atomic_marked_ptr m_pNext; ///< Next item in bottom-list (list at level 0)
public:
node * m_pDelChain; ///< Deleted node chain (local for a thread)
-# ifdef _DEBUG
- bool volatile m_bLinked;
- bool volatile m_bUnlinked;
-# endif
protected:
unsigned int m_nHeight; ///< Node height (size of m_arrNext array). For node at level 0 the height is 1.
atomic_marked_ptr * m_arrNext; ///< Array of next items for levels 1 .. m_nHeight - 1. For node at level 0 \p m_arrNext is \p nullptr
+ atomics::atomic<unsigned> m_nUnlink; ///< How many levels has been unlinked
public:
/// Constructs a node of height 1 (a bottom-list node)
CDS_CONSTEXPR node()
: m_pNext( nullptr )
, m_pDelChain( nullptr )
-# ifdef _DEBUG
- , m_bLinked( false )
- , m_bUnlinked( false )
-# endif
, m_nHeight(1)
, m_arrNext( nullptr )
+ , m_nUnlink(0)
{}
-# ifdef _DEBUG
- ~node()
- {
- assert( !m_bLinked || m_bUnlinked );
- }
-# endif
-
/// Constructs a node of height \p nHeight
void make_tower( unsigned int nHeight, atomic_marked_ptr * nextTower )
{
&& m_arrNext == nullptr
&& m_nHeight <= 1;
}
+
+ bool level_unlinked( unsigned nCount = 1 )
+ {
+ return m_nUnlink.fetch_add( nCount, std::memory_order_relaxed ) + 1 == height();
+ }
};
} // namespace skip_list
//@endcond
/// Result of \p get(), \p get_with() functions - pointer to the node found
typedef cds::urcu::raw_ptr< gc, value_type, raw_ptr_disposer > raw_ptr;
- protected:
- //@cond
-
- bool is_extracted( marked_node_ptr const p ) const
+ public:
+ /// Default constructor
+ SkipListSet()
+ : m_Head( c_nMaxHeight )
+ , m_nHeight( c_nMinHeight )
+ , m_pDeferredDelChain( nullptr )
{
- return (p.bits() & 2) != 0;
+ static_assert( (std::is_same< gc, typename node_type::gc >::value), "GC and node_type::gc must be the same type" );
+
+ // Barrier for head node
+ atomics::atomic_thread_fence( memory_model::memory_order_release );
}
- template <typename Q, typename Compare >
- bool find_position( Q const& val, position& pos, Compare cmp, bool bStopIfFound )
+ /// Clears and destructs the skip-list
+ ~SkipListSet()
{
- assert( gc::is_locked());
-
- node_type * pPred;
- marked_node_ptr pSucc;
- marked_node_ptr pCur;
- int nCmp = 1;
-
- retry:
- pPred = m_Head.head();
-
- for ( int nLevel = static_cast<int>(c_nMaxHeight - 1); nLevel >= 0; --nLevel ) {
-
- while ( true ) {
- pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
- if ( pCur.bits()) {
- // pCur.bits() means that pPred is logically deleted
- goto retry;
- }
-
- if ( pCur.ptr() == nullptr ) {
- // end of the list at level nLevel - goto next level
- break;
- }
-
- // pSucc contains deletion mark for pCur
- pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
+ clear();
+ }
- if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr())
- goto retry;
+ public:
+ ///@name Forward iterators (thread-safe under RCU lock)
+ //@{
+ /// Forward iterator
+ /**
+ The forward iterator has some features:
+ - it has no post-increment operator
+ - it depends on iterator of underlying \p OrderedList
- if ( pSucc.bits()) {
- // pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr());
-# ifdef _DEBUG
- if ( nLevel == 0 )
- pCur->m_bUnlinked = true;
-# endif
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr()),
- memory_model::memory_order_release, atomics::memory_order_relaxed ))
- {
- if ( nLevel == 0 ) {
- if ( !is_extracted( pSucc )) {
- // We cannot free the node at this moment since RCU is locked
- // Link deleted nodes to a chain to free later
- pos.dispose( pCur.ptr());
- m_Stat.onEraseWhileFind();
- }
- else {
- m_Stat.onExtractWhileFind();
- }
- }
- }
- goto retry;
- }
- else {
- nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr()), val );
- if ( nCmp < 0 )
- pPred = pCur.ptr();
- else if ( nCmp == 0 && bStopIfFound )
- goto found;
- else
- break;
- }
- }
+ You may safely use iterators in multi-threaded environment only under RCU lock.
+ Otherwise, a crash is possible if another thread deletes the element the iterator points to.
+ */
+ typedef skip_list::details::iterator< gc, node_traits, back_off, false > iterator;
- // Next level
- pos.pPrev[ nLevel ] = pPred;
- pos.pSucc[ nLevel ] = pCur.ptr();
- }
+ /// Const iterator type
+ typedef skip_list::details::iterator< gc, node_traits, back_off, true > const_iterator;
- if ( nCmp != 0 )
- return false;
+ /// Returns a forward iterator addressing the first element in a set
+ iterator begin()
+ {
+ return iterator( *m_Head.head());
+ }
- found:
- pos.pCur = pCur.ptr();
- return pCur.ptr() && nCmp == 0;
+ /// Returns a forward const iterator addressing the first element in a set
+ const_iterator begin() const
+ {
+ return const_iterator( *m_Head.head());
}
- bool find_min_position( position& pos )
+ /// Returns a forward const iterator addressing the first element in a set
+ const_iterator cbegin() const
{
- assert( gc::is_locked());
+ return const_iterator( *m_Head.head());
+ }
- node_type * pPred;
- marked_node_ptr pSucc;
- marked_node_ptr pCur;
+ /// Returns a forward iterator that addresses the location succeeding the last element in a set.
+ iterator end()
+ {
+ return iterator();
+ }
- retry:
- pPred = m_Head.head();
+ /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
+ const_iterator end() const
+ {
+ return const_iterator();
+ }
- for ( int nLevel = static_cast<int>(c_nMaxHeight - 1); nLevel >= 0; --nLevel ) {
+ /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
+ const_iterator cend() const
+ {
+ return const_iterator();
+ }
+ //@}
- pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
- // pCur.bits() means that pPred is logically deleted
- // head cannot be deleted
- assert( pCur.bits() == 0 );
+ public:
+ /// Inserts new node
+ /**
+ The function inserts \p val in the set if it does not contain
+ an item with key equal to \p val.
- if ( pCur.ptr()) {
+ The function applies RCU lock internally.
- // pSucc contains deletion mark for pCur
- pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
+ Returns \p true if \p val is placed into the set, \p false otherwise.
+ */
+ bool insert( value_type& val )
+ {
+ return insert( val, []( value_type& ) {} );
+ }
- if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr())
- goto retry;
+ /// Inserts new node
+ /**
+ This function is intended for derived non-intrusive containers.
- if ( pSucc.bits()) {
- // pCur is marked, i.e. logically deleted.
-# ifdef _DEBUG
- if ( nLevel == 0 )
- pCur->m_bUnlinked = true;
-# endif
- marked_node_ptr p( pCur.ptr());
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr()),
- memory_model::memory_order_release, atomics::memory_order_relaxed ))
- {
- if ( nLevel == 0 ) {
- if ( !is_extracted( pSucc )) {
- // We cannot free the node at this moment since RCU is locked
- // Link deleted nodes to a chain to free later
- pos.dispose( pCur.ptr());
- m_Stat.onEraseWhileFind();
- }
- else {
- m_Stat.onExtractWhileFind();
- }
- }
- }
- goto retry;
- }
- }
+ The function allows to split creating of new item into two part:
+ - create item with key only
+ - insert new item into the set
+ - if inserting is success, calls \p f functor to initialize value-field of \p val.
- // Next level
- pos.pPrev[ nLevel ] = pPred;
- pos.pSucc[ nLevel ] = pCur.ptr();
- }
- return (pos.pCur = pCur.ptr()) != nullptr;
- }
+ The functor signature is:
+ \code
+ void func( value_type& val );
+ \endcode
+ where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
+ \p val no any other changes could be made on this set's item by concurrent threads.
+ The user-defined functor is called only if the inserting is success.
- bool find_max_position( position& pos )
+ RCU \p synchronize method can be called. RCU should not be locked.
+ */
+ template <typename Func>
+ bool insert( value_type& val, Func f )
{
- assert( gc::is_locked());
+ check_deadlock_policy::check();
- node_type * pPred;
- marked_node_ptr pSucc;
- marked_node_ptr pCur;
+ position pos;
+ bool bRet;
- retry:
- pPred = m_Head.head();
+ {
+ node_type * pNode = node_traits::to_node_ptr( val );
+ scoped_node_ptr scp( pNode );
+ unsigned int nHeight = pNode->height();
+ bool bTowerOk = nHeight > 1 && pNode->get_tower() != nullptr;
+ bool bTowerMade = false;
- for ( int nLevel = static_cast<int>(c_nMaxHeight - 1); nLevel >= 0; --nLevel ) {
+ rcu_lock rcuLock;
- while ( true ) {
- pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
- if ( pCur.bits()) {
- // pCur.bits() means that pPred is logically deleted
- goto retry;
- }
+ while ( true )
+ {
+ bool bFound = find_position( val, pos, key_comparator(), true );
+ if ( bFound ) {
+ // scoped_node_ptr deletes the node tower if we create it
+ if ( !bTowerMade )
+ scp.release();
- if ( pCur.ptr() == nullptr ) {
- // end of the list at level nLevel - goto next level
+ m_Stat.onInsertFailed();
+ bRet = false;
break;
}
- // pSucc contains deletion mark for pCur
- pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
-
- if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr())
- goto retry;
-
- if ( pSucc.bits()) {
- // pCur is marked, i.e. logically deleted.
