//===- llvm/Support/Mutex.h - Mutex Operating System Concept -----*- 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 declares the llvm::sys::Mutex class.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_MUTEX_H

#define LLVM_SUPPORT_MUTEX_H

#include "llvm/Support/Threading.h"

#include <cassert>

#include <mutex>

namespace llvm

{

  namespace sys

  {

    /// 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 {

      std::recursive_mutex impl;

      unsigned acquired = 0;

    public:

      bool lock() {

        if (!mt_only || llvm_is_multithreaded()) {

          impl.lock();

          return true;

        } else {

          // Single-threaded debugging code.  This would be racy in

          // multithreaded mode, but provides not sanity checks in single

          // threaded mode.

          ++acquired;

          return true;

        }

      }

      bool unlock() {

        if (!mt_only || llvm_is_multithreaded()) {

          impl.unlock();

          return true;

        } else {

          // Single-threaded debugging code.  This would be racy in

          // multithreaded mode, but provides not sanity checks in single

          // threaded mode.

          assert(acquired && "Lock not acquired before release!");

          --acquired;

          return true;

        }

      }

      bool try_lock() {

        if (!mt_only || llvm_is_multithreaded())

          return impl.try_lock();

        else return true;

      }

    };

    /// Mutex - A standard, always enforced mutex.

    typedef SmartMutex<false> Mutex;

    template <bool mt_only>

    using SmartScopedLock = std::lock_guard<SmartMutex<mt_only>>;

    typedef SmartScopedLock<false> ScopedLock;

  }

}

#endif