RWMutex.cpp

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//===- 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/RWMutex.h"
#include "llvm/Config/config.h"
#include "llvm/Config/llvm-config.h" // for LLVM_ENABLE_THREADS
#include "llvm/Support/Allocator.h"
 
#if defined(LLVM_USE_RW_MUTEX_IMPL)
using namespace llvm;
using namespace sys;
 
#if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
// Define all methods as no-ops if threading is explicitly disabled
 
RWMutexImpl::RWMutexImpl() = default;
RWMutexImpl::~RWMutexImpl() = default;
 
bool RWMutexImpl::lock_shared() { return true; }
bool RWMutexImpl::unlock_shared() { return true; }
bool RWMutexImpl::try_lock_shared() { return true; }
bool RWMutexImpl::lock() { return true; }
bool RWMutexImpl::unlock() { return true; }
bool RWMutexImpl::try_lock() { return true; }
 
#else
 
#if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_RWLOCK_INIT)
 
#include <cassert>
#include <cstdlib>
#include <pthread.h>
 
// 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::lock_shared()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);
 
  int errorcode = pthread_rwlock_rdlock(rwlock);
  return errorcode == 0;
}
 
bool
RWMutexImpl::unlock_shared()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);
 
  int errorcode = pthread_rwlock_unlock(rwlock);
  return errorcode == 0;
}
 
bool RWMutexImpl::try_lock_shared() {
  pthread_rwlock_t *rwlock = static_cast<pthread_rwlock_t *>(data_);
  assert(rwlock != nullptr);
 
  int errorcode = pthread_rwlock_tryrdlock(rwlock);
  return errorcode == 0;
}
 
bool
RWMutexImpl::lock()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);
 
  int errorcode = pthread_rwlock_wrlock(rwlock);
  return errorcode == 0;
}
 
bool
RWMutexImpl::unlock()
{
  pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  assert(rwlock != nullptr);
 
  int errorcode = pthread_rwlock_unlock(rwlock);
  return errorcode == 0;
}
 
bool RWMutexImpl::try_lock() {
  pthread_rwlock_t *rwlock = static_cast<pthread_rwlock_t *>(data_);
  assert(rwlock != nullptr);
 
  int errorcode = pthread_rwlock_trywrlock(rwlock);
  return errorcode == 0;
}
 
#else
 
RWMutexImpl::RWMutexImpl() : data_(new MutexImpl(false)) { }
 
RWMutexImpl::~RWMutexImpl() {
  delete static_cast<MutexImpl *>(data_);
}
 
bool RWMutexImpl::lock_shared() {
  return static_cast<MutexImpl *>(data_)->acquire();
}
 
bool RWMutexImpl::unlock_shared() {
  return static_cast<MutexImpl *>(data_)->release();
}
 
bool RWMutexImpl::try_lock_shared() {
  return static_cast<MutexImpl *>(data_)->tryacquire();
}
 
bool RWMutexImpl::lock() {
  return static_cast<MutexImpl *>(data_)->acquire();
}
 
bool RWMutexImpl::unlock() {
  return static_cast<MutexImpl *>(data_)->release();
}
 
bool RWMutexImpl::try_lock() {
  return static_cast<MutexImpl *>(data_)->tryacquire();
}
 
#endif
#endif
#endif