Michael's lock-free ordered single-linked list. More...

#include <cds/intrusive/impl/michael_list.h>

Inheritance diagram for cds::intrusive::MichaelList< GC, T, Traits >:

Public Types
typedef T	value_type
	type of value stored in the list

typedef Traits	traits
	Traits template parameter.

typedef traits::hook	hook
	hook type

typedef hook::node_type	node_type
	node type

typedef implementation_defined	key_comparator
	key comparison functor based on opt::compare and opt::less option setter.

typedef traits::disposer	disposer
	disposer used

typedef traits::stat	stat
	Internal statistics.

typedef get_node_traits< value_type, node_type, hook >::type	node_traits
	node traits

typedef michael_list::get_link_checker< node_type, traits::link_checker >::type	link_checker
	link checker

typedef GC	gc
	Garbage collector.

typedef traits::back_off	back_off
	back-off strategy

typedef traits::item_counter	item_counter
	Item counting policy used.

typedef traits::memory_model	memory_model
	Memory ordering. See cds::opt::memory_model option.

typedef gc::template guarded_ptr< value_type >	guarded_ptr
	Guarded pointer.

Public Member Functions
	MichaelList ()
	Default constructor initializes empty list.

	~MichaelList ()
	Destroys the list object.

bool	insert (value_type &val)
	Inserts new node. More...

template<typename Func >
bool	insert (value_type &val, Func f)
	Inserts new node. More...

template<typename Func >
std::pair< bool, bool >	update (value_type &val, Func func, bool bInsert=true)
	Updates the node. More...

bool	unlink (value_type &val)
	Unlinks the item `val` from the list. More...

template<typename Q >
bool	erase (Q const &key)
	Deletes the item from the list. More...

template<typename Q , typename Less >
bool	erase_with (Q const &key, Less pred)
	Deletes the item from the list using `pred` predicate for searching. More...

template<typename Q , typename Func >
bool	erase (Q const &key, Func func)
	Deletes the item from the list. More...

template<typename Q , typename Less , typename Func >
bool	erase_with (Q const &key, Less pred, Func f)
	Deletes the item from the list using `pred` predicate for searching. More...

template<typename Q >
guarded_ptr	extract (Q const &key)
	Extracts the item from the list with specified `key`. More...

template<typename Q , typename Less >
guarded_ptr	extract_with (Q const &key, Less pred)
	Extracts the item using compare functor `pred`. More...

template<typename Q , typename Func >
bool	find (Q &key, Func f)
	Finds `key` in the list. More...

template<typename Q , typename Less , typename Func >
bool	find_with (Q &key, Less pred, Func f)
	Finds the `key` using `pred` predicate for searching. More...

template<typename Q >
bool	contains (Q const &key)
	Checks whether the list contains `key`. More...

template<typename Q , typename Less >
bool	contains (Q const &key, Less pred)
	Checks whether the list contains `key` using `pred` predicate for searching. More...

template<typename Q >
guarded_ptr	get (Q const &key)
	Finds the `key` and return the item found. More...

template<typename Q , typename Less >
guarded_ptr	get_with (Q const &key, Less pred)
	Finds the `key` and return the item found. More...

void	clear ()
	Clears the list. More...

bool	empty () const
	Checks whether the list is empty.

size_t	size () const
	Returns list's item count. More...

stat const &	statistics () const
	Returns const reference to internal statistics.

Static Public Attributes
static constexpr const size_t	c_nHazardPtrCount = 4
	Count of hazard pointer required for the algorithm.

Protected Types
typedef node_type::atomic_marked_ptr	atomic_node_ptr
	Atomic node pointer.

typedef node_type::marked_ptr	marked_node_ptr
	Node marked pointer.

typedef atomic_node_ptr	auxiliary_head
	Auxiliary head type (for split-list support)

Protected Attributes
atomic_node_ptr	m_pHead
	Head pointer.

item_counter	m_ItemCounter
	Item counter.

stat	m_Stat
	Internal statistics.

