33 Thread support library [thread]

33.2 Requirements [thread.req]

33.2.5 Requirements for Lockable types [thread.req.lockable] In general [thread.req.lockable.general]

An execution agent is an entity such as a thread that may perform work in parallel with other execution agents. [Note: Implementations or users may introduce other kinds of agents such as processes or thread-pool tasks. end note] The calling agent is determined by context, e.g. the calling thread that contains the call, and so on.

[Note: Some lockable objects are “agent oblivious” in that they work for any execution agent model because they do not determine or store the agent's ID (e.g., an ordinary spin lock). end note]

The standard library templates unique_­lock ([thread.lock.unique]), shared_­lock ([thread.lock.shared]), scoped_­lock ([thread.lock.scoped]), lock_­guard ([thread.lock.guard]), lock, try_­lock ([thread.lock.algorithm]), and condition_­variable_­any ([thread.condition.condvarany]) all operate on user-supplied lockable objects. The BasicLockable requirements, the Lockable requirements, and the TimedLockable requirements list the requirements imposed by these library types in order to acquire or release ownership of a lock by a given execution agent. [Note: The nature of any lock ownership and any synchronization it may entail are not part of these requirements. end note]