WaitingTaskList.h

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#ifndef FWCore_Concurrency_WaitingTaskList_h
#define FWCore_Concurrency_WaitingTaskList_h
// -*- C++ -*-
//
// Package:     Concurrency
// Class  :     WaitingTaskList
//
//
// Original Author:  Chris Jones
//         Created:  Thu Feb 21 13:46:31 CST 2013
// $Id$
//

// system include files
#include <atomic>

// user include files
#include "FWCore/Concurrency/interface/WaitingTask.h"
#include "FWCore/Utilities/interface/thread_safety_macros.h"

// forward declarations

namespace edm {
  class EmptyWaitingTask : public WaitingTask {
  public:
    EmptyWaitingTask() = default;

    tbb::task* execute() override { return nullptr; }
  };

  namespace waitingtask {
    struct TaskDestroyer {
      void operator()(tbb::task* iTask) const { tbb::task::destroy(*iTask); }
    };
  }  // namespace waitingtask
  inline std::unique_ptr<edm::EmptyWaitingTask, waitingtask::TaskDestroyer> make_empty_waiting_task() {
    return std::unique_ptr<edm::EmptyWaitingTask, waitingtask::TaskDestroyer>(new (tbb::task::allocate_root())
                                                                                  edm::EmptyWaitingTask{});
  }

  class WaitingTaskList {
  public:

    explicit WaitingTaskList(unsigned int iInitialSize = 2);
    ~WaitingTaskList() = default;

    // ---------- member functions ---------------------------

    void presetTaskAsFailed(std::exception_ptr iExcept);


    void add(WaitingTask*);


    void doneWaiting(std::exception_ptr iPtr);


    void reset();

  private:
    WaitingTaskList(const WaitingTaskList&) = delete;                   // stop default
    const WaitingTaskList& operator=(const WaitingTaskList&) = delete;  // stop default

    void announce();

    struct WaitNode {
      WaitingTask* m_task;
      std::atomic<WaitNode*> m_next;
      bool m_fromCache;

      void setNextNode(WaitNode* iNext) { m_next = iNext; }

      WaitNode* nextNode() const { return m_next; }
    };

    WaitNode* createNode(WaitingTask* iTask);

    // ---------- member data --------------------------------
    std::atomic<WaitNode*> m_head;
    std::unique_ptr<WaitNode[]> m_nodeCache;
    CMS_THREAD_GUARD(m_waiting) std::exception_ptr m_exceptionPtr;
    unsigned int m_nodeCacheSize;
    std::atomic<unsigned int> m_lastAssignedCacheIndex;
    std::atomic<bool> m_waiting;
  };
}  // namespace edm

#endif