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PidfdChildWatcher runs callbacks on the main thread eventloop and not the currently running loop #94182

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graingert opened this issue Jun 23, 2022 · 6 comments
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PidfdChildWatcher runs callbacks on the main thread eventloop and not the currently running loop #94182

graingert opened this issue Jun 23, 2022 · 6 comments
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topic-asyncio type-bug An unexpected behavior, bug, or error

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@graingert
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graingert commented Jun 23, 2022 •
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as of #93896 and #94593 asyncio.Runner(loop_factory=asyncio.new_event_loop) no longer calls asyncio.set_event_loop() and so the PidfdChildWatcher is never activated

this is unfortunate because it could run asyncio.get_running_loop().add_reader instead
@graingert graingert added the type-bug An unexpected behavior, bug, or error label Jun 23, 2022
@bedevere-bot bedevere-bot mentioned this issue Jun 23, 2022
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@kumaraditya303
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Wasn't this fixed by #94593?

@graingert
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Wasn't this fixed by #94593?

No

@graingert
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The purpose of os.open_pidfd is to allow a single event loop running in any thread to monitor processes without needing to interact with another event loop or thread. The pidfdchildwatcher is currently unnecessarily using another loop in another thread

@ezio-melotti ezio-melotti moved this to Todo in asyncio Jul 17, 2022
@graingert
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graingert commented Jul 19, 2022 •
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@kumaraditya303 I can demonstrate that the issue is still not resolved by using 5647edb (#94184) - I updated the description to clarify this

gvanrossum pushed a commit that referenced this issue Oct 8, 2022
@graingert @1st1 @JelleZijlstra
GH-94182: Run the PidfdChildWatcher on the running loop (#94184)
3d8b224 
There is no reason for this watcher to be attached to any particular loop.
This should make it safe to use regardless of the lifetime of the event loop running in the main thread
(relative to other loops).

Co-authored-by: Yury Selivanov <[email protected]>
Co-authored-by: Jelle Zijlstra <[email protected]>
@gvanrossum
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Thanks for the fix!

I don't think we should backport this (not even to 3.11.1).

Repository owner moved this from Todo to Done in asyncio Oct 8, 2022
carljm added a commit to carljm/cpython that referenced this issue Oct 8, 2022
@carljm
Merge branch 'main' into typewatch
d67d6fd 
* main:
  pythongh-68686: Retire eptag ptag scripts (python#98064)
  pythongh-97922: Run the GC only on eval breaker (python#97920)
  GitHub Workflows security hardening (python#96492)
  Add `@ezio-melotti` as codeowner for `.github/`. (python#98079)
  pythongh-97913 Docs: Add walrus operator to the index (python#97921)
  [doc] Fix broken links to C extensions accelerating stdlib modules (python#96914)
  pythongh-97822: Fix http.server documentation reference to test() function (python#98027)
  pythongh-91052: Add PyDict_Unwatch for unwatching a dictionary (python#98055)
  pythonGH-98023: Change default child watcher to PidfdChildWatcher on supported systems (python#98024)
  pythonGH-94182: Run the PidfdChildWatcher on the running loop (python#94184)
carljm added a commit to carljm/cpython that referenced this issue Oct 9, 2022
@carljm
Merge branch 'main' into urllibnonet
132c32e 
* main: (5519 commits)
  Minor edits to the Descriptor HowTo Guide (pythonGH-24901)
  Fix link to Lifecycle of a Pull Request in CONTRIBUTING (python#98102)
  pythonGH-94597: deprecate `SafeChildWatcher`, `FastChildWatcher` and `MultiLoopChildWatcher` child watchers  (python#98089)
  Auto-cancel old builds when new commit pushed to branch (python#98009)
  pythongh-95011: Migrate syslog module to Argument Clinic (pythonGH-95012)
  pythongh-68686: Retire eptag ptag scripts (python#98064)
  pythongh-97922: Run the GC only on eval breaker (python#97920)
  GitHub Workflows security hardening (python#96492)
  Add `@ezio-melotti` as codeowner for `.github/`. (python#98079)
  pythongh-97913 Docs: Add walrus operator to the index (python#97921)
  [doc] Fix broken links to C extensions accelerating stdlib modules (python#96914)
  pythongh-97822: Fix http.server documentation reference to test() function (python#98027)
  pythongh-91052: Add PyDict_Unwatch for unwatching a dictionary (python#98055)
  pythonGH-98023: Change default child watcher to PidfdChildWatcher on supported systems (python#98024)
  pythonGH-94182: Run the PidfdChildWatcher on the running loop (python#94184)
  pythongh-92886: make test_ast pass with -O (assertions off) (pythonGH-98058)
  pythongh-92886: make test_coroutines pass with -O (assertions off) (pythonGH-98060)
  pythongh-57179: Add note on symlinks for os.walk (python#94799)
  pythongh-94808: Fix regex on exotic platforms (python#98036)
  pythongh-90085: Remove vestigial -t and -c timeit options (python#94941)
  ...
mpage pushed a commit to mpage/cpython that referenced this issue Oct 11, 2022
@graingert @1st1
@JelleZijlstra @mpage
pythonGH-94182: Run the PidfdChildWatcher on the running loop (python…
6cd489d 
…#94184)

There is no reason for this watcher to be attached to any particular loop.
This should make it safe to use regardless of the lifetime of the event loop running in the main thread
(relative to other loops).

Co-authored-by: Yury Selivanov <[email protected]>
Co-authored-by: Jelle Zijlstra <[email protected]>
@serhiy-storchaka
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This test fails if run separately. See #109862.

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@graingert @gvanrossum @serhiy-storchaka @kumaraditya303 @AlexWaygood