gh-109955 : Update state transition comments for asyncio.Task #109910
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Lib/asyncio/tasks.py
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| # The transition from 2a to 2b happens when __wakeup() is executed, | ||
| # scheduling __step() to be called, leaving _fut_waiter in place. |
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This confuses me. Once __wakeup() executes, it proceeds without waiting to call __step() -- there's no scheduling involved that I can see in the source code (unless the .c extension is different). The call to future.result() immediately produces a value or raises -- it doesn't block (there's no await there). I do think it is possible to enter step 2b without going through 2a when __step() is scheduled directly by __init__(). So maybe it's clearer to say that we go through either 2a or 2b?
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I may have got my wires crossed here, because it is all confusing. Initially, I thought __wakeup() was called directly (futures just calling registered callbacks) and _wakeup scheduling __step,.. But then it turns out that futures schedule their callbacks... I'll have another look.
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Yes, you were right. So, there is no 2a or2b anymore just 2.
The main point I'm trying to get across here is that there can be a _fut_waiter present in a done state, i.e. the
mere presence of a _fut_waiter does not indicate that the Task is still blocked. I hope I'm not making this sound more complicated than it is.
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the mere presence of a
_fut_waiterdoes not indicate that the Task is still blocked
Yes, that's crucial information.
Co-authored-by: Adam Turner <[email protected]>
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needs backport to 3.11
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Thanks @kristjanvalur for the PR, and @gvanrossum for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12. |
…ythonGH-109910) (cherry picked from commit 45cf5b0) Co-authored-by: Kristján Valur Jónsson <[email protected]> Co-authored-by: Adam Turner <[email protected]>
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GH-109992 is a backport of this pull request to the 3.12 branch. |
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GH-109993 is a backport of this pull request to the 3.11 branch. |
…ythonGH-109910) (cherry picked from commit 45cf5b0) Co-authored-by: Kristján Valur Jónsson <[email protected]> Co-authored-by: Adam Turner <[email protected]>
…ython#109910) Co-authored-by: Adam Turner <[email protected]>
…H-109910) (#109993) gh-109955 : Update state transition comments for asyncio.Task (GH-109910) (cherry picked from commit 45cf5b0) Co-authored-by: Kristján Valur Jónsson <[email protected]> Co-authored-by: Adam Turner <[email protected]>
…H-109910) (#109992) gh-109955 : Update state transition comments for asyncio.Task (GH-109910) (cherry picked from commit 45cf5b0) Co-authored-by: Kristján Valur Jónsson <[email protected]> Co-authored-by: Adam Turner <[email protected]>
…ython#109910) Co-authored-by: Adam Turner <[email protected]>
The in-line comments for the state transition of asyncio.Task objects has been out of date
for quite some time.
_fut_waiterpersist in a done state on the Task between becoming done and until__step()is executed.__wakeup()is scheduled, followed by 2b when__step()is scheduled._step()and_wakeup()have been__step()and__wakeup()for quite some time.This PR attempts to rectify the situation.
asyncio.tasksare out of date #109955