descriptor_util.h

Go to the documentation of this file.

/*
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_MEMORY_RC_UTIL_DESCRIPTOR_H_
#define TERVEL_MEMORY_RC_UTIL_DESCRIPTOR_H_

#include <tervel/util/info.h>
#include <tervel/util/descriptor.h>
#include <tervel/util/recursive_action.h>
#include <tervel/util/memory/rc/pool_element.h>
#include <tervel/util/memory/rc/descriptor_pool.h>
#include <tervel/util/progress_assurance.h>
#include <tervel/util/memory/rc/descriptor_read_first_op.h>

namespace tervel {
namespace util {

class Descriptor;

namespace memory {
namespace rc {

template<typename DescrType, typename... Args>
inline DescrType * get_descriptor(Args&&... args) {
  auto rc_descr_pool = tervel::tl_thread_info->get_rc_descriptor_pool();
  return rc_descr_pool->get_descriptor<DescrType>(std::forward<Args>(args)...);
}

inline void free_descriptor(tervel::util::Descriptor *descr,
      bool dont_check = false) {
  tervel::tl_thread_info->get_rc_descriptor_pool()->free_descriptor(descr,
        dont_check);
}

inline bool is_watched(tervel::util::Descriptor *descr) {
  #ifdef TERVEL_MEM_RC_NO_WATCH
  return false;
  #endif  // TERVEL_MEM_RC_NO_WATCH
  PoolElement * elem = get_elem_from_descriptor(descr);
  int64_t ref_count = elem->header().ref_count.load();
  assert(ref_count >=0 && " Ref count of an object is negative, which implies some thread called unwatch multiple times on the same object");
  if (ref_count == 0) {
    return descr->on_is_watched();
  } else {
    return true;
  }
}

inline bool watch(tervel::util::Descriptor *descr, std::atomic<void *> *address,
        void *value) {
  #ifdef TERVEL_MEM_RC_NO_WATCH
    return true;
  #endif  // TERVEL_MEM_RC_NO_WATCH

  PoolElement *elem = get_elem_from_descriptor(descr);
  elem->header().ref_count.fetch_add(1);

  if (address->load() != value) {
    int64_t temp = elem->header().ref_count.fetch_add(-1);
    assert(temp > 0 && " Ref count of an object is negative, which implies some thread called unwatch multiple times on the same object");
    return false;
  } else {
    bool res = descr->on_watch(address, value);
    if (res) {
      assert(is_watched(descr) && "On watch returned true, but the object is not watched. Error could exist on either [on_]watch or [on_]is_watched functions");
     return true;
    } else {
      int64_t temp = elem->header().ref_count.fetch_add(-1);
      assert(temp > 0 && " Ref count of an object is negative, which implies some thread called unwatch multiple times on the same object");
      return false;
    }
  }
}

inline void unwatch(tervel::util::Descriptor *descr) {
  #ifdef TERVEL_MEM_RC_NO_WATCH
    return;
  #endif  // TERVEL_MEM_RC_NO_WATCH

  PoolElement *elem = get_elem_from_descriptor(descr);
  int64_t temp = elem->header().ref_count.fetch_add(-1);
  assert(temp > 0 && " Ref count of an object is negative, which implies some thread called unwatch multiple times on the same object");
  descr->on_unwatch();
}

inline void * mark_first(tervel::util::Descriptor *descr) {
  return reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(descr) | 0x1L);
}

inline void atomic_mark_first(std::atomic<void*> *address) {
  std::atomic<uintptr_t> *temp = reinterpret_cast<std::atomic<uintptr_t> *>(address);
  temp->fetch_or(0x1);
}

inline tervel::util::Descriptor * unmark_first(void *descr) {
  return reinterpret_cast<tervel::util::Descriptor *>(
      reinterpret_cast<uintptr_t>(descr) & ~0x1L);
}

inline bool is_descriptor_first(void *descr) {
  return (0x1L == (reinterpret_cast<uintptr_t>(descr) & 0x1L));
}

inline void * remove_descriptor(void *expected, std::atomic<void *> *address) {
  tervel::util::RecursiveAction recurse;
  void *newValue;
  if (tervel::util::RecursiveAction::recursive_return()) {
    newValue = nullptr;  // result not used
  } else {
    tervel::util::Descriptor *descr = unmark_first(expected);
    if (watch(descr, address, expected)) {
      newValue = descr->complete(expected, address);
      unwatch(descr);
    } else {
      newValue = address->load();
    }
  }
  return newValue;
}

inline void *descriptor_read_first(std::atomic<void *> *address) {
  void *current_value = address->load();

  util::ProgressAssurance::Limit progAssur;


  while (is_descriptor_first(current_value)) {

    if (progAssur.isDelayed()) {
      ReadFirstOp *op = new ReadFirstOp(address);
      tervel::util::ProgressAssurance::make_announcement(
          reinterpret_cast<tervel::util::OpRecord *>(op));
      current_value = op->load();
      op->safe_delete();
      return current_value;
    } else {
      tervel::util::Descriptor *descr = unmark_first(current_value);
      if (watch(descr, address, current_value)) {
        current_value = descr->get_logical_value();
        unwatch(descr);
      } else {
        current_value = address->load();
      }
    }
  }
  return current_value;
}

}  // namespace rc
}  // namespace memory
}  // namespace util
}  // namespace tervel


#endif  // TERVEL_MEMORY_RC_UTIL_DESCRIPTOR_H_