Forward iterators (only for debugging purpose)
typedef iterator_type< false >	iterator
	Forward iterator. More...

typedef iterator_type< true >	const_iterator
	Const forward iterator. More...

iterator	begin ()
	Returns a forward iterator addressing the first element in a list. More...

iterator	end ()
	Returns an iterator that addresses the location succeeding the last element in a list. More...

const_iterator	cbegin () const
	Returns a forward const iterator addressing the first element in a list.

const_iterator	begin () const
	Returns a forward const iterator addressing the first element in a list.

const_iterator	end () const
	Returns an const iterator that addresses the location succeeding the last element in a list.

const_iterator	cend () const
	Returns an const iterator that addresses the location succeeding the last element in a list.

Detailed Description

template<class GC, typename T, class Traits = michael_list::traits>
class cds::intrusive::MichaelList< GC, T, Traits >

Michael's lock-free ordered single-linked list.

Usually, ordered single-linked list is used as a building block for the hash table implementation. The complexity of searching is O(N).

Source:

[2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"

Template arguments:

GC - Garbage collector used. Note the GC must be the same as the GC used for item type T (see michael_list::node).
T - type to be stored in the list. The type must be based on michael_list::node (for michael_list::base_hook) or it must have a member of type michael_list::node (for michael_list::member_hook).
Traits - type traits, default is michael_list::traits. It is possible to declare option-based list with cds::intrusive::michael_list::make_traits metafunction: For example, the following traits-based declaration of gc::HP Michael's list
#include <cds/intrusive/michael_list_hp.h>
// Declare item stored in your list
struct item: public cds::intrusive::michael_list::node< cds::gc::HP >
{
int nKey;
// .... other data
};
// Declare comparator for the item
struct my_compare {
int operator()( item const& i1, item const& i2 ) const
{
return i1.nKey - i2.nKey;
}
};
// Declare traits
struct my_traits: public cds::intrusive::michael_list::traits
{
typedef cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::HP > > hook;
typedef my_compare compare;
};
// Declare traits-based list
typedef cds::intrusive::MichaelList< cds::gc::HP, item, my_traits > traits_based_list;
is equivalent for the following option-based list
#include <cds/intrusive/michael_list_hp.h>
// item struct and my_compare are the same
// Declare option-based list
typedef cds::intrusive::MichaelList< cds::gc::HP, item,
typename cds::intrusive::michael_list::make_traits<
cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::HP > > > // hook option
,cds::intrusive::opt::compare< my_compare > // item comparator option
>::type
> option_based_list;

Usage

There are different specializations of this template for each garbage collecting schema. You should select GC needed and include appropriate .h-file:

for gc::HP: <cds/intrusive/michael_list_hp.h>
for gc::DHP: <cds/intrusive/michael_list_dhp.h>
for RCU type - see RCU-based MichaelList
for gc::nogc: <cds/intrusive/michael_list_nogc.h> See non-GC MichaelList

Then, you should incorporate michael_list::node into your struct T and provide appropriate michael_list::traits::hook in your Traits template parameters. Usually, for Traits you define a struct based on michael_list::traits.

Example for gc::DHP and base hook:

// Include GC-related Michael's list specialization
#include <cds/intrusive/michael_list_dhp.h>
// Data stored in Michael's list
struct my_data: public cds::intrusive::michael_list::node< cds::gc::DHP >
{
    // key field
    std::string     strKey;
    // other data
    // ...
};
// my_data comparing functor
struct my_data_cmp {
    int operator()( const my_data& d1, const my_data& d2 )
    {
        return d1.strKey.compare( d2.strKey );
    }
    int operator()( const my_data& d, const std::string& s )
    {
        return d.strKey.compare(s);
    }
    int operator()( const std::string& s, const my_data& d )
    {
        return s.compare( d.strKey );
    }
};
// Declare traits
struct my_traits: public cds::intrusive::michael_list::traits
{
    typedef cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::DHP > >   hook;
    typedef my_data_cmp compare;
};
// Declare list type
typedef cds::intrusive::MichaelList< cds::gc::DHP, my_data, my_traits >     traits_based_list;

Equivalent option-based code:

// GC-related specialization
#include <cds/intrusive/michael_list_dhp.h>
struct my_data {
    // see above
};
struct compare {
    // see above
};
// Declare option-based list
typedef cds::intrusive::MichaelList< cds::gc::DHP
    ,my_data
    , typename cds::intrusive::michael_list::make_traits<
        cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::DHP > > >
        ,cds::intrusive::opt::compare< my_data_cmp >
    >::type
> option_based_list;

Member Typedef Documentation

◆ const_iterator

template<class GC, typename T, class Traits = michael_list::traits>

typedef iterator_type<true> cds::intrusive::MichaelList< GC, T, Traits >::const_iterator

Const forward iterator.

