// c_nMaxHeight * 2 - pPred/pSucc guards
// + 1 - for erase, unlink
// + 1 - for clear
- static size_t const c_nHazardPtrCount = c_nMaxHeight * 2 + 2; ///< Count of hazard pointer required for the skip-list
+ // + 1 - for help_remove
+ static size_t const c_nHazardPtrCount = c_nMaxHeight * 2 + 3; ///< Count of hazard pointer required for the skip-list
protected:
typedef typename node_type::atomic_marked_ptr atomic_node_ptr; ///< Atomic marked node pointer
node_type * pNode = node_traits::to_node_ptr( val );
scoped_node_ptr scp( pNode );
unsigned int nHeight = pNode->height();
- bool bTowerOk = pNode->has_tower(); // nHeight > 1 && pNode->get_tower() != nullptr;
+ bool bTowerOk = pNode->has_tower();
bool bTowerMade = false;
position pos;
disposer()( pVal );
}
+ void help_remove( int nLevel, node_type* pPred, marked_node_ptr pCur, marked_node_ptr pSucc )
+ {
+ typename gc::Guard succ_guard;
+ marked_node_ptr succ = succ_guard.protect( pCur->next( nLevel ), gc_protect );
+
+ typename node_type::state state = node_type::clean;
+ if ( succ == pSucc && ( succ.ptr() == nullptr ||
+ succ.ptr()->set_state( state, node_type::hand_off, memory_model::memory_order_acquire )))
+ {
+ marked_node_ptr p( pCur.ptr() );
+ if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( succ.ptr()),
+ memory_model::memory_order_acquire, atomics::memory_order_relaxed ) )
+ {
+ if ( nLevel == 0 ) {
+ gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
+ m_Stat.onEraseWhileFind();
+ }
+ }
+
+ if ( succ.ptr() )
+ succ.ptr()->clear_state( memory_model::memory_order_release );
+ }
+ else
+ m_Stat.onNodeHandOffFailed();
+ }
+
template <typename Q, typename Compare >
bool find_position( Q const& val, position& pos, Compare cmp, bool bStopIfFound )
{
goto retry;
if ( pSucc.bits() ) {
- // pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr() );
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
- memory_model::memory_order_acquire, atomics::memory_order_relaxed ) )
- {
- if ( nLevel == 0 ) {
- gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
- m_Stat.onEraseWhileFind();
- }
- }
+ // pCur is marked, i.e. logically deleted
+ // try to help deleting pCur if pSucc is not being deleted
+ help_remove( nLevel, pPred, pCur, pSucc );
goto retry;
}
else {
if ( pSucc.bits() ) {
// pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr() );
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
- memory_model::memory_order_acquire, atomics::memory_order_relaxed ) )
- {
- if ( nLevel == 0 ) {
- gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
- m_Stat.onEraseWhileFind();
- }
- }
+ // try to help deleting pCur if pSucc is not being deleted
+ help_remove( nLevel, pPred, pCur, pSucc );
goto retry;
}
}
if ( pSucc.bits() ) {
// pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr() );
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
- memory_model::memory_order_acquire, atomics::memory_order_relaxed ) )
- {
- if ( nLevel == 0 ) {
- gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
- m_Stat.onEraseWhileFind();
- }
- }
+ // try to help deleting pCur if pSucc is not being deleted
+ help_remove( nLevel, pPred, pCur, pSucc );
goto retry;
}
else {
// Insert at level 0
{
- marked_node_ptr p( pos.pSucc[0] );
+ node_type* succ = pos.pSucc[0];
+ typename node_type::state state = node_type::clean;
+ if ( succ != nullptr && !succ->set_state( state, node_type::hand_off, memory_model::memory_order_acquire ) )
+ return false;
+
+ marked_node_ptr p( succ );
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 ) )
+ if ( !pos.pPrev[0]->next( 0 ).compare_exchange_strong( p, marked_node_ptr( pNode ), memory_model::memory_order_release, atomics::memory_order_relaxed ) ) {
+ if ( succ )
+ succ->clear_state( memory_model::memory_order_release );
return false;
+ }
+ if ( succ )
+ succ->clear_state( memory_model::memory_order_release );
f( val );
}
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_release, 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;
+ typename node_type::state state = node_type::clean;
+ node_type* succ = pos.pSucc[nLevel];
+ if ( succ == nullptr ||
+ succ->set_state( state, node_type::hand_off, memory_model::memory_order_acquire ) )
+ {
+ marked_node_ptr q( succ );
+ if ( !pNode->next( nLevel ).compare_exchange_strong( p, q, memory_model::memory_order_release, atomics::memory_order_relaxed )) {
+ // pNode has been marked as removed while we are inserting it
+ // Stop inserting
+ if ( succ )
+ succ->clear_state( memory_model::memory_order_release );
+ assert( p.bits() );
+ m_Stat.onLogicDeleteWhileInsert();
+ return true;
+ }
+
+ p = q;
+ bool const result = pos.pPrev[nLevel]->next( nLevel ).compare_exchange_strong( q, marked_node_ptr( pNode ),
+ memory_model::memory_order_release, atomics::memory_order_relaxed );
+ if ( succ )
+ succ->clear_state( memory_model::memory_order_release );
+ if ( result )
+ break;
}
- 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;
// Renew insert position
m_Stat.onRenewInsertPosition();
{
assert( pDel != nullptr );
+ // set "removed" node state
+ {
+ back_off bkoff;
+ typename node_type::state state = node_type::clean;
+ while ( !( pDel->set_state( state, node_type::removed, memory_model::memory_order_release )
+ || state == node_type::removed ))
+ {
+ bkoff();
+ }
+ }
+
marked_node_ptr pSucc;
// logical deletion (marking)
position pos;
guarded_ptr gp;
- for ( ;;) {
+ for (;;) {
if ( !find_position( val, pos, cmp, false ) ) {
m_Stat.onExtractFailed();
return guarded_ptr();