-# ifdef _DEBUG
- if ( nLevel == 0 )
- pCur->m_bUnlinked = true;
-# endif
- marked_node_ptr p( pCur.ptr());
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr()),
- memory_model::memory_order_release, atomics::memory_order_relaxed ))
- {
- if ( nLevel == 0 ) {
- if ( !is_extracted( pSucc )) {
- // We cannot free the node at this moment since RCU is locked
- // Link deleted nodes to a chain to free later
- pos.dispose( pCur.ptr());
- m_Stat.onEraseWhileFind();
- }
- else {
- m_Stat.onExtractWhileFind();
- }
- }
- }
- goto retry;
+ if ( !bTowerOk ) {
+ build_node( pNode );
+ nHeight = pNode->height();
+ bTowerMade =
+ bTowerOk = true;
}
- else {
- if ( !pSucc.ptr())
- break;
- pPred = pCur.ptr();
+ if ( !insert_at_position( val, pNode, pos, f )) {
+ m_Stat.onInsertRetry();
+ continue;
}
- }
- // Next level
- pos.pPrev[ nLevel ] = pPred;
- pos.pSucc[ nLevel ] = pCur.ptr();
+ increase_height( nHeight );
+ ++m_ItemCounter;
+ m_Stat.onAddNode( nHeight );
+ m_Stat.onInsertSuccess();
+ scp.release();
+ bRet = true;
+ break;
+ }
}
- return (pos.pCur = pCur.ptr()) != nullptr;
+ return bRet;
}
- template <typename Func>
- bool insert_at_position( value_type& val, node_type * pNode, position& pos, Func f )
- {
- assert( gc::is_locked());
-
- unsigned int nHeight = pNode->height();
- pNode->clear_tower();
+ /// Updates the node
+ /**
+ The operation performs inserting or changing data with lock-free manner.
- {
- marked_node_ptr p( pos.pSucc[0] );
- pNode->next( 0 ).store( p, memory_model::memory_order_release );
- if ( !pos.pPrev[0]->next(0).compare_exchange_strong( p, marked_node_ptr(pNode), memory_model::memory_order_release, atomics::memory_order_relaxed )) {
- return false;
- }
-# ifdef _DEBUG
- pNode->m_bLinked = true;
-# endif
- f( val );
- }
+ If the item \p val is not found in the set, then \p val is inserted into the set
+ iff \p bInsert is \p true.
+ Otherwise, the functor \p func is called with item found.
+ The functor signature is:
+ \code
+ void func( bool bNew, value_type& item, value_type& val );
+ \endcode
+ with arguments:
+ - \p bNew - \p true if the item has been inserted, \p false otherwise
+ - \p item - item of the set
+ - \p val - argument \p val passed into the \p %update() function
+ If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
+ refer to the same thing.
- for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel ) {
- marked_node_ptr p;
- while ( true ) {
- marked_node_ptr q( pos.pSucc[ nLevel ]);
- if ( !pNode->next( nLevel ).compare_exchange_strong( p, q, memory_model::memory_order_acquire, atomics::memory_order_relaxed )) {
- // pNode has been marked as removed while we are inserting it
- // Stop inserting
- assert( p.bits());
- m_Stat.onLogicDeleteWhileInsert();
- return true;
- }
- p = q;
- if ( pos.pPrev[nLevel]->next(nLevel).compare_exchange_strong( q, marked_node_ptr( pNode ), memory_model::memory_order_release, atomics::memory_order_relaxed ))
- break;
+ The functor can change non-key fields of the \p item; however, \p func must guarantee
+ that during changing no any other modifications could be made on this item by concurrent threads.
- // Renew insert position
- m_Stat.onRenewInsertPosition();
- if ( !find_position( val, pos, key_comparator(), false )) {
- // The node has been deleted while we are inserting it
- m_Stat.onNotFoundWhileInsert();
- return true;
- }
- }
- }
- return true;
- }
+ RCU \p synchronize method can be called. RCU should not be locked.
+
+ Returns std::pair<bool, bool> where \p first is \p true if operation is successful,
+ i.e. the node has been inserted or updated,
+ \p second is \p true if new item has been added or \p false if the item with \p key
+ already exists.
+ @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
+ */
template <typename Func>
- bool try_remove_at( node_type * pDel, position& pos, Func f, bool bExtract )
+ std::pair<bool, bool> update( value_type& val, Func func, bool bInsert = true )
{
- assert( pDel != nullptr );
- assert( gc::is_locked());
-
- marked_node_ptr pSucc;
+ check_deadlock_policy::check();
- // logical deletion (marking)
- for ( unsigned int nLevel = pDel->height() - 1; nLevel > 0; --nLevel ) {
- pSucc = pDel->next(nLevel).load( memory_model::memory_order_relaxed );
- while ( true ) {
- if ( pSucc.bits()
- || pDel->next(nLevel).compare_exchange_weak( pSucc, pSucc | 1, memory_model::memory_order_acquire, atomics::memory_order_relaxed ))
- {
- break;
- }
- }
- }
+ position pos;
+ std::pair<bool, bool> bRet( true, false );
- pSucc = pDel->next(0).load( memory_model::memory_order_relaxed );
- while ( true ) {
- if ( pSucc.bits())
- return false;
+ {
+ node_type * pNode = node_traits::to_node_ptr( val );
+ scoped_node_ptr scp( pNode );
+ unsigned int nHeight = pNode->height();
+ bool bTowerOk = nHeight > 1 && pNode->get_tower() != nullptr;
+ bool bTowerMade = false;
- int const nMask = bExtract ? 3 : 1;
- if ( pDel->next(0).compare_exchange_strong( pSucc, pSucc | nMask, memory_model::memory_order_acquire, atomics::memory_order_relaxed ))
+ rcu_lock rcuLock;
+ while ( true )
{
- f( *node_traits::to_value_ptr( pDel ));
+ bool bFound = find_position( val, pos, key_comparator(), true );
+ if ( bFound ) {
+ // scoped_node_ptr deletes the node tower if we create it before
+ if ( !bTowerMade )
+ scp.release();
- // physical deletion
- // try fast erase
- pSucc = pDel;
- for ( int nLevel = static_cast<int>( pDel->height() - 1 ); nLevel >= 0; --nLevel ) {
- if ( !pos.pPrev[nLevel]->next(nLevel).compare_exchange_strong( pSucc,
- marked_node_ptr( pDel->next(nLevel).load(memory_model::memory_order_relaxed).ptr()),
- memory_model::memory_order_release, atomics::memory_order_relaxed))
- {
- // Do slow erase
- find_position( *node_traits::to_value_ptr(pDel), pos, key_comparator(), false );
- if ( bExtract )
- m_Stat.onSlowExtract();
- else
- m_Stat.onSlowErase();
-# ifdef _DEBUG
- assert( pDel->m_bUnlinked );
-# endif
- return true;
- }
+ func( false, *node_traits::to_value_ptr(pos.pCur), val );
+ m_Stat.onUpdateExist();
+ break;
}
-# ifdef _DEBUG
- pDel->m_bUnlinked = true;
-# endif
- if ( !bExtract ) {
- // We cannot free the node at this moment since RCU is locked
- // Link deleted nodes to a chain to free later
- pos.dispose( pDel );
- m_Stat.onFastErase();
+ if ( !bInsert ) {
+ scp.release();
+ bRet.first = false;
+ break;
}
- else
- m_Stat.onFastExtract();
- return true;
- }
- m_Stat.onEraseRetry();
- }
- }
-
- enum finsd_fastpath_result {
- find_fastpath_found,
- find_fastpath_not_found,
- find_fastpath_abort
- };
- template <typename Q, typename Compare, typename Func>
- finsd_fastpath_result find_fastpath( Q& val, Compare cmp, Func f ) const
- {
- node_type * pPred;
- marked_node_ptr pCur;
- marked_node_ptr pSucc;
- marked_node_ptr pNull;
-
- back_off bkoff;
-
- pPred = m_Head.head();
- for ( int nLevel = static_cast<int>(m_nHeight.load(memory_model::memory_order_relaxed) - 1); nLevel >= 0; --nLevel ) {
- pCur = pPred->next(nLevel).load( memory_model::memory_order_acquire );
- if ( pCur == pNull )
- continue;
-
- while ( pCur != pNull ) {
- if ( pCur.bits()) {
- // Wait until pCur is removed
- unsigned int nAttempt = 0;
- while ( pCur.bits() && nAttempt++ < 16 ) {
- bkoff();
- pCur = pPred->next(nLevel).load( memory_model::memory_order_acquire );
- }
- bkoff.reset();
- if ( pCur.bits()) {
- // Maybe, we are on deleted node sequence
- // Abort searching, try slow-path
- return find_fastpath_abort;
- }
+ if ( !bTowerOk ) {
+ build_node( pNode );
+ nHeight = pNode->height();
+ bTowerMade =
+ bTowerOk = true;
}
- if ( pCur.ptr()) {
- int nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr()), val );
- if ( nCmp < 0 ) {
- pPred = pCur.ptr();
- pCur = pCur->next(nLevel).load( memory_model::memory_order_acquire );
- }
- else if ( nCmp == 0 ) {
- // found
- f( *node_traits::to_value_ptr( pCur.ptr()), val );
- return find_fastpath_found;
- }
- else // pCur > val - go down
- break;
+ if ( !insert_at_position( val, pNode, pos, [&func]( value_type& item ) { func( true, item, item ); })) {
+ m_Stat.onInsertRetry();
+ continue;
}
+
+ increase_height( nHeight );
+ ++m_ItemCounter;
+ scp.release();
+ m_Stat.onAddNode( nHeight );
+ m_Stat.onUpdateNew();
+ bRet.second = true;
+ break;
}
}
- return find_fastpath_not_found;
- }
-
- template <typename Q, typename Compare, typename Func>
- bool find_slowpath( Q& val, Compare cmp, Func f, position& pos )
- {
- if ( find_position( val, pos, cmp, true )) {
- assert( cmp( *node_traits::to_value_ptr( pos.pCur ), val ) == 0 );
-
- f( *node_traits::to_value_ptr( pos.pCur ), val );
- return true;
- }
- else
- return false;
+ return bRet;
}
-
- template <typename Q, typename Compare, typename Func>
- bool do_find_with( Q& val, Compare cmp, Func f )
+ //@cond
+ template <typename Func>
+ CDS_DEPRECATED("ensure() is deprecated, use update()")
+ std::pair<bool, bool> ensure( value_type& val, Func func )
{
- position pos;
- return do_find_with( val, cmp, f, pos );
+ return update( val, func, true );
}
+ //@endcond
- template <typename Q, typename Compare, typename Func>
- bool do_find_with( Q& val, Compare cmp, Func f, position& pos )
- {
- bool bRet;
+ /// Unlinks the item \p val from the set
+ /**
+ The function searches the item \p val in the set and unlink it from the set
+ if it is found and is equal to \p val.