For iterator's features and requirements see iterator

◆ iterator

template<class GC, typename T, class Traits = michael_list::traits>

typedef iterator_type<false> cds::intrusive::MichaelList< GC, T, Traits >::iterator

Forward iterator.

The forward iterator for Michael's list has some features:

it has no post-increment operator
to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator. For some GC (like as gc::HP), a guard is a limited resource per thread, so an exception (or assertion) "no free guard" may be thrown if the limit of guard count per thread is exceeded.
The iterator cannot be moved across thread boundary since it contains thread-private GC's guard.
Iterator ensures thread-safety even if you delete the item the iterator points to. However, in case of concurrent deleting operations there is no guarantee that you iterate all item in the list. Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.

Warning: Use this iterator on the concurrent container for debugging purpose only.

The iterator interface:

class iterator {
public:
    // Default constructor
    iterator();
    // Copy construtor
    iterator( iterator const& src );
    // Dereference operator
    value_type * operator ->() const;
    // Dereference operator
    value_type& operator *() const;
    // Preincrement operator
    iterator& operator ++();
    // Assignment operator
    iterator& operator = (iterator const& src);
    // Equality operators
    bool operator ==(iterator const& i ) const;
    bool operator !=(iterator const& i ) const;
};

Member Function Documentation

◆ begin()

template<class GC, typename T, class Traits = michael_list::traits>

iterator cds::intrusive::MichaelList< GC, T, Traits >::begin ( )

inline

Returns a forward iterator addressing the first element in a list.

For empty list

begin() == end()

◆ clear()

template<class GC, typename T, class Traits = michael_list::traits>

void cds::intrusive::MichaelList< GC, T, Traits >::clear ( )

inline

Clears the list.

The function unlink all items from the list.

◆ contains() [1/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q >

bool cds::intrusive::MichaelList< GC, T, Traits >::contains ( Q const & key )

inline

Checks whether the list contains key.

The function searches the item with key equal to key and returns true if it is found, and false otherwise.

◆ contains() [2/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Less >

bool cds::intrusive::MichaelList< GC, T, Traits >::contains	(	Q const &	key,
		Less	pred
	)

inline

Checks whether the list contains key using pred predicate for searching.

The function is an analog of contains( key ) but pred is used for key comparing. Less functor has the interface like std::less. Less must imply the same element order as the comparator used for building the list.

◆ end()

template<class GC, typename T, class Traits = michael_list::traits>

iterator cds::intrusive::MichaelList< GC, T, Traits >::end ( )

inline

Returns an iterator that addresses the location succeeding the last element in a list.

Do not use the value returned by end function to access any item. Internally, end returning value equals to nullptr.

The returned value can be used only to control reaching the end of the list. For empty list begin() == end()

◆ erase() [1/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q >

bool cds::intrusive::MichaelList< GC, T, Traits >::erase ( Q const & key )

inline

Deletes the item from the list.

The function searches an item with key equal to key in the list, unlinks it from the list, and returns true. If key is not found the function return false.

disposer specified in Traits is called for deleted item.

◆ erase() [2/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Func >

bool cds::intrusive::MichaelList< GC, T, Traits >::erase	(	Q const &	key,
		Func	func
	)

inline

Deletes the item from the list.

The function searches an item with key equal to key in the list, call func functor with item found, unlinks it from the list, and returns true. The Func interface is

struct functor {
    void operator()( value_type const& item );
};

If key is not found the function return false, func is not called.

disposer specified in Traits is called for deleted item.

