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//===- llvm/Support/Mutex.h - Mutex Operating System Concept -----*- 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::Mutex class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_MUTEX_H
#define LLVM_SUPPORT_MUTEX_H
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Threading.h"
#include <cassert>
namespace llvm
{
namespace sys
{
/// @brief Platform agnostic Mutex class.
class MutexImpl
{
/// @name Constructors
/// @{
public:
/// Initializes the lock but doesn't acquire it. if \p recursive is set
/// to false, the lock will not be recursive which makes it cheaper but
/// also more likely to deadlock (same thread can't acquire more than
/// once).
/// @brief Default Constructor.
explicit MutexImpl(bool recursive = true);
/// Releases and removes the lock
/// @brief Destructor
~MutexImpl();
/// @}
/// @name Methods
/// @{
public:
/// Attempts to unconditionally acquire the lock. If the lock is held by
/// another thread, 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.
bool acquire();
/// Attempts to release the lock. If the lock is held by the current
/// thread, the lock is released allowing other threads to acquire the
/// lock.
/// @returns false if any kind of error occurs, true otherwise.
/// @brief Unconditionally release the lock.
bool release();
/// Attempts to acquire the lock without blocking. If the lock is not
/// available, this function returns false quickly (without blocking). If
/// the lock is available, it is acquired.
/// @returns false if any kind of error occurs or the lock is not
/// available, true otherwise.
/// @brief Try to acquire the lock.
bool tryacquire();
//@}
/// @name Platform Dependent Data
/// @{
private:
void* data_; ///< We don't know what the data will be
/// @}
/// @name Do Not Implement
/// @{
private:
MutexImpl(const MutexImpl &) = delete;
void operator=(const MutexImpl &) = delete;
/// @}
};
/// SmartMutex - A 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 SmartMutex {
MutexImpl impl;
unsigned acquired;
bool recursive;
public:
explicit SmartMutex(bool rec = true) :
impl(rec), acquired(0), recursive(rec) { }
bool lock() {
if (!mt_only || llvm_is_multithreaded()) {
return impl.acquire();
} else {
// Single-threaded debugging code. This would be racy in
// multithreaded mode, but provides not sanity checks in single
// threaded mode.
assert((recursive || acquired == 0) && "Lock already acquired!!");
++acquired;
return true;
}
}
bool unlock() {
if (!mt_only || llvm_is_multithreaded()) {
return impl.release();
} else {
// Single-threaded debugging code. This would be racy in
// multithreaded mode, but provides not sanity checks in single
// threaded mode.
assert(((recursive && acquired) || (acquired == 1)) &&
"Lock not acquired before release!");
--acquired;
return true;
}
}
bool try_lock() {
if (!mt_only || llvm_is_multithreaded())
return impl.tryacquire();
else return true;
}
private:
SmartMutex(const SmartMutex<mt_only> & original);
void operator=(const SmartMutex<mt_only> &);
};
/// Mutex - A standard, always enforced mutex.
typedef SmartMutex<false> Mutex;
template<bool mt_only>
class SmartScopedLock {
SmartMutex<mt_only>& mtx;
public:
SmartScopedLock(SmartMutex<mt_only>& m) : mtx(m) {
mtx.lock();
}
~SmartScopedLock() {
mtx.unlock();
}
};
typedef SmartScopedLock<false> ScopedLock;
}
}
#endif
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