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peterhinch opened this issue Jan 11, 2025 · 3 comments
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asyncio terminates unexpectedly #16569

peterhinch opened this issue Jan 11, 2025 · 3 comments
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@peterhinch
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Port, board and/or hardware

Unix build (also verified on RP2 2)

MicroPython version

MicroPython v1.24.1 on 2024-11-29; Raspberry Pi Pico2 with RP2350

Reproduction

Paste the following at the REPL

import asyncio

evt = asyncio.Event()
async def foo():
    data = [1,2,3]
    for d in data:
        print(d)
        await asyncio.sleep(1)
    await evt.wait()  # Should hang

async def main():
    await foo()

asyncio.run(main())

Expected behaviour

Should print 1, 2, 3 then hang. This happens under CPython 3.10.12

1
2
3

Observed behaviour

Under MP, after expected output, it returns to the REPL.

1
2
3
>>>

Additional Information

This may be related to #16318

I am encountering the phenomenon of premature return in a number of situations, notably in test scripts where there are no pending tasks. I have never observed it in applications where there are multiple concurrent tasks.

Code of Conduct

Yes, I agree
@peterhinch peterhinch added the bug label Jan 11, 2025
@peterhinch
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peterhinch commented Feb 1, 2025 •
edited
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To add a few observations.

The problem goes away if a second task is launched that simply does a repeated async sleep. This explains why the fault only occurs in simple scripts [EDIT] see below.

When the fault occurs the run_until_complete loop quits here. It seems that while paused on

    await evt.wait()  # Should hang

there is no cur_task, causing run_until_complete to quit prematurely.

While the example script is artificial I've encountered this bug a few times in simple scripts intended to test applications. The work-round is trivial, but the tendency for premature exit may confuse beginners.
[EDIT}
I have now encountered the bug in a fairly large application. The circumstances were involved but the behaviour was deterministic. In response to a particular condition while one task was waiting on an Event the application terminated unexpectedly.

The workround was to replace the Event with a ThreadSafeFlag. The application is pure asyncio with no threads or ISR's.

@Baker68
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Baker68 commented Feb 10, 2025

Also present on MicroPython v1.24.0 on ESP32

@peterhinch peterhinch mentioned this issue Feb 15, 2025
Closed
yoctopuce added a commit to yoctopuce/micropython that referenced this issue Feb 17, 2025
@yoctopuce
extmod/asyncio/core.py: Fix awaited task completion in run_until_comp…
6466921 
…lete.

The issue is described in details in
micropython#16759

This amended commit also fixes these issues:
micropython#16569
micropython#16318

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
@yoctopuce yoctopuce mentioned this issue Feb 18, 2025
Merged
yoctopuce added a commit to yoctopuce/micropython that referenced this issue Feb 18, 2025
@yoctopuce
extmod/asyncio: Fix awaited task completion in run_until_complete.
5ceaa21 
The issue is described in details in
micropython#16759

This amended commit also fixes these issues:
micropython#16569
micropython#16318

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
yoctopuce added a commit to yoctopuce/micropython that referenced this issue Feb 18, 2025
@yoctopuce
extmod/asyncio: Fix awaited task completion in run_until_complete.
5e4c8c8 
The issue is described in details in
micropython#16759

This amended commit also fixes these issues:
micropython#16569
micropython#16318

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
yoctopuce added a commit to yoctopuce/micropython that referenced this issue Mar 3, 2025
@yoctopuce
extmod/asyncio: Fix awaited task completion in run_until_complete.
212b9ca 
The issue is described in details in
micropython#16759

This amended commit also fixes these issues:
micropython#16569
micropython#16318

Test cases have been updated to document the unauthorized
use of Event.set() from soft IRQ, and to be skipped in
unsupported environments (webassembly and emit native).

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
yoctopuce added a commit to yoctopuce/micropython that referenced this issue Mar 5, 2025
@yoctopuce
extmod/asyncio: Fix awaited task completion in run_until_complete.
e84f166 
The issue is described in details in
micropython#16759

This amended commit also fixes these issues:
micropython#16569
micropython#16318

Test cases have been updated to document the unauthorized
use of Event.set() from soft IRQ, and to be skipped in
unsupported environments (webassembly and emit native).

Code has been improved according to review from dpgeorge.

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
yoctopuce added a commit to yoctopuce/micropython that referenced this issue Mar 5, 2025
@yoctopuce
extmod/asyncio: Fix awaited task completion in run_until_complete.
779b6ac 
The issue is described in details in
micropython#16759

This amended commit also fixes these issues:
micropython#16569
micropython#16318

Test cases have been updated to document the unauthorized
use of Event.set() from soft IRQ, and to be skipped in
unsupported environments (webassembly and emit native).

Code has been improved according to review from dpgeorge.

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
dpgeorge pushed a commit to yoctopuce/micropython that referenced this issue May 7, 2025
@yoctopuce @dpgeorge
extmod/asyncio: Fix early exit of asyncio scheduler.
bdb7e03 
This commit fixes three open issues related to the asyncio scheduler
exiting prematurely when the main task queue is empty, in cases where
CPython would not exit (for example, because the main task is not done
because it's on a different queue).

In the first case, the scheduler exits because running a task via
`run_until_complete` did not schedule any dependent tasks.

In the other two cases, the scheduler exits because the tasks are queued in
an event queue.

Tests have been added which reproduce the original issues.  These test
cases document the unauthorized use of `Event.set()` from a soft IRQ, and
are skipped in unsupported environments (webassembly and native emitter).

Fixes issues micropython#16759, micropython#16569 and micropython#16318.

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>
@dpgeorge
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dpgeorge commented May 7, 2025

Fixed by bdb7e03

@dpgeorge dpgeorge closed this as completed May 7, 2025
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@dpgeorge @peterhinch @Baker68