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Find "dangerous" blocking constructs in async contexts (.wait(), block_on, etc.) #4427

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emk opened this issue Aug 21, 2019 · 1 comment
Open

Find "dangerous" blocking constructs in async contexts (.wait(), block_on, etc.) #4427

emk opened this issue Aug 21, 2019 · 1 comment
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A-lint Area: New lints T-async-await Type: Issues related to async/await

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@emk
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emk commented Aug 21, 2019 •
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This is related to #4377, which proposed warning about blocking operations like println! inside an async context. That is definitely a promising idea, but it's also very ambitious, because almost anything could block.

But there's also a specific set of blocking constructs that can potentially deadlock the entire tokio (or other) runtime. These include things like calling block_on or .wait inside an async context. There are easy to include by mistake when converting non-async code to async. And there are fewer of these dangerous calls, which would make them easier to lint for.
@emk emk changed the title Find "dangerous" blocking constructs in async contexts Find "dangerous" blocking constructs in async contexts (.wait(), block_on, etc.) Aug 21, 2019
emk added a commit to dbcrossbar/dbcrossbar that referenced this issue Aug 21, 2019
@emk
Fix deadlock in copy_reader_to_stream
c0bf620 
Inside an `async` block, we're support to call `my_future.await`, and
_never_ use the sync-mode blocking equivalent `my_future.wait()`.
Apparently, doing this can deadlock the entire `tokio` runtime, or at
least the portions touching file I/O.

Fixes #16. Fixes #46.

We've also submitted a "lint" proposal to the clippy project which would
automatically detect errors of this class in the future:
rust-lang/rust-clippy#4427
@flip1995 flip1995 added A-lint Area: New lints T-async-await Type: Issues related to async/await labels Aug 26, 2019
@michaelsproul michaelsproul mentioned this issue Nov 16, 2022
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@michaelsproul
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Hi @emk! I've built a prototype of this lint which I've been running on CI for the last few months: #9857.

I'm looking for some help to get it to a merge-ready state

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A-lint Area: New lints T-async-await Type: Issues related to async/await
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New lint disallowed_from_async michaelsproul/rust-clippy
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@emk @michaelsproul @flip1995