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Showing content from https://timsong-cpp.github.io/cppwp/n4659/thread.timedmutex.requirements below:

[thread.timedmutex.requirements]

The timed mutex types are the standard library types timed_­mutex, recursive_­timed_­mutex, and shared_­timed_­mutex. They shall meet the requirements set out below. In this description, m denotes an object of a mutex type, rel_­time denotes an object of an instantiation of duration, and abs_­time denotes an object of an instantiation of time_­point.

The expression m.try_­lock_­for(rel_­time) shall be well-formed and have the following semantics:

Requires: If m is of type timed_­mutex or shared_­timed_­mutex, the calling thread does not own the mutex.

Effects: The function attempts to obtain ownership of the mutex within the relative timeout ([thread.req.timing]) specified by rel_­time. If the time specified by rel_­time is less than or equal to rel_­time.zero(), the function attempts to obtain ownership without blocking (as if by calling try_­lock()). The function shall return within the timeout specified by rel_­time only if it has obtained ownership of the mutex object. [ Note: As with try_­lock(), there is no guarantee that ownership will be obtained if the lock is available, but implementations are expected to make a strong effort to do so.  — end note ]

Returns: true if ownership was obtained, otherwise false.

Synchronization: If try_­lock_­for() returns true, prior unlock() operations on the same object synchronize with this operation.

The expression m.try_­lock_­until(abs_­time) shall be well-formed and have the following semantics:

Requires: If m is of type timed_­mutex or shared_­timed_­mutex, the calling thread does not own the mutex.

Effects: The function attempts to obtain ownership of the mutex. If abs_­time has already passed, the function attempts to obtain ownership without blocking (as if by calling try_­lock()). The function shall return before the absolute timeout ([thread.req.timing]) specified by abs_­time only if it has obtained ownership of the mutex object. [ Note: As with try_­lock(), there is no guarantee that ownership will be obtained if the lock is available, but implementations are expected to make a strong effort to do so.  — end note ]

Returns: true if ownership was obtained, otherwise false.

Synchronization: If try_­lock_­until() returns true, prior unlock() operations on the same object synchronize with this operation.

namespace std {
  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();

    using native_handle_type = implementation-defined;     native_handle_type native_handle();                  };
}

The class timed_­mutex provides a non-recursive mutex with exclusive ownership semantics. If one thread owns a timed_­mutex object, attempts by another thread to acquire ownership of that object will fail (for try_­lock()) or block (for lock(), try_­lock_­for(), and try_­lock_­until()) until the owning thread has released ownership with a call to unlock() or the call to try_­lock_­for() or try_­lock_­until() times out (having failed to obtain ownership).

The behavior of a program is undefined if:

• it destroys a timed_­mutex object owned by any thread,

• a thread that owns a timed_­mutex object calls lock(), try_­lock(), try_­lock_­for(), or try_­lock_­until() on that object, or

• a thread terminates while owning a timed_­mutex object.

namespace std {
  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();

    using native_handle_type = implementation-defined;     native_handle_type native_handle();                  };
}

The class recursive_­timed_­mutex provides a recursive mutex with exclusive ownership semantics. If one thread owns a recursive_­timed_­mutex object, attempts by another thread to acquire ownership of that object will fail (for try_­lock()) or block (for lock(), try_­lock_­for(), and try_­lock_­until()) until the owning thread has completely released ownership or the call to try_­lock_­for() or try_­lock_­until() times out (having failed to obtain ownership).

A thread that owns a recursive_­timed_­mutex object may acquire additional levels of ownership by calling lock(), try_­lock(), try_­lock_­for(), or try_­lock_­until() on that object. It is unspecified how many levels of ownership may be acquired by a single thread. If a thread has already acquired the maximum level of ownership for a recursive_­timed_­mutex object, additional calls to try_­lock(), try_­lock_­for(), or try_­lock_­until() shall fail, and additional calls to lock() shall throw an exception of type system_­error. A thread shall call unlock() once for each level of ownership acquired by calls to lock(), try_­lock(), try_­lock_­for(), and try_­lock_­until(). Only when all levels of ownership have been released may ownership of the object be acquired by another thread.

The behavior of a program is undefined if:

• it destroys a recursive_­timed_­mutex object owned by any thread, or

• a thread terminates while owning a recursive_­timed_­mutex object.

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