write_op.h

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/*
The MIT License (MIT)

Copyright (c) 2015 University of Central Florida's Computer Software Engineering
Scalable & Secure Systems (CSE - S3) Lab

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
#ifndef __TERVEL_CONTAINERS_WF_VECTOR_WRITE_OP_H
#define __TERVEL_CONTAINERS_WF_VECTOR_WRITE_OP_H


#include <tervel/util/info.h>
#include <tervel/util/descriptor.h>
#include <tervel/util/progress_assurance.h>
#include <tervel/util/memory/hp/hazard_pointer.h>
#include <tervel/util/memory/rc/descriptor_util.h>


#include <tervel/containers/wf/vector/vector.hpp>

namespace tervel {
namespace containers {
namespace wf {
namespace vector {

template<typename T>
class WriteHelper;


template<typename T>
class WriteOp: public tervel::util::OpRecord {
 public:
  WriteOp(Vector<T> *vec, size_t idx, T expected, T val)
    : vec_(vec)
    , idx_(idx)
    , expected_(expected)
    , new_val_(val) {}

  ~WriteOp() {
    WriteHelper<T> * c_fail_pointer_ =
        reinterpret_cast<WriteHelper<T> *>(~0x1L);
    WriteHelper<T> * temp = helper_.load();
    assert(temp != nullptr);
    if (temp != c_fail_pointer_) {
      util::memory::rc::free_descriptor(temp, true);
    }
  }

  void help_complete() {
    tervel::tl_control_word = reinterpret_cast< std::atomic<void *>*>(&helper_);
    WriteHelper<T> * c_fail_pointer_ =
        reinterpret_cast<WriteHelper<T> *>(~0x1L);

    if (idx_ < vec_->size()) {
      std::atomic<T> *spot = vec_->internal_array.get_spot(idx_, false);

      while (helper_.load() == nullptr) {
        T cvalue = spot->load();

        if (cvalue == Vector<T>::c_not_value_) {
          break;  // will set to failed
        } else if (vec_->internal_array.is_descriptor(cvalue, spot)) {
          continue;
        } else {
          assert(vec_->internal_array.is_valid(cvalue));
          WriteHelper<T> *helper = tervel::util::memory::rc::get_descriptor<
            WriteHelper<T> >(this, cvalue);

          T help_t = reinterpret_cast<T>(util::memory::rc::mark_first(helper));
          bool res = spot->compare_exchange_strong(cvalue, help_t);
          if (res) {
            WriteHelper<T> * helper_null = nullptr;
            res = helper_.compare_exchange_strong(helper_null, helper);
            res = (res || (helper_null == helper));
            assert(helper_.load() !=  nullptr);

            T new_val;
            if (res && (expected_ == cvalue)) {
              new_val = new_val_;
            } else {
              new_val = cvalue;
            }
            spot->compare_exchange_strong(help_t, new_val);

            if (!res) {
              util::memory::rc::free_descriptor(helper);
            }
            return;

          } else {
            util::memory::rc::free_descriptor(helper, true);
          }
        }
      }  // while value_ is c_not_value
    }


    WriteHelper<T> *helper_null = nullptr;
    helper_.compare_exchange_strong(helper_null, c_fail_pointer_);
    assert(helper_.load() !=  nullptr);
  };

  bool result(T &expected) {
    WriteHelper<T> * c_fail_pointer_ =
        reinterpret_cast<WriteHelper<T> *>(~0x1L);
    WriteHelper<T> * temp = helper_.load();
    if (temp == c_fail_pointer_) {
      return false;  // out of bounds exception
    } else if (temp->value() == expected_) {
      return true;
    } else {
      expected = temp->value();
      return false;
    }
    assert(false);
    return false;
  };

  bool is_watched() {
    WriteHelper<T> * temp = helper_.load();

    if (temp == nullptr) {
      assert(false);  // THis state should not be reached
      return false;
    } else if (temp == reinterpret_cast<WriteHelper<T> *>(~0x1L)) {
      return false;
    } else {
      return (helper_.load())->is_watched();
    }
  }

 private:
  friend class WriteHelper<T>;
  Vector<T> *vec_;
  size_t idx_;
  T expected_;
  T new_val_;
  std::atomic<WriteHelper<T> *> helper_ {nullptr};
};  // class WriteOp

template<typename T>
class WriteHelper: public tervel::util::Descriptor {
 public:
  explicit WriteHelper(WriteOp<T> *op, T val)
    : op_(op)
    , val_(val) {}

  T value() {
    return val_;
  }

  using util::Descriptor::complete;
  void * complete(void *value, std::atomic<void *> *address) {
    void * marked = reinterpret_cast<void *>(
          util::memory::rc::mark_first(this));
    assert(marked == value);

    WriteHelper<T> * helper_null = nullptr;
    bool res = op_->helper_.compare_exchange_strong(helper_null, this);
    res = (res || (helper_null == this));
    assert(op_->helper_.load() !=  nullptr);

    void *new_val;
    if (res && (op_->expected_ == val_)) {
      new_val = reinterpret_cast<void *>(op_->new_val_);
    } else {
      new_val = reinterpret_cast<void *>(val_);
    }

    res = address->compare_exchange_strong(marked, new_val);
    if (res) {
      return new_val;
    } else {
      return marked;
    }
  }

  void * get_logical_value() {
    WriteHelper<T> * helper = op_->helper_.load();
    if (helper == this) {
      return reinterpret_cast<void *>(op_->new_val_);
    } else {
      return reinterpret_cast<void *>(val_);
    }
  }

  using util::Descriptor::on_watch;
  bool on_watch(std::atomic<void *> *address, void * value) {
    typedef util::memory::hp::HazardPointer::SlotID t_SlotID;
    bool success = util::memory::hp::HazardPointer::watch(
          t_SlotID::SHORTUSE, op_, address, value);

    if (success) {
      /* Success, means that the WriteOP referenced by this Helper can not
       * be freed while we check to make sure this Helper is associated with
       * it. */
      WriteHelper<T> *helper = op_->helper_.load();
      if (helper == nullptr) {
         if (op_->helper_.compare_exchange_strong(helper, this)) {
           /* If this passed then helper == nullptr, so we set it to be ==
            * this */
            helper = this;
         }
      }

      assert(op_->helper_.load() == helper);

      if (helper != this) {
        /* This Helper was placed in error, remove it and replace it with the
         * logic value of this object (expected_value)
         */
        address->compare_exchange_strong(value, reinterpret_cast<void *>(val_));
      } else {
        address->compare_exchange_strong(value, reinterpret_cast<void *>(op_->new_val_));
      }
      /* No longer need HP protection, if we have RC protection on an associated
       * Helper. If we don't it, the value at this address must have changed and
       * we don't need it either way.
       */
      util::memory::hp::HazardPointer::unwatch(t_SlotID::SHORTUSE);
    }  // End Successful watch

    return false;
  };

  private:
    friend class WriteOp<T>;
    WriteOp<T> *op_;
    const T val_;
};  // class WriteHelper
}  // namespace vector
}  // namespace wf
}  // namespace containers
}  // namespace tervel
#endif  // __TERVEL_CONTAINERS_WF_VECTOR_WRITE_OP_H