Refactor sync::batch_semaphore::Semaphore::poll_acquire
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This commit tries to make the logic in `poll_acquire` flow more naturally, while also using more descriptive names and improving commentary (including the addition of a missing "SAFETY:" annotation). There should be no functional changes.
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Darksonn
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Jan 8, 2025
tokio/src/sync/batch_semaphore.rs
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| return Poll::Ready(Err(AcquireError::closed())); | ||
| } | ||
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| acquired >>= Self::PERMIT_SHIFT; |
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I find it to be confusing when the meaning of this is changed like this. Previously, it's the number of permits shifted, and after it's the actual number of permits. Can we use a different variable name prior to this that makes it clear that it's not just the number of permits?
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Agreed, but gosh is it hard to find a good name. I renamed to acquired_shifted before the shift, but now I feel I should append _shifted to a bunch of other variables, for consistency. But then it just looks awkward...
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Motivation
I found the implementation of the low-level semaphore a bit hard to read compared to other code (possibly because it has been untouched for some years). It could potentially benefit from small rewrites, better documentation, and the like.
Solution
Well, I thought it would be faster to attempt a PR for an initial change, rather than opening an issue. But I have no expectations that it will be merged. :)
I reworked the
poll_acquiremethod, these are the major changes:This probably needs a thorough review to make sure that I haven't messed up anything (or more likely, figure out what I have). If this kind of refactoring is accepted in core modules, I'm also happy to follow up with similar ones.