.. SPDX-FileCopyrightText: 2019-2021 Intel Corporation .. .. SPDX-License-Identifier: CC-BY-4.0

========== null_mutex

[mutex.null_mutex]

A null_mutex is a class that models the :doc:Mutex requirement <../named_requirements/mutexes/mutex> concept syntactically, but does nothing. It is useful for instantiating a template that expects a Mutex, but no mutual exclusion is actually needed for that instance.

.. code:: cpp

// Defined in header <oneapi/tbb/null_mutex.h>

namespace oneapi {
namespace tbb {
    class null_mutex {
    public:
        constexpr null_mutex() noexcept;
        ~null_mutex();

        null_mutex(const null_mutex&) = delete;
        null_mutex& operator=(const null_mutex&) = delete;

        class scoped_lock;

        void lock();
        bool try_lock();
        void unlock();

        static constexpr bool is_rw_mutex = false;
        static constexpr bool is_recursive_mutex = true;
        static constexpr bool is_fair_mutex = true;
    };
} // namespace tbb
} // namespace oneapi

Member classes

.. cpp:class:: scoped_lock

Corresponding ``scoped_lock`` class. See the :doc:`Mutex requirement <../named_requirements/mutexes/mutex>`.

Member functions

.. cpp:function:: null_mutex()

Constructs unlocked mutex.

.. cpp:function:: ~null_mutex()

Destroys unlocked mutex.

.. cpp:function:: void lock()

Acquires lock.

.. cpp:function:: bool try_lock()

Tries acquiring lock (non-blocking).

.. cpp:function:: void unlock()

Releases the lock.