llvm-project/llvm/lib/Support/RWMutex.cpp

//===- RWMutex.cpp - Reader/Writer Mutual Exclusion Lock --------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the llvm::sys::RWMutex class.
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/Allocator.h"
#include "llvm/Support/RWMutex.h"
#include "llvm/Config/config.h"

//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only TRULY operating system
//===          independent code.
//===----------------------------------------------------------------------===//

#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
// Define all methods as no-ops if threading is explicitly disabled

using namespace llvm;
using namespace sys;

RWMutexImpl::RWMutexImpl() = default;
RWMutexImpl::~RWMutexImpl() = default;

bool RWMutexImpl::reader_acquire() { return true; }
bool RWMutexImpl::reader_release() { return true; }
bool RWMutexImpl::writer_acquire() { return true; }
bool RWMutexImpl::writer_release() { return true; }

#else

#if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_RWLOCK_INIT)

#include <cassert>
#include <cstdlib>
#include <pthread.h>

using namespace llvm;
using namespace sys;

// Construct a RWMutex using pthread calls
RWMutexImpl::RWMutexImpl()
{
  // Declare the pthread_rwlock data structures
  pthread_rwlock_t* rwlock =
    static_cast<pthread_rwlock_t*>(safe_malloc(sizeof(pthread_rwlock_t)));

#ifdef __APPLE__
  // Workaround a bug/mis-feature in Darwin's pthread_rwlock_init.
  bzero(rwlock, sizeof(pthread_rwlock_t));
#endif

  // Initialize the rwlock
  int errorcode = pthread_rwlock_init(rwlock, nullptr);
  (void)errorcode;
  assert(errorcode == 0);

  // Assign the data member
  data_ = rwlock;
}

// Destruct a RWMutex
RWMutexImpl::~RWMutexImpl()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);
  pthread_rwlock_destroy(rwlock);
  free(rwlock);
}

bool
RWMutexImpl::reader_acquire()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);

  int errorcode = pthread_rwlock_rdlock(rwlock);
  return errorcode == 0;
}

bool
RWMutexImpl::reader_release()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);

  int errorcode = pthread_rwlock_unlock(rwlock);
  return errorcode == 0;
}

bool
RWMutexImpl::writer_acquire()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);

  int errorcode = pthread_rwlock_wrlock(rwlock);
  return errorcode == 0;
}

bool
RWMutexImpl::writer_release()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);

  int errorcode = pthread_rwlock_unlock(rwlock);
  return errorcode == 0;
}

#elif defined(LLVM_ON_UNIX)
#include "Unix/RWMutex.inc"
#elif defined( _WIN32)
#include "Windows/RWMutex.inc"
#else
#warning Neither LLVM_ON_UNIX nor _WIN32 was set in Support/Mutex.cpp
#endif
#endif