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() {
 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());
   embb_counter_init(embb_thread_index_counter());
 }
 }

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

@@ -30,386 +30,381 @@
 namespace embb {
 namespace embb {
 namespace containers {
 namespace containers {
 namespace internal {
 namespace internal {
-template< typename ElementT >
-FixedSizeList<ElementT>::FixedSizeList(size_t max_size) :
-  max_size(max_size),
-  size(0) {
-  elementsArray = static_cast<ElementT*>(
-    embb::base::Allocation::Allocate(sizeof(ElementT) *
-    max_size));
-}
-
-template< typename ElementT >
-inline size_t FixedSizeList<ElementT>::GetSize() const {
-  return size;
-}
-
-template< typename ElementT >
-inline size_t FixedSizeList<ElementT>::GetMaxSize() const {
-  return max_size;
-}
-
-template< typename ElementT >
-inline void FixedSizeList<ElementT>::clear() {
-  size = 0;
-}
 
 
-template< typename ElementT >
-typename FixedSizeList<ElementT>::iterator
-FixedSizeList<ElementT>::begin() const {
-  return &elementsArray[0];
-}
+// Visual Studio is complaining, that the return in the last line of this
+// function is not reachable. This is true, as long as exceptions are enabled.
+// Otherwise, the exception becomes an assertion and with disabling assertions,
+// the code becomes reachable. So, disabling this warning.
+#ifdef EMBB_PLATFORM_COMPILER_MSVC
+#pragma warning(push)
+#pragma warning(disable:4702)
+#endif
+template< typename GuardType >
+unsigned int HazardPointer< GuardType >::GetCurrentThreadIndex() {
 
 
-template< typename ElementT >
-typename FixedSizeList<ElementT>::iterator
-FixedSizeList<ElementT>::end() const {
-  return &elementsArray[size];
-}
+  // first, get the EMBB native thread id.
+  unsigned int embbThreadIndex;
 
 
-template< typename ElementT >
-FixedSizeList< ElementT > &
-FixedSizeList<ElementT>::operator= (const FixedSizeList & other) {
-  size = 0;
+  int return_val = embb_internal_thread_index(&embbThreadIndex);
 
 
-  if (max_size < other.size) {
-    EMBB_THROW(embb::base::ErrorException, "Copy target to small");
+  if (return_val != EMBB_SUCCESS) {
+    EMBB_THROW(embb::base::ErrorException, "Could not get thread id");
   }
   }
 
 
-  for (const_iterator it = other.begin(); it != other.end(); ++it) {
-    PushBack(*it);
-  }
-  return *this;
-}
+  // iterate over the mappings array
+  for (unsigned int i = 0; i != accessorCount; ++i) {
+    // end of mappings? then we need to write our id
+    if (threadIdMapping[i] == -1) {
+      // try to CAS the initial value with out thread id
+      int expected = -1;
+      if (threadIdMapping[i].CompareAndSwap(expected,
+        static_cast<int>(embbThreadIndex))) {
+        //successful, return our mapping
+        return i;
+      }
+    }
 
 
-template< typename ElementT >
-bool FixedSizeList<ElementT>::PushBack(ElementT const el) {
-  if (size + 1 > max_size) {
-    return false;
+    if (threadIdMapping[i] == static_cast<int>(embbThreadIndex)) {
+      // found our mapping!
+      return i;
+    }
   }
   }
-  elementsArray[size] = el;
-  size++;
-  return true;
-}
 
 
-template< typename ElementT >
-FixedSizeList<ElementT>::~FixedSizeList() {
-  embb::base::Allocation::Free(elementsArray);
-}
+  // when we reach this point, we have too many accessors
+  // (no mapping possible)
+  EMBB_THROW(embb::base::ErrorException, "Too many accessors");
 
 
-template< typename GuardType >
-bool HazardPointerThreadEntry<GuardType>::IsActive() {
-  return is_active;
+  return 0;
 }
 }
+#ifdef EMBB_PLATFORM_COMPILER_MSVC
+#pragma warning(pop)
+#endif
 
 
 template< typename GuardType >
 template< typename GuardType >
-bool HazardPointerThreadEntry<GuardType>::TryReserve() {
-  bool expected = false;
-  return is_active.CompareAndSwap(expected, true);
-}
+void HazardPointer< GuardType >::RemoveGuard(int guardPosition){
+  const unsigned int myThreadId = GetCurrentThreadIndex();
 
 
-template< typename GuardType >
-void HazardPointerThreadEntry<GuardType>::Deactivate() {
-  is_active = false;
-}
+  // check invariants...
+  assert(guardPosition < guardsPerThread && myThreadId < accessorCount);
 
 
-template< typename GuardType >
-size_t HazardPointerThreadEntry<GuardType>::GetRetiredCounter() {
-  return retired_list.GetSize();
+  // set guard
+  guards[guardPosition*accessorCount + myThreadId] = undefinedGuard;
 }
 }
 
 
 template< typename GuardType >
 template< typename GuardType >
-FixedSizeList< GuardType >& HazardPointerThreadEntry<GuardType>::
-GetRetired() {
-  return retired_list;
-}
+HazardPointer< GuardType >::HazardPointer(
+  embb::base::Function<void, GuardType> freeGuardCallback,
+  GuardType undefinedGuard, int guardsPerThread, int accessors) :
+  accessorCount(accessors == -1 ?
+  embb::base::Thread::GetThreadsMaxCount() :
+  accessors),
+  undefinedGuard(undefinedGuard),
+  guardsPerThread(guardsPerThread),
+  freeGuardCallback(freeGuardCallback) {
+
+  threadIdMapping =
+    static_cast<embb::base::Atomic<int>*>(
+    embb::base::Allocation::Allocate(sizeof(embb::base::Atomic<int>)
+    *accessorCount));
+
+  for (unsigned int i = 0; i != accessorCount; ++i) {
+    //in-place new for each cell
+    new (&threadIdMapping[i]) embb::base::Atomic < int > ;
+  }
 
 
-template< typename GuardType >
-FixedSizeList< GuardType >& HazardPointerThreadEntry<GuardType>::
-GetRetiredTemp() {
-  return retired_list_temp;
-}
+  guards = static_cast<embb::base::Atomic< GuardType >*>
+    (embb::base::Allocation::Allocate(
+    sizeof(embb::base::Atomic< GuardType >) *
+    guardsPerThread * accessorCount
+    ));
 
 
-template< typename GuardType >
-FixedSizeList< GuardType >& HazardPointerThreadEntry<GuardType>::
-GetHazardTemp() {
-  return hazard_pointer_list_temp;
-}
+  for (unsigned int i = 0; i != guardsPerThread * accessorCount; ++i) {
+    //in-place new for each cell
+    new (&guards[i]) embb::base::Atomic < GuardType > ;
+  }
 
 
-template< typename GuardType >
-void HazardPointerThreadEntry<GuardType>::
-SetRetired(internal::FixedSizeList< GuardType > const & retired_list) {
-  this->retired_list = retired_list;
-}
+  threadLocalRetiredListsTemp = static_cast<GuardType*>
+    (embb::base::Allocation::Allocate(
+    sizeof(GuardType) *
+    guardsPerThread * accessorCount * accessorCount
+    ));
+
+  for (unsigned int i = 0; i !=
+    guardsPerThread * accessorCount * accessorCount; ++i) {
+    //in-place new for each cell
+    new (&threadLocalRetiredListsTemp[i]) GuardType;
+  }
 
 
-template< typename GuardType >
-HazardPointerThreadEntry<GuardType>::
-HazardPointerThreadEntry(GuardType undefined_guard, int guards_per_thread,
-  size_t max_size_retired_list) :
-#ifdef EMBB_DEBUG
-  who_is_scanning(-1),
-#endif
-  undefined_guard(undefined_guard),
-  guards_per_thread(guards_per_thread),
-  max_size_retired_list(max_size_retired_list),
-  // initially, each potential thread is active... if that is not the case
-  // another thread could call "HelpScan", and block this thread in making
-  // progress.
-  // Still, threads can be leave the hazard pointer processing (deactivation),
-  // but this can only be done once, i.e., this is not revertable...
-  is_active(1),
-  retired_list(max_size_retired_list),
-  retired_list_temp(max_size_retired_list),
-  hazard_pointer_list_temp(embb::base::Thread::GetThreadsMaxCount() *
-    guards_per_thread) {
-  // Initialize guarded pointer list
-  guarded_pointers = static_cast<embb::base::Atomic<GuardType>*>
+  threadLocalRetiredLists = static_cast<GuardType*>
     (embb::base::Allocation::Allocate(
     (embb::base::Allocation::Allocate(
-    sizeof(embb::base::Atomic<GuardType>)*guards_per_thread));
+    sizeof(GuardType) *
+    guardsPerThread * accessorCount * accessorCount
+    ));
+
+  for (unsigned int i = 0; i !=
+    guardsPerThread * accessorCount * accessorCount; ++i) {
+    //in-place new for each cell
+    new (&threadLocalRetiredLists[i]) GuardType;
+  }
 
 
-  for (int i = 0; i != guards_per_thread; ++i) {
-    new (static_cast<void*>(&guarded_pointers[i]))
-      embb::base::Atomic<GuardType>(undefined_guard);
+  // init guards and retired lists to the undefined guard
+  for (unsigned int i = 0; i != static_cast<unsigned int>(guardsPerThread);
+    ++i) {
+    for (unsigned int i2 = 0; i2 != accessorCount; ++i2) {
+      guards[i*accessorCount + i2] = undefinedGuard;
+    }
   }
   }
-}
 
