YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

// Licensed to the Apache Software Foundation (ASF) under one

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// regarding copyright ownership.  The ASF licenses this file

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// "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

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// KIND, either express or implied.  See the License for the

// specific language governing permissions and limitations

// under the License.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// Licensed 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.

//

#include "yb/util/rw_mutex.h"

#include <mutex>

#include <glog/logging.h>

#include "yb/gutil/map-util.h"

#include "yb/util/env.h"

using std::lock_guard;

namespace {

void unlock_rwlock(pthread_rwlock_t* rwlock) {

  int rv = pthread_rwlock_unlock(rwlock);

  DCHECK_EQ(0, rv) << strerror(rv);

}

} // anonymous namespace

namespace yb {

RWMutex::RWMutex()

#ifndef NDEBUG

    : writer_tid_(0)

#endif

{

  Init(Priority::PREFER_READING);

}

RWMutex::RWMutex(Priority prio)

#ifndef NDEBUG

    : writer_tid_(0)

#endif

{

  Init(prio);

}

void RWMutex::Init(Priority prio) {

#ifdef __linux__

  // Adapt from priority to the pthread type.

  int kind = PTHREAD_RWLOCK_PREFER_READER_NP;

  switch (prio) {

    case Priority::PREFER_READING:

      kind = PTHREAD_RWLOCK_PREFER_READER_NP;

      break;

    case Priority::PREFER_WRITING:

      kind = PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP;

      break;

  }

  // Initialize the new rwlock with the user's preference.

  pthread_rwlockattr_t attr;

  int rv = pthread_rwlockattr_init(&attr);

  DCHECK_EQ(0, rv) << strerror(rv);

  rv = pthread_rwlockattr_setkind_np(&attr, kind);

  DCHECK_EQ(0, rv) << strerror(rv);

  rv = pthread_rwlock_init(&native_handle_, &attr);

  DCHECK_EQ(0, rv) << strerror(rv);

  rv = pthread_rwlockattr_destroy(&attr);

  DCHECK_EQ(0, rv) << strerror(rv);

#else

  int rv = pthread_rwlock_init(&native_handle_, NULL);

  DCHECK_EQ(0, rv) << strerror(rv);

#endif

}

RWMutex::~RWMutex() {

  int rv = pthread_rwlock_destroy(&native_handle_);

  DCHECK_EQ(0, rv) << strerror(rv);

}

void RWMutex::ReadLock() {

  CheckLockState(LockState::NEITHER);

  int rv = pthread_rwlock_rdlock(&native_handle_);

  DCHECK_EQ(0, rv) << strerror(rv);

  MarkForReading();

}

void RWMutex::ReadUnlock() {

  CheckLockState(LockState::READER);

  UnmarkForReading();

  unlock_rwlock(&native_handle_);

}

bool RWMutex::TryReadLock() {

  CheckLockState(LockState::NEITHER);

  int rv = pthread_rwlock_tryrdlock(&native_handle_);

  if (rv == EBUSY) {

    return false;

  }

  DCHECK_EQ(0, rv) << strerror(rv);

  MarkForReading();

  return true;

}

void RWMutex::WriteLock() {

  CheckLockState(LockState::NEITHER);

  int rv = pthread_rwlock_wrlock(&native_handle_);

  DCHECK_EQ(0, rv) << strerror(rv);

  MarkForWriting();

}

void RWMutex::WriteUnlock() {

  CheckLockState(LockState::WRITER);

  UnmarkForWriting();

  unlock_rwlock(&native_handle_);

}

bool RWMutex::TryWriteLock() {

  CheckLockState(LockState::NEITHER);

  int rv = pthread_rwlock_trywrlock(&native_handle_);

  if (rv == EBUSY) {

    return false;

  }

  DCHECK_EQ(0, rv) << strerror(rv);

  MarkForWriting();

  return true;

}

#ifndef NDEBUG

void RWMutex::AssertAcquiredForReading() const {

  lock_guard<simple_spinlock> l(tid_lock_);

  CHECK(ContainsKey(reader_tids_, Env::Default()->gettid()));

}

void RWMutex::AssertAcquiredForWriting() const {

  lock_guard<simple_spinlock> l(tid_lock_);

  CHECK_EQ(Env::Default()->gettid(), writer_tid_);

}

void RWMutex::CheckLockState(LockState state) const {

  auto my_tid = Env::Default()->gettid();

  bool is_reader;

  bool is_writer;

  {

    lock_guard<simple_spinlock> l(tid_lock_);

    is_reader = ContainsKey(reader_tids_, my_tid);

    is_writer = writer_tid_ == my_tid;

  }

  switch (state) {

    case LockState::NEITHER:

      CHECK(!is_reader) << "Invalid state, already holding lock for reading";

      CHECK(!is_writer) << "Invalid state, already holding lock for writing";

      break;

    case LockState::READER:

      CHECK(!is_writer) << "Invalid state, already holding lock for writing";

      CHECK(is_reader) << "Invalid state, wasn't holding lock for reading";

      break;

    case LockState::WRITER:

      CHECK(!is_reader) << "Invalid state, already holding lock for reading";

      CHECK(is_writer) << "Invalid state, wasn't holding lock for writing";

      break;

  }

}

void RWMutex::MarkForReading() {

  lock_guard<simple_spinlock> l(tid_lock_);

  reader_tids_.insert(Env::Default()->gettid());

}

void RWMutex::MarkForWriting() {

  lock_guard<simple_spinlock> l(tid_lock_);

  writer_tid_ = Env::Default()->gettid();

}

void RWMutex::UnmarkForReading() {

  lock_guard<simple_spinlock> l(tid_lock_);

  reader_tids_.erase(Env::Default()->gettid());

}

void RWMutex::UnmarkForWriting() {

  lock_guard<simple_spinlock> l(tid_lock_);

  writer_tid_ = 0;

}

#endif

} // namespace yb