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//===- RWMutex.h - 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 declares the llvm::sys::RWMutex class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SYSTEM_RWMUTEX_H
#define LLVM_SYSTEM_RWMUTEX_H
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Threading.h"
#include <cassert>
namespace llvm { namespace sys { /// @brief Platform agnostic RWMutex class.
class RWMutexImpl { /// @name Constructors
/// @{
public:
/// Initializes the lock but doesn't acquire it.
/// @brief Default Constructor.
explicit RWMutexImpl();
/// Releases and removes the lock
/// @brief Destructor
~RWMutexImpl();
/// @}
/// @name Methods
/// @{
public:
/// Attempts to unconditionally acquire the lock in reader mode. If the
/// lock is held by a writer, this method will wait until it can acquire
/// the lock.
/// @returns false if any kind of error occurs, true otherwise.
/// @brief Unconditionally acquire the lock in reader mode.
bool reader_acquire();
/// Attempts to release the lock in reader mode.
/// @returns false if any kind of error occurs, true otherwise.
/// @brief Unconditionally release the lock in reader mode.
bool reader_release();
/// Attempts to unconditionally acquire the lock in reader mode. If the
/// lock is held by any readers, this method will wait until it can
/// acquire the lock.
/// @returns false if any kind of error occurs, true otherwise.
/// @brief Unconditionally acquire the lock in writer mode.
bool writer_acquire();
/// Attempts to release the lock in writer mode.
/// @returns false if any kind of error occurs, true otherwise.
/// @brief Unconditionally release the lock in write mode.
bool writer_release();
//@}
/// @name Platform Dependent Data
/// @{
private: void* data_; ///< We don't know what the data will be
/// @}
/// @name Do Not Implement
/// @{
private: RWMutexImpl(const RWMutexImpl & original) LLVM_DELETED_FUNCTION; void operator=(const RWMutexImpl &) LLVM_DELETED_FUNCTION; /// @}
};
/// SmartMutex - An R/W mutex with a compile time constant parameter that
/// indicates whether this mutex should become a no-op when we're not
/// running in multithreaded mode.
template<bool mt_only> class SmartRWMutex : public RWMutexImpl { unsigned readers, writers; public: explicit SmartRWMutex() : RWMutexImpl(), readers(0), writers(0) { }
bool reader_acquire() { if (!mt_only || llvm_is_multithreaded()) return RWMutexImpl::reader_acquire();
// Single-threaded debugging code. This would be racy in multithreaded
// mode, but provides not sanity checks in single threaded mode.
++readers; return true; }
bool reader_release() { if (!mt_only || llvm_is_multithreaded()) return RWMutexImpl::reader_release();
// Single-threaded debugging code. This would be racy in multithreaded
// mode, but provides not sanity checks in single threaded mode.
assert(readers > 0 && "Reader lock not acquired before release!"); --readers; return true; }
bool writer_acquire() { if (!mt_only || llvm_is_multithreaded()) return RWMutexImpl::writer_acquire();
// Single-threaded debugging code. This would be racy in multithreaded
// mode, but provides not sanity checks in single threaded mode.
assert(writers == 0 && "Writer lock already acquired!"); ++writers; return true; }
bool writer_release() { if (!mt_only || llvm_is_multithreaded()) return RWMutexImpl::writer_release();
// Single-threaded debugging code. This would be racy in multithreaded
// mode, but provides not sanity checks in single threaded mode.
assert(writers == 1 && "Writer lock not acquired before release!"); --writers; return true; }
private: SmartRWMutex(const SmartRWMutex<mt_only> & original); void operator=(const SmartRWMutex<mt_only> &); }; typedef SmartRWMutex<false> RWMutex;
/// ScopedReader - RAII acquisition of a reader lock
template<bool mt_only> struct SmartScopedReader { SmartRWMutex<mt_only>& mutex;
explicit SmartScopedReader(SmartRWMutex<mt_only>& m) : mutex(m) { mutex.reader_acquire(); }
~SmartScopedReader() { mutex.reader_release(); } }; typedef SmartScopedReader<false> ScopedReader;
/// ScopedWriter - RAII acquisition of a writer lock
template<bool mt_only> struct SmartScopedWriter { SmartRWMutex<mt_only>& mutex;
explicit SmartScopedWriter(SmartRWMutex<mt_only>& m) : mutex(m) { mutex.writer_acquire(); }
~SmartScopedWriter() { mutex.writer_release(); } }; typedef SmartScopedWriter<false> ScopedWriter; } }
#endif
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