[thread.timedmutex.recursive]

# 32 Concurrency support library [[thread]](./#thread)

## 32.6 Mutual exclusion [[thread.mutex]](thread.mutex#thread.timedmutex.recursive)

### 32.6.4 Mutex requirements [[thread.mutex.requirements]](thread.mutex.requirements#thread.timedmutex.recursive)

#### 32.6.4.3 Timed mutex types [[thread.timedmutex.requirements]](thread.timedmutex.requirements#thread.timedmutex.recursive)

#### 32.6.4.3.3 Class recursive_timed_mutex [thread.timedmutex.recursive]

[🔗](#lib:recursive_timed_mutex)

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(); // blockingbool 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*; // see [[thread.req.native]](thread.req.native "32.2.3 Native handles") native_handle_type native_handle(); // see [[thread.req.native]](thread.req.native "32.2.3 Native handles")};}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7774)

The class recursive_timed_mutex provides a recursive mutex with exclusive
ownership semantics[.](#1.sentence-1)

If one thread owns a recursive_timed_mutex object,
attempts by another thread to acquire ownership of that object will fail (fortry_lock()) or block (for lock(), try_lock_for(), andtry_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)[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7784)

The class recursive_timed_mutex meets
all of the timed mutex requirements ([[thread.timedmutex.requirements]](thread.timedmutex.requirements "32.6.4.3 Timed mutex types"))[.](#2.sentence-1)

It is a standard-layout class ([[class.prop]](class.prop "11.2 Properties of classes"))[.](#2.sentence-2)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7789)

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[.](#3.sentence-1)

It is
unspecified how many levels of ownership may be acquired by a single thread[.](#3.sentence-2)

If
a thread has already acquired the maximum level of ownership for arecursive_timed_mutex object, additional calls to try_lock(),try_lock_for(), or try_lock_until() fail, and additional
calls to lock() throw an exception of type system_error[.](#3.sentence-3)

A
thread shall call unlock() once for each level of ownership acquired by
calls to lock(), try_lock(), try_lock_for(), andtry_lock_until()[.](#3.sentence-4)

Only when all levels of ownership have been released
may ownership of the object be acquired by another thread[.](#3.sentence-5)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7803)

The behavior of a program is undefined if

- [(4.1)](#4.1)

it destroys a recursive_timed_mutex object owned by any thread, or

- [(4.2)](#4.2)

a thread terminates while owning a recursive_timed_mutex object[.](#4.sentence-1)