| commit | 82e07c6117d38c388bfb1a1c15bfe5b4c0cec26b | [log] [tgz] |
|---|---|---|
| author | Android Build Coastguard Worker <[email protected]> | Wed Feb 16 08:21:26 2022 +0000 |
| committer | Android Build Coastguard Worker <[email protected]> | Wed Feb 16 08:21:26 2022 +0000 |
| tree | a3acf4ff2edd7c51a897225a12fa5a5290aaa408 | |
| parent | a0784645fdcde1ef1d470726b69c741eadf630f3 [diff] | |
| parent | 3b9ccd1daed9870e484cf8921cf349713d62d11b [diff] |
Snap for 8189365 from 3b9ccd1daed9870e484cf8921cf349713d62d11b to tm-frc-scheduling-release Change-Id: I1b9a52ad41e92587806a5cc756c0a6822c76a6f1
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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