- {
- rcu_lock l;
+ Difference between \p erase() and \p %unlink() functions: \p erase() finds <i>a key</i>
+ and deletes the item found. \p %unlink() searches an item by key and deletes it
+ only if \p val is an item of that set, i.e. the pointer to item found
+ is equal to <tt> &val </tt>.
- switch ( find_fastpath( val, cmp, f )) {
- case find_fastpath_found:
- m_Stat.onFindFastSuccess();
- return true;
- case find_fastpath_not_found:
- m_Stat.onFindFastFailed();
- return false;
- default:
- break;
- }
+ RCU \p synchronize method can be called. RCU should not be locked.
- if ( find_slowpath( val, cmp, f, pos )) {
- m_Stat.onFindSlowSuccess();
- bRet = true;
- }
- else {
- m_Stat.onFindSlowFailed();
- bRet = false;
- }
- }
- return bRet;
- }
+ The \ref disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC asynchronously.
- template <typename Q, typename Compare, typename Func>
- bool do_erase( Q const& val, Compare cmp, Func f )
+ The function returns \p true if success and \p false otherwise.
+ */
+ bool unlink( value_type& val )
{
check_deadlock_policy::check();
bool bRet;
{
- rcu_lock rcuLock;
+ rcu_lock l;
- if ( !find_position( val, pos, cmp, false )) {
- m_Stat.onEraseFailed();
+ if ( !find_position( val, pos, key_comparator(), false )) {
+ m_Stat.onUnlinkFailed();
bRet = false;
}
else {
node_type * pDel = pos.pCur;
- assert( cmp( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+ assert( key_comparator()( *node_traits::to_value_ptr( pDel ), val ) == 0 );
unsigned int nHeight = pDel->height();
- if ( try_remove_at( pDel, pos, f, false )) {
+
+ if ( node_traits::to_value_ptr( pDel ) == &val && try_remove_at( pDel, pos, [](value_type const&) {}, false )) {
--m_ItemCounter;
m_Stat.onRemoveNode( nHeight );
- m_Stat.onEraseSuccess();
+ m_Stat.onUnlinkSuccess();
bRet = true;
}
else {
- m_Stat.onEraseFailed();
+ m_Stat.onUnlinkFailed();
bRet = false;
}
}
return bRet;
}
- template <typename Q, typename Compare>
- value_type * do_extract_key( Q const& key, Compare cmp, position& pos )
- {
- // RCU should be locked!!!
- assert( gc::is_locked());
-
- node_type * pDel;
-
- if ( !find_position( key, pos, cmp, false )) {
- m_Stat.onExtractFailed();
- pDel = nullptr;
- }
- else {
- pDel = pos.pCur;
- assert( cmp( *node_traits::to_value_ptr( pDel ), key ) == 0 );
+ /// Extracts the item from the set with specified \p key
+ /** \anchor cds_intrusive_SkipListSet_rcu_extract
+ The function searches an item with key equal to \p key in the set,
+ unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
+ If the item with key equal to \p key is not found the function returns an empty \p exempt_ptr.
- unsigned int const nHeight = pDel->height();
+ Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- if ( try_remove_at( pDel, pos, [](value_type const&) {}, true )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onExtractSuccess();
- }
- else {
- m_Stat.onExtractFailed();
- pDel = nullptr;
- }
- }
+ RCU \p synchronize method can be called. RCU should NOT be locked.
+ The function does not call the disposer for the item found.
+ The disposer will be implicitly invoked when the returned object is destroyed or when
+ its \p release() member function is called.
+ Example:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
- return pDel ? node_traits::to_value_ptr( pDel ) : nullptr;
- }
+ typename skip_list::exempt_ptr ep( theList.extract( 5 ));
+ if ( ep ) {
+ // Deal with ep
+ //...
+ // Dispose returned item.
+ ep.release();
+ }
+ \endcode
+ */
template <typename Q>
- value_type * do_extract( Q const& key )
+ exempt_ptr extract( Q const& key )
{
- check_deadlock_policy::check();
- value_type * pDel = nullptr;
- position pos;
- {
- rcu_lock l;
- pDel = do_extract_key( key, key_comparator(), pos );
- }
-
- return pDel;
+ return exempt_ptr( do_extract( key ));
}
+ /// Extracts the item from the set with comparing functor \p pred
+ /**
+ The function is an analog of \p extract(Q const&) but \p pred predicate is used for key comparing.
+ \p Less has the interface like \p std::less.
+ \p pred must imply the same element order as the comparator used for building the set.
+ */
template <typename Q, typename Less>
- value_type * do_extract_with( Q const& key, Less pred )
+ exempt_ptr extract_with( Q const& key, Less pred )
{
- CDS_UNUSED(pred);
- check_deadlock_policy::check();
- value_type * pDel = nullptr;
- position pos;
- {
- rcu_lock l;
- pDel = do_extract_key( key, cds::opt::details::make_comparator_from_less<Less>(), pos );
- }
-
- return pDel;
+ return exempt_ptr( do_extract_with( key, pred ));
}
- value_type * do_extract_min()
- {
- assert( !gc::is_locked());
-
- position pos;
- node_type * pDel;
+ /// Extracts an item with minimal key from the list
+ /**
+ The function searches an item with minimal key, unlinks it, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
+ If the skip-list is empty the function returns an empty \p exempt_ptr.
- {
- rcu_lock l;
+ RCU \p synchronize method can be called. RCU should NOT be locked.
+ The function does not call the disposer for the item found.
+ The disposer will be implicitly invoked when the returned object is destroyed or when
+ its \p release() member function is manually called.
+ Example:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
- if ( !find_min_position( pos )) {
- m_Stat.onExtractMinFailed();
- pDel = nullptr;
- }
- else {
- pDel = pos.pCur;
- unsigned int const nHeight = pDel->height();
+ typename skip_list::exempt_ptr ep(theList.extract_min());
+ if ( ep ) {
+ // Deal with ep
+ //...
- if ( try_remove_at( pDel, pos, []( value_type const& ) {}, true )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onExtractMinSuccess();
- }
- else {
- m_Stat.onExtractMinFailed();
- pDel = nullptr;
- }
- }
+ // Dispose returned item.
+ ep.release();
}
+ \endcode
- return pDel ? node_traits::to_value_ptr( pDel ) : nullptr;
- }
-
- value_type * do_extract_max()
+ @note Due the concurrent nature of the list, the function extracts <i>nearly</i> minimum key.
+ It means that the function gets leftmost item and tries to unlink it.
+ During unlinking, a concurrent thread may insert an item with key less than leftmost item's key.
+ So, the function returns the item with minimum key at the moment of list traversing.
