lib/cpp/src/concurrency/Mutex.cpp

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "Mutex.h"
#include "Util.h"

#include <assert.h>
#ifdef HAVE_PTHREAD_H
#include <pthread.h>
#endif
#include <signal.h>

using boost::shared_ptr;

namespace apache { namespace thrift { namespace concurrency {

#ifndef THRIFT_NO_CONTENTION_PROFILING

static sig_atomic_t mutexProfilingSampleRate = 0;
static MutexWaitCallback mutexProfilingCallback = 0;

volatile static sig_atomic_t mutexProfilingCounter = 0;

void enableMutexProfiling(int32_t profilingSampleRate,
                          MutexWaitCallback callback) {
  mutexProfilingSampleRate = profilingSampleRate;
  mutexProfilingCallback = callback;
}

#define PROFILE_MUTEX_START_LOCK() \
    int64_t _lock_startTime = maybeGetProfilingStartTime();

#define PROFILE_MUTEX_NOT_LOCKED() \
  do { \
    if (_lock_startTime > 0) { \
      int64_t endTime = Util::currentTimeUsec(); \
      (*mutexProfilingCallback)(this, endTime - _lock_startTime); \
    } \
  } while (0)

#define PROFILE_MUTEX_LOCKED() \
  do { \
    profileTime_ = _lock_startTime; \
    if (profileTime_ > 0) { \
      profileTime_ = Util::currentTimeUsec() - profileTime_; \
    } \
  } while (0)

#define PROFILE_MUTEX_START_UNLOCK() \
  int64_t _temp_profileTime = profileTime_; \
  profileTime_ = 0;

#define PROFILE_MUTEX_UNLOCKED() \
  do { \
    if (_temp_profileTime > 0) { \
      (*mutexProfilingCallback)(this, _temp_profileTime); \
    } \
  } while (0)

static inline int64_t maybeGetProfilingStartTime() {
  if (mutexProfilingSampleRate && mutexProfilingCallback) {
    // This block is unsynchronized, but should produce a reasonable sampling
    // rate on most architectures.  The main race conditions are the gap
    // between the decrement and the test, the non-atomicity of decrement, and
    // potential caching of different values at different CPUs.
    //
    // - if two decrements race, the likeliest result is that the counter
    //      decrements slowly (perhaps much more slowly) than intended.
    //
    // - many threads could potentially decrement before resetting the counter
    //      to its large value, causing each additional incoming thread to
    //      profile every call.  This situation is unlikely to persist for long
    //      as the critical gap is quite short, but profiling could be bursty.
    sig_atomic_t localValue = --mutexProfilingCounter;
    if (localValue <= 0) {
      mutexProfilingCounter = mutexProfilingSampleRate;
      return Util::currentTimeUsec();
    }
  }

  return 0;
}

#else
#  define PROFILE_MUTEX_START_LOCK()
#  define PROFILE_MUTEX_NOT_LOCKED()
#  define PROFILE_MUTEX_LOCKED()
#  define PROFILE_MUTEX_START_UNLOCK()
#  define PROFILE_MUTEX_UNLOCKED()
#endif // THRIFT_NO_CONTENTION_PROFILING

/**
 * Implementation of Mutex class using POSIX mutex
 *
 * @version $Id:$
 */
class Mutex::impl {
 public:
  impl(Initializer init) : initialized_(false) {
#ifndef THRIFT_NO_CONTENTION_PROFILING
    profileTime_ = 0;
#endif
    init(&pthread_mutex_);
    initialized_ = true;
  }

  ~impl() {
    if (initialized_) {
      initialized_ = false;
      int ret = pthread_mutex_destroy(&pthread_mutex_);
      assert(ret == 0);
    }
  }

  void lock() const {
    PROFILE_MUTEX_START_LOCK();
    pthread_mutex_lock(&pthread_mutex_);
    PROFILE_MUTEX_LOCKED();
  }

  bool trylock() const { return (0 == pthread_mutex_trylock(&pthread_mutex_)); }

  bool timedlock(int64_t milliseconds) const {
#if defined(_POSIX_TIMEOUTS) && _POSIX_TIMEOUTS >= 200112L
    PROFILE_MUTEX_START_LOCK();

    struct timespec ts;
    Util::toTimespec(ts, milliseconds);
    int ret = pthread_mutex_timedlock(&pthread_mutex_, &ts);
    if (ret == 0) {
      PROFILE_MUTEX_LOCKED();
      return true;
    }

    PROFILE_MUTEX_NOT_LOCKED();
    return false;
#else
    (void)milliseconds;
    // If pthread_mutex_timedlock isn't supported, the safest thing to do
    // is just do a nonblocking trylock.
    return trylock();
#endif
  }

  void unlock() const {
    PROFILE_MUTEX_START_UNLOCK();
    pthread_mutex_unlock(&pthread_mutex_);
    PROFILE_MUTEX_UNLOCKED();
  }

  void* getUnderlyingImpl() const { return (void*) &pthread_mutex_; }

 private:
  mutable pthread_mutex_t pthread_mutex_;
  mutable bool initialized_;
#ifndef THRIFT_NO_CONTENTION_PROFILING
  mutable int64_t profileTime_;
#endif
};

