[thread.stoptoken.intro] (original) (raw)
32 Thread support library [thread]
32.3 Stop tokens [thread.stoptoken]
32.3.1 Introduction [thread.stoptoken.intro]
This clause describes components that can be used to asynchonously request that an operation stops execution in a timely manner, typically because the result is no longer required.
Such a request is called a stop request.
stop_source, stop_token, and stop_callbackimplement semantics of shared ownership of a stop state.
Any stop_source, stop_token, or stop_callbackthat shares ownership of the same stop state is an associated stop_source, stop_token, or stop_callback, respectively.
The last remaining owner of the stop state automatically releases the resources associated with the stop state.
A stop_token can be passed to an operation which can either
- actively poll the token to check if there has been a stop request, or
- register a callback using the stop_callback class template which will be called in the event that a stop request is made.
A stop request made via a stop_source will be visible to all associated stop_token and stop_source objects.
Once a stop request has been made it cannot be withdrawn (a subsequent stop request has no effect).
Callbacks registered via a stop_callback object are called when a stop request is first made by any associated stop_source object.
Calls to the functions request_stop, stop_requested, and stop_possibledo not introduce data races.
A call to request_stop that returns truesynchronizes with a call to stop_requestedon an associated stop_token or stop_source object that returns true.
Registration of a callback synchronizes with the invocation of that callback.