+ */
+ exempt_ptr extract_min()
{
- assert( !gc::is_locked());
-
- position pos;
- node_type * pDel;
+ return exempt_ptr( do_extract_min());
+ }
- {
- rcu_lock l;
+ /// Extracts an item with maximal key from the list
+ /**
+ The function searches an item with maximal key, unlinks it, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
+ If the skip-list is empty the function returns an empty \p exempt_ptr.
- if ( !find_max_position( pos )) {
- m_Stat.onExtractMaxFailed();
- pDel = nullptr;
- }
- else {
- pDel = pos.pCur;
- unsigned int const nHeight = pDel->height();
+ RCU \p synchronize method can be called. RCU should NOT be locked.
+ The function does not call the disposer for the item found.
+ The disposer will be implicitly invoked when the returned object is destroyed or when
+ its \p release() member function is manually called.
+ Example:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
- if ( try_remove_at( pDel, pos, []( value_type const& ) {}, true )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onExtractMaxSuccess();
- }
- else {
- m_Stat.onExtractMaxFailed();
- pDel = nullptr;
- }
- }
+ typename skip_list::exempt_ptr ep( theList.extract_max());
+ if ( ep ) {
+ // Deal with ep
+ //...
+ // Dispose returned item.
+ ep.release();
}
+ \endcode
- return pDel ? node_traits::to_value_ptr( pDel ) : nullptr;
- }
-
- void increase_height( unsigned int nHeight )
+ @note Due the concurrent nature of the list, the function extracts <i>nearly</i> maximal key.
+ It means that the function gets rightmost item and tries to unlink it.
+ During unlinking, a concurrent thread can insert an item with key greater than rightmost item's key.
+ So, the function returns the item with maximum key at the moment of list traversing.
+ */
+ exempt_ptr extract_max()
{
- unsigned int nCur = m_nHeight.load( memory_model::memory_order_relaxed );
- if ( nCur < nHeight )
- m_nHeight.compare_exchange_strong( nCur, nHeight, memory_model::memory_order_release, atomics::memory_order_relaxed );
+ return exempt_ptr( do_extract_max());
}
- //@endcond
- public:
- /// Default constructor
- SkipListSet()
- : m_Head( c_nMaxHeight )
- , m_nHeight( c_nMinHeight )
- , m_pDeferredDelChain( nullptr )
- {
- static_assert( (std::is_same< gc, typename node_type::gc >::value), "GC and node_type::gc must be the same type" );
+ /// Deletes the item from the set
+ /** \anchor cds_intrusive_SkipListSet_rcu_erase
+ The function searches an item with key equal to \p key in the set,
+ unlinks it from the set, and returns \p true.
+ If the item with key equal to \p key is not found the function return \p false.
- // Barrier for head node
- atomics::atomic_thread_fence( memory_model::memory_order_release );
- }
+ Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- /// Clears and destructs the skip-list
- ~SkipListSet()
+ RCU \p synchronize method can be called. RCU should not be locked.
+ */
+ template <typename Q>
+ bool erase( const Q& key )
{
- clear();
+ return do_erase( key, key_comparator(), [](value_type const&) {} );
}
- public:
- ///@name Forward iterators (thread-safe under RCU lock)
- //@{
- /// Forward iterator
+ /// Delete the item from the set with comparing functor \p pred
/**
- The forward iterator has some features:
- - it has no post-increment operator
- - it depends on iterator of underlying \p OrderedList
-
- You may safely use iterators in multi-threaded environment only under RCU lock.
- Otherwise, a crash is possible if another thread deletes the element the iterator points to.
+ The function is an analog of \ref cds_intrusive_SkipListSet_rcu_erase "erase(Q const&)"
+ but \p pred predicate is used for key comparing.
+ \p Less has the interface like \p std::less.
+ \p pred must imply the same element order as the comparator used for building the set.
*/
- typedef skip_list::details::iterator< gc, node_traits, back_off, false > iterator;
-
- /// Const iterator type
- typedef skip_list::details::iterator< gc, node_traits, back_off, true > const_iterator;
-
- /// Returns a forward iterator addressing the first element in a set
- iterator begin()
+ template <typename Q, typename Less>
+ bool erase_with( const Q& key, Less pred )
{
- return iterator( *m_Head.head());
+ CDS_UNUSED( pred );
+ return do_erase( key, cds::opt::details::make_comparator_from_less<Less>(), [](value_type const&) {} );
}
- /// Returns a forward const iterator addressing the first element in a set
- const_iterator begin() const
- {
- return const_iterator( *m_Head.head());
- }
+ /// Deletes the item from the set
+ /** \anchor cds_intrusive_SkipListSet_rcu_erase_func
+ The function searches an item with key equal to \p key in the set,
+ call \p f functor with item found, unlinks it from the set, and returns \p true.
+ The \ref disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC asynchronously.
- /// Returns a forward const iterator addressing the first element in a set
- const_iterator cbegin() const
- {
- return const_iterator( *m_Head.head());
- }
+ The \p Func interface is
+ \code
+ struct functor {
+ void operator()( value_type const& item );
+ };
+ \endcode
+ If the item with key equal to \p key is not found the function return \p false.
- /// Returns a forward iterator that addresses the location succeeding the last element in a set.
- iterator end()
- {
- return iterator();
- }
+ Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
- const_iterator end() const
+ RCU \p synchronize method can be called. RCU should not be locked.
+ */
+ template <typename Q, typename Func>
+ bool erase( Q const& key, Func f )
{
- return const_iterator();
+ return do_erase( key, key_comparator(), f );
}
- /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
- const_iterator cend() const
- {
- return const_iterator();
+ /// Delete the item from the set with comparing functor \p pred
+ /**
+ The function is an analog of \ref cds_intrusive_SkipListSet_rcu_erase_func "erase(Q const&, Func)"
+ but \p pred predicate is used for key comparing.
+ \p Less has the interface like \p std::less.
+ \p pred must imply the same element order as the comparator used for building the set.
+ */
+ template <typename Q, typename Less, typename Func>
+ bool erase_with( Q const& key, Less pred, Func f )
+ {
+ CDS_UNUSED( pred );
+ return do_erase( key, cds::opt::details::make_comparator_from_less<Less>(), f );
}
- //@}
- public:
- /// Inserts new node
- /**
- The function inserts \p val in the set if it does not contain
- an item with key equal to \p val.
+ /// Finds \p key
+ /** @anchor cds_intrusive_SkipListSet_rcu_find_func
+ The function searches the item with key equal to \p key and calls the functor \p f for item found.
+ The interface of \p Func functor is:
+ \code
+ struct functor {
+ void operator()( value_type& item, Q& key );
+ };
+ \endcode
+ where \p item is the item found, \p key is the <tt>find</tt> function argument.
+
+ The functor can change non-key fields of \p item. Note that the functor is only guarantee
+ that \p item cannot be disposed during functor is executing.
+ The functor does not serialize simultaneous access to the set \p item. If such access is
+ possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
+
+ The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
+ can modify both arguments.
The function applies RCU lock internally.
- Returns \p true if \p val is placed into the set, \p false otherwise.
+ The function returns \p true if \p key is found, \p false otherwise.
*/
- bool insert( value_type& val )
+ template <typename Q, typename Func>
+ bool find( Q& key, Func f )
{
- return insert( val, []( value_type& ) {} );
+ return do_find_with( key, key_comparator(), f );
+ }
+ //@cond
+ template <typename Q, typename Func>
+ bool find( Q const& key, Func f )
+ {
+ return do_find_with( key, key_comparator(), f );
}
+ //@endcond
- /// Inserts new node
+ /// Finds the key \p key with comparing functor \p pred
/**
- This function is intended for derived non-intrusive containers.
-
- The function allows to split creating of new item into two part:
- - create item with key only
- - insert new item into the set
- - if inserting is success, calls \p f functor to initialize value-field of \p val.
-
- The functor signature is:
- \code
- void func( value_type& val );
- \endcode
- where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
- \p val no any other changes could be made on this set's item by concurrent threads.
- The user-defined functor is called only if the inserting is success.
-
- RCU \p synchronize method can be called. RCU should not be locked.
+ The function is an analog of \ref cds_intrusive_SkipListSet_rcu_find_func "find(Q&, Func)"
+ but \p cmp is used for key comparison.
+ \p Less functor has the interface like \p std::less.
+ \p cmp must imply the same element order as the comparator used for building the set.
*/
- template <typename Func>
- bool insert( value_type& val, Func f )
+ template <typename Q, typename Less, typename Func>
+ bool find_with( Q& key, Less pred, Func f )
{
- check_deadlock_policy::check();
-
- position pos;
- bool bRet;
+ CDS_UNUSED( pred );
+ return do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(), f );
+ }
+ //@cond
+ template <typename Q, typename Less, typename Func>
+ bool find_with( Q const& key, Less pred, Func f )
+ {
+ CDS_UNUSED( pred );
+ return do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(), f );
+ }
+ //@endcond
- {
- node_type * pNode = node_traits::to_node_ptr( val );
- scoped_node_ptr scp( pNode );
- unsigned int nHeight = pNode->height();
- bool bTowerOk = nHeight > 1 && pNode->get_tower() != nullptr;
- bool bTowerMade = false;
+ /// Checks whether the set contains \p key
+ /**
+ The function searches the item with key equal to \p key
+ and returns \p true if it is found, and \p false otherwise.