 
-template< typename GuardType >
-HazardPointerThreadEntry<GuardType>::~HazardPointerThreadEntry() {
-  for (int i = 0; i != guards_per_thread; ++i) {
-    guarded_pointers[i].~Atomic();
+  for (unsigned int j = 0; j != accessorCount; ++j) {
+    for (unsigned int i = 0; i != guardsPerThread*accessorCount; ++i) {
+      threadLocalRetiredListsTemp
+        [j*(accessorCount*guardsPerThread) + i] =
+        undefinedGuard;
+      threadLocalRetiredLists
+        [j*(accessorCount*guardsPerThread) + i] =
+        undefinedGuard;
+    }
   }
   }
 
 
-  embb::base::Allocation::Free(guarded_pointers);
+  for (unsigned int i = 0; i != accessorCount; ++i) {
+    //in-place new for each cell
+    threadIdMapping[i] = -1;
+  }
 }
 }
 
 
 template< typename GuardType >
 template< typename GuardType >
-GuardType HazardPointerThreadEntry<GuardType>::GetGuard(int pos) const {
-  return guarded_pointers[pos];
-}
+HazardPointer< GuardType >::~HazardPointer() {
 
 
-template< typename GuardType >
-void HazardPointerThreadEntry<GuardType>::AddRetired(GuardType pointerToGuard) {
-  retired_list.PushBack(pointerToGuard);
-}
+  // Release references from all retired lists. Note that for this to work, the
+  // data structure using hazard pointer has still to be active... So first, the
+  // hazard pointer class shall be destructed, then the memory management class
+  // (e.g. some pool). Otherwise, the hazard pointer class would try to return
+  // memory to an already destructed memory manager.
+  for (unsigned int j = 0; j != accessorCount; ++j) {
+    for (unsigned int i = 0; i != accessorCount*guardsPerThread; ++i) {
+      GuardType pointerToFree =
+        threadLocalRetiredLists
+        [j * accessorCount * guardsPerThread + i];
+      if (pointerToFree == undefinedGuard) {
+        break;
+      }
+      freeGuardCallback(pointerToFree);
+    }
+  }
 
 
-template< typename GuardType >
-void HazardPointerThreadEntry<GuardType>::
-GuardPointer(int guardNumber, GuardType pointerToGuard) {
-  guarded_pointers[guardNumber] = pointerToGuard;
-}
+  for (unsigned int i = 0; i != accessorCount; ++i) {
+    threadIdMapping[i].~Atomic();
+  }
 
 
-template< typename GuardType >
-void HazardPointerThreadEntry<GuardType>::SetActive(bool active) {
-  is_active = active;
-}
+  embb::base::Allocation::Free(threadIdMapping);
 
 
-template< typename GuardType >
-unsigned int HazardPointer< GuardType >::GetCurrentThreadIndex() {
-  unsigned int thread_index;
-  int return_val = embb_internal_thread_index(&thread_index);
+  for (unsigned int i = 0; i != guardsPerThread * accessorCount; ++i) {
+    guards[i].~Atomic();
+  }
 
 
-  if (return_val != EMBB_SUCCESS)
-    EMBB_THROW(embb::base::ErrorException, "Could not get thread id!");
+  embb::base::Allocation::Free(guards);
 
 
-  return thread_index;
-}
-template< typename GuardType >
-bool HazardPointer< GuardType >::IsThresholdExceeded() {
-  double retiredCounterLocThread =
-    static_cast<double>(GetHazardPointerElementForCurrentThread().
-    GetRetiredCounter());
-
-  return (retiredCounterLocThread >=
-    RETIRE_THRESHOLD *
-    static_cast<double>(active_hazard_pointer)*
-    static_cast<double>(guards_per_thread));
+  for (unsigned int i = 0; i !=
+    guardsPerThread * accessorCount * accessorCount; ++i) {
+    threadLocalRetiredListsTemp[i].~GuardType();
+  }
+
+  embb::base::Allocation::Free(threadLocalRetiredListsTemp);
+
+  for (unsigned int i = 0; i !=
+    guardsPerThread * accessorCount * accessorCount; ++i) {
+    threadLocalRetiredLists[i].~GuardType();
+  }
+
+  embb::base::Allocation::Free(threadLocalRetiredLists);
 }
 }
 
 
 template< typename GuardType >
 template< typename GuardType >
-size_t HazardPointer< GuardType >::GetActiveHazardPointers() {
-  return active_hazard_pointer;
+void HazardPointer< GuardType >::Guard(int guardPosition,
+  GuardType guardedElement) {
+  const unsigned int myThreadId = GetCurrentThreadIndex();
+
+  // check invariants...
+  assert(guardPosition < guardsPerThread && myThreadId < accessorCount);
+
+  // set guard
+  guards[guardPosition*accessorCount + myThreadId] = guardedElement;
 }
 }
+
 template< typename GuardType >
 template< typename GuardType >
-typename HazardPointer< GuardType >::HazardPointerThreadEntry_t &
-HazardPointer< GuardType >::GetHazardPointerElementForCurrentThread() {
-  // For each thread, there is a slot in the hazard pointer array.
-  // Initially, the active flag of a hazard pointer entry is false.
-  // Only the respective thread changes the flag from true to false.
-  // This means that the current thread tells that he is about to
-  // stop operating, and the others are responsible for his retired
-  // list.
-
-  return hazard_pointer_thread_entry_array[GetCurrentThreadIndex()];
+size_t HazardPointer< GuardType >::ComputeMaximumRetiredObjectCount(
+size_t guardsPerThread, int accessors) {
+
+  unsigned int accessorCount = (accessors == -1 ?
+    embb::base::Thread::GetThreadsMaxCount() :
+    accessors);
+
+  return static_cast<size_t>(
+      guardsPerThread * accessorCount * accessorCount);
 }
 }
 
 
 template< typename GuardType >
 template< typename GuardType >
-void HazardPointer< GuardType >::HelpScan() {
-  // This is a little bit different than in the paper. In the paper,
-  // the retired nodes from other threads are added to our retired list.
-  // To be able to give a bound on memory consumption, we execute scan
-  // for those threads, without moving elements. The effect shall be
-  // the same.
-
-  for (size_t i = 0; i != hazard_pointers; ++i) {
-    // Try to find non active lists...
-    if (!hazard_pointer_thread_entry_array[i].IsActive() &&
-      hazard_pointer_thread_entry_array[i].TryReserve()) {
-      // Here: grab retired things, first check if there are any...
-      if (hazard_pointer_thread_entry_array[i].GetRetiredCounter() > 0) {
-        Scan(&hazard_pointer_thread_entry_array[i]);
+void HazardPointer< GuardType >::CopyRetiredList(GuardType* sourceList,
+  GuardType* targetList, unsigned int retiredListSize,
+  GuardType undefinedGuard) {
+  bool done = false;
+  for (unsigned int ii = 0; ii != retiredListSize; ++ii) {
+    if (!done) {
+      GuardType guardToCopy = sourceList[ii];
+
+      if (guardToCopy == undefinedGuard) {
+        done = true;
+
+        if (targetList[ii] == undefinedGuard) {
+          // end of target list
+          break;
+        }
+      }
+      targetList[ii] = guardToCopy;
+    }
+    else {
+      // we copied the whole source list, remaining values in the target
+      // have to be zeroed.
+      if (targetList[ii] == undefinedGuard) {
+        // end of target list
+        break;
+      }
+      else {
+        targetList[ii] = undefinedGuard;
       }
       }
-
-      // We are done, mark it as deactivated again
-      hazard_pointer_thread_entry_array[i].Deactivate();
     }
     }
   }
   }
 }
 }
 
 
 template< typename GuardType >
 template< typename GuardType >
-void HazardPointer< GuardType >::
-Scan(HazardPointerThreadEntry_t* currentHazardPointerEntry) {
-#ifdef EMBB_DEBUG
-  // scan should only be executed by one thread at a time, otherwise we have
-  // a bug... this assertions checks that
-  int expected = -1;
-  if (!currentHazardPointerEntry->GetScanningThread().CompareAndSwap(
-    expected, static_cast<int>(GetCurrentThreadIndex()))) {
-    assert(false);
-  }
-#endif
-  // In this function, we compute the intersection between local retired
-  // pointers and all hazard pointers. This intersection cannot be deleted and
-  // forms the new local retired pointers list.
-  // It is assumed that the union of all retired pointers contains no two
-  // pointers with the same value. However, the union of all hazard guards
-  // might.
-
-  // Here, we store the temporary hazard pointers. We have to store them,
-  // as iterating multiple time over them might be expensive, as this
-  // atomic array is shared between threads.
-  currentHazardPointerEntry->GetHazardTemp().clear();
-
-  // Get all active hazard pointers!
-  for (unsigned int i = 0; i != hazard_pointers; ++i) {
-    // Only consider guards of active threads
-    if (hazard_pointer_thread_entry_array[i].IsActive()) {
-      // For each guard in an hazard pointer entry
-      for (int pos = 0; pos != guards_per_thread; ++pos) {
-        GuardType guard = hazard_pointer_thread_entry_array[i].GetGuard(pos);
-
-        // UndefinedGuard means not guarded
-        if (guard == undefined_guard)
-          continue;
-
-        currentHazardPointerEntry->GetHazardTemp().PushBack(guard);
-      }
+void HazardPointer< GuardType >::UpdateRetiredList(GuardType* retiredList,
+  GuardType* updatedRetiredList, unsigned int retiredListSize,
+  GuardType guardedElement, GuardType consideredHazard,
+  GuardType undefinedGuard) {
+
+  // no hazard set here
+  if (consideredHazard == undefinedGuard)
+      return;
+
+  // if this hazard is currently in the union of
+  // threadLocalRetiredLists and pointerToRetire, but not yet in
+  // threadLocalRetiredListsTemp, add it to that list
+  bool containedInUnion = false;
+
+  // first iterate over our retired list
+  for (unsigned int ii = 0; ii != retiredListSize; ++ii) {
+    // when reaching 0, we can stop iterating (end of the "list")
+    if (retiredList[ii] == 0)
+        break;
+
+    // the hazard is contained in the retired list... it shall go
+    // into the temp list, if not already there
+    if (retiredList[ii] == consideredHazard) {
+      containedInUnion = true;
+      break;
     }
     }
   }
   }
 
