics (by default, disabled)
199 Possible option value are: \p treiber_stack::stat, \p treiber_stack::empty_stat (the default),
200 user-provided class that supports \p %treiber_stack::stat interface.
202 typedef treiber_stack::empty_stat stat;
204 /// Link checking, see \p cds::opt::link_checker
205 static CDS_CONSTEXPR const opt::link_check_type link_checker = opt::debug_check_link;
207 /** @name Elimination back-off traits
208 The following traits is used only if elimination enabled
212 /// Enable elimination back-off; by default, it is disabled
213 static CDS_CONSTEXPR const bool enable_elimination = false;
215 /// Back-off strategy to wait for elimination, default is \p cds::backoff::delay<>
216 typedef cds::backoff::delay<> elimination_backoff;
218 /// Buffer type for elimination array
220 Possible types are \p opt::v::initialized_static_buffer, \p opt::v::initialized_dynamic_buffer.
221 The buffer can be any size: \p Exp2 template parameter of those classes can be \p false.
222 The size should be selected empirically for your application and hardware, there are no common rules for that.
223 Default is <tt> %opt::v::initialized_static_buffer< any_type, 4 > </tt>.
225 typedef opt::v::initialized_static_buffer< int, 4 > buffer;
227 /// Random engine to generate a random position in elimination array
228 typedef opt::v::c_rand random_engine;
230 /// Lock type used in elimination, default is cds::sync::spin
231 typedef cds::sync::spin lock_type;
236 /// Metafunction converting option list to \p treiber_stack::traits
238 Supported \p Options are:
239 - \p opt::hook - hook used. Possible hooks are: \p treiber_stack::base_hook, \p treiber_stack::member_hook, \p treiber_stack::traits_hook.
240 If the option is not specified, \p %treiber_stack::base_hook<> is used.
241 - \p opt::back_off - back-off strategy used. If the option is not specified, the \p cds::backoff::Default is used.
242 - \p opt::disposer - the functor used for dispose removed items. Default is \p opt::v::empty_disposer. This option is used only
243 in \p TreiberStack::clear function.
244 - \p opt::link_checker - the type of node's link fields checking. Default is \ref opt::debug_check_link.
245 - \p opt::memory_model - C++ memory ordering model. Can be \p opt::v::relaxed_ordering (relaxed memory model, the default)
246 or \p opt::v::sequential_consistent (sequentially consisnent memory model).
247 - \p opt::item_counter - the type of item counting feature. Default is \p cds::atomicity::empty_item_counter, i.e.
248 no item counting. Use \p cds::atomicity::item_counter to enable item counting.
249 - \p opt::stat - the type to gather internal statistics.
250 Possible option value are: \p treiber_stack::stat, \p treiber_stack::empty_stat (the default),
251 user-provided class that supports \p treiber_stack::stat interface.
252 - \p opt::enable_elimination - enable elimination back-off for the stack. Default value is \p false.
254 If elimination back-off is enabled, additional options can be specified:
255 - \p opt::buffer - a buffer type for elimination array, see \p opt::v::initialized_static_buffer, \p opt::v::initialized_dynamic_buffer.
256 The buffer can be any size: \p Exp2 template parameter of those classes can be \p false.
257 The size should be selected empirically for your application and hardware, there are no common rules for that.
258 Default is <tt> %opt::v::initialized_static_buffer< any_type, 4 > </tt>.
259 - \p opt::random_engine - a random engine to generate a random position in elimination array.
