This resolves ticket #523 - rework hazard pointer:

   - Do not use lists
   - Remove HelpScan
   - Release memory to memory manager when destructed (before that, memory had to be released by the memory manager in its destructor).
   - Avoid stdlib algorithms

base_c/src/internal/thread_index.c

@@ -129,5 +129,13 @@ void embb_internal_thread_index_set_max(unsigned int max) {
 }
 
 void embb_internal_thread_index_reset() {
+  // This function is only called in tests, usually when all other threads
+  // except the main thread have terminated. However, the main thread still has
+  // potentially still stored its old index value in its thread local storage,
+  // which might be assigned additionally to another thread (as the counter is
+  // reset), which may lead to hard to detect bugs. Therefore, reset the thread
+  // local thread id here.
+  embb_internal_thread_index_var = UINT_MAX;
+
   embb_counter_init(embb_thread_index_counter());
 }

containers_cpp/include/embb/containers/internal/lock_free_mpmc_queue-inl.h

@@ -77,7 +77,12 @@ LockFreeMPMCQueue<Type, ValuePool>::~LockFreeMPMCQueue() {
 
 template< typename Type, typename ValuePool >
 LockFreeMPMCQueue<Type, ValuePool>::LockFreeMPMCQueue(size_t capacity) :
-capacity(capacity),
+  capacity(capacity),
+  // Object pool, size with respect to the maximum number of retired nodes not
+  // eligible for reuse. +1 for dummy node.
+  objectPool(
+  MPMCQueueNodeHazardPointer_t::ComputeMaximumRetiredObjectCount(2) +
+   capacity + 1),
 // Disable "this is used in base member initializer" warning.
 // We explicitly want this.
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
@@ -89,13 +94,7 @@ delete_pointer_callback(*this,
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #pragma warning(pop)
 #endif
-  hazardPointer(delete_pointer_callback, NULL, 2),
-  // Object pool, size with respect to the maximum number of retired nodes not
-  // eligible for reuse. +1 for dummy node.
-  objectPool(
-  hazardPointer.GetRetiredListMaxSize()*
-  embb::base::Thread::GetThreadsMaxCount() +
-  capacity + 1) {
+  hazardPointer(delete_pointer_callback, NULL, 2) {
   // Allocate dummy node to reduce the number of special cases to consider.
   internal::LockFreeMPMCQueueNode<Type>* dummyNode = objectPool.Allocate();
   // Initially, head and tail point to the dummy node.
@@ -120,7 +119,7 @@ bool LockFreeMPMCQueue<Type, ValuePool>::TryEnqueue(Type const& element) {
   for (;;) {
     my_tail = tail;
 
-    hazardPointer.GuardPointer(0, my_tail);
+    hazardPointer.Guard(0, my_tail);
 
     // Check if pointer is still valid after guarding.
     if (my_tail != tail) {
@@ -163,12 +162,12 @@ bool LockFreeMPMCQueue<Type, ValuePool>::TryDequeue(Type & element) {
   Type data;
   for (;;) {
     my_head = head;
-    hazardPointer.GuardPointer(0, my_head);
+    hazardPointer.Guard(0, my_head);
     if (my_head != head) continue;
 
     my_tail = tail;
     my_next = my_head->GetNext();
-    hazardPointer.GuardPointer(1, my_next);
+    hazardPointer.Guard(1, my_next);
     if (head != my_head) continue;
 
     if (my_next == NULL)
@@ -187,7 +186,7 @@ bool LockFreeMPMCQueue<Type, ValuePool>::TryDequeue(Type & element) {
       break;
   }
 
-  hazardPointer.EnqueuePointerForDeletion(my_head);
+  hazardPointer.EnqueueForDeletion(my_head);
   element = data;
   return true;
 }

containers_cpp/include/embb/containers/internal/lock_free_stack-inl.h

@@ -81,13 +81,13 @@ capacity(capacity),
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #pragma warning(pop)
 #endif
-  hazardPointer(delete_pointer_callback, NULL, 1),
   // Object pool, size with respect to the maximum number of retired nodes not
   // eligible for reuse:
   objectPool(
-  hazardPointer.GetRetiredListMaxSize()*
-  embb::base::Thread::GetThreadsMaxCount() +
-  capacity) {
+  StackNodeHazardPointer_t::ComputeMaximumRetiredObjectCount(1) +
+  capacity),
+  hazardPointer(delete_pointer_callback, NULL, 1)
+{
 }
 
 template< typename Type, typename ValuePool >
@@ -128,7 +128,7 @@ bool LockFreeStack< Type, ValuePool >::TryPop(Type & element) {
       return false;
 
     // Guard top_cached
-    hazardPointer.GuardPointer(0, top_cached);
+    hazardPointer.Guard(0, top_cached);
 