 
-  currentHazardPointerEntry->GetRetiredTemp().clear();
-
-  // Sort them, we will do a binary search on each entry from the retired list
-  std::sort(
-    currentHazardPointerEntry->GetHazardTemp().begin(),
-    currentHazardPointerEntry->GetHazardTemp().end());
-
-  for (
-    EMBB_CONTAINERS_CPP_DEPENDANT_TYPENAME FixedSizeList< GuardType >::iterator
-      it = currentHazardPointerEntry->GetRetired().begin();
-  it != currentHazardPointerEntry->GetRetired().end(); ++it) {
-    if (false == ::std::binary_search(
-      currentHazardPointerEntry->GetHazardTemp().begin(),
-      currentHazardPointerEntry->GetHazardTemp().end(), *it)) {
-      this->free_guard_callback(*it);
-    } else {
-      currentHazardPointerEntry->GetRetiredTemp().PushBack(*it);
-    }
+  // the union also contains pointerToRetire
+  if (!containedInUnion) {
+    containedInUnion = (consideredHazard == guardedElement);
   }
   }
-  currentHazardPointerEntry->SetRetired(
-    currentHazardPointerEntry->GetRetiredTemp());
 
 
-#ifdef EMBB_DEBUG
-  currentHazardPointerEntry->GetScanningThread().Store(-1);
-#endif
-}
+  // add the pointer to temp. retired list, if not already there
+  if (containedInUnion) {
+    for (unsigned int iii = 0; iii != retiredListSize; ++iii) {
 
 
-template< typename GuardType >
-size_t HazardPointer< GuardType >::GetRetiredListMaxSize() const {
-  return static_cast<size_t>(RETIRE_THRESHOLD *
-        static_cast<double>(embb::base::Thread::GetThreadsMaxCount()) *
-        static_cast<double>(guards_per_thread)) + 1;
-}
+      // is it already there?
+      if (updatedRetiredList[iii] == consideredHazard)
+          break;
 
 
-template< typename GuardType >
-HazardPointer< GuardType >::HazardPointer(
-  embb::base::Function<void, GuardType> free_guard_callback,
-  GuardType undefined_guard, int guards_per_thread) :
-  undefined_guard(undefined_guard),
-  guards_per_thread(guards_per_thread),
-  //initially, all potential hazard pointers are active...
-  active_hazard_pointer(embb::base::Thread::GetThreadsMaxCount()),
-  free_guard_callback(free_guard_callback) {
-  hazard_pointers = embb::base::Thread::GetThreadsMaxCount();
-
-  hazard_pointer_thread_entry_array = static_cast<HazardPointerThreadEntry_t*>(
-    embb::base::Allocation::Allocate(sizeof(HazardPointerThreadEntry_t) *
-    hazard_pointers));
-
-  for (size_t i = 0; i != hazard_pointers; ++i) {
-    new (static_cast<void*>(&(hazard_pointer_thread_entry_array[i])))
-      HazardPointerThreadEntry_t(undefined_guard, guards_per_thread,
-      GetRetiredListMaxSize());
+      // end of the list
+      if (updatedRetiredList[iii] == undefinedGuard) {
+
+        // add hazard
+        updatedRetiredList[iii] = consideredHazard;
+
+        // we are done here...
+        break;
+      }
+    }
   }
   }
 }
 }
 
 
 template< typename GuardType >
 template< typename GuardType >
-HazardPointer< GuardType >::~HazardPointer() {
-  for (size_t i = 0; i != hazard_pointers; ++i) {
-    hazard_pointer_thread_entry_array[i].~HazardPointerThreadEntry_t();
-  }
+void HazardPointer< GuardType >::EnqueueForDeletion(GuardType toRetire) {
 
 
-  embb::base::Allocation::Free(static_cast < void* >
-    (hazard_pointer_thread_entry_array));
-}
+  unsigned int myThreadId = GetCurrentThreadIndex();
 
 
-template< typename GuardType >
-void HazardPointer< GuardType >::DeactivateCurrentThread() {
-  HazardPointerThreadEntry_t* current_thread_entry =
-    &hazard_pointer_thread_entry_array[GetCurrentThreadIndex()];
-
-  // Deactivating a non-active hazard pointer entry has no effect!
-  if (!current_thread_entry->IsActive()) {
-    return;
-  } else {
-    current_thread_entry->SetActive(false);
-    active_hazard_pointer--;
+  // check for invariant
+  assert(myThreadId < accessorCount);
+
+  unsigned int retiredListSize = accessorCount * guardsPerThread;
+
+  GuardType* retiredList =
+    &threadLocalRetiredLists[myThreadId * retiredListSize];
+
+  GuardType* retiredListTemp =
+    &threadLocalRetiredListsTemp[myThreadId * retiredListSize];
+
+  // wipe my temp. retired list...
+  for (unsigned int i = 0; i < retiredListSize; ++i) {
+    // the list is filled always from left to right, so occurring the first
+    // undefinedGuard, the remaining ones are also undefinedGuard...
+    if (retiredListTemp[i] == undefinedGuard)
+        break;
+
+    retiredListTemp[i] = undefinedGuard;
   }
   }
-}
 
 
-template< typename GuardType >
-void HazardPointer< GuardType >::GuardPointer(int guardPosition,
-  GuardType guardedElement) {
-  GetHazardPointerElementForCurrentThread().GuardPointer(
-    guardPosition, guardedElement);
-}
+  // we test each hazard if it is in the union of retiredList and
+  // guardedElement. If it is, it goes into the new retired list...
+  for (unsigned int i = 0; i != accessorCount*guardsPerThread; ++i) {
+    // consider each current active guard
+    GuardType consideredHazard = guards[i].Load();
+    UpdateRetiredList(retiredList, retiredListTemp, retiredListSize,
+      toRetire, consideredHazard, undefinedGuard);
+  }
 
 
-template< typename GuardType >
-void HazardPointer< GuardType >::EnqueuePointerForDeletion(
-  GuardType guardedElement) {
-  GetHazardPointerElementForCurrentThread().AddRetired(guardedElement);
-  if (IsThresholdExceeded()) {
-    HazardPointerThreadEntry_t* currentHazardPointerEntry =
-      &GetHazardPointerElementForCurrentThread();
+  // now we created a a new retired list... the elements that are "removed" from
+  // the old retired list can be safely deleted now...
+  for (int ii = -1; ii != static_cast<int>(retiredListSize); ++ii) {
+    // we iterate over the current retired list... -1 is used as dummy element
+    // in the iteration, to also iterate over the pointerToRetire, which is
+    // logically also part of the current retired list...
+
+    // end of the list, stop iterating
+    if (ii >= 0 && retiredList[ii] == undefinedGuard)
+        break;
 
 
-    Scan(currentHazardPointerEntry);
+    GuardType toCheckIfInNewList = undefinedGuard;
 
 
-    // Help deactivated threads to clean their retired nodes.
-    HelpScan();
+    toCheckIfInNewList = (ii == -1 ? toRetire : retiredList[ii]);
+
+    // still in the new retired list?
+    bool stillInList = false;
+    for (unsigned int iii = 0; iii != retiredListSize; ++iii) {
+      // end of list
+      if (retiredListTemp[iii] == undefinedGuard)
+          break;
+
+      if (toCheckIfInNewList == retiredListTemp[iii]) {
+        // still in list, cannot delete!
+        stillInList = true;
+        break;
+      }
+    }
+
+    if (!stillInList) {
+      this->freeGuardCallback(toCheckIfInNewList);
+    }
   }
   }
+
+  // copy the updated retired list (temp) to the retired list...
+  CopyRetiredList(retiredListTemp, retiredList, retiredListSize,
+    undefinedGuard);
 }
 }
 
 
-template<typename GuardType>
-const double embb::containers::internal::HazardPointer<GuardType>::
-  RETIRE_THRESHOLD = 1.25f;
 } // namespace internal
 } // namespace internal
 } // namespace containers
 } // namespace containers
 } // namespace embb
 } // namespace embb

containers_cpp/include/embb/containers/internal/hazard_pointer.h

@@ -40,451 +40,217 @@
 #define EMBB_CONTAINERS_CPP_DEPENDANT_TYPENAME typename
 #define EMBB_CONTAINERS_CPP_DEPENDANT_TYPENAME typename
 #endif
 #endif
 
