Mutex Types and Locking Methods

C++ has five different mutexes that can lock recursively (i.e., multiple layers of locking), tentative with and without time constraints.

Method	mutex	recursive_mutex	timed_mutex	recursive_timed_mutex	shared_timed_mutex
m.lock	yes	yes	yes	yes	yes
m.unlock	yes	yes	yes	yes	yes
m.try_lock	yes	yes	yes

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