- rcu_lock rcuLock;
+ The function applies RCU lock internally.
+ */
+ template <typename Q>
+ bool contains( Q const& key )
+ {
+ return do_find_with( key, key_comparator(), [](value_type& , Q const& ) {} );
+ }
+ //@cond
+ template <typename Q>
+ CDS_DEPRECATED("deprecated, use contains()")
+ bool find( Q const& key )
+ {
+ return contains( key );
+ }
+ //@endcond
- while ( true )
- {
- bool bFound = find_position( val, pos, key_comparator(), true );
- if ( bFound ) {
- // scoped_node_ptr deletes the node tower if we create it
- if ( !bTowerMade )
- scp.release();
+ /// Checks whether the set contains \p key using \p pred predicate for searching
+ /**
+ The function is similar to <tt>contains( key )</tt> but \p pred is used for key comparing.
+ \p Less functor has the interface like \p std::less.
+ \p Less must imply the same element order as the comparator used for building the set.
+ */
+ template <typename Q, typename Less>
+ bool contains( Q const& key, Less pred )
+ {
+ CDS_UNUSED( pred );
+ return do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(), [](value_type& , Q const& ) {} );
+ }
+ //@cond
+ template <typename Q, typename Less>
+ CDS_DEPRECATED("deprecated, use contains()")
+ bool find_with( Q const& key, Less pred )
+ {
+ return contains( key, pred );
+ }
+ //@endcond
- m_Stat.onInsertFailed();
- bRet = false;
- break;
- }
+ /// Finds \p key and return the item found
+ /** \anchor cds_intrusive_SkipListSet_rcu_get
+ The function searches the item with key equal to \p key and returns a \p raw_ptr object pointed to item found.
+ If \p key is not found it returns empty \p raw_ptr.
- if ( !bTowerOk ) {
- build_node( pNode );
- nHeight = pNode->height();
- bTowerMade =
- bTowerOk = true;
- }
+ Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- if ( !insert_at_position( val, pNode, pos, f )) {
- m_Stat.onInsertRetry();
- continue;
- }
+ RCU should be locked before call of this function.
+ Returned item is valid only while RCU is locked:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
+ typename skip_list::raw_ptr pVal;
+ {
+ // Lock RCU
+ skip_list::rcu_lock lock;
- increase_height( nHeight );
- ++m_ItemCounter;
- m_Stat.onAddNode( nHeight );
- m_Stat.onInsertSuccess();
- scp.release();
- bRet = true;
- break;
+ pVal = theList.get( 5 );
+ if ( pVal ) {
+ // Deal with pVal
+ //...
}
}
+ // You can manually release pVal after RCU-locked section
+ pVal.release();
+ \endcode
+ */
+ template <typename Q>
+ raw_ptr get( Q const& key )
+ {
+ assert( gc::is_locked());
- return bRet;
+ position pos;
+ value_type * pFound;
+ if ( do_find_with( key, key_comparator(), [&pFound](value_type& found, Q const& ) { pFound = &found; }, pos ))
+ return raw_ptr( pFound, raw_ptr_disposer( pos ));
+ return raw_ptr( raw_ptr_disposer( pos ));
}
- /// Updates the node
+ /// Finds \p key and return the item found
/**
- The operation performs inserting or changing data with lock-free manner.
-
- If the item \p val is not found in the set, then \p val is inserted into the set
- iff \p bInsert is \p true.
- Otherwise, the functor \p func is called with item found.
- The functor signature is:
- \code
- void func( bool bNew, value_type& item, value_type& val );
- \endcode
- with arguments:
- - \p bNew - \p true if the item has been inserted, \p false otherwise
- - \p item - item of the set
- - \p val - argument \p val passed into the \p %update() function
- If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
- refer to the same thing.
-
- The functor can change non-key fields of the \p item; however, \p func must guarantee
- that during changing no any other modifications could be made on this item by concurrent threads.
-
- RCU \p synchronize method can be called. RCU should not be locked.
-
- Returns std::pair<bool, bool> where \p first is \p true if operation is successful,
- i.e. the node has been inserted or updated,
- \p second is \p true if new item has been added or \p false if the item with \p key
- already exists.
+ The function is an analog of \ref cds_intrusive_SkipListSet_rcu_get "get(Q const&)"
+ but \p pred is used for comparing the keys.
- @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
+ \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
+ in any order.
+ \p pred must imply the same element order as the comparator used for building the set.
*/
- template <typename Func>
- std::pair<bool, bool> update( value_type& val, Func func, bool bInsert = true )
+ template <typename Q, typename Less>
+ raw_ptr get_with( Q const& key, Less pred )
{
- check_deadlock_policy::check();
+ CDS_UNUSED( pred );
+ assert( gc::is_locked());
+ value_type * pFound = nullptr;
position pos;
- std::pair<bool, bool> bRet( true, false );
-
+ if ( do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(),
+ [&pFound](value_type& found, Q const& ) { pFound = &found; }, pos ))
{
- node_type * pNode = node_traits::to_node_ptr( val );
- scoped_node_ptr scp( pNode );
- unsigned int nHeight = pNode->height();
- bool bTowerOk = nHeight > 1 && pNode->get_tower() != nullptr;
- bool bTowerMade = false;
+ return raw_ptr( pFound, raw_ptr_disposer( pos ));
+ }
+ return raw_ptr( raw_ptr_disposer( pos ));
+ }
- rcu_lock rcuLock;
- while ( true )
- {
- bool bFound = find_position( val, pos, key_comparator(), true );
- if ( bFound ) {
- // scoped_node_ptr deletes the node tower if we create it before
- if ( !bTowerMade )
- scp.release();
-
- func( false, *node_traits::to_value_ptr(pos.pCur), val );
- m_Stat.onUpdateExist();
- break;
- }
+ /// Returns item count in the set
+ /**
+ The value returned depends on item counter type provided by \p Traits template parameter.
+ For \p atomicity::empty_item_counter the function always returns 0.
+ Therefore, the function is not suitable for checking the set emptiness, use \p empty()
+ member function for this purpose.
+ */
+ size_t size() const
+ {
+ return m_ItemCounter;
+ }
- if ( !bInsert ) {
- scp.release();
- bRet.first = false;
- break;
- }
+ /// Checks if the set is empty
+ bool empty() const
+ {
+ return m_Head.head()->next( 0 ).load( memory_model::memory_order_relaxed ) == nullptr;
+ }
- if ( !bTowerOk ) {
- build_node( pNode );
- nHeight = pNode->height();
- bTowerMade =
- bTowerOk = true;
- }
+ /// Clears the set (not atomic)
+ /**
+ The function unlink all items from the set.
+ The function is not atomic, thus, in multi-threaded environment with parallel insertions
+ this sequence
+ \code
+ set.clear();
+ assert( set.empty());
+ \endcode
+ the assertion could be raised.
- if ( !insert_at_position( val, pNode, pos, [&func]( value_type& item ) { func( true, item, item ); })) {
- m_Stat.onInsertRetry();
- continue;
- }
+ For each item the \p disposer will be called automatically after unlinking.
+ */
+ void clear()
+ {
+ exempt_ptr ep;
+ while ( (ep = extract_min()));
+ }
- increase_height( nHeight );
- ++m_ItemCounter;
- scp.release();
- m_Stat.onAddNode( nHeight );
- m_Stat.onUpdateNew();
- bRet.second = true;
- break;
- }
- }
+ /// Returns maximum height of skip-list. The max height is a constant for each object and does not exceed 32.
+ static CDS_CONSTEXPR unsigned int max_height() CDS_NOEXCEPT
+ {
+ return c_nMaxHeight;
+ }
- return bRet;
+ /// Returns const reference to internal statistics
+ stat const& statistics() const
+ {
+ return m_Stat;
}
+
+ protected:
//@cond
- template <typename Func>
- CDS_DEPRECATED("ensure() is deprecated, use update()")
- std::pair<bool, bool> ensure( value_type& val, Func func )
+
+ bool is_extracted( marked_node_ptr const p ) const
{
- return update( val, func, true );
+ return ( p.bits() & 2 ) != 0;
}
- //@endcond
- /// Unlinks the item \p val from the set
- /**
- The function searches the item \p val in the set and unlink it from the set
- if it is found and is equal to \p val.
+ void help_remove( int nLevel, node_type* pPred, marked_node_ptr pCur, marked_node_ptr pSucc, position& pos )
+ {
+ marked_node_ptr p( pCur.ptr() );
+ if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
+ memory_model::memory_order_release, atomics::memory_order_relaxed ) )
+ {
+ if ( pCur->level_unlinked()) {
+ if ( !is_extracted( pSucc ) ) {
+ // We cannot free the node at this moment because RCU is locked
+ // Link deleted nodes to a chain to free later
+ pos.dispose( pCur.ptr() );
+ m_Stat.onEraseWhileFind();
+ }
+ else
+ m_Stat.onExtractWhileFind();
+ }
+ }
+ }
- Difference between \p erase() and \p %unlink() functions: \p erase() finds <i>a key</i>
- and deletes the item found. \p %unlink() searches an item by key and deletes it
- only if \p val is an item of that set, i.e. the pointer to item found
- is equal to <tt> &val </tt>.