260 Default is \p opt::v::c_rand.
261 - \p opt::elimination_backoff - back-off strategy to wait for elimination, default is \p cds::backoff::delay<>
262 - \p opt::lock_type - a lock type used in elimination back-off, default is \p cds::sync::spin
264 Example: declare \p %TreiberStack with elimination enabled and internal statistics
266 typedef cds::intrusive::TreiberStack< cds::gc::HP, Foo,
267 typename cds::intrusive::treiber_stack::make_traits<
268 cds::opt::enable_elimination< true >,
269 cds::opt::stat< cds::intrusive::treiber_stack::stat<> >
274 template <typename... Options>
276 # ifdef CDS_DOXYGEN_INVOKED
277 typedef implementation_defined type; ///< Metafunction result
279 typedef typename cds::opt::make_options<
280 typename cds::opt::find_type_traits< traits, Options... >::type
290 template <bool EnableElimination, typename T, typename Traits>
291 class elimination_backoff;
293 template <typename T, typename Traits>
294 class elimination_backoff<false, T, Traits>
296 typedef typename Traits::back_off back_off;
307 template <typename Stat>
308 bool backoff( treiber_stack::operation< T >&, Stat& )
316 elimination_backoff()
319 elimination_backoff( size_t )
322 typedef wrapper type;
329 template <typename T, typename Traits>
330 class elimination_backoff<true, T, Traits>
332 typedef typename Traits::back_off back_off;
334 /// Back-off for elimination (usually delay)
335 typedef typename Traits::elimination_backoff elimination_backoff_type;
336 /// Lock type used in elimination back-off
337 typedef typename Traits::lock_type elimination_lock_type;
338 /// Random engine used in elimination back-off
339 typedef typename Traits::random_engine elimination_random_engine;
341 /// Per-thread elimination record
342 typedef cds::algo::elimination::record elimination_rec;
344 /// Collision array record
345 struct collision_array_record {
346 elimination_rec * pRec;
347 elimination_lock_type lock;
350 /// Collision array used in elimination-backoff; each item is optimized for cache-line size
351 typedef typename Traits::buffer::template rebind<
352 typename cds::details::type_padding<collision_array_record, cds::c_nCacheLineSize >::type
353 >::other collision_array;
355 /// Operation descriptor used in elimination back-off
356 typedef treiber_stack::operation< T > operation_desc;
358 /// Elimination back-off data
359 struct elimination_data {
360 mutable elimination_random_engine randEngine; ///< random engine
361 collision_array collisions; ///< collision array
365 //TODO: check Traits::buffer must be static!
367 elimination_data( size_t nCollisionCapacity )
368 : collisions( nCollisionCapacity )
372 elimination_data m_Elimination;
374 enum operation_status {
380 typedef std::unique_lock< elimination_lock_type > slot_scoped_lock;
382 template <bool Exp2 = collision_array::c_bExp2>
383 typename std::enable_if< Exp2, size_t >::type slot_index() const
385 return m_Elimination.randEngine() & (m_Elimination.collisions.capacity() - 1);
388 template <bool Exp2 = collision_array::c_bExp2>
389 typename std::enable_if< !Exp2, size_t >::type slot_index() const
391 return m_Elimination.randEngine() % m_Elimination.collisions.capacity();
395 elimination_backoff()
397 m_Elimination.collisions.zeroize();
400 elimination_backoff( size_t nCollisionCapacity )
401 : m_Elimination( nCollisionCapacity )
403 m_Elimination.collisions.zeroize();
406 typedef elimination_backoff& type;
416 template <typename Stat>
417 bool backoff( operation_desc& op, Stat& stat )
419 elimination_backoff_type bkoff;
420 op.nStatus.store( op_waiting, atomics::memory_order_relaxed );
422 elimination_rec * myRec = cds::algo::elimination::init_record( op );
424 collision_array_record& slot = m_Elimination.collisions[ slot_index() ];
427 elimination_rec * himRec = slot.pRec;
429 operation_desc * himOp = static_cast<operation_desc *>( himRec->pOp );
431 if ( himOp->idOp != op.idOp ) {
433 if ( op.idOp == treiber_stack::op_push )
434 himOp->pVal = op.pVal;
436 op.pVal = himOp->pVal;
439 himOp->nStatus.store( op_collided, atomics::memory_order_release );
442 cds::algo::elimination::clear_record();
443 stat.onActiveCollision( op.idOp );
446 //himOp->nStatus.store( op_free, atomics::memory_order_release );
452 // Wait for colliding operation
453 bkoff( [&op]() CDS_NOEXCEPT -> bool { return op.nStatus.load( atomics::memory_order_acquire ) != op_waiting; } );
456 slot_scoped_lock l( slot.lock );
457 if ( slot.pRec == myRec )
461 bool bCollided = op.nStatus.load( atomics::memory_order_relaxed ) == op_collided;
464 stat.onEliminationFailed();
466 stat.onPassiveCollision( op.idOp );
468 cds::algo::elimination::clear_record();
473 } // namespace details
475 } // namespace treiber_stack
477 /// Treiber intrusive stack
478 /** @ingroup cds_intrusive_stack
479 Intrusive implementation of well-known Treiber's stack algorithm:
480 - R. K. Treiber. Systems programming: Coping with parallelism. Technical Report RJ 5118, IBM Almaden Research Center, April 1986.