◆ erase_with() [1/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Less >

bool cds::intrusive::MichaelList< GC, T, Traits >::erase_with	(	Q const &	key,
		Less	pred
	)

inline

Deletes the item from the list using pred predicate for searching.

The function is an analog of erase(Q const&) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

disposer specified in Traits is called for deleted item.

◆ erase_with() [2/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::intrusive::MichaelList< GC, T, Traits >::erase_with	(	Q const &	key,
		Less	pred,
		Func	f
	)

inline

Deletes the item from the list using pred predicate for searching.

The function is an analog of erase(Q const&, Func) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

disposer specified in Traits is called for deleted item.

◆ extract()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q >

guarded_ptr cds::intrusive::MichaelList< GC, T, Traits >::extract ( Q const & key )

inline

Extracts the item from the list with specified key.

The function searches an item with key equal to key, unlinks it from the list, and returns it as guarded_ptr. If key is not found returns an empty guarded pointer.

Note the compare functor should accept a parameter of type Q that can be not the same as value_type.

The disposer specified in Traits class template parameter is called automatically by garbage collector GC when returned guarded_ptr object will be destroyed or released.

Note: Each guarded_ptr object uses the GC's guard that can be limited resource.

Usage:

typedef cds::intrusive::MichaelList< cds::gc::HP, foo, my_traits >  ord_list;
ord_list theList;
// ...
{
    ord_list::guarded_ptr gp(theList.extract( 5 ));
    if ( gp ) {
        // Deal with gp
        // ...
    }
    // Destructor of gp releases internal HP guard
}

◆ extract_with()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Less >

guarded_ptr cds::intrusive::MichaelList< GC, T, Traits >::extract_with	(	Q const &	key,
		Less	pred
	)

inline

Extracts the item using compare functor pred.

The function is an analog of extract(Q const&) but pred predicate is used for key comparing.

Less functor has the semantics like std::less but should take arguments of type value_type and Q in any order. pred must imply the same element order as the comparator used for building the list.

◆ find()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Func >

bool cds::intrusive::MichaelList< GC, T, Traits >::find	(	Q &	key,
		Func	f
	)

inline

Finds key in the list.

The function searches the item with key equal to key and calls the functor f for item found. The interface of Func functor is:

struct functor {
    void operator()( value_type& item, Q& key );
};

where item is the item found, key is the find function argument.

The functor may change non-key fields of item. Note that the function is only guarantee that item cannot be disposed during functor is executing. The function does not serialize simultaneous access to the item. If such access is possible you must provide your own synchronization schema to keep out unsafe item modifications.

The key argument is non-const since it can be used as f functor destination i.e., the functor may modify both arguments.

The function returns true if val is found, false otherwise.

◆ find_with()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::intrusive::MichaelList< GC, T, Traits >::find_with	(	Q &	key,
		Less	pred,
		Func	f
	)

inline

Finds the key using pred predicate for searching.

The function is an analog of find(Q&, Func) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

◆ get()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q >

guarded_ptr cds::intrusive::MichaelList< GC, T, Traits >::get ( Q const & key )

inline

Finds the key and return the item found.

The function searches the item with key equal to key and returns it as guarded_ptr. If key is not found the function returns an empty guarded pointer.

The disposer specified in Traits class template parameter is called by garbage collector GC automatically when returned guarded_ptr object will be destroyed or released.

Note: Each guarded_ptr object uses one GC's guard which can be limited resource.

Usage:

typedef cds::intrusive::MichaelList< cds::gc::HP, foo, my_traits >  ord_list;
ord_list theList;
// ...
{
    ord_list::guarded_ptr gp(theList.get( 5 ));
    if ( gp ) {
        // Deal with gp
        //...
    }
    // Destructor of guarded_ptr releases internal HP guard
}

Note the compare functor specified for Traits template parameter should accept a parameter of type Q that can be not the same as value_type.

◆ get_with()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Q , typename Less >

guarded_ptr cds::intrusive::MichaelList< GC, T, Traits >::get_with	(	Q const &	key,
		Less	pred
	)

inline

Finds the key and return the item found.

The function is an analog of get( Q const&) but pred is used for comparing the keys.