     // Check if top is still top. If this is the case, it has not been
     // retired yet (because before retiring that thing, the retiring thread
@@ -144,16 +144,16 @@ bool LockFreeStack< Type, ValuePool >::TryPop(Type & element) {
       break;
     } else {
       // We continue with the next and can unguard top_cached
-      hazardPointer.GuardPointer(0, NULL);
+      hazardPointer.Guard(0, NULL);
     }
   }
 
   Type data = top_cached->GetElement();
 
   // We don't need to read from this reference anymore, unguard it
-  hazardPointer.GuardPointer(0, NULL);
+  hazardPointer.Guard(0, NULL);
 
-  hazardPointer.EnqueuePointerForDeletion(top_cached);
+  hazardPointer.EnqueueForDeletion(top_cached);
 
   element = data;
   return true;

containers_cpp/include/embb/containers/lock_free_mpmc_queue.h

@@ -113,8 +113,17 @@ class LockFreeMPMCQueue {
    * least as many elements, maybe more.
    */
   size_t capacity;
-  // Do not change the ordering of class local variables.
-  // Important for initialization.
+
+  /**
+   * The object pool, used for lock-free memory allocation.
+   *
+   * Warning: the objectPool has to be initialized before the hazardPointer
+   * object, to be sure that the hazardPointer object is destructed before the
+   * Pool as the hazardPointer object might return elements to the pool in its
+   * destructor. So the ordering of the members objectPool and hazardPointer is
+   * important here!
+   */
+  ObjectPool< internal::LockFreeMPMCQueueNode<Type>, ValuePool > objectPool;
 
   /**
    * Callback to the method that is called by hazard pointers if a pointer is
@@ -124,15 +133,17 @@ class LockFreeMPMCQueue {
     delete_pointer_callback;
 
   /**
-   * The hazard pointer object, used for memory management.
+   * Definition of the used hazard pointer type
    */
-  embb::containers::internal::HazardPointer
-    < internal::LockFreeMPMCQueueNode<Type>* > hazardPointer;
+  typedef embb::containers::internal::HazardPointer
+    < internal::LockFreeMPMCQueueNode<Type>* >
+    MPMCQueueNodeHazardPointer_t;
 
   /**
-   * The object pool, used for lock-free memory allocation.
+   * The hazard pointer object, used for memory management.
    */
-  ObjectPool< internal::LockFreeMPMCQueueNode<Type>, ValuePool > objectPool;
+  MPMCQueueNodeHazardPointer_t hazardPointer;
+
 
   /**
    * Atomic pointer to the head node of the queue

containers_cpp/include/embb/containers/lock_free_stack.h

@@ -187,11 +187,6 @@ class LockFreeStack {
     delete_pointer_callback;
 
   /**
-   * The hazard pointer object, used for memory management.
-   */
-  internal::HazardPointer<internal::LockFreeStackNode<Type>*> hazardPointer;
-
-  /**
    * The callback function, used to cleanup non-hazardous pointers.
    * \see delete_pointer_callback
    */
@@ -199,10 +194,27 @@ class LockFreeStack {
 
   /**
    * The object pool, used for lock-free memory allocation.
+   *
+   * Warning: the objectPool has to be initialized before the hazardPointer
+   * object, to be sure that the hazardPointer object is destructed before the
+   * Pool as the hazardPointer object might return elements to the pool in its
+   * destructor. So the ordering of the members objectPool and hazardPointer is
+   * important here!
    */
   ObjectPool< internal::LockFreeStackNode<Type>, ValuePool > objectPool;
 
   /**
+   * Definition of the used hazard pointer type
+   */
+  typedef internal::HazardPointer < internal::LockFreeStackNode<Type>* >
+    StackNodeHazardPointer_t;
+
+  /**
+   * The hazard pointer object, used for memory management.
+   */
+  StackNodeHazardPointer_t hazardPointer;
+
+  /**
    * Atomic pointer to the top node of the stack (element that is popped next)
    */
   embb::base::Atomic<internal::LockFreeStackNode<Type>*> top;

containers_cpp/test/hazard_pointer_test.h

@@ -36,33 +36,116 @@
 namespace embb {
 namespace containers {
 namespace test {
+
+/**
+ * @brief a very simple wait-free object pool implementation to have tests
+ * being independent of the EMBB object pool implementation.
+ */
+class IntObjectTestPool {
+ private:
+  int* simplePoolObjects;
+  embb::base::Atomic<int>* simplePool;
+
+ public:
+  static const int ALLOCATED_MARKER = 1;
+  static const int FREE_MARKER = 0;
+  unsigned int poolSize;
+
+  IntObjectTestPool(unsigned int poolSize);
+
+  ~IntObjectTestPool();
+
+  /**
+   * Allocate object from the pool
+   *
+   * @return the allocated object
+   */
+  int* Allocate();
+
+  /**
+   * Return an element to the pool
+   *
+   * @param objectPointer the object to be freed
+   */
+  void Release(int* objectPointer);
+};
+
 class HazardPointerTest : public partest::TestCase {
  private:
-  embb::base::Function<void, embb::base::Atomic<int>*> delete_pointer_callback;
+  embb::base::Function<void, embb::base::Atomic<int>*> deletePointerCallback;
 
