Fixed MichaelList assertion

[libcds.git] / cds / intrusive / impl / michael_list.h

diff --git a/cds/intrusive/impl/michael_list.h b/cds/intrusive/impl/michael_list.h
index 84f0b5540c46e774580fb653d6fa933b8f71080d..079996d4af20b0677756d7d25a9fb2637a62f2c5 100644 (file)
--- a/cds/intrusive/impl/michael_list.h
+++ b/cds/intrusive/impl/michael_list.h
@@ -274,7 +274,11 @@ namespace cds { namespace intrusive {
 
             marked_node_ptr cur(pos.pCur);
             pNode->m_pNext.store( cur, memory_model::memory_order_release );
-            return pos.pPrev->compare_exchange_strong( cur, marked_node_ptr(pNode), memory_model::memory_order_release, atomics::memory_order_relaxed );
+            if ( pos.pPrev->compare_exchange_strong( cur, marked_node_ptr(pNode), memory_model::memory_order_release, atomics::memory_order_relaxed ))
+                return true;
+
+            pNode->m_pNext.store( marked_node_ptr(), memory_model::memory_order_relaxed );
+            return false;
         }
 
         static bool unlink_node( position& pos )
@@ -408,6 +412,8 @@ namespace cds { namespace intrusive {
         //@endcond
 
     public:
+    ///@name Forward iterators (only for debugging purpose)
+    //@{
         /// Forward iterator
         /**
             The forward iterator for Michael's list has some features:
@@ -417,10 +423,10 @@ namespace cds { namespace intrusive {
               may be thrown if the limit of guard count per thread is exceeded.
             - The iterator cannot be moved across thread boundary since it contains thread-private GC's guard.
             - Iterator ensures thread-safety even if you delete the item the iterator points to. However, in case of concurrent
-              deleting operations there is no guarantee that you iterate all item in the list.
+              deleting operations there is no guarantee that you iterate all item in the list. 
+              Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
 
-            Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
-            for debug purpose only.
+            @warning Use this iterator on the concurrent container for debugging purpose only.
 
             The iterator interface:
             \code
@@ -502,6 +508,7 @@ namespace cds { namespace intrusive {
         {
             return const_iterator();
         }
+    //@}
 
     public:
         /// Default constructor initializes empty list