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tokio: wake localset on spawn_local #3369

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merged 2 commits into from Jan 9, 2021
Merged

tokio: wake localset on spawn_local #3369

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a0d48e7
tokio: wake localset on spawn_local
Jan 3, 2021
5a23be6
remove implementation detail from comment
Jan 8, 2021
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3 changes: 3 additions & 0 deletions tokio/src/task/local.rs
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Expand Up @@ -242,6 +242,8 @@ impl LocalSet {
///
/// This task is guaranteed to be run on the current thread.
///
/// Calls to this function will result in waking the current localset.
///
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I'm not sure this is necessary to have in the doc?

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Happy to remove it if you don't think it is necessary. I added it because a side effect that changes program behavior is worth noting imo.

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I don't think it is necessary. The "wake" is an implementation detail.

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Besides, notes about changes in behavior go in the changelog instead. (You don't have to put it in this PR, we do them together when making the release.)

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Makes sense - Thanks for the review! Pushed the suggested changes.

/// Unlike the free function [`spawn_local`], this method may be used to
/// spawn local tasks when the task set is _not_ running. For example:
/// ```rust
Expand Down Expand Up @@ -283,6 +285,7 @@ impl LocalSet {
let future = crate::util::trace::task(future, "local");
let (task, handle) = unsafe { task::joinable_local(future) };
self.context.tasks.borrow_mut().queue.push_back(task);
self.context.shared.waker.wake();
handle
}

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14 changes: 14 additions & 0 deletions tokio/tests/task_local_set.rs
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@@ -1,6 +1,11 @@
#![warn(rust_2018_idioms)]
#![cfg(feature = "full")]

use futures::{
future::{pending, ready},
FutureExt,
};

use tokio::runtime::{self, Runtime};
use tokio::sync::{mpsc, oneshot};
use tokio::task::{self, LocalSet};
Expand Down Expand Up @@ -486,6 +491,15 @@ async fn acquire_mutex_in_drop() {
drop(local);
}

#[tokio::test]
async fn spawn_wakes_localset() {
let local = LocalSet::new();
futures::select! {
_ = local.run_until(pending::<()>()).fuse() => unreachable!(),
ret = async { local.spawn_local(ready(())).await.unwrap()}.fuse() => ret
}
}

fn rt() -> Runtime {
tokio::runtime::Builder::new_current_thread()
.enable_all()
Expand Down