text: /*
   * Copyright (c) 2017 Advanced Micro Devices, Inc.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met: redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer;
   * redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution;
   * neither the name of the copyright holders nor the names of its
   * contributors may be used to endorse or promote products derived from
   * this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef __FUTEX_MAP_HH__
  #define __FUTEX_MAP_HH__
  
  #include <unordered_map>
  #include <unordered_set>
  
  #include <cpu/thread_context.hh>
  
  namespace gem5
  {
  
  /**
   * FutexKey class defines an unique identifier for a particular futex in the
   * system. The tgid and an address are the unique values needed as the key.
   */
  class FutexKey
  {
    public:
      uint64_t addr;
      uint64_t tgid;
  
      FutexKey(uint64_t addr_in, uint64_t tgid_in);
  
      bool operator==(const FutexKey &in) const;
  };
  
  } // namespace gem5
  
  namespace std
  {
      /**
       * The unordered_map structure needs the parenthesis operator defined for
       * std::hash if a user defined key is used. Our key is is user defined
       * so we need to provide the hash functor.
       */
      template <>
      struct hash<gem5::FutexKey>
      {
          size_t operator()(const gem5::FutexKey& in) const
          {
              size_t hash = 65521;
              for (int i = 0; i < sizeof(uint64_t) / sizeof(size_t); i++) {
                  hash ^= (size_t)(in.addr >> sizeof(size_t) * i) ^
                          (size_t)(in.tgid >> sizeof(size_t) * i);
              }
              return hash;
          }
      };
  } // namespace std
  
  namespace gem5
  {
  
  /**
   * WaiterState defines internal state of a waiter thread. The state
   * includes a pointer to the thread's context and its associated bitmask.
   */
  class WaiterState
  {
    public:
      ThreadContext* tc;
      int bitmask;
  
      /**
       * this constructor is used if futex ops with bitset are used
       */
      WaiterState(ThreadContext* _tc, int _bitmask);
  
      /**
       * return true if the bit-wise AND of the wakeup_bitmask given by
       * a waking thread and this thread's internal bitmask is non-zero
       */
      bool checkMask(int wakeup_bitmask) const;
  };
  
  typedef std::list<WaiterState> WaiterList;
  
  /**
   * FutexMap class holds a map of all futexes used in the system
   */
  class FutexMap : public std::unordered_map<FutexKey, WaiterList>
  {
    public:
      /** Inserts a futex into the map with one waiting TC */
      void suspend(Addr addr, uint64_t tgid, ThreadContext *tc);
  
      /** Wakes up at most count waiting threads on a futex */
      int wakeup(Addr addr, uint64_t tgid, int count);
  
      void suspend_bitset(Addr addr, uint64_t tgid, ThreadContext *tc,
                     int bitmask);
  
      int wakeup_bitset(Addr addr, uint64_t tgid, int bitmask);
  
      /**
       * This operation wakes a given number (val) of waiters. If there are
       * more threads waiting than woken, they are removed from the wait
       * queue of the futex pointed to by addr1 and added to the wait queue
       * of the futex pointed to by addr2. The number of waiter moved is
       * capped by count2 (misused timeout parameter).
       *
       * The return value is the number of waiters that are woken or
       * requeued.
       */
      int requeue(Addr addr1, uint64_t tgid, int count, int count2, Addr addr2);
  
      /**
       * Determine if the given thread context is currently waiting on a
       * futex wait operation on any of the futexes tracked by this FutexMap.
       */
      bool is_waiting(ThreadContext *tc);
  
    private:
  
      std::unordered_set<ThreadContext *> waitingTcs;
  };
  
  } // namespace gem5
  
  #endif // __FUTEX_MAP_HH__
  