Michael's lock-free ordered single-linked list (template specialization for RCU) More...

#include <cds/intrusive/michael_list_rcu.h>

Inheritance diagram for cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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 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 cds::urcu::gc< RCU >	gc
	RCU schema.

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 traits::rcu_check_deadlock	rcu_check_deadlock
	Deadlock checking policy.

typedef traits::stat	stat
	Internal statistics.

typedef gc::scoped_lock	rcu_lock
	RCU scoped lock.

using	exempt_ptr = cds::urcu::exempt_ptr< gc, value_type, value_type, clear_and_dispose, void >
	pointer to extracted node

typedef cds::urcu::raw_ptr< gc, value_type, raw_ptr_disposer >	raw_ptr
	Result of `get()`, `get_with()` functions - pointer to the node found.

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

	~MichaelList ()
	Destroy list.

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 bAllowInsert=true)
	Updates the item. 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 func)
	Deletes the item from the list using `pred` predicate for searching. More...

template<typename Q >
exempt_ptr	extract (Q const &key)
	Extracts an item from the list. More...

template<typename Q , typename Less >
exempt_ptr	extract_with (Q const &key, Less pred)
	Extracts an item from the list using `pred` predicate for searching. More...

template<typename Q , typename Func >
bool	find (Q &key, Func f)
	Find the key `val`. More...

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

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

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

void	clear ()
	Clears the list using default disposer. More...

bool	empty () const
	Check if 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 bool	c_bExtractLockExternal = false
	Group of `extract_xxx` functions do not require external locking.

Protected Types
typedef node_type::marked_ptr	marked_node_ptr
	Marked node pointer.

typedef node_type::atomic_marked_ptr	atomic_node_ptr
	Atomic node 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 (thread-safe only under RCU lock)
typedef iterator_type< false >	iterator
	Forward iterator. More...

typedef iterator_type< true >	const_iterator
	Const forward iterator.

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

const_iterator	cbegin () 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<typename RCU, typename T, class Traits = michael_list::traits>
class cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >

Michael's lock-free ordered single-linked list (template specialization for RCU)

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

Template arguments:

RCU - one of RCU type
T - type to be stored in the list; the type T should be based on (or has a member of type) cds::intrusive::micheal_list::node
Traits - type traits. See michael_list::traits for explanation. It is possible to declare option-based list with cds::intrusive::michael_list::make_traits metafunction, see here for explanations.

Usage: Before including <cds/intrusive/michael_list_rcu.h> you should include appropriate RCU header file, see RCU type for list of existing RCU class and corresponding header files. For example, for general-purpose buffered RCU you should include:
#include <cds/urcu/general_buffered.h>
#include <cds/intrusive/michael_list_rcu.h>
// Now, you can declare Michael's list for type Foo and default traits:
typedef cds::intrusive::MichaelList<cds::urcu::gc< cds::urcu::general_buffered<> >, Foo > rcu_michael_list;

Member Typedef Documentation

◆ iterator

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

typedef iterator_type<false> cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::iterator

Forward iterator.

You may safely use iterators in multi-threaded environment only under RCU lock. Otherwise, a crash is possible if another thread deletes the item the iterator points to.

Member Function Documentation

◆ begin()

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

iterator cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::begin ( )

inline

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

For empty list

begin() == end()

◆ clear()

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

void cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::clear ( )

inline

Clears the list using default disposer.

The function clears the list using default (provided by Traits class template argument) disposer functor.

RCU synchronize method can be called. Note that depending on RCU type used the disposer invocation can be deferred.

The function can throw cds::urcu::rcu_deadlock exception if a deadlock is encountered and deadlock checking policy is opt::v::rcu_throw_deadlock.

◆ contains() [1/2]

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

template<typename Q >

bool cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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<typename RCU , typename T , class Traits = michael_list::traits>

template<typename Q , typename Less >

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

inline

Checks whether the map 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<typename RCU , typename T , class Traits = michael_list::traits>

iterator cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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<typename RCU , typename T , class Traits = michael_list::traits>

template<typename Q >

bool cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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 the item with the key equal to key is not found the function return false.

RCU synchronize method can be called. Note that depending on RCU type used the disposer call can be deferred.

disposer specified in Traits is called for deleted item.

The function can throw cds::urcu::rcu_deadlock exception if a deadlock is detected and the deadlock checking policy is opt::v::rcu_throw_deadlock.

◆ erase() [2/2]

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

template<typename Q , typename Func >

bool cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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 the item with the key equal to key is not found the function return false.

RCU synchronize method can be called. Note that depending on RCU type used the disposer call can be deferred.

disposer specified in Traits is called for deleted item.

The function can throw cds::urcu::rcu_deadlock exception if a deadlock is detected and the deadlock checking policy is opt::v::rcu_throw_deadlock.