482 \ref cds_elimination_description "Elimination back-off technique" can be used optionally.
483 The idea of elimination algorithm is taken from:
484 - [2004] Danny Hendler, Nir Shavit, Lena Yerushalmi "A Scalable Lock-free Stack Algorithm"
486 The elimination algorithm uses a single elimination array as a back-off schema
487 on a shared lock-free stack. If the threads fail on the stack, they attempt to eliminate
488 on the array, and if they fail in eliminating, they attempt to access the stack again and so on.
490 @note Hendler's et al paper describes a lock-free implementation of elimination back-off which is quite complex.
491 The main difficulty is the managing life-time of elimination record.
492 This implementation uses simplified lock-based (spin-based) approach which allows
493 the elimination record allocation on thread's stack.
494 This approach demonstrates sufficient performance under high load.
497 - \p GC - garbage collector type: \p gc::HP, \p gc::DHP.
498 Garbage collecting schema must be the same as \p treiber_stack::node GC.
499 - \p T - a type the stack contains. A value of type \p T must be derived
500 from \p treiber_stack::node for \p treiber_stack::base_hook,
501 or it should have a member of type \p %treiber_stack::node for \p treiber_stack::member_hook,
502 or it should be convertible to \p %treiber_stack::node for \p treiber_stack::traits_hook.
503 - \p Traits - stack traits, default is \p treiber_stack::traits. You can use \p treiber_stack::make_traits
504 metafunction to make your traits or just derive your traits from \p %treiber_stack::traits:
506 struct myTraits: public cds::intrusive::treiber_stack::traits {
507 typedef cds::intrusive::treiber_stack::stat<> stat;
509 typedef cds::intrusive::TreiberStack< cds::gc::HP, Foo, myTraits > myStack;
511 // Equivalent make_traits example:
512 typedef cds::intrusive::TreiberStack< cds::gc::HP, Foo,
513 typename cds::intrusive::treiber_stack::make_traits<
514 cds::opt::stat< cds::intrusive::treiber_stack::stat<> >
519 @note Be careful when you want destroy an item popped, see \ref cds_intrusive_item_destroying "Destroying items of intrusive containers".
521 @anchor cds_intrusive_TreiberStack_examples
524 Example of how to use \p treiber_stack::base_hook.
525 Your class that objects will be pushed on \p %TreiberStack should be based on \p treiber_stack::node class
527 #include <cds/intrusive/treiber_stack.h>
528 #include <cds/gc/hp.h>
530 namespace ci = cds::intrusive;
531 typedef cds::gc::HP gc;
533 struct myData: public ci::treiber_stack::node< gc >
539 typedef ci::TreiberStack< gc,
541 typename cds::intrusive::treiber_stack::make_traits<
542 ci::opt::hook< ci::treiber_stack::base_hook< gc > >
546 // Stack with elimination back-off enabled
547 typedef ci::TreiberStack< gc,
549 typename ci::treiber_stack::make_traits<
550 ci::opt::hook< ci::treiber_stack::base_hook< gc > >,
551 cds::opt::enable_elimination< true >
553 > elimination_stack_t;