 
+// forward declaration for white-box test, used in friend declaration of
+// HazardPointer class.
+namespace embb {
+namespace containers{
+namespace test {
+class HazardPointerTest2;
+}
+}
+}
+
 namespace embb {
 namespace embb {
 namespace containers {
 namespace containers {
 namespace internal {
 namespace internal {
+
 /**
 /**
- * A list with fixed size, implemented as an array. Replaces std::vector that
- * was used in previous hazard pointer implementation.
+ * This class contains a hazard pointer implementation following publication:
  *
  *
- * Provides iterators, so we can apply algorithms from the STL.
+ * Maged M. Michael. "Hazard pointers: Safe memory reclamation for lock-free
+ * objects." IEEE Transactions on Parallel and Distributed Systems, 15.6 (2004)
+ * : 491-504.
  *
  *
- * \tparam ElementT Type of the elements contained in the list.
- */
-template< typename ElementT >
-class FixedSizeList {
- private:
-   /**
-    * Capacity of the list
-    */
-  size_t max_size;
-
-  /**
-   * Size of the list
-   */
-  size_t size;
-
-  /**
-   * Pointer to the array containing the list
-   */
-  ElementT* elementsArray;
-
-  /**
-   * Copy constructor not implemented. Would require dynamic memory allocation.
-   */
-  FixedSizeList(
-    const FixedSizeList &
-    /**< [IN] Other list */);
-
- public:
-  /**
-   * Definition of an iterator
-   */
-  typedef ElementT * iterator;
-
-  /**
-   * Definition of a const iterator
-   */
-  typedef const ElementT * const_iterator;
-
-  /**
-   * Constructor, initializes list with given capacity
-   */
-  FixedSizeList(
-    size_t max_size
-    /**< [IN] Capacity of the list */);
-
-  /**
-   * Gets the current size of the list
-   *
-   * \return Size of the list
-   */
-  inline size_t GetSize() const;
-
-  /**
-   * Gets the capacity of the list
-   *
-   * \return The capacity of the list
-   */
-  inline size_t GetMaxSize() const;
-
-  /**
-   * Removes all elements from the list without changing the capacity
-   */
-  inline void clear();
-
-  /**
-   * Iterator pointing to the first element
-   *
-   * \return Begin iterator
-   */
-  iterator begin() const;
-
-  /**
-   * Iterator pointing beyond the last element
-   *
-   * \return End iterator
-   */
-  iterator end() const;
-
-  /**
-   * Copies the elements of another list to this list. The capacity of
-   * this list has to be greater than or equal to the size of the other list.
-   */
-  FixedSizeList & operator=(
-    const FixedSizeList & other
-    /**< [IN] Other list */);
-
-  /**
-   * Appends an element to the end of the list
-   *
-   * \return \c false if the operation was not successful because the list is
-   *         full, otherwise \c true.
-   */
-  bool PushBack(
-    ElementT const el
-    /**< [IN] Element to append to the list */);
-
-  /**
-   * Destructs the list.
-   */
-  ~FixedSizeList();
-};
-
-/**
- * Hazard pointer entry for a single thread. Holds the actual guards that
- * determine if the current thread is about to use the guarded pointer.
- * Guarded pointers are protected and not deleted.
+ * Hazard pointer are a wait-free memory reclamation scheme for lock-free
+ * algorithms. Loosely speaking, they act as garbage collector. The release of
+ * objects contained within the memory, managed by the hazard pointer class, is
+ * intercepted and possibly delayed to avoid concurrency bugs.
  *
  *
- * Moreover, the retired list for this thread is contained. It determines
- * the pointers that have been allocated from this thread, but are not used
- * anymore by this thread. However, another thread could have a guard on it,
- * so the pointer cannot be deleted immediately.
+ * Before accessing an object, threads announce their intention to do so (i.e.
+ * the intention to dereference the respective pointer) to the hazard pointer
+ * class. This is called guarding. From now on, the hazard pointer class will
+ * prohibit the release or reuse of the guarded object. This is necessary, to
+ * assure that the object is not released or reused while it is accessed and to
+ * assure that it has not unnoticed changed (effectively avoiding the ABA
+ * problem).
  *
  *
- * For the scan operation, the intersection of the guarded pointers from all
- * threads and the retired list has to be computed. For this computation, we
- * need thread local temporary lists which are also contained here.
+ * Note that after guarding an object, a consecutive check that the object (i.e.
+ * its pointer) is still valid is necessary; the object release could already
+ * have been started when guarding the object. Guarding is repeated, until this
+ * check eventually succeeds. Note that this "guard-and-check" loop makes the
+ * usage of the hazard pointer class lock-free, even though its implementation
+ * is wait-free.
  *
  *
- * \tparam GuardType The type of guard, usually a pointer.
- */
-template< typename GuardType >
-class HazardPointerThreadEntry {
-#ifdef EMBB_DEBUG
-
- public:
-    embb::base::Atomic<int>& GetScanningThread() {
-      return who_is_scanning;
-    }
-
- private:
-    embb::base::Atomic<int> who_is_scanning;
-#endif
-
- private:
-   /**
-    * Value of the undefined guard (means that no guard is set).
-    */
-  GuardType undefined_guard;
-
-  /**
-   * The number of guards per thread. Determines the size of the guard array.
-   */
-  int guards_per_thread;
-
-  /**
-   * The capacity of the retired list. It is determined by number of guards,
-   * retired threshold, and maximum number of threads.
-   */
-  size_t max_size_retired_list;
-
-  /**
-   * Set to true if the current thread is active. Is used for a thread to
-   * signal that it is leaving. If a thread has left, the other threads are
-   * responsible for cleaning up its retired list.
-   */
-  embb::base::Atomic< bool > is_active;
-
-  /**
-   * The guarded pointer of this thread, has size \c guard_per_thread.
-   */
-  embb::base::Atomic< GuardType >* guarded_pointers;
-
-  /**
-   * The retired list of this thread, contains pointer that shall be released
-   * when no thread holds a guard on it anymore.
-   */
-  FixedSizeList< GuardType > retired_list;
-
-  /**
-   * Temporary retired list, has same capacity as \c retired_list, It is used to
-   * compute the intersection of all guards and the \c retired list.
-   */
-  FixedSizeList< GuardType > retired_list_temp;
-
-  /**
-   * Temporary guards list. Used to compute the intersection of all guards and
-   * the \c retired_list.
-   */
-  FixedSizeList< GuardType > hazard_pointer_list_temp;
-
-  /**
-   * HazardPointerThreadEntry shall not be copied
-   */
-  HazardPointerThreadEntry(const HazardPointerThreadEntry&);
-
-  /**
-   * HazardPointerThreadEntry shall not be assigned
-   */
-  HazardPointerThreadEntry & operator= (const HazardPointerThreadEntry&);
-
- public:
-  /**
-   * Checks if current thread is active (with respect to participating in hazard
-   * pointer management)
-   *
-   * \return \c true if the current thread is active, otherwise \c false.
-   */
-  bool IsActive();
-
-  /**
-   * Tries to set the active flag to true (atomically). Used if the current
-   * thread is not active anymore as lock for another thread to help cleaning
-   * up hazard pointer.
-   *
-   * \return \c true if this thread was successful setting the active flag,
-   *         otherwise \c false.
-   */
-  bool TryReserve();
-
-  /**
-   * Deactivates current thread by atomically setting active flag to false.
-   */
-  void Deactivate();
-
-  /**
-   * Gets the count of current retired pointer for the current thread.
-   *
-   * \return Count of current retired pointer
-   */
-  size_t GetRetiredCounter();
-
-  /**
-   * Gets the retired list.
-   *
-   * \return Reference to \c retired_list
-   */
-  FixedSizeList< GuardType >& GetRetired();
-
-  /**
-   * Gets the temporary retired list.
-   *
-   * \return Reference to \c retired_list_temp
-   */
-  FixedSizeList< GuardType >& GetRetiredTemp();
-
-  /**
-   * Gets the temporary hazard pointer list.
-   *
-   * \return Reference to \c hazard_pointer_list_temp
-   */
-  FixedSizeList< GuardType >& GetHazardTemp();
-
-  /**
-   * Sets the retired list.
-   */
-  void SetRetired(
-    embb::containers::internal::FixedSizeList< GuardType > const & retired_list
-    /**< [IN] Retired list */);
-
-  /**
-   * Constructor
-   */
-  HazardPointerThreadEntry(
-    GuardType undefined_guard,
-    /**< [IN] Value of the undefined guard (e.g. NULL) */
-    int guards_per_thread,
-    /**< [IN] Number of guards per thread */
-    size_t max_size_retired_list
-    /**< [IN] The capacity of the retired list(s) */);
-
-  /**
-   * Destructor
-   *
-   * Deallocate lists
-   */
-  ~HazardPointerThreadEntry();
-
-  /**
-   * Gets the guard at the specified position.
-   * Positions are numbered, beginning with 0.
-   */
-  GuardType GetGuard(
-    int pos
-    /**< [IN] Position of the guard */) const;
-
-  /**
-   * Adds pointer to the retired list
-   */
-  void AddRetired(
-    GuardType pointerToGuard
-    /**< [IN] Guard to retire */);
-
-  /**
-   * Guards pointer
-   */
-  void GuardPointer(
-    int guardNumber,
-    /**< [IN] Position of guard */
-    GuardType pointerToGuard
-    /**<[IN] Pointer to guard */);
-
-  /**
-   * Sets the current thread active, i.e., announce that the thread
-   * participates in managing hazard pointer.
-   */
-  void SetActive(
-    bool active
-    /**<[IN] \c true for active, \c false for inactive */);
-};
-
-/**
- * HazardPointer implementation as presented in:
+ * Internally, guarding is realized by providing each thread slots, where
+ * pointers can be placed that should not be freed (so called guards). When
+ * trying to release an object, it is checked if the object's pointer is
+ * guarded, and if so this object is not released, but instead put into a
+ * retired list for later release, when all guards for this object have been
+ * removed.
  *
  *
- * Maged M. Michael. "Hazard pointers: Safe memory reclamation for lock-free
- * objects." IEEE Transactions on Parallel and Distributed Systems, 15.6 (2004)
- * : 491-504.
+ * In contrast to the original implementation, our implementation consumes only
+ * fixed-size memory. Note that the number of threads accessing the hazard
+ * pointer object accounts quadratic for the memory consumption: managed objects
+ * are provided from outside and the number of accessors accounts quadric for
+ * the minimum count of those objects.
  *
  *
- * In contrast to the original implementation, our implementation only uses
- * fixed-size memory. There is a safe upper limit, hazard pointer are guaranteed
- * to not consume more memory. Memory is allocated solely at initialization.
+ * Also in contrast to the original implementation, we do not provide a HelpScan
+ * functionality, which gives threads the possibility, to not participate in the
+ * garbage collection anymore: other threads will help to clean-up the objects
+ * protected by the exiting thread. The reason is, that the only use-case would
+ * be a crashing thread, not participating anymore. However, as the thread has
+ * to signal its exit himself, this is not possible to realize anyways. In the
+ * end, it is still guaranteed that all memory is properly returned (in the
+ * destructor).
  *
  *
- * Hazard pointers solve the ABA problem for lock-free algorithms. Before
- * accessing a pointer, threads announce that they want to access this pointer
- * and then check if the pointer is still valid. This announcement is done by
- * placing a guard. It is guaranteed that the pointer is not reused until all
- * threads remove their guards to this pointer. Objects, these pointers are
- * pointing to, can therefore not be deleted directly. Instead, these pointers
- * are put into a list for later deletion (retired list). Regularly, this list
- * is processed to check which pointers can be deleted. If a pointer can be
- * deleted, a callback function provided by the user is called. The user can
- * then, e.g., free the respective object, so that the pointer can be safely
- * reused.
+ * Additionally, the original implementation holds a threshold, which determines
+ * when objects shall be freed. In this implementation, we free whenever it is
+ * possibly to do so, as we want to keep the memory footprint as low as
+ * possible. We also don't see a performance drop in the current algorithms that
+ * are using hazard pointer, when not using a threshold.
+ *
+ * \tparam GuardType the type of the guards. Usually the pointer type of some
+ *         object to protect.
  */
  */
 template< typename GuardType >
 template< typename GuardType >
 class HazardPointer  {
 class HazardPointer  {
  private:
  private:
-   /**
-    * Concrete hazard pointer entry type
-    */
-  typedef HazardPointerThreadEntry < GuardType >
-    HazardPointerThreadEntry_t;
-
   /**
   /**
-   * The guard value denoting "not guarding"
+   * HazardPointerTest2 is a white-box test, needing access to private members
+   * of this class. So declaring it as friend.
    */
    */
-  GuardType undefined_guard;
 
