Fixed max bucket count error in SplitList

[libcds.git] / cds / intrusive / split_list_nogc.h

diff --git a/cds/intrusive/split_list_nogc.h b/cds/intrusive/split_list_nogc.h
index 04994be5efbd0de16c4a31b0f7cbf1b81d2785cd..5eeb991fc03edf5ba8872b6e9dbdc2c24728d82e 100644 (file)
--- a/cds/intrusive/split_list_nogc.h
+++ b/cds/intrusive/split_list_nogc.h
@@ -3,6 +3,8 @@
 #ifndef CDSLIB_INTRUSIVE_SPLIT_LIST_NOGC_H
 #define CDSLIB_INTRUSIVE_SPLIT_LIST_NOGC_H
 
+#include <limits>
+
 #include <cds/intrusive/details/split_list_base.h>
 #include <cds/gc/nogc.h>
 
@@ -144,6 +146,7 @@ namespace cds { namespace intrusive {
         ordered_list_wrapper    m_List;             ///< Ordered list containing split-list items
         bucket_table            m_Buckets;          ///< bucket table
         atomics::atomic<size_t> m_nBucketCountLog2; ///< log2( current bucket count )
+        atomics::atomic<size_t> m_nMaxItemCount;    ///< number of items container can hold, before we have to resize
         item_counter            m_ItemCounter;      ///< Item counter
         hash                    m_HashFunctor;      ///< Hash functor
         stat                    m_Stat;             ///< Internal statistics
@@ -172,7 +175,7 @@ namespace cds { namespace intrusive {
 
         size_t bucket_no( size_t nHash ) const
         {
-            return nHash & ( (1 << m_nBucketCountLog2.load(atomics::memory_order_relaxed)) - 1 );
+            return nHash & ( (1 << m_nBucketCountLog2.load(memory_model::memory_order_relaxed)) - 1 );
         }
 
         static size_t parent_bucket( size_t nBucket )
@@ -253,12 +256,30 @@ namespace cds { namespace intrusive {
             m_Buckets.bucket( 0, pNode );
         }
 
-        void    inc_item_count()
+        static size_t max_item_count( size_t nBucketCount, size_t nLoadFactor )
         {
-            size_t sz = m_nBucketCountLog2.load(atomics::memory_order_relaxed);
-            if ( ( ++m_ItemCounter >> sz ) > m_Buckets.load_factor() && ((size_t)(1 << sz )) < m_Buckets.capacity() )
-            {
-                m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, atomics::memory_order_seq_cst, atomics::memory_order_relaxed );
+            return nBucketCount * nLoadFactor;
+        }
+
+        void inc_item_count()
+        {
+            size_t nMaxCount = m_nMaxItemCount.load(memory_model::memory_order_relaxed);
+            if ( ++m_ItemCounter <= nMaxCount )
+                return;
+
+            size_t sz = m_nBucketCountLog2.load(memory_model::memory_order_relaxed);
+            const size_t nBucketCount = static_cast<size_t>(1) << sz;
+            if ( nBucketCount < m_Buckets.capacity() ) {
+                // we may grow the bucket table
+                const size_t nLoadFactor = m_Buckets.load_factor();
+                if ( nMaxCount < max_item_count( nBucketCount, nLoadFactor ))
+                    return; // someone already have updated m_nBucketCountLog2, so stop here
+
+                const size_t nNewMaxCount = (nBucketCount < m_Buckets.capacity()) ? max_item_count( nBucketCount << 1, nLoadFactor )
+                                                                                  : std::numeric_limits<size_t>::max();
+                m_nMaxItemCount.compare_exchange_strong( nMaxCount, nNewMaxCount, memory_model::memory_order_relaxed,
+                    atomics::memory_order_relaxed );
+                m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_relaxed, atomics::memory_order_relaxed );
             }
         }
 
@@ -273,6 +294,7 @@ namespace cds { namespace intrusive {
         */
         SplitListSet()
             : m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }
@@ -284,6 +306,7 @@ namespace cds { namespace intrusive {
             )
             : m_Buckets( nItemCount, nLoadFactor )
             , m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }