namespace std {
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; // See [thread.req.native]
native_handle_type native_handle(); // See [thread.req.native]
};
}
The class recursive_mutex provides a recursive mutex with exclusive ownership semantics. If one thread owns a recursive_mutex object, attempts by another thread to acquire ownership of that object will fail (for try_lock()) or block (for lock()) until the first thread has completely released ownership.
The class recursive_mutex shall satisfy all the Mutex requirements ([thread.mutex.requirements]). It shall be a standard-layout class (Clause [class]).
A thread that owns a recursive_mutex object may acquire additional levels of ownership by calling lock() or try_lock() 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_mutex object, additional calls to try_lock() 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() and try_lock(). Only when all levels of ownership have been released may ownership be acquired by another thread.