+ template <typename Q, typename Compare >
+ bool find_position( Q const& val, position& pos, Compare cmp, bool bStopIfFound )
+ {
+ assert( gc::is_locked() );
- RCU \p synchronize method can be called. RCU should not be locked.
+ node_type * pPred;
+ marked_node_ptr pSucc;
+ marked_node_ptr pCur;
+ int nCmp = 1;
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC asynchronously.
+ retry:
+ pPred = m_Head.head();
- The function returns \p true if success and \p false otherwise.
- */
- bool unlink( value_type& val )
- {
- check_deadlock_policy::check();
+ for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
- position pos;
- bool bRet;
+ while ( true ) {
+ pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
+ if ( pCur.bits() ) {
+ // pCur.bits() means that pPred is logically deleted
+ goto retry;
+ }
- {
- rcu_lock l;
+ if ( pCur.ptr() == nullptr ) {
+ // end of the list at level nLevel - goto next level
+ break;
+ }
- if ( !find_position( val, pos, key_comparator(), false )) {
- m_Stat.onUnlinkFailed();
- bRet = false;
- }
- else {
- node_type * pDel = pos.pCur;
- assert( key_comparator()( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+ // pSucc contains deletion mark for pCur
+ pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
- unsigned int nHeight = pDel->height();
+ if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr() )
+ goto retry;
- if ( node_traits::to_value_ptr( pDel ) == &val && try_remove_at( pDel, pos, [](value_type const&) {}, false )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onUnlinkSuccess();
- bRet = true;
+ if ( pSucc.bits() ) {
+ // pCur is marked, i.e. logically deleted.
+ help_remove( nLevel, pPred, pCur, pSucc, pos );
+ goto retry;
}
else {
- m_Stat.onUnlinkFailed();
- bRet = false;
+ nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr() ), val );
+ if ( nCmp < 0 )
+ pPred = pCur.ptr();
+ else if ( nCmp == 0 && bStopIfFound )
+ goto found;
+ else
+ break;
}
}
+
+ // Next level
+ pos.pPrev[nLevel] = pPred;
+ pos.pSucc[nLevel] = pCur.ptr();
}
- return bRet;
+ if ( nCmp != 0 )
+ return false;
+
+ found:
+ pos.pCur = pCur.ptr();
+ return pCur.ptr() && nCmp == 0;
}
- /// Extracts the item from the set with specified \p key
- /** \anchor cds_intrusive_SkipListSet_rcu_extract
- The function searches an item with key equal to \p key in the set,
- unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
- If the item with key equal to \p key is not found the function returns an empty \p exempt_ptr.
+ bool find_min_position( position& pos )
+ {
+ assert( gc::is_locked() );
- Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ node_type * pPred;
+ marked_node_ptr pSucc;
+ marked_node_ptr pCur;
- RCU \p synchronize method can be called. RCU should NOT be locked.
- The function does not call the disposer for the item found.
- The disposer will be implicitly invoked when the returned object is destroyed or when
- its \p release() member function is called.
- Example:
- \code
- typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
- skip_list theList;
- // ...
+ retry:
+ pPred = m_Head.head();
- typename skip_list::exempt_ptr ep( theList.extract( 5 ));
- if ( ep ) {
- // Deal with ep
- //...
+ for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
- // Dispose returned item.
- ep.release();
- }
- \endcode
- */
- template <typename Q>
- exempt_ptr extract( Q const& key )
- {
- return exempt_ptr( do_extract( key ));
- }
+ pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
+ // pCur.bits() means that pPred is logically deleted
+ // head cannot be deleted
+ assert( pCur.bits() == 0 );
- /// Extracts the item from the set with comparing functor \p pred
- /**
- The function is an analog of \p extract(Q const&) but \p pred predicate is used for key comparing.
- \p Less has the interface like \p std::less.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- exempt_ptr extract_with( Q const& key, Less pred )
- {
- return exempt_ptr( do_extract_with( key, pred ));
- }
+ if ( pCur.ptr() ) {
- /// Extracts an item with minimal key from the list
- /**
- The function searches an item with minimal key, unlinks it, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
- If the skip-list is empty the function returns an empty \p exempt_ptr.
+ // pSucc contains deletion mark for pCur
+ pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
- RCU \p synchronize method can be called. RCU should NOT be locked.
- The function does not call the disposer for the item found.
- The disposer will be implicitly invoked when the returned object is destroyed or when
- its \p release() member function is manually called.
- Example:
- \code
- typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
- skip_list theList;
- // ...
+ if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr() )
+ goto retry;
- typename skip_list::exempt_ptr ep(theList.extract_min());
- if ( ep ) {
- // Deal with ep
- //...
+ if ( pSucc.bits() ) {
+ // pCur is marked, i.e. logically deleted.
+ help_remove( nLevel, pPred, pCur, pSucc, pos );
+ goto retry;
+ }
+ }
- // Dispose returned item.
- ep.release();
+ // Next level
+ pos.pPrev[nLevel] = pPred;
+ pos.pSucc[nLevel] = pCur.ptr();
}
- \endcode
+ return ( pos.pCur = pCur.ptr() ) != nullptr;
+ }
- @note Due the concurrent nature of the list, the function extracts <i>nearly</i> minimum key.
- It means that the function gets leftmost item and tries to unlink it.
- During unlinking, a concurrent thread may insert an item with key less than leftmost item's key.
- So, the function returns the item with minimum key at the moment of list traversing.
- */
- exempt_ptr extract_min()
+ bool find_max_position( position& pos )
{
- return exempt_ptr( do_extract_min());
- }
+ assert( gc::is_locked() );
- /// Extracts an item with maximal key from the list
- /**
- The function searches an item with maximal key, unlinks it, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
- If the skip-list is empty the function returns an empty \p exempt_ptr.
+ node_type * pPred;
+ marked_node_ptr pSucc;
+ marked_node_ptr pCur;
- RCU \p synchronize method can be called. RCU should NOT be locked.
- The function does not call the disposer for the item found.
- The disposer will be implicitly invoked when the returned object is destroyed or when
- its \p release() member function is manually called.
- Example:
- \code
- typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
- skip_list theList;
- // ...
+ retry:
+ pPred = m_Head.head();
- typename skip_list::exempt_ptr ep( theList.extract_max());
- if ( ep ) {
- // Deal with ep
- //...
- // Dispose returned item.
- ep.release();
+ for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
+
+ while ( true ) {
+ pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
+ if ( pCur.bits() ) {
+ // pCur.bits() means that pPred is logically deleted
+ goto retry;
+ }
+
+ if ( pCur.ptr() == nullptr ) {
+ // end of the list at level nLevel - goto next level
+ break;
+ }
+
+ // pSucc contains deletion mark for pCur
+ pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
+
+ if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr() )
+ goto retry;
+
+ if ( pSucc.bits() ) {
+ // pCur is marked, i.e. logically deleted.
+ help_remove( nLevel, pPred, pCur, pSucc, pos );
+ goto retry;
+ }
+ else {
+ if ( !pSucc.ptr() )
+ break;
+
+ pPred = pCur.ptr();
+ }
+ }
+
+ // Next level
+ pos.pPrev[nLevel] = pPred;
+ pos.pSucc[nLevel] = pCur.ptr();
}
- \endcode
- @note Due the concurrent nature of the list, the function extracts <i>nearly</i> maximal key.
- It means that the function gets rightmost item and tries to unlink it.
- During unlinking, a concurrent thread can insert an item with key greater than rightmost item's key.
- So, the function returns the item with maximum key at the moment of list traversing.
- */
- exempt_ptr extract_max()
- {
- return exempt_ptr( do_extract_max());
+ return ( pos.pCur = pCur.ptr() ) != nullptr;
}
- /// Deletes the item from the set
- /** \anchor cds_intrusive_SkipListSet_rcu_erase
- The function searches an item with key equal to \p key in the set,
- unlinks it from the set, and returns \p true.
- If the item with key equal to \p key is not found the function return \p false.
+ template <typename Func>
+ bool insert_at_position( value_type& val, node_type * pNode, position& pos, Func f )
+ {
+ assert( gc::is_locked() );
- Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ unsigned int const nHeight = pNode->height();
+ pNode->clear_tower();
- RCU \p synchronize method can be called. RCU should not be locked.