 
+  friend class embb::containers::test::HazardPointerTest2;
   /**
   /**
-   * The capacity of the retired list (safe upper bound for retired list size)
+   * The hazard pointer guards, represented as array. Each thread has a fixed
+   * set of slots (guardsPerThread) within this array.
    */
    */
-  int retired_list_max_size;
+  embb::base::Atomic<GuardType>* guards;
 
 
   /**
   /**
-   * Guards that can be set per thread
+   * \see threadLocalRetiredLists documentation
    */
    */
-  int guards_per_thread;
+  GuardType* threadLocalRetiredListsTemp;
 
 
   /**
   /**
-   * Array of HazardPointerElements. Each thread is assigned to one.
+   * A lists of lists, represented as single array. Each thread maintains a
+   * list of retired pointers, that are objects that are logically released
+   * but not released because some thread placed a guard on it.
    */
    */
-  HazardPointerThreadEntry_t* hazard_pointer_thread_entry_array;
+  GuardType* threadLocalRetiredLists;
 
 
   /**
   /**
-   * The threshold, determines at which size of the retired list pointers
-   * are tried to be deleted.
+   * This number determines the amount of maximal accessors (threads) that
+   * will access this hazard pointer instance. Note that a thread once
+   * accessing this object will be permanently count as accessor, even if not
+   * participating anymore. If too many threads access this object, an
+   * assertion is thrown.
    */
    */
-  static const double RETIRE_THRESHOLD;
+  unsigned int accessorCount;
 
 
   /**
   /**
-   * Each thread is assigned a thread index (starting with 0).
-   * Get the index of the current thread.
+   * The guard value denoting "not guarded"
    */
    */
-  static unsigned int GetCurrentThreadIndex();
+  GuardType undefinedGuard;
 
 
   /**
   /**
-   * The number of hazard pointers currently active.
+   * The count of guards that can be set per thread.
    */
    */
-  size_t active_hazard_pointer;
+  int guardsPerThread;
 
 
   /**
   /**
-   * Count of all hazard pointers.
+   * The functor that is called to release an object. This is called by this
+   * class, when it is safe to do so, i.e., no thread accesses this object
+   * anymore.
    */
    */
-  size_t hazard_pointers;
+  embb::base::Function<void, GuardType> freeGuardCallback;
 
 
   /**
   /**
-   * The callback that is triggered when a retired guard can be
-   * freed. Usually, the user will call a free here.
+   * Mapping from EMBB thread id to internal thread ids Internal thread ids
+   * are in range [0;accesor_count-1]. The position of a EMBB thread id in
+   * that array determines the respective internal thread id.
    */
    */
-  embb::base::Function<void, GuardType> free_guard_callback;
+  embb::base::Atomic<int>* threadIdMapping;
 
 
   /**
   /**
-   * Checks if the current size of the retired list exceeds the threshold, so
-   * that each retired guard is checked for being not hazardous anymore.
+   * Each thread is assigned a thread index (starting with 0). Get the index of
+   * the current thread. Note that this is not the global index, but an internal
+   * one. The user is free to define less accessors than the amount of default
+   * threads. This is useful, as the number of accessors accounts quadratic for
+   * the memory consumption, so the user should have the possibility to avoid
+   * memory wastage, when only having a small, fixed size, number of accessors.
    *
    *
-   * \return \c true is threshold is exceeded, otherwise \c false.
-   */
-  bool IsThresholdExceeded();
-
-  /**
-   * Gets the number of hazard pointe, currently active
-   *
-   * \return Number of active hazard pointers
-   */
-  size_t GetActiveHazardPointers();
-
-  /**
-   * Gets the hazard pointer entry for the current thread
-   *
-   * \return Hazard pointer entry for current thread
-   */
-  HazardPointerThreadEntry_t&
-    GetHazardPointerElementForCurrentThread();
-
-  /**
-   * Threads might leave from participating in hazard pointer management.
-   * This method helps all those threads processing their retired list.
-   */
-  void HelpScan();
-
-  /**
-   * Checks the retired list of a hazard pointer entry for elements of the
-   * retired list that can be freed, and executes the delete callback for those
-   * elements.
-   */
-  void Scan(
-    HazardPointerThreadEntry_t* currentHazardPointerEntry
-    /**<[IN] Hazard pointer entry that should be checked for elements that
-             can be deleted*/);
+   * @return current thread index
+   */
+  unsigned int GetCurrentThreadIndex();
+
+  /**
+   * Copy retired list \c sourceList to retired list \c targetList
+   */
+  static void CopyRetiredList(GuardType* sourceList,
+    /**<[IN] the source retired list*/
+    GuardType* targetList,
+    /**<[IN] the target retired list*/
+    unsigned int singleRetiredListSize,
+    /**<[IN] the size of a thread local retired list*/
+    GuardType undefinedGuard
+    /**<[IN] the undefined guard (usually the NULL pointer)*/
+    );
+
+  static void UpdateRetiredList(
+    GuardType* retiredList,
+    /**<[IN] the old retired list*/
+    GuardType* updatedRetiredList,
+    /**<[IN] the updated retired list*/
+    unsigned int retiredListSize,
+    /**<[IN] the size of a thread local retired list*/
+    GuardType toRetire,
+    /**<[IN] the element to retire*/
+    GuardType consideredHazard,
+    /**<[IN] the currently considered hazard*/
+    GuardType undefinedGuard
+    /**<[IN] the undefined guard (usually the NULL pointer)*/
+    );
 
 
  public:
  public:
+
   /**
   /**
-   * Gets the capacity of one retired list
+   * The user of the hazard pointer class has to provide the memory that is
+   * managed here. The user has to take into account, that releasing of memory
+   * might be delayed. He has therefore to provide more memory than he wants to
+   * guarantee at each point in time. More specific, on top of the guaranteed
+   * count of objects, he has to provide the additional count of objects that
+   * can be (worst-case) contained in the retired lists and therefore are not
+   * released yet. The size of all retired lists is guardsPerThread *
+   * accessorCount * accessorCount, which is computed using this function. So
+   * the result of function denotes to the user, how many objects he has to
+   * allocate additionally to the guaranteed count.
    *
    *
    * \waitfree
    * \waitfree
    */
    */
-  size_t GetRetiredListMaxSize() const;
+  static size_t ComputeMaximumRetiredObjectCount(
+    size_t guardsPerThread,
+      /**<[IN] the count of guards per thread*/
+      int accessors = -1
+    /**<[IN] Number of accessors. Determines, how many threads will access
+              the hazard pointer object. Default value -1 will allow the
+              maximum amount of threads as defined with
+              \c embb::base::Thread::GetThreadsMaxCount()*/
+      );
 
