72 lines
2.9 KiB
Markdown
72 lines
2.9 KiB
Markdown
[thread.mutex.recursive]
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# 32 Concurrency support library [[thread]](./#thread)
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## 32.6 Mutual exclusion [[thread.mutex]](thread.mutex#recursive)
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### 32.6.4 Mutex requirements [[thread.mutex.requirements]](thread.mutex.requirements#thread.mutex.recursive)
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#### 32.6.4.2 Mutex types [[thread.mutex.requirements.mutex]](thread.mutex.requirements.mutex#thread.mutex.recursive)
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#### 32.6.4.2.3 Class recursive_mutex [thread.mutex.recursive]
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[ð](#lib:recursive_mutex)
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namespace std {class recursive_mutex {public: recursive_mutex(); ~recursive_mutex();
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recursive_mutex(const recursive_mutex&) = delete;
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recursive_mutex& operator=(const recursive_mutex&) = delete; void lock(); bool try_lock() noexcept; 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")};}
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7566)
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The class recursive_mutex provides a recursive mutex with exclusive ownership
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semantics[.](#1.sentence-1)
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If one thread owns a recursive_mutex object, attempts by another
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thread to acquire ownership of that object will fail (for try_lock()) or block
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(for lock()) until the first thread has completely released ownership[.](#1.sentence-2)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7573)
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The class recursive_mutex meets
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all of the mutex requirements ([[thread.mutex.requirements]](thread.mutex.requirements "32.6.4 Mutex requirements"))[.](#2.sentence-1)
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It is a standard-layout class ([[class.prop]](class.prop "11.2 Properties of classes"))[.](#2.sentence-2)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7578)
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A thread that owns a recursive_mutex object may acquire additional levels of
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ownership by calling lock() or try_lock() on that object[.](#3.sentence-1)
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It is
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unspecified how many levels of ownership may be acquired by a single thread[.](#3.sentence-2)
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If a thread
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has already acquired the maximum level of ownership for a recursive_mutex object, additional calls to try_lock() fail, and additional calls tolock() throw an exception of type system_error[.](#3.sentence-3)
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A thread
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shall call unlock() once for each level of ownership acquired by calls tolock() and try_lock()[.](#3.sentence-4)
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Only when all levels of ownership have been
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released may ownership be acquired by another thread[.](#3.sentence-5)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/threads.tex#L7589)
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The behavior of a program is undefined if
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- [(4.1)](#4.1)
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it destroys a recursive_mutex object owned by any thread or
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- [(4.2)](#4.2)
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a thread terminates while owning a recursive_mutex object[.](#4.sentence-1)
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