- */
- template <typename Q>
- bool erase( const Q& key )
- {
- return do_erase( key, key_comparator(), [](value_type const&) {} );
+ // Insert at level 0
+ {
+ marked_node_ptr p( pos.pSucc[0] );
+ pNode->next( 0 ).store( p, memory_model::memory_order_relaxed );
+ if ( !pos.pPrev[0]->next( 0 ).compare_exchange_strong( p, marked_node_ptr( pNode ), memory_model::memory_order_release, atomics::memory_order_relaxed ) ) {
+ return false;
+ }
+
+ f( val );
+ }
+
+ // Insert at level 1..max
+ for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel ) {
+ marked_node_ptr p;
+ while ( true ) {
+ marked_node_ptr pSucc( pos.pSucc[nLevel] );
+
+ // Set pNode->next
+ // pNode->next must be null but can have a "logical deleted" flag if another thread is removing pNode right now
+ if ( !pNode->next( nLevel ).compare_exchange_strong( p, pSucc,
+ memory_model::memory_order_acq_rel, atomics::memory_order_acquire ))
+ {
+ // pNode has been marked as removed while we are inserting it
+ // Stop inserting
+ assert( p.bits() != 0 );
+
+ if ( pNode->level_unlinked( nHeight - nLevel ) && p.bits() == 1 ) {
+ pos.dispose( pNode );
+ m_Stat.onEraseWhileInsert();
+ }
+ else
+ m_Stat.onLogicDeleteWhileInsert();
+
+ return true;
+ }
+ p = pSucc;
+
+ // Link pNode into the list at nLevel
+ if ( pos.pPrev[nLevel]->next( nLevel ).compare_exchange_strong( pSucc, marked_node_ptr( pNode ),
+ memory_model::memory_order_release, atomics::memory_order_relaxed ))
+ {
+ // go to next level
+ break;
+ }
+
+ // Renew insert position
+ m_Stat.onRenewInsertPosition();
+ if ( !find_position( val, pos, key_comparator(), false ) ) {
+ // The node has been deleted while we are inserting it
+ m_Stat.onNotFoundWhileInsert();
+ return true;
+ }
+ }
+ }
+ return true;
}
- /// Delete the item from the set with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_rcu_erase "erase(Q const&)"
- but \p pred predicate is used for key comparing.
- \p Less has the interface like \p std::less.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- bool erase_with( const Q& key, Less pred )
+ template <typename Func>
+ bool try_remove_at( node_type * pDel, position& pos, Func f, bool bExtract )
{
- CDS_UNUSED( pred );
- return do_erase( key, cds::opt::details::make_comparator_from_less<Less>(), [](value_type const&) {} );
- }
+ assert( pDel != nullptr );
+ assert( gc::is_locked() );
- /// Deletes the item from the set
- /** \anchor cds_intrusive_SkipListSet_rcu_erase_func
- The function searches an item with key equal to \p key in the set,
- call \p f functor with item found, unlinks it from the set, and returns \p true.
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC asynchronously.
+ marked_node_ptr pSucc;
+ back_off bkoff;
- The \p Func interface is
- \code
- struct functor {
- void operator()( value_type const& item );
- };
- \endcode
- If the item with key equal to \p key is not found the function return \p false.
+ unsigned const nMask = bExtract ? 3u : 1u;
- Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ // logical deletion (marking)
+ for ( unsigned int nLevel = pDel->height() - 1; nLevel > 0; --nLevel ) {
+ pSucc = pDel->next( nLevel ).load( memory_model::memory_order_relaxed );
+ if ( pSucc.bits() == 0 ) {
+ bkoff.reset();
+ while ( !pDel->next( nLevel ).compare_exchange_weak( pSucc, pSucc | nMask,
+ memory_model::memory_order_release, atomics::memory_order_acquire ))
+ {
+ if ( pSucc.bits() == 0 ) {
+ bkoff();
+ m_Stat.onMarkFailed();
+ }
+ else if ( pSucc.bits() != nMask )
+ return false;
+ }
+ }
+ }
- RCU \p synchronize method can be called. RCU should not be locked.
- */
- template <typename Q, typename Func>
- bool erase( Q const& key, Func f )
- {
- return do_erase( key, key_comparator(), f );
+ marked_node_ptr p( pDel->next( 0 ).load( memory_model::memory_order_relaxed ).ptr() );
+ while ( true ) {
+ if ( pDel->next( 0 ).compare_exchange_strong( p, p | nMask, memory_model::memory_order_release, atomics::memory_order_acquire ))
+ {
+ f( *node_traits::to_value_ptr( pDel ) );
+
+ // physical deletion
+ // try fast erase
+ p = pDel;
+ unsigned nCount = 0;
+ for ( int nLevel = static_cast<int>( pDel->height() - 1 ); nLevel >= 0; --nLevel ) {
+
+ pSucc = pDel->next( nLevel ).load( memory_model::memory_order_relaxed );
+ if ( !pos.pPrev[nLevel]->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr()),
+ memory_model::memory_order_acq_rel, atomics::memory_order_acquire ) )
+ {
+ // Do slow erase
+ if ( nCount ) {
+ if ( pDel->level_unlinked( nCount )) {
+ if ( p.bits() == 1 ) {
+ pos.dispose( pDel );
+ m_Stat.onFastEraseHelped();
+ }
+ else
+ m_Stat.onFastExtractHelped();
+ return true;
+ }
+ }
+
+ // Make slow erase
+ find_position( *node_traits::to_value_ptr( pDel ), pos, key_comparator(), false );
+ if ( bExtract )
+ m_Stat.onSlowExtract();
+ else
+ m_Stat.onSlowErase();
+
+ return true;
+ }
+ ++nCount;
+ }
+
+ if ( !bExtract ) {
+ // We cannot free the node at this moment since RCU is locked
+ // Link deleted nodes to a chain to free later
+ pos.dispose( pDel );
+ m_Stat.onFastErase();
+ }
+ else
+ m_Stat.onFastExtract();
+ return true;
+ }
+ else if ( p.bits() ) {
+ // Another thread is deleting pDel right now
+ return false;
+ }
+
+ m_Stat.onEraseRetry();
+ bkoff();
+ }
}
- /// Delete the item from the set with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_rcu_erase_func "erase(Q const&, Func)"
- but \p pred predicate is used for key comparing.
- \p Less has the interface like \p std::less.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less, typename Func>
- bool erase_with( Q const& key, Less pred, Func f )
+ enum finsd_fastpath_result {
+ find_fastpath_found,
+ find_fastpath_not_found,
+ find_fastpath_abort
+ };
+ template <typename Q, typename Compare, typename Func>
+ finsd_fastpath_result find_fastpath( Q& val, Compare cmp, Func f ) const
{
- CDS_UNUSED( pred );
- return do_erase( key, cds::opt::details::make_comparator_from_less<Less>(), f );
- }
+ node_type * pPred;
+ marked_node_ptr pCur;
+ marked_node_ptr pSucc;
+ marked_node_ptr pNull;
- /// Finds \p key
- /** @anchor cds_intrusive_SkipListSet_rcu_find_func
- The function searches the item with key equal to \p key and calls the functor \p f for item found.
- The interface of \p Func functor is:
- \code
- struct functor {
- void operator()( value_type& item, Q& key );
- };
- \endcode
- where \p item is the item found, \p key is the <tt>find</tt> function argument.
+ back_off bkoff;
+ unsigned attempt = 0;
- The functor can change non-key fields of \p item. Note that the functor is only guarantee
- that \p item cannot be disposed during functor is executing.
- The functor does not serialize simultaneous access to the set \p item. If such access is
- possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
+ try_again:
+ pPred = m_Head.head();
+ for ( int nLevel = static_cast<int>( m_nHeight.load( memory_model::memory_order_relaxed ) - 1 ); nLevel >= 0; --nLevel ) {
+ pCur = pPred->next( nLevel ).load( memory_model::memory_order_acquire );
+ if ( pCur == pNull )
+ continue;
- The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
- can modify both arguments.
+ while ( pCur != pNull ) {
+ if ( pCur.bits() ) {
+ // pPrev is being removed
+ if ( ++attempt < 4 ) {
+ bkoff();
+ goto try_again;
+ }
- The function applies RCU lock internally.
+ return find_fastpath_abort;
+ }
- The function returns \p true if \p key is found, \p false otherwise.
- */
- template <typename Q, typename Func>
- bool find( Q& key, Func f )
+ if ( pCur.ptr() ) {
+ int nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr() ), val );
+ if ( nCmp < 0 ) {
+ pPred = pCur.ptr();
+ pCur = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
+ }
+ else if ( nCmp == 0 ) {
+ // found
+ f( *node_traits::to_value_ptr( pCur.ptr() ), val );
+ return find_fastpath_found;
+ }
+ else // pCur > val - go down
+ break;
+ }
+ }
+ }
+
+ return find_fastpath_not_found;
+ }
+
+ template <typename Q, typename Compare, typename Func>
+ bool find_slowpath( Q& val, Compare cmp, Func f, position& pos )
{
- return do_find_with( key, key_comparator(), f );
+ if ( find_position( val, pos, cmp, true ) ) {
+ assert( cmp( *node_traits::to_value_ptr( pos.pCur ), val ) == 0 );
+
+ f( *node_traits::to_value_ptr( pos.pCur ), val );
+ return true;
+ }
+ else
+ return false;
}
- //@cond
- template <typename Q, typename Func>
- bool find( Q const& key, Func f )
+
+ template <typename Q, typename Compare, typename Func>
+ bool do_find_with( Q& val, Compare cmp, Func f )
{
- return do_find_with( key, key_comparator(), f );
+ position pos;
+ return do_find_with( val, cmp, f, pos );
}
- //@endcond
- /// Finds the key \p key with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_rcu_find_func "find(Q&, Func)"
- but \p cmp is used for key comparison.
- \p Less functor has the interface like \p std::less.