 
   /**
   /**
-   * Initializes hazard pointer
+   * Initializes the hazard pointer object
    *
    *
    * \notthreadsafe
    * \notthreadsafe
    *
    *
-   * \memory
-   *  - Let \c t be the number of maximal threads determined by EMBB
-   *  - Let \c g be the number of guards per thread
-   *  - Let \c x be 1.25*t*g + 1
+   * \memory We dynamically allocate the following:
+   *
+   * (sizeof(Atomic<int>) * accessorCount) + (sizeof(Atomic<GuardType>) *
+   * guards_per_thread * accessorCount) + (2*sizeof(GuardType) *
+   * guards_per_thread * accessorCount^2)
    *
    *
-   * We dynamically allocate \c x*(3*t+1) elements of size \c sizeof(void*).
+   * The last addend is the dominant one, as accessorCount accounts
+   * quadratically for it.
    */
    */
   HazardPointer(
   HazardPointer(
     embb::base::Function<void, GuardType> free_guard_callback,
     embb::base::Function<void, GuardType> free_guard_callback,
@@ -492,35 +258,48 @@ class HazardPointer  {
              guard can be deleted */
              guard can be deleted */
     GuardType undefined_guard,
     GuardType undefined_guard,
     /**<[IN] The guard value denoting "not guarded"*/
     /**<[IN] The guard value denoting "not guarded"*/
-    int guards_per_thread
-    /**<[IN] Number of guards per thread*/);
-
-  /**
-   * Deallocates lists for hazard pointer management. Note that no objects
-   * currently in the retired lists are deleted. This is the responsibility
-   * of the user. Usually, HazardPointer manages pointers of an object pool.
-   * After destructing HazardPointer, the object pool is deleted, so that
-   * everything is properly cleaned up.
+    int guards_per_thread,
+    /**<[IN] Number of guards per thread*/
+    int accessors = -1
+    /**<[IN] Number of accessors. Determines, how many threads will access
+              this hazard pointer object. Default value -1 will allow the
+              maximum amount of threads as defined with
+              \c embb::base::Thread::GetThreadsMaxCount()*/
+    );
+
+  /**
+   * Deallocates internal data structures. Additionally releases all objects
+   * currently held in the retired lists, using the release functor passed in
+   * the constructor.
+   *
+   * \notthreadsafe
    */
    */
   ~HazardPointer();
   ~HazardPointer();
 
 
   /**
   /**
-   * Announces that the current thread stops participating in hazard pointer
-   * management. The other threads now take care of his retired list.
+   * Guards \c toGuard. If the guardedElement is passed to \c EnqueueForDeletion
+   * it is prevented from release from now on. The user must have a check, that
+   * EnqueueForDeletion has not been called on toGuard, before the guarding took
+   * effect.
    *
    *
    * \waitfree
    * \waitfree
    */
    */
-  void DeactivateCurrentThread();
+  void Guard(int guardPosition, GuardType toGuard);
 
 
   /**
   /**
-   * Guards \c guardedElement with the guard at position \c guardPosition
+   * Enqueue a pointer for deletion. If not guarded, it is deleted immediately.
+   * If it is guarded, it is added to a thread local retired list, and deleted
+   * in a subsequent call to \c EnqueueForDeletion, when no guard is placed on
+   * it anymore.
    */
    */
-  void GuardPointer(int guardPosition, GuardType guardedElement);
+  void EnqueueForDeletion(GuardType guardedElement);
+
   /**
   /**
-   * Enqueue a pointer for deletion. It is added to the retired list and
-   * deleted when no thread accesses it anymore.
+   * Explicitly remove guard from thread local slot.
+   *
+   * \waitfree
    */
    */
-  void EnqueuePointerForDeletion(GuardType guardedElement);
+  void RemoveGuard(int guardPosition);
 };
 };
 } // namespace internal
 } // namespace internal
 } // namespace containers
 } // namespace containers

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 >
 template< typename Type, typename ValuePool >
 LockFreeMPMCQueue<Type, ValuePool>::LockFreeMPMCQueue(size_t capacity) :
 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.
 // Disable "this is used in base member initializer" warning.
 // We explicitly want this.
 // We explicitly want this.
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
@@ -89,13 +94,7 @@ delete_pointer_callback(*this,
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #pragma warning(pop)
 #pragma warning(pop)
 #endif
 #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.
   // Allocate dummy node to reduce the number of special cases to consider.
   internal::LockFreeMPMCQueueNode<Type>* dummyNode = objectPool.Allocate();
   internal::LockFreeMPMCQueueNode<Type>* dummyNode = objectPool.Allocate();
   // Initially, head and tail point to the dummy node.
   // Initially, head and tail point to the dummy node.
@@ -120,7 +119,7 @@ bool LockFreeMPMCQueue<Type, ValuePool>::TryEnqueue(Type const& element) {
   for (;;) {
   for (;;) {
     my_tail = tail;
     my_tail = tail;
 
 
-    hazardPointer.GuardPointer(0, my_tail);
+    hazardPointer.Guard(0, my_tail);
 
 
     // Check if pointer is still valid after guarding.
     // Check if pointer is still valid after guarding.
     if (my_tail != tail) {
     if (my_tail != tail) {
@@ -163,12 +162,12 @@ bool LockFreeMPMCQueue<Type, ValuePool>::TryDequeue(Type & element) {
   Type data;
   Type data;
   for (;;) {
   for (;;) {
     my_head = head;
     my_head = head;
-    hazardPointer.GuardPointer(0, my_head);
+    hazardPointer.Guard(0, my_head);
     if (my_head != head) continue;
     if (my_head != head) continue;
 
 
     my_tail = tail;
     my_tail = tail;
     my_next = my_head->GetNext();
     my_next = my_head->GetNext();
-    hazardPointer.GuardPointer(1, my_next);
+    hazardPointer.Guard(1, my_next);
     if (head != my_head) continue;
     if (head != my_head) continue;
 
 
     if (my_next == NULL)
     if (my_next == NULL)
@@ -187,7 +186,7 @@ bool LockFreeMPMCQueue<Type, ValuePool>::TryDequeue(Type & element) {
       break;
       break;
   }
   }
 
 
-  hazardPointer.EnqueuePointerForDeletion(my_head);
+  hazardPointer.EnqueueForDeletion(my_head);
   element = data;
   element = data;
   return true;
   return true;
 }
 }

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

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

containers_cpp/include/embb/containers/lock_free_mpmc_queue.h

@@ -113,8 +113,17 @@ class LockFreeMPMCQueue {
    * least as many elements, maybe more.
    * least as many elements, maybe more.
    */
    */
   size_t capacity;
   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
    * Callback to the method that is called by hazard pointers if a pointer is
@@ -124,15 +133,17 @@ class LockFreeMPMCQueue {
     delete_pointer_callback;
     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
    * 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;
     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.
    * The callback function, used to cleanup non-hazardous pointers.
    * \see delete_pointer_callback
    * \see delete_pointer_callback
    */
    */
@@ -199,10 +194,27 @@ class LockFreeStack {
 
 
   /**
   /**
    * The object pool, used for lock-free memory allocation.
    * 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;
   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)
    * Atomic pointer to the top node of the stack (element that is popped next)
    */
    */
   embb::base::Atomic<internal::LockFreeStackNode<Type>*> top;
   embb::base::Atomic<internal::LockFreeStackNode<Type>*> top;

containers_cpp/test/hazard_pointer_test.cc

@@ -31,24 +31,73 @@
 namespace embb {
 namespace embb {
 namespace containers {
 namespace containers {
 namespace test {
 namespace test {
+
+IntObjectTestPool::IntObjectTestPool(unsigned int poolSize) :
+poolSize(poolSize)
+{
+  simplePoolObjects = static_cast<int*>(
+    embb::base::Allocation::Allocate(sizeof(int)*poolSize));
+
+  simplePool = static_cast<embb::base::Atomic<int>*> (
+    embb::base::Allocation::Allocate(sizeof(embb::base::Atomic<int>)*
+    poolSize));
+
+  for (unsigned int i = 0; i != poolSize; ++i) {
+    //in-place new for each array cell
+    new (&simplePool[i]) embb::base::Atomic<int>;
+  }
+
+  for (unsigned int i = 0; i != poolSize; ++i) {
+    simplePool[i] = FREE_MARKER;
+    simplePoolObjects[i] = 0;
+  }
+}
+
+IntObjectTestPool::~IntObjectTestPool() {
+  embb::base::Allocation::Free(simplePoolObjects);
+
+  for (unsigned int i = 0; i != poolSize; ++i) {
+    //in-place new for each array cell
+    simplePool[i].~Atomic();
+  }
+
+  embb::base::Allocation::Free(simplePool);
+}
+
+int* IntObjectTestPool::Allocate() {
+  for (unsigned int i = 0; i != poolSize; ++i) {
+    int expected = FREE_MARKER;
+    if (simplePool[i].CompareAndSwap
+      (expected, ALLOCATED_MARKER)) {
+      return &simplePoolObjects[i];
+    }
+  }
+  return 0;
+}
+
+void IntObjectTestPool::Release(int* objectPointer) {
+  int cell = objectPointer - simplePoolObjects;
+  simplePool[cell].Store(FREE_MARKER);
+}
+
 HazardPointerTest::HazardPointerTest() :
 HazardPointerTest::HazardPointerTest() :
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #pragma warning(push)
 #pragma warning(push)
 #pragma warning(disable:4355)
 #pragma warning(disable:4355)
 #endif
 #endif
-  delete_pointer_callback(*this, &HazardPointerTest::DeletePointerCallback),
+deletePointerCallback(*this, &HazardPointerTest::DeletePointerCallback),
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #ifdef EMBB_PLATFORM_COMPILER_MSVC
 #pragma warning(pop)
 #pragma warning(pop)
 #endif
 #endif
-  object_pool(NULL),
+  objectPool(NULL),
   stack(NULL),
   stack(NULL),
-  hp(NULL),
-n_threads(static_cast<int>
+  hazardPointer(NULL),
+  nThreads(static_cast<int>
   (partest::TestSuite::GetDefaultNumThreads())) {
   (partest::TestSuite::GetDefaultNumThreads())) {
-  n_elements_per_thread = 100;
-  n_elements = n_threads*n_elements_per_thread;
+  nElementsPerThread = 100;
+  nElements = nThreads*nElementsPerThread;
   embb::base::Function < void, embb::base::Atomic<int>* >
   embb::base::Function < void, embb::base::Atomic<int>* >
-    delete_pointer_callback(
+    deletePointerCallback(
     *this,
     *this,
     &HazardPointerTest::DeletePointerCallback);
     &HazardPointerTest::DeletePointerCallback);
 
