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sync: Implement Clone for watch::Sender #6388

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merged 5 commits into from
Mar 12, 2024

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@mox692 mox692 commented Mar 10, 2024

Motivation

This PR attempt to resolve #4809.

Currently, watch channel has only one sender but this enable it to be mpmc by adding a clone of the sender.

Solution

As with the reciever, the ref_count_tx field is added to the shared structure to record the number of senders; this counter is incremented by the sender's clone method and decremented by the drop method.

@github-actions github-actions bot added the R-loom-sync Run loom sync tests on this PR label Mar 10, 2024
@Darksonn Darksonn added A-tokio Area: The main tokio crate M-sync Module: tokio/sync labels Mar 10, 2024
tokio/src/sync/watch.rs Outdated Show resolved Hide resolved
@mox692 mox692 marked this pull request as draft March 10, 2024 16:47
@mox692 mox692 marked this pull request as ready for review March 11, 2024 12:08
@@ -146,6 +146,16 @@ pub struct Sender<T> {
shared: Arc<Shared<T>>,
}

impl<T> Clone for Sender<T> {
fn clone(&self) -> Self {
self.shared.ref_count_tx.fetch_add(1, AcqRel);
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When it comes to incrementing refcounts (but not decrementing), relaxed is generally enough.

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Fixed.

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Thanks.

@Darksonn Darksonn merged commit a3d2548 into tokio-rs:master Mar 12, 2024
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@mox692 mox692 deleted the add_sender_clone branch March 12, 2024 11:12
@mox692 mox692 mentioned this pull request Apr 22, 2024
bjackman added a commit to bjackman/local-ci that referenced this pull request Jul 7, 2024
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A-tokio Area: The main tokio crate M-sync Module: tokio/sync R-loom-sync Run loom sync tests on this PR
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Implement Clone for watch::Sender to make it multi-producer
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