◆ erase_with() [1/2]

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

template<typename Q , typename Less >

bool cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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<typename RCU , typename T , class Traits = michael_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::erase_with	(	Q const &	key,
		Less	pred,
		Func	func
	)

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<typename RCU , typename T , class Traits = michael_list::traits>

template<typename Q >

exempt_ptr cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::extract ( Q const & key )

inline

Extracts an item from the list.

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

Note: The function does NOT dispose the item found. It just unlinks the item from the list and returns a pointer to item found. You shouldn't lock RCU for current thread before calling this function, and you should manually release the returned exempt pointer before reusing it.

#include <cds/urcu/general_buffered.h>
#include <cds/intrusive/michael_list_rcu.h>
typedef cds::urcu::gc< general_buffered<> > rcu;
typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
rcu_michael_list theList;
// ...
rcu_michael_list::exempt_ptr p1;
// The RCU should NOT be locked when extract() is called!
assert( !rcu::is_locked());
// You can call extract() function
p1 = theList.extract( 10 );
if ( p1 ) {
    // do something with p1
    ...
}
// We may safely release p1 here
// release() passes the pointer to RCU reclamation cycle:
// it invokes RCU retire_ptr function with the disposer you provided for the list.
p1.release();

◆ extract_with()

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

template<typename Q , typename Less >

exempt_ptr cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::extract_with	(	Q const &	key,
		Less	pred
	)

inline

Extracts an item from the list using pred predicate for searching.

This function is the analog for extract(Q const&)

The pred is a predicate used for key comparing. Less has the interface like std::less. pred must imply the same element order as key_comparator.

◆ find()

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

template<typename Q , typename Func >

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

inline

Find the key val.

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 can change non-key fields of item. The function find does not serialize simultaneous access to the list item. If such access is possible you must provide your own synchronization schema to exclude unsafe item modifications.

The function makes RCU lock internally.

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

◆ find_with()

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

template<typename Q , typename Less , typename Func >

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

inline

Finds 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<typename RCU , typename T , class Traits = michael_list::traits>

template<typename Q >

raw_ptr cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::get ( Q const & key )

inline

Finds key and return the item found.

The function searches the item with key equal to key and returns the pointer to item found. If key is not found it returns empty raw_ptr object.

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

RCU should be locked before call of this function. Returned item is valid only while RCU is locked:

typedef cds::intrusive::MichaelList< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > ord_list;
ord_list theList;
// ...
typename ord_list::raw_ptr rp;
{
    // Lock RCU
    ord_list::rcu_lock lock;
    rp = theList.get( 5 );
    if ( rp ) {
        // Deal with rp
        //...
    }
    // Unlock RCU by rcu_lock destructor
    // Node owned by rp can be retired by disposer at any time after RCU has been unlocked
}
// You can manually release rp after RCU-locked section
rp.release();

◆ get_with()

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

template<typename Q , typename Less >

raw_ptr cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::get_with	(	Q const &	key,
		Less	pred
	)

inline

Finds 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<typename RCU , typename T , class Traits = michael_list::traits>

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

inline

Inserts new node.

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

The function makes RCU lock internally.

Returns true if val is linked into the list, false otherwise.

◆ insert() [2/2]

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

template<typename Func >

bool cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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.

The function makes RCU lock internally.

Warning: See insert item troubleshooting

◆ size()

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

size_t cds::intrusive::MichaelList< cds::urcu::gc< RCU >, 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 emptyness use empty() method.

◆ unlink()

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

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

inline

Unlinks the item val from the list.

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

Difference between erase() and unlink() functions: 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 that list, i.e. the pointer to the item found is equal to &val .

The function returns true if success and false otherwise.

RCU synchronize method can be called. Note that depending on RCU type used the disposer call can be deferred.

disposer specified in Traits is called for unlinked item.

The function can throw cds::urcu::rcu_deadlock exception if deadlock is encountered and deadlock checking policy is opt::v::rcu_throw_deadlock.

◆ update()

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

template<typename Func >

std::pair<bool, bool> cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >::update	(	value_type &	val,
		Func	func,
		bool	bAllowInsert = `true`
	)

inline

Updates the item.

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

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

struct functor {
    void operator()( 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 refer 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 key already is in the list.

The function makes RCU lock internally.

Warning: See insert item troubleshooting

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

cds/intrusive/michael_list_rcu.h

Public Types

Public Member Functions

Static Public Attributes

Protected Types

Protected Attributes

Forward iterators (thread-safe only under RCU lock)

Detailed Description

template<typename RCU, typename T, class Traits = michael_list::traits> class cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >

Member Typedef Documentation

◆ 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<typename RCU, typename T, class Traits = michael_list::traits>
class cds::intrusive::MichaelList< cds::urcu::gc< RCU >, T, Traits >