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bugfix: Remove erroneous wake call in SinkWriter #5436

Merged
merged 2 commits into from
Feb 7, 2023
Merged

bugfix: Remove erroneous wake call in SinkWriter #5436

merged 2 commits into from
Feb 7, 2023

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funbringer
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Per review comment #5070 (comment):

Adding a wake call here will be a busy loop that consumes 100% CPU
waiting for it to become ready. We shouldn't do that.

Furthermore, according to https://docs.rs/futures-sink/latest/futures_sink/trait.Sink.html#tymethod.poll_ready, poll_ready will make sure that the current task is notified.

Discussion: https://discord.com/channels/500028886025895936/500336346770964480/1072534504981418024

@funbringer
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cc @Darksonn

@funbringer funbringer force-pushed the funbringer/tokio-util-sink-writer-remove-wake branch from 78b1da0 to 28d294c Compare February 7, 2023 16:39
@funbringer
bugfix: Remove erroneous wake call in SinkWriter
33e7e91 
Per review comment tokio-rs#5070 (comment):
> Adding a wake call here will be a busy loop that consumes 100% CPU
> waiting for it to become ready. We shouldn't do that.

Furthermore, according to
https://docs.rs/futures-sink/latest/futures_sink/trait.Sink.html#tymethod.poll_ready,
poll_ready will make sure that the current task is notified.

Discussion: https://discord.com/channels/500028886025895936/500336346770964480/1072534504981418024
@funbringer funbringer force-pushed the funbringer/tokio-util-sink-writer-remove-wake branch from 28d294c to 33e7e91 Compare February 7, 2023 16:40
@Darksonn Darksonn added A-tokio-util Area: The tokio-util crate M-io Module: tokio/io labels Feb 7, 2023
@funbringer @Darksonn
Update tokio-util/src/io/sink_writer.rs
8fe91be 
Co-authored-by: Alice Ryhl <aliceryhl@google.com>
Darksonn
Darksonn approved these changes Feb 7, 2023
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Thanks.

@Darksonn Darksonn enabled auto-merge (squash) February 7, 2023 18:26
@Darksonn Darksonn merged commit 5653b45 into tokio-rs:master Feb 7, 2023
@funbringer funbringer deleted the funbringer/tokio-util-sink-writer-remove-wake branch February 7, 2023 18:51
@Darksonn Darksonn mentioned this pull request Feb 9, 2023
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Darksonn commented Feb 9, 2023

Note that this bug never appeared in a published release.

@little-arhat
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Hello! Is it possible to copy discussion from discord (or provide summary) here?

@Darksonn
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Sure, here is the discussion:

@funbringer

Hi there!

Sorry if it's a wrong place to ask questions, but I've been pointed at this piece of code over here. There's a review comment saying that this essentially introduces a busy loop (I tend to agree), but it seems this has never been addressed.

Do you think there's still a problem there?

@Darksonn

UHH. Is that on master?

@funbringer

I believe so.

There you go: https://github.com/tokio-rs/tokio/blob/master/tokio-util/src/io/sink_writer.rs#L111

@Darksonn

Can you submit a PR that removes it?

@funbringer

Sure.

@Darksonn

Thanks!

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@funbringer @Darksonn @little-arhat