556 Example of how to use \p treiber_stack::base_hook with different tags.
558 #include <cds/intrusive/treiber_stack.h>
559 #include <cds/gc/hp.h>
561 namespace ci = cds::intrusive;
562 typedef cds::gc::HP gc;
564 // It is not necessary to declare complete type for tags
569 : public ci::treiber_stack::node< gc, tag1 >
570 , public ci::treiber_stack::node< gc, tag2 >
575 typedef ci::TreiberStack< gc,
577 typename ci::treiber_stack::make_traits<
578 ci::opt::hook< ci::treiber_stack::base_hook< gc, tag1 > >
582 typedef ci::TreiberStack< gc,
584 typename ci::treiber_stack::make_traits<
585 ci::opt::hook< ci::treiber_stack::base_hook< gc, tag2 > >
589 // You may add myData objects into stack1_t and stack2_t independently
597 s2.push( i1 ) ; // i1 is now contained in s1 and s2.
601 p = s1.pop() ; // pop i1 from s1
602 p = s1.pop() ; // p == nullptr, s1 is empty
603 p = s2.pop() ; // pop i1 from s2
604 p = s2.pop() ; // pop i2 from s2
605 p = s2.pop() ; // p == nullptr, s2 is empty
609 Example of how to use \p treiber_stack::member_hook.
610 Your class should have a member of type \p treiber_stack::node
612 #include <stddef.h> // offsetof macro
613 #include <cds/intrusive/treiber_stack.h>
614 #include <cds/gc/hp.h>
616 namespace ci = cds::intrusive;
617 typedef cds::gc::HP gc;
622 ci::treiber_stack::node< gc > member_hook_;
626 typedef ci::TreiberStack< gc,
628 typename ci::treiber_stack::make_traits<
629 ci::opt::hook< ci::treiber_stack::member_hook< offsetof(myData, member_hook_), gc >>
637 typename Traits = treiber_stack::traits
642 /// Rebind template arguments
643 template <typename GC2, typename T2, typename Traits2>
645 typedef TreiberStack< GC2, T2, Traits2 > other ; ///< Rebinding result
649 typedef GC gc; ///< Garbage collector
650 typedef T value_type; ///< type of value stored in the stack
651 typedef Traits traits; ///< Stack traits
653 typedef typename traits::hook hook; ///< hook type
654 typedef typename hook::node_type node_type; ///< node type
655 typedef typename traits::disposer disposer; ///< disposer used
656 typedef typename get_node_traits< value_type, node_type, hook>::type node_traits ; ///< node traits
657 typedef typename single_link::get_link_checker< node_type, traits::link_checker >::type link_checker ; ///< link checker
658 typedef typename traits::memory_model memory_model; ///< Memory ordering. See \p cds::opt::memory_model option
659 typedef typename traits::item_counter item_counter; ///< Item counter class
660 typedef typename traits::stat stat; ///< Internal statistics
661 typedef typename traits::back_off back_off; ///< back-off strategy
663 /// How many Hazard pointers is required for Treiber's stack implementation
664 static CDS_CONSTEXPR size_t const c_nHazardPtrCount = 1;
666 public: // related to elimination back-off
668 /// Elimination back-off is enabled or not
669 static CDS_CONSTEXPR const bool enable_elimination = traits::enable_elimination;
670 /// back-off strategy used to wait for elimination
671 typedef typename traits::elimination_backoff elimination_backoff_type;
672 /// Lock type used in elimination back-off
673 typedef typename traits::lock_type elimination_lock_type;
674 /// Random engine used in elimination back-off
675 typedef typename traits::random_engine elimination_random_engine;
678 typename node_type::atomic_node_ptr m_Top; ///< Top of the stack
679 item_counter m_ItemCounter; ///< Item counter
680 stat m_stat; ///< Internal statistics
683 typedef treiber_stack::details::elimination_backoff<enable_elimination, value_type, traits> elimination_backoff;
684 elimination_backoff m_Backoff;
686 typedef treiber_stack::operation< value_type > operation_desc;
688 // GC and node_type::gc must be the same
689 static_assert( std::is_same<gc, typename node_type::gc>::value, "GC and node_type::gc must be the same");
691 static_assert( !enable_elimination || std::is_same<typename elimination_random_engine::result_type, unsigned int>::value,
692 "Random engine result type must be unsigned int");
697 void clear_links( node_type * pNode ) CDS_NOEXCEPT
699 pNode->m_pNext.store( nullptr, memory_model::memory_order_relaxed );
702 template <bool EnableElimination>
703 struct elimination_backoff_impl;
707 /// Constructs empty stack
712 /// Constructs empty stack and initializes elimination back-off data
714 This form should be used if you use elimination back-off with dynamically allocated collision array, i.e
715 \p Traits contains <tt>typedef cds::opt::v::initialized_dynamic_buffer buffer</tt>.