Less functor has the semantics like std::less but should take arguments of type value_type and Q in any order. pred must imply the same element order as the comparator used for building the list.

◆ insert() [1/2]

template<class GC, typename T, class Traits = michael_list::traits>

bool cds::intrusive::MichaelList< GC, T, Traits >::insert ( value_type & val )

inline

Inserts new node.

The function inserts val into the list if the list does not contain an item with key equal to val.

Returns true if val has been linked to the list, false otherwise.

◆ insert() [2/2]

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Func >

bool cds::intrusive::MichaelList< GC, T, Traits >::insert	(	value_type &	val,
		Func	f
	)

inline

Inserts new node.

This function is intended for derived non-intrusive containers.

The function allows to split new item creating into two part:

create item with key only
insert new item into the list
if inserting is success, calls f functor to initialize value-field of val.

The functor signature is:

void func( value_type& val );

where val is the item inserted. User-defined functor f should guarantee that during changing val no any other changes could be made on this list's item by concurrent threads. The user-defined functor is called only if the inserting is success.

Warning: See insert item troubleshooting

◆ size()

template<class GC, typename T, class Traits = michael_list::traits>

size_t cds::intrusive::MichaelList< GC, T, Traits >::size ( ) const

inline

Returns list's item count.

The value returned depends on item counter provided by Traits. For atomicity::empty_item_counter, this function always returns 0.

Note: Even if you use real item counter and it returns 0, this fact does not mean that the list is empty. To check list emptiness use empty() method.

◆ unlink()

template<class GC, typename T, class Traits = michael_list::traits>

bool cds::intrusive::MichaelList< GC, T, Traits >::unlink ( value_type & val )

inline

Unlinks the item val from the list.

The function searches the item val in the list and unlinks it from the list if it is found and it is equal to val.

Difference between erase() and unlink(): erase() finds a key and deletes the item found. unlink() finds an item by key and deletes it only if val is an item of the list, i.e. the pointer to item found is equal to &val .

disposer specified in Traits is called for deleted item.

The function returns true if success and false otherwise.

◆ update()

template<class GC, typename T, class Traits = michael_list::traits>

template<typename Func >

std::pair<bool, bool> cds::intrusive::MichaelList< GC, T, Traits >::update	(	value_type &	val,
		Func	func,
		bool	bInsert = `true`
	)

inline

Updates the node.

The operation performs inserting or changing data with lock-free manner.

If the item val is not found in the list, then val is inserted iff bInsert is true. Otherwise, the functor func is called with item found. The functor signature is:

void func( bool bNew, value_type& item, value_type& val );

with arguments:

bNew - true if the item has been inserted, false otherwise
item - item of the list
val - argument val passed into the update() function If new item has been inserted (i.e. bNew is true) then item and val arguments refers to the same thing.

The functor may change non-key fields of the item; however, func must guarantee that during changing no any other modifications could be made on this item by concurrent threads.

Returns std::pair<bool, bool> where first is true if operation is successful, second is true if new item has been added or false if the item with that key already in the list.

Warning: See insert item troubleshooting

The documentation for this class was generated from the following file:

cds/intrusive/impl/michael_list.h

Public Types

Public Member Functions

Static Public Attributes

Protected Types

Protected Attributes

Forward iterators (only for debugging purpose)

Detailed Description

template<class GC, typename T, class Traits = michael_list::traits> class cds::intrusive::MichaelList< GC, T, Traits >

Member Typedef Documentation

◆ const_iterator

◆ iterator

Member Function Documentation

◆ begin()

◆ clear()

◆ contains() [1/2]

◆ contains() [2/2]

◆ end()

◆ erase() [1/2]

◆ erase() [2/2]

◆ erase_with() [1/2]

◆ erase_with() [2/2]

◆ extract()

◆ extract_with()

◆ find()

◆ find_with()

◆ get()

◆ get_with()

◆ insert() [1/2]

◆ insert() [2/2]

◆ size()

◆ unlink()

◆ update()

template<class GC, typename T, class Traits = michael_list::traits>
class cds::intrusive::MichaelList< GC, T, Traits >