30 Thread support library [thread]

30.4 Mutual exclusion [thread.mutex]

30.4.1 Mutex requirements [thread.mutex.requirements] Timed mutex types [thread.timedmutex.requirements] Class recursive_timed_mutex [thread.timedmutex.recursive]

namespace std {
  class recursive_timed_mutex {

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

    void lock();  // blocking
    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; // See [thread.req.native]
    native_handle_type native_handle();                // See [thread.req.native]

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).

The class recursive_timed_mutex shall satisfy all of the TimedMutex requirements ([thread.timedmutex.requirements]). It shall be a standard-layout class (Clause [class]).

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.