macros: make select! budget-aware
#7164
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maminrayej
added
A-tokio
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Previously the test would hang on the |
| // Return `Pending` when the task budget is depleted since budget-aware futures | ||
| // are going to yield anyway and other futures will not cooperate. | ||
| if !$crate::macros::support::has_budget_remaining() { | ||
| cx.waker().wake_by_ref(); | ||
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| return ::std::task::Poll::Pending; | ||
| } |
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I wonder if this is really the best way to go about it. Does our other coop logic run cx.waker().wake_by_ref() directly, or do they stash the waker in the array used by yield_now()?
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poll_proceed calls wake_by_ref directly instead of going through context::defer.
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I looked at poll_proceed, and it does use wake_by_ref. However, I don't know if that is intentional or if we forgot to update that code when yield_now() switched to the defer strategy. My guess is that it is an intentional artifact, and we should update it.
I think the logic (if no budget remaining, then yield) should be wrapped up as a utility that lives in the coop module, so we keep the logic in one place. Separately, we should determine if coop yielding should use the defer path.
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This PR is where the defer list was introduced. It feels like coop yielding should use the same path. We can fix this after this PR lands, though. However, it would be nice if all coop code uses a single method that does the actual yielding.
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I filed #7185 to fix the coop issue.
Co-authored-by: Alice Ryhl <[email protected]>
Resolves #7108.