From Jason Turner

[thread.stoptoken.intro]

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  Subclause [[thread.stoptoken]] describes components that can be used to
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  asynchronously request that an operation stops execution in a timely
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  manner, typically because the result is no longer required. Such a
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  request is called a *stop request*.
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- `stop_source`, `stop_token`, and `stop_callback` implement semantics of
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- shared ownership of a *stop state*. Any `stop_source`, `stop_token`, or
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- `stop_callback` that shares ownership of the same stop state is an
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- *associated* `stop_source`, `stop_token`, or `stop_callback`,
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- respectively. The last remaining owner of the stop state automatically
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- releases the resources associated with the stop state.
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- A `stop_token` can be passed to an operation which can either
 
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  - actively poll the token to check if there has been a stop request, or
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- - register a callback using the `stop_callback` class template which
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- will be called in the event that a stop request is made.
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- A stop request made via a `stop_source` will be visible to all
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- associated `stop_token` and `stop_source` objects. Once a stop request
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- has been made it cannot be withdrawn (a subsequent stop request has no
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- effect).
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- Callbacks registered via a `stop_callback` object are called when a stop
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- request is first made by any associated `stop_source` object.
 
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- Calls to the functions `request_stop`, `stop_requested`, and
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- `stop_possible` do not introduce data races. A call to `request_stop`
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- that returns `true` synchronizes with a call to `stop_requested` on an
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- associated `stop_token` or `stop_source` object that returns `true`.
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- Registration of a callback synchronizes with the invocation of that
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- callback.
 
 
 
 
 
 
 
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  Subclause [[thread.stoptoken]] describes components that can be used to
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  asynchronously request that an operation stops execution in a timely
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  manner, typically because the result is no longer required. Such a
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  request is called a *stop request*.
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+ The concepts `stoppable-source`, `stoppable_token`, and
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+ `stoppable-callback-for` specify the required syntax and semantics of
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+ shared access to a *stop state*. Any object modeling `stoppable-source`,
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+ `stoppable_token`, or `stoppable-callback-for` that refers to the same
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+ stop state is an *associated* `stoppable-source`, `stoppable_token`, or
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+ `stoppable-callback-for`, respectively.
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+ An object of a type that models `stoppable_token` can be passed to an
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+ operation that can either
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  - actively poll the token to check if there has been a stop request, or
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+ - register a callback that will be called in the event that a stop
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+ request is made.
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+ A stop request made via an object whose type models `stoppable-source`
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+ will be visible to all associated `stoppable_token` and
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+ `stoppable-source` objects. Once a stop request has been made it cannot
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+ be withdrawn (a subsequent stop request has no effect).
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+ Callbacks registered via an object whose type models
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+ `stoppable-callback-for` are called when a stop request is first made by
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+ any associated `stoppable-source` object.
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+ The types `stop_source` and `stop_token` and the class template
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+ `stop_callback` implement the semantics of shared ownership of a stop
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+ state. The last remaining owner of the stop state automatically releases
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+ the resources associated with the stop state.
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+
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+ An object of type `inplace_stop_source` is the sole owner of its stop
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+ state. An object of type `inplace_stop_token` or of a specialization of
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+ the class template `inplace_stop_callback` does not participate in
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+ ownership of its associated stop state.
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+
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+ [*Note 1*: They are for use when all uses of the associated token and
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+ callback objects are known to nest within the lifetime of the
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+ `inplace_stop_source` object. — *end note*]
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