Mutex::Mutex(Initializer init) : impl_(new Mutex::impl(init)) {}

void* Mutex::getUnderlyingImpl() const { return impl_->getUnderlyingImpl(); }

void Mutex::lock() const { impl_->lock(); }

bool Mutex::trylock() const { return impl_->trylock(); }

bool Mutex::timedlock(int64_t ms) const { return impl_->timedlock(ms); }

void Mutex::unlock() const { impl_->unlock(); }

void Mutex::DEFAULT_INITIALIZER(void* arg) {
  pthread_mutex_t* pthread_mutex = (pthread_mutex_t*)arg;
  int ret = pthread_mutex_init(pthread_mutex, NULL);
  assert(ret == 0);
}

#if defined(PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP) || defined(PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP)
static void init_with_kind(pthread_mutex_t* mutex, int kind) {
  pthread_mutexattr_t mutexattr;
  int ret = pthread_mutexattr_init(&mutexattr);
  assert(ret == 0);

  // Apparently, this can fail.  Should we really be aborting?
  ret = pthread_mutexattr_settype(&mutexattr, kind);
  assert(ret == 0);

  ret = pthread_mutex_init(mutex, &mutexattr);
  assert(ret == 0);

  ret = pthread_mutexattr_destroy(&mutexattr);
  assert(ret == 0);
}
#endif

#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
void Mutex::ADAPTIVE_INITIALIZER(void* arg) {
  // From mysql source: mysys/my_thr_init.c
  // Set mutex type to "fast" a.k.a "adaptive"
  //
  // In this case the thread may steal the mutex from some other thread
  // that is waiting for the same mutex. This will save us some
  // context switches but may cause a thread to 'starve forever' while
  // waiting for the mutex (not likely if the code within the mutex is
  // short).
  init_with_kind((pthread_mutex_t*)arg, PTHREAD_MUTEX_ADAPTIVE_NP);
}
#endif

#ifdef PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
void Mutex::RECURSIVE_INITIALIZER(void* arg) {
  init_with_kind((pthread_mutex_t*)arg, PTHREAD_MUTEX_RECURSIVE_NP);
}
#endif


/**
 * Implementation of ReadWriteMutex class using POSIX rw lock
 *
 * @version $Id:$
 */
class ReadWriteMutex::impl {
public:
  impl() : initialized_(false) {
#ifndef THRIFT_NO_CONTENTION_PROFILING
    profileTime_ = 0;
#endif
    int ret = pthread_rwlock_init(&rw_lock_, NULL);
    assert(ret == 0);
    initialized_ = true;
  }

  ~impl() {
    if(initialized_) {
      initialized_ = false;
      int ret = pthread_rwlock_destroy(&rw_lock_);
      assert(ret == 0);
    }
  }

  void acquireRead() const {
    PROFILE_MUTEX_START_LOCK();
    pthread_rwlock_rdlock(&rw_lock_);
    PROFILE_MUTEX_NOT_LOCKED();  // not exclusive, so use not-locked path
  }

  void acquireWrite() const {
    PROFILE_MUTEX_START_LOCK();
    pthread_rwlock_wrlock(&rw_lock_);
    PROFILE_MUTEX_LOCKED();
  }

  bool attemptRead() const { return !pthread_rwlock_tryrdlock(&rw_lock_); }

  bool attemptWrite() const { return !pthread_rwlock_trywrlock(&rw_lock_); }

  void release() const {
    PROFILE_MUTEX_START_UNLOCK();
    pthread_rwlock_unlock(&rw_lock_);
    PROFILE_MUTEX_UNLOCKED();
  }

private:
  mutable pthread_rwlock_t rw_lock_;
  mutable bool initialized_;
#ifndef THRIFT_NO_CONTENTION_PROFILING
  mutable int64_t profileTime_;
#endif
};

ReadWriteMutex::ReadWriteMutex() : impl_(new ReadWriteMutex::impl()) {}

void ReadWriteMutex::acquireRead() const { impl_->acquireRead(); }

void ReadWriteMutex::acquireWrite() const { impl_->acquireWrite(); }

bool ReadWriteMutex::attemptRead() const { return impl_->attemptRead(); }

bool ReadWriteMutex::attemptWrite() const { return impl_->attemptWrite(); }

void ReadWriteMutex::release() const { impl_->release(); }

NoStarveReadWriteMutex::NoStarveReadWriteMutex() : writerWaiting_(false) {}

void NoStarveReadWriteMutex::acquireRead() const
{
  if (writerWaiting_) {
    // writer is waiting, block on the writer's mutex until he's done with it
    mutex_.lock();
    mutex_.unlock();
  }

  ReadWriteMutex::acquireRead();
}

void NoStarveReadWriteMutex::acquireWrite() const
{
  // if we can acquire the rwlock the easy way, we're done
  if (attemptWrite()) {
    return;
  }

  // failed to get the rwlock, do it the hard way:
  // locking the mutex and setting writerWaiting will cause all new readers to
  // block on the mutex rather than on the rwlock.
  mutex_.lock();
  writerWaiting_ = true;
  ReadWriteMutex::acquireWrite();
  writerWaiting_ = false;
  mutex_.unlock();
}

}}} // apache::thrift::concurrency