 
@@ -59,39 +108,46 @@ n_threads(static_cast<int>
   // placed, the pointer is not allowed to be deleted until the second thread
   // placed, the pointer is not allowed to be deleted until the second thread
   // removes this guard.
   // removes this guard.
   CreateUnit("HazardPointerTestThatGuardWorks").
   CreateUnit("HazardPointerTestThatGuardWorks").
-    Pre(&HazardPointerTest::HazardPointerTest1_Pre, this).
+    Pre(&HazardPointerTest::HazardPointerTest1Pre, this).
     Add(
     Add(
-    &HazardPointerTest::HazardPointerTest1_ThreadMethod,
-    this, static_cast<size_t>(n_threads)).
-    Post(&HazardPointerTest::HazardPointerTest1_Post, this);
+    &HazardPointerTest::HazardPointerTest1ThreadMethod,
+    this, static_cast<size_t>(nThreads)).
+    Post(&HazardPointerTest::HazardPointerTest1Post, this);
 }
 }
 
 
-void HazardPointerTest::HazardPointerTest1_Pre() {
+void HazardPointerTest::HazardPointerTest1Pre() {
   embb_internal_thread_index_reset();
   embb_internal_thread_index_reset();
-  object_pool = new embb::containers::ObjectPool< embb::base::Atomic<int> >
-    (static_cast<size_t>(n_elements));
-  stack = new embb::containers::LockFreeStack< embb::base::Atomic<int>* >
-    (static_cast<size_t>(n_elements));
-  hp = new embb::containers::internal::HazardPointer< embb::base::Atomic<int>*>
-    (delete_pointer_callback,
-    NULL,
+
+  objectPool =
+     embb::base::Allocation::
+     New<embb::containers::ObjectPool< embb::base::Atomic<int> > >
+     (static_cast<size_t>(nElements));
+
+  stack = embb::base::Allocation::
+    New<embb::containers::LockFreeStack< embb::base::Atomic<int>* > >
+    (static_cast<size_t>(nElements));
+
+  hazardPointer = embb::base::Allocation::
+    New<embb::containers::internal::HazardPointer < embb::base::Atomic<int>* > >
+    (deletePointerCallback,
+    static_cast<embb::base::Atomic<int>*>(NULL),
     1);
     1);
 }
 }
 
 
-void HazardPointerTest::HazardPointerTest1_Post() {
-  delete object_pool;
-  delete stack;
-  delete hp;
+void HazardPointerTest::HazardPointerTest1Post() {
+  embb::base::Allocation::Delete(hazardPointer);
+  embb::base::Allocation::Delete(objectPool);
+  embb::base::Allocation::Delete(stack);
 }
 }
 
 
-void HazardPointerTest::HazardPointerTest1_ThreadMethod() {
+void HazardPointerTest::HazardPointerTest1ThreadMethod() {
   unsigned int thread_index;
   unsigned int thread_index;
   embb_internal_thread_index(&thread_index);
   embb_internal_thread_index(&thread_index);
 
 
-  for (int i = 0; i != n_elements_per_thread; ++i) {
-    embb::base::Atomic<int>* allocated_object = object_pool->Allocate(0);
+  for (int i = 0; i != nElementsPerThread; ++i) {
+    embb::base::Atomic<int>* allocated_object = objectPool->Allocate(0);
 
 
-    hp->GuardPointer(0, allocated_object);
+    hazardPointer->Guard(0, allocated_object);
 
 
     bool success = stack->TryPush(allocated_object);
     bool success = stack->TryPush(allocated_object);
 
 
@@ -120,36 +176,360 @@ void HazardPointerTest::HazardPointerTest1_ThreadMethod() {
     }
     }
     PT_ASSERT(success_pop == true);
     PT_ASSERT(success_pop == true);
     allocated_object->Store(1);
     allocated_object->Store(1);
-    hp->EnqueuePointerForDeletion(allocated_object);
+    hazardPointer->EnqueueForDeletion(allocated_object);
 
 
     if (!same) {
     if (!same) {
-      hp->GuardPointer(0, allocated_object_from_different_thread);
+      hazardPointer->Guard(0, allocated_object_from_different_thread);
 
 
       // if this holds, we were successful in guarding... otherwise we
       // if this holds, we were successful in guarding... otherwise we
       // were to late, because the pointer has already been added
       // were to late, because the pointer has already been added
       // to the retired list.
       // to the retired list.
       if (*allocated_object_from_different_thread == 0) {
       if (*allocated_object_from_different_thread == 0) {
         // the pointer must not be deleted here!
         // the pointer must not be deleted here!
-        vector_mutex.Lock();
+        vectorMutex.Lock();
         for (std::vector< embb::base::Atomic<int>* >::iterator
         for (std::vector< embb::base::Atomic<int>* >::iterator
-          it = deleted_vector.begin();
-          it != deleted_vector.end();
+          it = deletedVector.begin();
+          it != deletedVector.end();
         ++it) {
         ++it) {
           PT_ASSERT(*it != allocated_object_from_different_thread);
           PT_ASSERT(*it != allocated_object_from_different_thread);
         }
         }
-        vector_mutex.Unlock();
+        vectorMutex.Unlock();
       }
       }
-      hp->GuardPointer(0, NULL);
+      hazardPointer->Guard(0, NULL);
     }
     }
   }
   }
 }
 }
 