- \p cmp must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less, typename Func>
- bool find_with( Q& key, Less pred, Func f )
+ template <typename Q, typename Compare, typename Func>
+ bool do_find_with( Q& val, Compare cmp, Func f, position& pos )
{
- CDS_UNUSED( pred );
- return do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(), f );
+ bool bRet;
+
+ {
+ rcu_lock l;
+
+ switch ( find_fastpath( val, cmp, f ) ) {
+ case find_fastpath_found:
+ m_Stat.onFindFastSuccess();
+ return true;
+ case find_fastpath_not_found:
+ m_Stat.onFindFastFailed();
+ return false;
+ default:
+ break;
+ }
+
+ if ( find_slowpath( val, cmp, f, pos ) ) {
+ m_Stat.onFindSlowSuccess();
+ bRet = true;
+ }
+ else {
+ m_Stat.onFindSlowFailed();
+ bRet = false;
+ }
+ }
+ return bRet;
}
- //@cond
- template <typename Q, typename Less, typename Func>
- bool find_with( Q const& key, Less pred, Func f )
+
+ template <typename Q, typename Compare, typename Func>
+ bool do_erase( Q const& val, Compare cmp, Func f )
{
- CDS_UNUSED( pred );
- return do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(), f );
- }
- //@endcond
+ check_deadlock_policy::check();
- /// Checks whether the set contains \p key
- /**
- The function searches the item with key equal to \p key
- and returns \p true if it is found, and \p false otherwise.
+ position pos;
+ bool bRet;
- The function applies RCU lock internally.
- */
- template <typename Q>
- bool contains( Q const& key )
- {
- return do_find_with( key, key_comparator(), [](value_type& , Q const& ) {} );
- }
- //@cond
- template <typename Q>
- CDS_DEPRECATED("deprecated, use contains()")
- bool find( Q const& key )
- {
- return contains( key );
- }
- //@endcond
+ {
+ rcu_lock rcuLock;
- /// Checks whether the set contains \p key using \p pred predicate for searching
- /**
- The function is similar to <tt>contains( key )</tt> but \p pred is used for key comparing.
- \p Less functor has the interface like \p std::less.
- \p Less must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- bool contains( Q const& key, Less pred )
- {
- CDS_UNUSED( pred );
- return do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(), [](value_type& , Q const& ) {} );
+ if ( !find_position( val, pos, cmp, false ) ) {
+ m_Stat.onEraseFailed();
+ bRet = false;
+ }
+ else {
+ node_type * pDel = pos.pCur;
+ assert( cmp( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+
+ unsigned int nHeight = pDel->height();
+ if ( try_remove_at( pDel, pos, f, false ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onEraseSuccess();
+ bRet = true;
+ }
+ else {
+ m_Stat.onEraseFailed();
+ bRet = false;
+ }
+ }
+ }
+
+ return bRet;
}
- //@cond
- template <typename Q, typename Less>
- CDS_DEPRECATED("deprecated, use contains()")
- bool find_with( Q const& key, Less pred )
+
+ template <typename Q, typename Compare>
+ value_type * do_extract_key( Q const& key, Compare cmp, position& pos )
{
- return contains( key, pred );
- }
- //@endcond
+ // RCU should be locked!!!
+ assert( gc::is_locked() );
- /// Finds \p key and return the item found
- /** \anchor cds_intrusive_SkipListSet_rcu_get
- The function searches the item with key equal to \p key and returns a \p raw_ptr object pointed to item found.
- If \p key is not found it returns empty \p raw_ptr.
+ node_type * pDel;
- Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ if ( !find_position( key, pos, cmp, false ) ) {
+ m_Stat.onExtractFailed();
+ pDel = nullptr;
+ }
+ else {
+ pDel = pos.pCur;
+ assert( cmp( *node_traits::to_value_ptr( pDel ), key ) == 0 );
- RCU should be locked before call of this function.
- Returned item is valid only while RCU is locked:
- \code
- typedef cds::intrusive::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
- skip_list theList;
- // ...
- typename skip_list::raw_ptr pVal;
- {
- // Lock RCU
- skip_list::rcu_lock lock;
+ unsigned int const nHeight = pDel->height();
- pVal = theList.get( 5 );
- if ( pVal ) {
- // Deal with pVal
- //...
+ if ( try_remove_at( pDel, pos, []( value_type const& ) {}, true ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onExtractSuccess();
+ }
+ else {
+ m_Stat.onExtractFailed();
+ pDel = nullptr;
}
}
- // You can manually release pVal after RCU-locked section
- pVal.release();
- \endcode
- */
+
+ return pDel ? node_traits::to_value_ptr( pDel ) : nullptr;
+ }
+
template <typename Q>
- raw_ptr get( Q const& key )
+ value_type * do_extract( Q const& key )
{
- assert( gc::is_locked());
-
+ check_deadlock_policy::check();
+ value_type * pDel = nullptr;
position pos;
- value_type * pFound;
- if ( do_find_with( key, key_comparator(), [&pFound](value_type& found, Q const& ) { pFound = &found; }, pos ))
- return raw_ptr( pFound, raw_ptr_disposer( pos ));
- return raw_ptr( raw_ptr_disposer( pos ));
- }
+ {
+ rcu_lock l;
+ pDel = do_extract_key( key, key_comparator(), pos );
+ }
- /// Finds \p key and return the item found
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_rcu_get "get(Q const&)"
- but \p pred is used for comparing the keys.
+ return pDel;
+ }
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
template <typename Q, typename Less>
- raw_ptr get_with( Q const& key, Less pred )
+ value_type * do_extract_with( Q const& key, Less pred )
{
CDS_UNUSED( pred );
- assert( gc::is_locked());
-
- value_type * pFound = nullptr;
+ check_deadlock_policy::check();
+ value_type * pDel = nullptr;
position pos;
- if ( do_find_with( key, cds::opt::details::make_comparator_from_less<Less>(),
- [&pFound](value_type& found, Q const& ) { pFound = &found; }, pos ))
{
- return raw_ptr( pFound, raw_ptr_disposer( pos ));
+ rcu_lock l;
+ pDel = do_extract_key( key, cds::opt::details::make_comparator_from_less<Less>(), pos );
}
- return raw_ptr( raw_ptr_disposer( pos ));
- }
- /// Returns item count in the set
- /**
- The value returned depends on item counter type provided by \p Traits template parameter.
- For \p atomicity::empty_item_counter the function always returns 0.
- Therefore, the function is not suitable for checking the set emptiness, use \p empty()
- member function for this purpose.
- */
- size_t size() const
- {
- return m_ItemCounter;
+ return pDel;
}
- /// Checks if the set is empty
- bool empty() const
+ value_type * do_extract_min()
{
- return m_Head.head()->next( 0 ).load( memory_model::memory_order_relaxed ) == nullptr;
- }
+ assert( !gc::is_locked() );
- /// Clears the set (not atomic)
- /**
- The function unlink all items from the set.
- The function is not atomic, thus, in multi-threaded environment with parallel insertions
- this sequence
- \code
- set.clear();
- assert( set.empty());
- \endcode
- the assertion could be raised.
+ position pos;
+ node_type * pDel;
- For each item the \p disposer will be called automatically after unlinking.
- */
- void clear()
- {
- exempt_ptr ep;
- while ( (ep = extract_min()));
+ {
+ rcu_lock l;
+
+ if ( !find_min_position( pos ) ) {
+ m_Stat.onExtractMinFailed();
+ pDel = nullptr;
+ }
+ else {
+ pDel = pos.pCur;
+ unsigned int const nHeight = pDel->height();
+
+ if ( try_remove_at( pDel, pos, []( value_type const& ) {}, true ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onExtractMinSuccess();
+ }
+ else {
+ m_Stat.onExtractMinFailed();
+ pDel = nullptr;
+ }
+ }
+ }
+
+ return pDel ? node_traits::to_value_ptr( pDel ) : nullptr;
}
- /// Returns maximum height of skip-list. The max height is a constant for each object and does not exceed 32.
- static CDS_CONSTEXPR unsigned int max_height() CDS_NOEXCEPT
+ value_type * do_extract_max()
{
- return c_nMaxHeight;
+ assert( !gc::is_locked() );
+
+ position pos;
+ node_type * pDel;
+
+ {
+ rcu_lock l;
+
+ if ( !find_max_position( pos ) ) {
+ m_Stat.onExtractMaxFailed();
+ pDel = nullptr;
+ }
+ else {
+ pDel = pos.pCur;
+ unsigned int const nHeight = pDel->height();
+
+ if ( try_remove_at( pDel, pos, []( value_type const& ) {}, true ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onExtractMaxSuccess();
+ }
+ else {
+ m_Stat.onExtractMaxFailed();
+ pDel = nullptr;
+ }
+ }
+ }
+
+ return pDel ? node_traits::to_value_ptr( pDel ) : nullptr;
}
- /// Returns const reference to internal statistics
- stat const& statistics() const
+ void increase_height( unsigned int nHeight )
{
- return m_Stat;
+ unsigned int nCur = m_nHeight.load( memory_model::memory_order_relaxed );
+ if ( nCur < nHeight )
+ m_nHeight.compare_exchange_strong( nCur, nHeight, memory_model::memory_order_release, atomics::memory_order_relaxed );
}
+ //@endcond
};
}} // namespace cds::intrusive
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