| commit | fc59545de29a8febe231e98c0ba3870a174bd80e | [log] [tgz] |
|---|---|---|
| author | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed Feb 01 14:09:14 2023 +0000 |
| committer | Android Build Coastguard Worker <android-build-coastguard-worker@google.com> | Wed Feb 01 14:09:14 2023 +0000 |
| tree | 56bc37db1ea300bbe1dd13de239d70038b816283 | |
| parent | de861550982f984d861521fdde94390d4eb60003 [diff] | |
| parent | 7006c6da6d4e48a973e95a6c527a25c8f28a2251 [diff] |
Snap for 9550733 from 7006c6da6d4e48a973e95a6c527a25c8f28a2251 to mainline-tzdata5-release Change-Id: Id0e951fedc80445291d6ffc50e690b7f60b4adb4
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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