IterableList: fixed a complex bug that can be called "ABA problem of null pointer"
[libcds.git] / cds / intrusive / segmented_queue.h
index dfb93882d32f6dd7b313ba87c10d91b68b49d8b7..a463751fdb817d206c88d834790815a5808d83cf 100644 (file)
@@ -5,7 +5,7 @@
 
     Source code repo: http://github.com/khizmax/libcds/
     Download: http://sourceforge.net/projects/libcds/files/
-    
+
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions are met:
 
@@ -25,7 +25,7 @@
     SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.     
+    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
 #ifndef CDSLIB_INTRUSIVE_SEGMENTED_QUEUE_H
@@ -152,7 +152,7 @@ namespace cds { namespace intrusive {
             all other \p %segmented_queue::traits members left unchanged.
 
             \p Options are:
-            - \p opt::disposer - the functor used for dispose removed items.
+            - \p opt::disposer - the functor used to dispose removed items.
             - \p opt::stat - internal statistics, possible type: \p segmented_queue::stat, \p segmented_queue::empty_stat (the default)
             - \p opt::item_counter - item counting feature. Note that \p atomicity::empty_item_counetr is not suitable
                 for segmented queue.
@@ -324,7 +324,7 @@ namespace cds { namespace intrusive {
 
             ~segment_list()
             {
-                m_List.clear_and_dispose( gc_segment_disposer() );
+                m_List.clear_and_dispose( gc_segment_disposer());
             }
 
             segment * head( typename gc::Guard& guard )
@@ -343,7 +343,7 @@ namespace cds { namespace intrusive {
                 // The lock should be held
                 cell const * pLastCell = s.cells + quasi_factor();
                 for ( cell const * pCell = s.cells; pCell < pLastCell; ++pCell ) {
-                    if ( !pCell->data.load( memory_model::memory_order_relaxed ).all() )
+                    if ( !pCell->data.load( memory_model::memory_order_relaxed ).all())
                         return false;
                 }
                 return true;
@@ -353,7 +353,7 @@ namespace cds { namespace intrusive {
                 // The lock should be held
                 cell const * pLastCell = s.cells + quasi_factor();
                 for ( cell const * pCell = s.cells; pCell < pLastCell; ++pCell ) {
-                    if ( !pCell->data.load( memory_model::memory_order_relaxed ).bits() )
+                    if ( !pCell->data.load( memory_model::memory_order_relaxed ).bits())
                         return false;
                 }
                 return true;
@@ -371,15 +371,17 @@ namespace cds { namespace intrusive {
                 if ( !m_List.empty() && ( pTail != &m_List.back() || get_version(pTail) != m_List.back().version )) {
                     m_pTail.store( &m_List.back(), memory_model::memory_order_relaxed );
 
-                    return guard.assign( &m_List.back() );
+                    return guard.assign( &m_List.back());
                 }
 
-                assert( m_List.empty() || populated( m_List.back() ));
+#           ifdef _DEBUG
+                assert( m_List.empty() || populated( m_List.back()));
+#           endif
 
                 segment * pNew = allocate_segment();
                 m_Stat.onSegmentCreated();
 
-                if ( m_List.empty() )
+                if ( m_List.empty())
                     m_pHead.store( pNew, memory_model::memory_order_release );
                 m_List.push_back( *pNew );
                 m_pTail.store( pNew, memory_model::memory_order_release );
@@ -395,7 +397,7 @@ namespace cds { namespace intrusive {
                 {
                     scoped_lock l( m_Lock );
 
-                    if ( m_List.empty() ) {
+                    if ( m_List.empty()) {
                         m_pTail.store( nullptr, memory_model::memory_order_relaxed );
                         m_pHead.store( nullptr, memory_model::memory_order_relaxed );
                         return guard.assign( nullptr );
@@ -403,18 +405,20 @@ namespace cds { namespace intrusive {
 
                     if ( pHead != &m_List.front() || get_version(pHead) != m_List.front().version ) {
                         m_pHead.store( &m_List.front(), memory_model::memory_order_relaxed );
-                        return guard.assign( &m_List.front() );
+                        return guard.assign( &m_List.front());
                     }
 
-                    assert( exhausted(m_List.front()) );
+#           ifdef _DEBUG
+                    assert( exhausted( m_List.front()));
+#           endif
 
                     m_List.pop_front();
-                    if ( m_List.empty() ) {
+                    if ( m_List.empty()) {
                         pRet = guard.assign( nullptr );
                         m_pTail.store( nullptr, memory_model::memory_order_relaxed );
                     }
                     else
-                        pRet = guard.assign( &m_List.front() );
+                        pRet = guard.assign( &m_List.front());
                     m_pHead.store( pRet, memory_model::memory_order_release );
                 }
 
