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//===- RWMutex.cpp - Reader/Writer Mutual Exclusion Lock --------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the llvm::sys::RWMutex class.
//
//===----------------------------------------------------------------------===//
#include "llvm/Config/config.h"
#include "llvm/System/RWMutex.h"
#include <cstring>
//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only TRULY operating system
//=== independent code.
//===----------------------------------------------------------------------===//
#if !defined(ENABLE_THREADS) || ENABLE_THREADS == 0
// Define all methods as no-ops if threading is explicitly disabled
namespace llvm {
using namespace sys;
RWMutexImpl::RWMutexImpl() { }
RWMutexImpl::~RWMutexImpl() { }
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 <pthread.h>
#include <stdlib.h>
namespace llvm {
using namespace sys;
// This variable is useful for situations where the pthread library has been
// compiled with weak linkage for its interface symbols. This allows the
// threading support to be turned off by simply not linking against -lpthread.
// In that situation, the value of pthread_mutex_init will be 0 and
// consequently pthread_enabled will be false. In such situations, all the
// pthread operations become no-ops and the functions all return false. If
// pthread_rwlock_init does have an address, then rwlock support is enabled.
// Note: all LLVM tools will link against -lpthread if its available since it
// is configured into the LIBS variable.
// Note: this line of code generates a warning if pthread_rwlock_init is not
// declared with weak linkage. It's safe to ignore the warning.
static const bool pthread_enabled = true;
// Construct a RWMutex using pthread calls
RWMutexImpl::RWMutexImpl()
: data_(0)
{
if (pthread_enabled)
{
// Declare the pthread_rwlock data structures
pthread_rwlock_t* rwlock =
static_cast<pthread_rwlock_t*>(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
pthread_rwlockattr_t attr;
// Initialize the rwlock attributes
int errorcode = pthread_rwlockattr_init(&attr);
assert(errorcode == 0);
#if !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__) && !defined(__DragonFly__)
// Make it a process local rwlock
errorcode = pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_PRIVATE);
#endif
// Initialize the rwlock
errorcode = pthread_rwlock_init(rwlock, &attr);
assert(errorcode == 0);
// Destroy the attributes
errorcode = pthread_rwlockattr_destroy(&attr);
assert(errorcode == 0);
// Assign the data member
data_ = rwlock;
}
}
// Destruct a RWMutex
RWMutexImpl::~RWMutexImpl()
{
if (pthread_enabled)
{
pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
assert(rwlock != 0);
pthread_rwlock_destroy(rwlock);
free(rwlock);
}
}
bool
RWMutexImpl::reader_acquire()
{
if (pthread_enabled)
{
pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
assert(rwlock != 0);
int errorcode = pthread_rwlock_rdlock(rwlock);
return errorcode == 0;
} else return false;
}
bool
RWMutexImpl::reader_release()
{
if (pthread_enabled)
{
pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
assert(rwlock != 0);
int errorcode = pthread_rwlock_unlock(rwlock);
return errorcode == 0;
} else return false;
}
bool
RWMutexImpl::writer_acquire()
{
if (pthread_enabled)
{
pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
assert(rwlock != 0);
int errorcode = pthread_rwlock_wrlock(rwlock);
return errorcode == 0;
} else return false;
}
bool
RWMutexImpl::writer_release()
{
if (pthread_enabled)
{
pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
assert(rwlock != 0);
int errorcode = pthread_rwlock_unlock(rwlock);
return errorcode == 0;
} else return false;
}
}
#elif defined(LLVM_ON_UNIX)
#include "Unix/RWMutex.inc"
#elif defined( LLVM_ON_WIN32)
#include "Win32/RWMutex.inc"
#else
#warning Neither LLVM_ON_UNIX nor LLVM_ON_WIN32 was set in System/Mutex.cpp
#endif
#endif
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