716 \p nCollisionCapacity parameter specifies the capacity of collision array.
718 TreiberStack( size_t nCollisionCapacity )
720 , m_Backoff( nCollisionCapacity )
723 /// \p %TreiberStack is not copy-constructible
724 TreiberStack( TreiberStack const& ) = delete;
726 /// Destructor calls \ref cds_intrusive_TreiberStack_clear "clear" member function
732 /// Push the item \p val on the stack
734 No copying is made since it is intrusive stack.
736 bool push( value_type& val )
738 node_type * pNew = node_traits::to_node_ptr( val );
739 link_checker::is_empty( pNew );
741 typename elimination_backoff::type bkoff = m_Backoff.init();
744 if ( enable_elimination ) {
745 op.idOp = treiber_stack::op_push;
749 node_type * t = m_Top.load( memory_model::memory_order_relaxed );
751 pNew->m_pNext.store( t, memory_model::memory_order_relaxed );
752 if ( m_Top.compare_exchange_weak( t, pNew, memory_model::memory_order_release, atomics::memory_order_acquire )) {
759 if ( bkoff.backoff( op, m_stat ))
764 /// Pop an item from the stack
766 If stack is empty, returns \p nullptr.
767 The disposer is <b>not</b> called for popped item.
768 See \ref cds_intrusive_item_destroying "Destroying items of intrusive containers".
772 typename elimination_backoff::type bkoff = m_Backoff.init();
773 typename gc::Guard guard;
776 if ( enable_elimination ) {
777 op.idOp = treiber_stack::op_pop;
781 node_type * t = guard.protect( m_Top,
782 []( node_type * p ) -> value_type * {
783 return node_traits::to_value_ptr( p );
786 return nullptr; // stack is empty
788 node_type * pNext = t->m_pNext.load(memory_model::memory_order_relaxed);
789 if ( m_Top.compare_exchange_weak( t, pNext, memory_model::memory_order_acquire, atomics::memory_order_relaxed )) {
793 return node_traits::to_value_ptr( *t );
797 if ( bkoff.backoff( op, m_stat )) {
798 // may return nullptr if stack is empty
804 /// Check if stack is empty
807 return m_Top.load( memory_model::memory_order_relaxed ) == nullptr;
811 /** @anchor cds_intrusive_TreiberStack_clear
812 For each removed item the disposer is called.
814 @note It is possible that after <tt>clear()</tt> the <tt>empty()</tt> returns \p false
815 if some other thread pushes an item into the stack during \p clear works
822 pTop = m_Top.load( memory_model::memory_order_relaxed );
823 if ( pTop == nullptr )
825 if ( m_Top.compare_exchange_weak( pTop, nullptr, memory_model::memory_order_acquire, atomics::memory_order_relaxed )) {
826 m_ItemCounter.reset();
833 node_type * p = pTop;
834 pTop = p->m_pNext.load(memory_model::memory_order_relaxed);
836 gc::template retire<disposer>( node_traits::to_value_ptr( *p ));
840 /// Returns stack's item count
842 The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
843 this function always returns 0.
845 @warning Even if you use real item counter and it returns 0, this fact is not mean that the stack
846 is empty. To check emptyness use \ref empty() method.
850 return m_ItemCounter.value();
853 /// Returns reference to internal statistics
854 stat const& statistics() const
860 }} // namespace cds::intrusive
862 #endif // #ifndef CDSLIB_INTRUSIVE_TREIBER_STACK_H