@@ -439,7 +443,7 @@ namespace cds { namespace intrusive {
 
             segment * allocate_segment()
             {
-                return segment_allocator().NewBlock( sizeof(segment) + sizeof(cell) * m_nQuasiFactor, quasi_factor() );
+                return segment_allocator().NewBlock( sizeof(segment) + sizeof(cell) * m_nQuasiFactor, quasi_factor());
             }
 
             static void free_segment( segment * pSegment )
@@ -493,7 +497,7 @@ namespace cds { namespace intrusive {
                 assert( pTailSegment );
             }
 
-            permutation_generator gen( quasi_factor() );
+            permutation_generator gen( quasi_factor());
 
             // First, increment item counter.
             // We sure that the item will be enqueued
@@ -506,7 +510,7 @@ namespace cds { namespace intrusive {
                 do {
                     typename permutation_generator::integer_type i = gen;
                     CDS_DEBUG_ONLY( ++nLoopCount );
-                    if ( pTailSegment->cells[i].data.load(memory_model::memory_order_relaxed).all() ) {
+                    if ( pTailSegment->cells[i].data.load(memory_model::memory_order_relaxed).all()) {
                         // Cell is not empty, go next
                         m_Stat.onPushPopulated();
                     }
@@ -520,10 +524,10 @@ namespace cds { namespace intrusive {
                             m_Stat.onPush();
                             return true;
                         }
-                        assert( nullCell.ptr() );
+                        assert( nullCell.ptr());
                         m_Stat.onPushContended();
                     }
-                } while ( gen.next() );
+                } while ( gen.next());
 
                 assert( nLoopCount == quasi_factor());
 
@@ -599,12 +603,12 @@ namespace cds { namespace intrusive {
 
         /// Clear the queue
         /**
-            The function repeatedly calls \ref dequeue until it returns \p nullptr.
+            The function repeatedly calls \p dequeue() until it returns \p nullptr.
             The disposer specified in \p Traits template argument is called for each removed item.
         */
         void clear()
         {
-            clear_with( disposer() );
+            clear_with( disposer());
         }
 
         /// Clear the queue
@@ -616,9 +620,9 @@ namespace cds { namespace intrusive {
         void clear_with( Disposer )
         {
             typename gc::Guard itemGuard;
-            while ( do_dequeue( itemGuard ) ) {
-                assert( itemGuard.template get<value_type>() );
-                gc::template retire<Disposer>( itemGuard.template get<value_type>() );
+            while ( do_dequeue( itemGuard )) {
+                assert( itemGuard.template get<value_type>());
+                gc::template retire<Disposer>( itemGuard.template get<value_type>());
                 itemGuard.clear();
             }
         }
@@ -651,7 +655,7 @@ namespace cds { namespace intrusive {
             typename gc::Guard segmentGuard;
             segment * pHeadSegment = m_SegmentList.head( segmentGuard );
 
-            permutation_generator gen( quasi_factor() );
+            permutation_generator gen( quasi_factor());
             while ( true ) {
                 if ( !pHeadSegment ) {
                     // Queue is empty
@@ -670,15 +674,15 @@ namespace cds { namespace intrusive {
                     // In segmented queue the cell cannot be reused
                     // So no loop is needed here to protect the cell
                     item = pHeadSegment->cells[i].data.load( memory_model::memory_order_relaxed );
-                    itemGuard.assign( item.ptr() );
+                    itemGuard.assign( item.ptr());
 
                     // Check if this cell is empty, which means an element
                     // can be enqueued to this cell in the future
-                    if ( !item.ptr() )
+                    if ( !item.ptr())
                         bHadNullValue = true;
                     else {
                         // If the item is not deleted yet
-                        if ( !item.bits() ) {
+                        if ( !item.bits()) {
                             // Try to mark the cell as deleted
                             if ( pHeadSegment->cells[i].data.compare_exchange_strong( item, item | 1,
                                 memory_model::memory_order_acquire, atomics::memory_order_relaxed ))
@@ -688,13 +692,13 @@ namespace cds { namespace intrusive {
 
                                 return true;
                             }
-                            assert( item.bits() );
+                            assert( item.bits());
                             m_Stat.onPopContended();
                         }
                     }
-                } while ( gen.next() );
+                } while ( gen.next());
 
-                assert( nLoopCount == quasi_factor() );
+                assert( nLoopCount == quasi_factor());
 
                 // scanning the entire segment without finding a candidate to dequeue
                 // If there was an empty cell, the queue is considered empty