Standard library header <mutex>

This header is part of the thread support library.

Classes
mutex (C++11)	provides basic mutual exclusion facility (class)
timed_mutex (C++11)	provides mutual exclusion facility which implements locking with a timeout (class)
recursive_mutex (C++11)	provides mutual exclusion facility which can be locked recursively by the same thread (class)
recursive_timed_mutex (C++11)	provides mutual exclusion facility which can be locked recursively by the same thread and implements locking with a timeout (class)
lock_guard (C++11)	implements a strictly scope-based mutex ownership wrapper (class template)
unique_lock (C++11)	implements movable mutex ownership wrapper (class template)
scoped_lock (C++17)	deadlock-avoiding RAII wrapper for multiple mutexes (class template)
defer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11)	tag type used to specify locking strategy (class)
defer_locktry_to_lockadopt_lock (C++11)(C++11)(C++11)	tag constants used to specify locking strategy (constant)
once_flag (C++11)	helper object to ensure that `call_once` invokes the function only once (class)
Functions
try_lock (C++11)	attempts to obtain ownership of mutexes via repeated calls to `try_lock` (function template)
lock (C++11)	locks specified mutexes, blocks if any are unavailable (function template)
call_once (C++11)	invokes a function only once even if called from multiple threads (function template)
std::swap(std::unique_lock) (C++11)	specialization of std::swap for `unique_lock` (function template)

Synopsis

namespace std {
    class mutex;
    class recursive_mutex;
    class timed_mutex;
    class recursive_timed_mutex;

    struct defer_lock_t { explicit defer_lock_t() = default; };
    inline constexpr defer_lock_t defer_lock { };

    struct try_to_lock_t { explicit try_to_lock_t() = default; };
    inline constexpr try_to_lock_t try_to_lock { };

    struct adopt_lock_t { explicit adopt_lock_t() = default; };
    inline constexpr adopt_lock_t adopt_lock { };

    template <class Mutex> class lock_guard;
    template <class Mutex> class unique_lock;

    template <class Mutex>
    void swap(unique_lock<Mutex>& x,
              unique_lock<Mutex>& y) noexcept;

    template <class L1, class L2, class... L3>
    int try_lock(L1&, L2&, L3&...);

    template <class L1, class L2, class... L3>
    void lock(L1&, L2&, L3&...);

    struct once_flag;

    template<class Callable, class ...Args>
    void call_once(once_flag& flag, Callable func, Args&&... args);
}

Class std::mutex

class mutex {
 public:
    constexpr mutex() noexcept;
    ~mutex();
    mutex(const mutex&) = delete;
    mutex& operator=(const mutex&) = delete;

    void lock();
    bool try_lock();
    void unlock();
    typedef /*implementation-defined*/ native_handle_type;
    native_handle_type native_handle();
};

Class std::recursive_mutex

class recursive_mutex {
 public:
    recursive_mutex();
    ~recursive_mutex();
    recursive_mutex(const recursive_mutex&) = delete;
    recursive_mutex& operator=(const recursive_mutex&) = delete;

    void lock();
    bool try_lock() noexcept;
    void unlock();
    typedef /*implementation-defined*/ native_handle_type;
    native_handle_type native_handle();
};

Class std::timed_mutex

class timed_mutex {
 public:
    timed_mutex();
    ~timed_mutex();
    timed_mutex(const timed_mutex&) = delete;
    timed_mutex& operator=(const timed_mutex&) = delete;

    void lock();
    bool try_lock();
    template <class Rep, class Period>
        bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
        bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock();
    typedef /*implementation-defined*/ native_handle_type;
    native_handle_type native_handle();
};

Class std::recursive_timed_mutex

class recursive_timed_mutex {
 public:
    recursive_timed_mutex();
    ~recursive_timed_mutex();
    recursive_timed_mutex(const recursive_timed_mutex&) = delete;
    recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;

    void lock();
    bool try_lock() noexcept;
    template <class Rep, class Period>
        bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
        bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock();
    typedef /*implementation-defined*/ native_handle_type;
    native_handle_type native_handle();
};

Class std::lock_guard

template <class Mutex>
class lock_guard {
 public:
    typedef Mutex mutex_type;
    explicit lock_guard(mutex_type& m);
    lock_guard(mutex_type& m, adopt_lock_t);
    ~lock_guard();
    lock_guard(lock_guard const&) = delete;
    lock_guard& operator=(lock_guard const&) = delete;
 private:
    mutex_type& pm; // exposition only
};

Class std::scoped_lock

template<class... MutexTypes>
class scoped_lock {
public:
    using mutex_type = Mutex; // If MutexTypes... consists of the single type Mutex

    explicit scoped_lock(MutexTypes&... m);
    explicit scoped_lock(adopt_lock_t, MutexTypes&... m);
    ~scoped_lock();

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

private:
    tuple<MutexTypes&...> pm; // exposition only
};

Class std::unique_lock

template <class Mutex>
class unique_lock {
 public:
    typedef Mutex mutex_type;

    // construct/copy/destroy:
    unique_lock() noexcept;
    explicit unique_lock(mutex_type& m);
    unique_lock(mutex_type& m, defer_lock_t) noexcept;
    unique_lock(mutex_type& m, try_to_lock_t);
    unique_lock(mutex_type& m, adopt_lock_t);
    template <class Clock, class Duration>
    unique_lock(mutex_type& m, const chrono::time_point<Clock, Duration>& abs_time);
    template <class Rep, class Period>
    unique_lock(mutex_type& m, const chrono::duration<Rep, Period>& rel_time);
    ~unique_lock();
    unique_lock(unique_lock const&) = delete;
    unique_lock& operator=(unique_lock const&) = delete;
    unique_lock(unique_lock&& u) noexcept;
    unique_lock& operator=(unique_lock&& u) noexcept;

    // locking:
    void lock();
    bool try_lock();
    template <class Rep, class Period>
    bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
    bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock();

    // modifiers:
    void swap(unique_lock& u) noexcept;
    mutex_type *release() noexcept;

    // observers:
    bool owns_lock() const noexcept;
    explicit operator bool () const noexcept;
    mutex_type* mutex() const noexcept;

 private:
    mutex_type *pm; // exposition only
    bool owns; // exposition only
};

Class std::once_flag

struct once_flag {
    constexpr once_flag() noexcept;
    once_flag(const once_flag&) = delete;
    once_flag& operator=(const once_flag&) = delete;
};

Language
Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Standard library header <mutex>

Classes

Functions

Synopsis

Class std::mutex

Class std::recursive_mutex

Class std::timed_mutex

Class std::recursive_timed_mutex

Class std::lock_guard

Class std::scoped_lock

Class std::unique_lock

Class std::once_flag