[thread.sharedmutex.class]

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

## 32.6 Mutual exclusion [[thread.mutex]](thread.mutex#thread.sharedmutex.class)

### 32.6.4 Mutex requirements [[thread.mutex.requirements]](thread.mutex.requirements#thread.sharedmutex.class)

#### 32.6.4.4 Shared mutex types [[thread.sharedmutex.requirements]](thread.sharedmutex.requirements#thread.sharedmutex.class)

#### 32.6.4.4.2 Class shared_mutex [thread.sharedmutex.class]

[🔗](#lib:shared_mutex)

namespace std {class shared_mutex {public: shared_mutex(); ~shared_mutex();

 shared_mutex(const shared_mutex&) = delete;
 shared_mutex& operator=(const shared_mutex&) = delete; // exclusive ownershipvoid lock(); // blockingbool try_lock(); void unlock(); // shared ownershipvoid lock_shared(); // blockingbool try_lock_shared(); void unlock_shared(); 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#L7963)

The class shared_mutex provides a non-recursive mutex
with shared ownership semantics[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7967)

The class shared_mutex meets
all of the shared mutex requirements ([[thread.sharedmutex.requirements]](thread.sharedmutex.requirements "32.6.4.4 Shared 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#L7972)

The behavior of a program is undefined if

- [(3.1)](#3.1)

it destroys a shared_mutex object owned by any thread,

- [(3.2)](#3.2)

a thread attempts to recursively gain any ownership of a shared_mutex, or

- [(3.3)](#3.3)

a thread terminates while possessing any ownership of a shared_mutex[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7980)

shared_mutex may be a synonym for shared_timed_mutex[.](#4.sentence-1)