mutex.hpp

/* Copyright © 2017 Apple Inc. All rights reserved.
 *
 * Use of this source code is governed by a BSD-3-clause license that can
 * be found in the LICENSE.txt file or at
 * https://opensource.org/licenses/BSD-3-Clause
 */
#ifndef TURI_MUTEX_HPP
#define TURI_MUTEX_HPP

#include <core/parallel/pthread_h.h>
#include <core/logging/assertions.hpp>
#include <mutex>

namespace turi {

/**
 * \ingroup threading
 *
 * Simple wrapper around pthread's mutex.
 * Before you use, see \ref parallel_object_intricacies.
 *
 * Windows recursive mutex are annoyingly recursive.
 * We need to prevent recursive locks. We do this by associating an
 * addition boolean "locked" to the mutex.
 * Hence in the event of a double lock, on Windows the behavior is slightly
 * different. On Linux/Mac this will trigger a deadlock. On Windows,
 * this will trigger an assertion failure.
 */
class mutex {
 public:
  // mutable not actually needed
  mutable pthread_mutex_t m_mut;
#ifdef _WIN32
  mutable volatile bool locked = false;
#endif
  /// constructs a mutex
  mutex() {
    int error = pthread_mutex_init(&m_mut, NULL);
    ASSERT_MSG(!error, "Mutex create error %d", error);
  }
  /** Copy constructor which does not copy. Do not use!
      Required for compatibility with some STL implementations (LLVM).
      which use the copy constructor for vector resize,
      rather than the standard constructor.    */
  mutex(const mutex&) {
    int error = pthread_mutex_init(&m_mut, NULL);
    ASSERT_MSG(!error, "Mutex create error %d", error);
  }

  ~mutex() noexcept {
    int error = pthread_mutex_destroy(&m_mut);
    if (error) {
      try {
        std::cerr << "Mutex destroy error " << error << std::endl;
      } catch (...) {
      }
      abort();
    }
  }

  // not copyable
  void operator=(const mutex& m) {}
    /// Acquires a lock on the mutex
    inline void lock() const {
      TURI_ATTRIBUTE_UNUSED_NDEBUG int error = pthread_mutex_lock( &m_mut  );
      DASSERT_MSG(!error, "Mutex lock error code: %d", error);
#ifdef _WIN32
    DASSERT_TRUE(!locked);
    locked = true;
#endif
  }
  /// Releases a lock on the mutex
  inline void unlock() const {
#ifdef _WIN32
    locked = false;
#endif

    TURI_ATTRIBUTE_UNUSED_NDEBUG int error = pthread_mutex_unlock(&m_mut);
    DASSERT_MSG(!error, "Mutex unlock error %d", error);
  }
  /// Non-blocking attempt to acquire a lock on the mutex
  inline bool try_lock() const {
#ifdef _WIN32
    if (locked) return false;
#endif
    return pthread_mutex_trylock(&m_mut) == 0;
  }
  friend class conditional;
};  // End of Mutex

/**
 * \ingroup threading
 *
 * Simple wrapper around pthread's recursive mutex.
 * Before you use, see \ref parallel_object_intricacies.
 */
class recursive_mutex {
 public:
  // mutable not actually needed
  mutable pthread_mutex_t m_mut;
  /// constructs a mutex
  recursive_mutex() {
    pthread_mutexattr_t attr;
    int error = pthread_mutexattr_init(&attr);
    ASSERT_TRUE(!error);
    error = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
    ASSERT_TRUE(!error);
    error = pthread_mutex_init(&m_mut, &attr);
    ASSERT_TRUE(!error);
    pthread_mutexattr_destroy(&attr);
  }
  /** Copy constructor which does not copy. Do not use!
      Required for compatibility with some STL implementations (LLVM).
      which use the copy constructor for vector resize,
      rather than the standard constructor.    */
  recursive_mutex(const recursive_mutex&) {
    pthread_mutexattr_t attr;
    int error = pthread_mutexattr_init(&attr);
    ASSERT_TRUE(!error);
    error = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
    ASSERT_TRUE(!error);
    error = pthread_mutex_init(&m_mut, &attr);
    ASSERT_TRUE(!error);
    pthread_mutexattr_destroy(&attr);
  }

  ~recursive_mutex() {
    TURI_ATTRIBUTE_UNUSED_NDEBUG int error = pthread_mutex_destroy(&m_mut);
    DASSERT_TRUE(!error);
  }

  // not copyable
  void operator=(const recursive_mutex& m) {}

  /// Acquires a lock on the mutex
  inline void lock() const {
    TURI_ATTRIBUTE_UNUSED_NDEBUG int error = pthread_mutex_lock(&m_mut);
    // if (error) std::cerr << "mutex.lock() error: " << error << std::endl;
    DASSERT_TRUE(!error);
  }
  /// Releases a lock on the mutex
  inline void unlock() const {
    TURI_ATTRIBUTE_UNUSED_NDEBUG int error = pthread_mutex_unlock(&m_mut);
    DASSERT_TRUE(!error);
  }
  /// Non-blocking attempt to acquire a lock on the mutex
  inline bool try_lock() const { return pthread_mutex_trylock(&m_mut) == 0; }
  friend class conditional;
};  // End of Mutex

}  // namespace turi

#endif