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#ifndef SHARE_VM_GC_CONCURRENTGCPHASEMANAGER_HPP

#define SHARE_VM_GC_CONCURRENTGCPHASEMANAGER_HPP

#include "memory/allocation.hpp"

// Manage concurrent phase information, to support WhiteBox testing.

// Managers are stack allocated.  Managers may be nested, to support

// nested subphases.

class ConcurrentGCPhaseManager : public StackObj {

public:

  // Special phase ids used by all GC's that use this facility.

  static const int UNCONSTRAINED_PHASE = 0; // Unconstrained or no request.

  static const int IDLE_PHASE = 1;          // Concurrent processing is idle.

  // Stack of phase managers.

    friend class ConcurrentGCPhaseManager;

  public:

    // Create an empty stack of phase managers.

    Stack();

  private:

    int _requested_phase;

    ConcurrentGCPhaseManager* _top;

    // Non-copyable - never defined.

    Stack(const Stack&);

    Stack& operator=(const Stack&);

  };

  // Construct and push a new manager on the stack, activating phase.

  // Notifies callers in wait_for_phase of the phase change.

  //

  // Preconditions:

  // - Calling thread must be a ConcurrentGC thread

  // - phase != UNCONSTRAINED_PHASE

  // - stack != NULL

  // - other managers on stack must all be active.

  ConcurrentGCPhaseManager(int phase, Stack* stack);

  // Pop this manager off the stack, deactivating phase.  Before

  // changing phases, if is_requested() is true, wait until the

  // request is changed.  After changing phases, notifies callers of

  // wait_for_phase of the phase change.

  //

  // Preconditions:

  // - Calling thread must be a ConcurrentGC thread

  // - this must be the current top of the manager stack

  ~ConcurrentGCPhaseManager();

  // Returns true if this phase is active and is currently requested.

  //

  // Preconditions:

  // - Calling thread must be a ConcurrentGC thread

  // - this must be the current top of manager stack

  bool is_requested() const;

  // Wait until is_requested() is false.  Returns true if waited.

  //

  // Preconditions:

  // - Calling thread must be a ConcurrentGC thread

  // - this must be the current top of manager stack

  bool wait_when_requested() const;

  // Directly step from one phase to another, without needing to pop a

  // manager from the stack and allocate a new one.  Before changing

  // phases, if is_requested() is true and force is false, wait until

  // the request is changed.  After changing phases, notifies callers

  // of wait_for_phase of the phase change.

  //

  // Preconditions:

  // - Calling thread must be a ConcurrentGC thread

  // - phase != UNCONSTRAINED_PHASE

  // - this must be the current top of manager stack

  void set_phase(int phase, bool force);

  // Deactivate the manager.  An inactive manager no longer blocks

  // transitions out of the associated phase when that phase has been

  // requested.

  //

  // Preconditions:

  // - Calling thread must be a ConcurrentGC thread

  // - this must be the current top of manager stack

  void deactivate();

  // Used to implement CollectorPolicy::request_concurrent_phase().

  // Updates request to the new phase, and notifies threads blocked on

  // the old request of the change.  Returns true if the phase is

  // UNCONSTRAINED_PHASE.  Otherwise, waits until an active phase is

  // the requested phase (returning true) or IDLE_PHASE (returning

  // false if not also the requested phase).

  //

  // Preconditions:

  // - Calling thread must be a Java thread

  // - stack must be non-NULL

  static bool wait_for_phase(int phase, Stack* stack);

private:

  int _phase;

  bool _active;

  ConcurrentGCPhaseManager* _prev;

  Stack* _stack;

  // Non-copyable - never defined.

  ConcurrentGCPhaseManager(const ConcurrentGCPhaseManager&);

  ConcurrentGCPhaseManager& operator=(const ConcurrentGCPhaseManager&);

  bool wait_when_requested_impl() const;

};

#endif // include guard