| commit | ec3a3680647a0fe76190f37a27684587fc1aa45b | [log] [tgz] |
|---|---|---|
| author | Android Build Coastguard Worker <[email protected]> | Thu Aug 25 07:51:44 2022 +0000 |
| committer | Android Build Coastguard Worker <[email protected]> | Thu Aug 25 07:51:44 2022 +0000 |
| tree | 1eb2b44d6c50027d5ac9d6db465034e877033b13 | |
| parent | 323f15d71a15420994069c5b39b5badc714979fc [diff] | |
| parent | 3e470bf5f77131953fa3d9793b2e3cfb876ad94b [diff] |
Snap for 8992082 from 3e470bf5f77131953fa3d9793b2e3cfb876ad94b to gki13-boot-release Change-Id: Ia8d79060362b28334dead2fa7e8afa588a03f216
Task abstraction for building executors.
To spawn a future onto an executor, we first need to allocate it on the heap and keep some state attached to it. The state indicates whether the future is ready for polling, waiting to be woken up, or completed. Such a stateful future is called a task.
All executors have a queue that holds scheduled tasks:
let (sender, receiver) = flume::unbounded();
A task is created using either spawn(), spawn_local(), or spawn_unchecked() which return a Runnable and a Task:
// A future that will be spawned. let future = async { 1 + 2 }; // A function that schedules the task when it gets woken up. let schedule = move |runnable| sender.send(runnable).unwrap(); // Construct a task. let (runnable, task) = async_task::spawn(future, schedule); // Push the task into the queue by invoking its schedule function. runnable.schedule();
The Runnable is used to poll the task's future, and the Task is used to await its output.
Finally, we need a loop that takes scheduled tasks from the queue and runs them:
for runnable in receiver { runnable.run(); }
Method run() polls the task's future once. Then, the Runnable vanishes and only reappears when its Waker wakes the task, thus scheduling it to be run again.
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