 
 void HazardPointerTest::DeletePointerCallback
 void HazardPointerTest::DeletePointerCallback
 (embb::base::Atomic<int>* to_delete) {
 (embb::base::Atomic<int>* to_delete) {
-  vector_mutex.Lock();
-  deleted_vector.push_back(to_delete);
-  vector_mutex.Unlock();
+  vectorMutex.Lock();
+  deletedVector.push_back(to_delete);
+  vectorMutex.Unlock();
+}
+
+void HazardPointerTest2::DeletePointerCallback(int* toDelete) {
+  testPool->Release(toDelete);
+}
+
+bool HazardPointerTest2::SetRelativeGuards() {
+  unsigned int threadIndex;
+  embb_internal_thread_index(&threadIndex);
+
+  unsigned int my_begin = guardsPerThreadCount*threadIndex;
+  int guardNumber = 0;
+  unsigned int alreadyGuarded = 0;
+
+  for (unsigned int i = my_begin; i != my_begin + guardsPerThreadCount; ++i){
+    if (sharedGuarded[i] != 0) {
+      alreadyGuarded++;
+      guardNumber++;
+      continue;
+    }
+
+    int * toGuard = sharedAllocated[i];
+    if (toGuard) {
+      hazardPointer->Guard(guardNumber, toGuard);
+
+      // changed in the meantime?
+      if (toGuard == sharedAllocated[i].Load()) {
+        // guard was successful. Communicate to other threads.
+        sharedGuarded[i] = toGuard;
+      }
+      else {
+        // reset the guard, couldn't guard...
+        hazardPointer->RemoveGuard(guardNumber);
+      }
+    }
+    guardNumber++;
+  }
+  return(alreadyGuarded == guardsPerThreadCount);
+}
+
+void HazardPointerTest2::HazardPointerTest2Master() {
+  // while the hazard pointer guard array is not full
+  int** allocatedLocal = static_cast<int**>(
+  embb::base::Allocation::Allocate(sizeof(int*)*guaranteedCapacityPool));
+
+  bool full = false;
+  while (!full) {
+    full = true;
+    for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+      if (sharedGuarded[i] == 0) {
+        full = false;
+        break;
+      }
+    }
+
+    // not all guards set
+    for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+      allocatedLocal[i] = testPool->Allocate();
+      sharedAllocated[i].Store(allocatedLocal[i]);
+    }
+
+    // set my hazards. We do not have to check, this must be successful
+    // here.
+    SetRelativeGuards();
+
+    // free
+    for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+      sharedAllocated[i].Store(0);
+      hazardPointer->EnqueueForDeletion(allocatedLocal[i]);
+    }
+  }
+
+  embb::base::Allocation::Free(allocatedLocal);
+}
+
+void HazardPointerTest2::HazardPointerTest2Slave() {
+  unsigned int thread_index;
+  embb_internal_thread_index(&thread_index);
+
+  while (!SetRelativeGuards()) {};
+}
+
+void HazardPointerTest2::HazardPointerTest2Pre() {
+  embb_internal_thread_index_reset();
+  currentMaster = 0;
+  sync1 = 0;
+  sync2 = 0;
+
+  // first the test pool has to be created
+  testPool = embb::base::Allocation::New<IntObjectTestPool>(poolSizeUsingHazardPointer);
+
+  // after the pool has been created, we create the hp class
+  hazardPointer = embb::base::Allocation::New <
+    embb::containers::internal::HazardPointer<int*> >
+    (deletePointerCallback, static_cast<int*>(NULL),
+    static_cast<int>(guardsPerThreadCount), nThreads);
+
+  sharedGuarded = static_cast<embb::base::Atomic<int*>*>(
+    embb::base::Allocation::Allocate(sizeof(embb::base::Atomic<int*>)*
+    guaranteedCapacityPool)
+  );
+
+  for (unsigned int i = 0; i !=
+  guaranteedCapacityPool; ++i) {
+    //in-place new for each array cell
+    new (&sharedGuarded[i]) embb::base::Atomic < int* > ;
+  }
+
+  sharedAllocated = static_cast<embb::base::Atomic<int*>*>(
+    embb::base::Allocation::Allocate(sizeof(embb::base::Atomic<int*>)*
+    guaranteedCapacityPool)
+  );
+
+  for (unsigned int i = 0; i !=
+  guaranteedCapacityPool; ++i) {
+    //in-place new for each array cell
+    new (&sharedAllocated[i]) embb::base::Atomic < int* > ;
+  }
+
+  for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+    sharedGuarded[i] = 0;
+    sharedAllocated[i] = 0;
+  }
+}
+
+void HazardPointerTest2::HazardPointerTest2Post() {
+
+  for (unsigned int i = 0; i != static_cast<unsigned int>(nThreads); ++i) {
+    for (unsigned int i2 = 0; i2 != static_cast<unsigned int>(nThreads)*
+      guardsPerThreadCount; ++i2) {
+      if (hazardPointer->threadLocalRetiredLists
+        [i2 + i*nThreads*guardsPerThreadCount] == NULL) {
+        // all retired lists must be completely filled
+        PT_ASSERT(false);
+      }
+    }
+  }
+
+  unsigned int checks = 0;
+  for (unsigned int i = 0; i != static_cast<unsigned int>(nThreads); ++i) {
+    for (unsigned int i2 = 0; i2 != static_cast<unsigned int>(nThreads)*
+      guardsPerThreadCount; ++i2) {
+      for (unsigned int j = 0; j != static_cast<unsigned int>(nThreads); ++j) {
+        for (unsigned int j2 = 0; j2 != static_cast<unsigned int>(nThreads)*
+          guardsPerThreadCount; ++j2) {
+          if (i2 == j2 && i == j)
+            continue;
+
+          // all retired elements have to be disjoint
+          PT_ASSERT(
+            hazardPointer->threadLocalRetiredLists
+            [i2 + i*nThreads*guardsPerThreadCount] !=
+            hazardPointer->threadLocalRetiredLists
+            [j2 + j*nThreads*guardsPerThreadCount]
+          );
+
+          checks++;
+        }
+      }
+    }
+  }
+
+  // sanity check on the count of expected comparisons.
+  PT_ASSERT(
+    checks ==
+    nThreads*nThreads*guardsPerThreadCount *
+    (nThreads*nThreads*guardsPerThreadCount - 1)
+    );
+
+  std::vector< int* > additionallyAllocated;
+
+  // we should be able to still allocate the guaranteed capacity of
+  // elements from the pool.
+  for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+    int* allocated = testPool->Allocate();
+
+    // allocated is not allowed to be zero
+    PT_ASSERT(allocated != NULL);
+
+    // push to vector, to check if elements are disjunctive and to release
+    // afterwards.
+    additionallyAllocated.push_back(allocated);
+  }
+
+  // the pool should now be empty
+  PT_ASSERT(testPool->Allocate() == NULL);
+
+  // release allocated elements...
+  for (unsigned int i = 0; i != additionallyAllocated.size(); ++i) {
+    testPool->Release(additionallyAllocated[i]);
+  }
+
+  // the additionallyAllocated elements shall be disjoint
+  for (unsigned int i = 0; i != additionallyAllocated.size(); ++i) {
+    for (unsigned int i2 = 0; i2 != additionallyAllocated.size(); ++i2) {
+      if (i == i2)
+        continue;
+      PT_ASSERT(additionallyAllocated[i] !=
+        additionallyAllocated[i2]);
+    }
+  }
+
+  // no allocated element should be in any retired list...
+  for (unsigned int a = 0; a != additionallyAllocated.size(); ++a) {
+    for (unsigned int i = 0; i != static_cast<unsigned int>(nThreads); ++i) {
+      for (unsigned int i2 = 0; i2 != static_cast<unsigned int>(nThreads)*
+        guardsPerThreadCount; ++i2) {
+        PT_ASSERT(
+          hazardPointer->threadLocalRetiredLists
+          [i2 + i*nThreads*guardsPerThreadCount] !=
+          additionallyAllocated[a]
+          );
+      }
+    }
+  }
+
+  for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+    //in-place new for each array cell
+    sharedGuarded[i].~Atomic();
+  }
+
+  embb::base::Allocation::Free(sharedGuarded);
+
+  for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+    //in-place new for each array cell
+    sharedAllocated[i].~Atomic();
+  }
+
+  embb::base::Allocation::Free(sharedAllocated);
+  embb::base::Allocation::Delete(hazardPointer);
+
+  // after deleting the hazard pointer object, all retired pointers have
+  // to be returned to the pool!
+  std::vector<int*> elementsInPool;
+
+  int* nextElement;
+  while ((nextElement = testPool->Allocate()) != NULL) {
+    for (unsigned int i = 0; i != elementsInPool.size(); ++i) {
+      // all elements need to be disjoint
+      PT_ASSERT(elementsInPool[i] != nextElement);
+    }
+    elementsInPool.push_back(nextElement);
+  }
+
+  // all elements should have been returned by the hp object, so we should be
+  // able to acquire all elements.
+  PT_ASSERT(elementsInPool.size() == poolSizeUsingHazardPointer);
+
+  embb::base::Allocation::Delete(testPool);
+}
+
+void HazardPointerTest2::HazardPointerTest2ThreadMethod() {
+  for (;;) {
+    unsigned int threadIndex;
+    embb_internal_thread_index(&threadIndex);
+
+    if (threadIndex == currentMaster) {
+      HazardPointerTest2Master();
+    }
+    else {
+      HazardPointerTest2Slave();
+    }
+
+    sync1.FetchAndAdd(1);
+
+    // wait until cleanup thread signals to be finished
+    while (sync1 != 0) {
+      int expected = nThreads;
+      int desired = finishMarker;
+      // select thread, responsible for cleanup
+      if (sync1.CompareAndSwap(expected, desired)) {
+
+        //wipe arrays!
+        for (unsigned int i = 0; i != guaranteedCapacityPool; ++i) {
+          sharedGuarded[i] = 0;
+          sharedAllocated[i] = 0;
+        }
+
+        // increase master
+        currentMaster.FetchAndAdd(1);
+        sync2 = 0;
+        sync1.Store(0);
+      }
+    }
+
+    // wait for all threads to reach this position
+    sync2.FetchAndAdd(1);
+    while (sync2 != static_cast<unsigned int>(nThreads)) {}
+
+    // if each thread was master once, terminate.
+    if (currentMaster == static_cast<unsigned int>(nThreads)) {
+      return;
+    }
+  }
 }
 }
+
+HazardPointerTest2::HazardPointerTest2() :
+nThreads(static_cast<int>
+(partest::TestSuite::GetDefaultNumThreads())),
+
+#ifdef EMBB_PLATFORM_COMPILER_MSVC
+#pragma warning(push)
+#pragma warning(disable:4355)
+#endif
+   deletePointerCallback(
+   *this,
+   &HazardPointerTest2::DeletePointerCallback)
+#ifdef EMBB_PLATFORM_COMPILER_MSVC
+#pragma warning(pop)
+#endif
+{
+  guardsPerThreadCount = 5;
+  guaranteedCapacityPool = guardsPerThreadCount*nThreads;
+  poolSizeUsingHazardPointer = guaranteedCapacityPool +
+    guardsPerThreadCount*nThreads*nThreads;
+
+  embb::base::Thread::GetThreadsMaxCount();
+  CreateUnit("HazardPointerTestSimulateMemoryWorstCase").
+    Pre(&HazardPointerTest2::HazardPointerTest2Pre, this).
+    Add(
+    &HazardPointerTest2::HazardPointerTest2ThreadMethod,
+    this, static_cast<size_t>(nThreads)).
+    Post(&HazardPointerTest2::HazardPointerTest2Post, this);
+}
+
 } // namespace test
 } // namespace test
 } // namespace containers
 } // namespace containers
 } // namespace embb
 } // namespace embb

containers_cpp/test/hazard_pointer_test.h

@@ -36,33 +36,116 @@
 namespace embb {
 namespace embb {
 namespace containers {
 namespace containers {
 namespace test {
 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 {
 class HazardPointerTest : public partest::TestCase {
  private:
  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
   //used to allocate random stuff, we will just use the pointers, not the
   //contents
   //contents
-  embb::containers::ObjectPool< embb::base::Atomic<int> >* object_pool;
+  embb::containers::ObjectPool< embb::base::Atomic<int> >* objectPool;
 
 
   //used to move pointer between threads
   //used to move pointer between threads
   embb::containers::LockFreeStack< embb::base::Atomic<int>* >* stack;
   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:
  public:
   /**
   /**
   * Adds test methods.
   * Adds test methods.
   */
   */
   HazardPointerTest();
   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 test
 } // namespace containers
 } // namespace containers
 } // namespace embb
 } // 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::QueueTest;
 using embb::containers::test::StackTest;
 using embb::containers::test::StackTest;
 using embb::containers::test::ObjectPoolTest;
 using embb::containers::test::ObjectPoolTest;
+using embb::containers::test::HazardPointerTest2;
 
 
 PT_MAIN("Data Structures C++") {
 PT_MAIN("Data Structures C++") {
   unsigned int max_threads = static_cast<unsigned int>(
   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< WaitFreeArrayValuePool<int COMMA -1> >);
   PT_RUN(PoolTest< LockFreeTreeValuePool<int COMMA -1> >);
   PT_RUN(PoolTest< LockFreeTreeValuePool<int COMMA -1> >);
   PT_RUN(HazardPointerTest);
   PT_RUN(HazardPointerTest);
+  PT_RUN(HazardPointerTest2);
   PT_RUN(QueueTest< WaitFreeSPSCQueue< ::std::pair<size_t COMMA int> > >);
   PT_RUN(QueueTest< WaitFreeSPSCQueue< ::std::pair<size_t COMMA int> > >);
   PT_RUN(QueueTest< LockFreeMPMCQueue< ::std::pair<size_t COMMA int> >
   PT_RUN(QueueTest< LockFreeMPMCQueue< ::std::pair<size_t COMMA int> >
     COMMA true COMMA true >);
     COMMA true COMMA true >);