   //used to allocate random stuff, we will just use the pointers, not the
   //contents
-  embb::containers::ObjectPool< embb::base::Atomic<int> >* object_pool;
+  embb::containers::ObjectPool< embb::base::Atomic<int> >* objectPool;
 
   //used to move pointer between threads
   embb::containers::LockFreeStack< embb::base::Atomic<int>* >* stack;
-  embb::base::Mutex vector_mutex;
-  embb::containers::internal::HazardPointer<embb::base::Atomic<int>*>* hp;
-  std::vector< embb::base::Atomic<int>* > deleted_vector;
-  int n_threads;
-  int n_elements_per_thread;
-  int n_elements;
+  embb::base::Mutex vectorMutex;
+  embb::containers::internal::HazardPointer<embb::base::Atomic<int>*>*
+    hazardPointer;
+  std::vector< embb::base::Atomic<int>* > deletedVector;
+  int nThreads;
+  int nElementsPerThread;
+  int nElements;
 
  public:
   /**
   * Adds test methods.
   */
   HazardPointerTest();
-  void HazardPointerTest1_Pre();
-  void HazardPointerTest1_Post();
-  void HazardPointerTest1_ThreadMethod();
-  void DeletePointerCallback(embb::base::Atomic<int>* to_delete);
+  void HazardPointerTest1Pre();
+  void HazardPointerTest1Post();
+  void HazardPointerTest1ThreadMethod();
+  void DeletePointerCallback(embb::base::Atomic<int>* toDelete);
+};
+
+class HazardPointerTest2 : public partest::TestCase {
+ private:
+  // number of threads, participating in that test
+  int nThreads;
+
+  embb::base::Function<void, int*> deletePointerCallback;
+  // the thread id of the master
+  embb::base::Atomic<unsigned int> currentMaster;
+
+  // variables, to synchronize threads. At each point in time, one master,
+  // the master changes each round until each thread was assigned master once.
+  embb::base::Atomic<int> sync1;
+  embb::base::Atomic<unsigned int> sync2;
+
+  unsigned int guardsPerThreadCount;
+  unsigned int guaranteedCapacityPool;
+  unsigned int poolSizeUsingHazardPointer;
+
+  // The threads write here, if they guarded an object successfully. Used to
+  // determine when all allocated objects were guarded successfully.
+  embb::base::Atomic<int*>* sharedGuarded;
+
+  // This array is used by the master, to communicate and share what he has
+  // allocated with the slaves.
+  embb::base::Atomic<int*>* sharedAllocated;
+
+  // Reference to the object pool
+  IntObjectTestPool* testPool;
+
+  embb::containers::internal::HazardPointer<int*>* hazardPointer;
+  static const int finishMarker = -1;
+
+ public:
+  void DeletePointerCallback(int* toDelete);
+  bool SetRelativeGuards();
+  void HazardPointerTest2Master();
+  void HazardPointerTest2Slave();
+
+  void HazardPointerTest2Pre();
+  void HazardPointerTest2Post();
+
+  void HazardPointerTest2ThreadMethod();
+
+  HazardPointerTest2();
 };
+
+
 } // namespace test
 } // namespace containers
 } // namespace embb

containers_cpp/test/main.cc

@@ -55,6 +55,7 @@ using embb::containers::test::HazardPointerTest;
 using embb::containers::test::QueueTest;
 using embb::containers::test::StackTest;
 using embb::containers::test::ObjectPoolTest;
+using embb::containers::test::HazardPointerTest2;
 
 PT_MAIN("Data Structures C++") {
   unsigned int max_threads = static_cast<unsigned int>(
@@ -64,6 +65,7 @@ PT_MAIN("Data Structures C++") {
   PT_RUN(PoolTest< WaitFreeArrayValuePool<int COMMA -1> >);
   PT_RUN(PoolTest< LockFreeTreeValuePool<int COMMA -1> >);
   PT_RUN(HazardPointerTest);
+  PT_RUN(HazardPointerTest2);
   PT_RUN(QueueTest< WaitFreeSPSCQueue< ::std::pair<size_t COMMA int> > >);
   PT_RUN(QueueTest< LockFreeMPMCQueue< ::std::pair<size_t COMMA int> >
     COMMA true COMMA true >);