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GC may have inconsistent view of stacktop with deferred references #118926

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Tracked by #117139
Fidget-Spinner opened this issue May 10, 2024 · 2 comments · Fixed by #122730
Closed
Tracked by #117139

GC may have inconsistent view of stacktop with deferred references #118926

Fidget-Spinner opened this issue May 10, 2024 · 2 comments · Fixed by #122730
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interpreter-core (Objects, Python, Grammar, and Parser dirs) type-bug An unexpected behavior, bug, or error

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@Fidget-Spinner
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Fidget-Spinner commented May 10, 2024 •
edited by bedevere-app bot
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In #118450, Sam pointed out that GC can occur at any Py_DECREF. With deferred references, we will need to traverse the object's stacks. The main problem is that frame->stacktop might not represent the true stacktop at a GC collection, because frame->stacktop is not set in between opcodes.

This requires either scanning the entire stack (not just up to stacktop), or deferring GC to safe points.

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This was referenced Jul 3, 2024
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markshannon added a commit that referenced this issue Jul 9, 2024
@markshannon
GH-118926: Better distinguish between pointer and arrays in interpret…
bf8686e 
…er generator (GH-121496)
noahbkim pushed a commit to hudson-trading/cpython that referenced this issue Jul 11, 2024
@markshannon @noahbkim
pythonGH-118926: Better distinguish between pointer and arrays in int…
1242036 
…erpreter generator (pythonGH-121496)
estyxx pushed a commit to estyxx/cpython that referenced this issue Jul 17, 2024
@markshannon @estyxx
pythonGH-118926: Better distinguish between pointer and arrays in int…
ee7a613 
…erpreter generator (pythonGH-121496)
@markshannon markshannon mentioned this issue Aug 6, 2024
Merged
colesbury added a commit to colesbury/cpython that referenced this issue Aug 6, 2024
@colesbury @Fidget-Spinner
pythongh-118926: Spill deferred references to stack in cases generator
70272dc 
This automatically spills the results from `_PyStackRef_FromPyObjectNew`
to the in-memory stack so that the deferred references are visible to
the GC before we make any possibly escaping call.

Co-authored-by: Ken Jin <kenjin@python.org>
@bedevere-app bedevere-app bot mentioned this issue Aug 6, 2024
Merged
@colesbury colesbury reopened this Aug 6, 2024
colesbury added a commit that referenced this issue Aug 7, 2024
@colesbury @Fidget-Spinner
gh-118926: Spill deferred references to stack in cases generator (#12…
3e753c6 
…2748)

This automatically spills the results from `_PyStackRef_FromPyObjectNew`
to the in-memory stack so that the deferred references are visible to
the GC before we make any possibly escaping call.

Co-authored-by: Ken Jin <kenjin@python.org>
blhsing pushed a commit to blhsing/cpython that referenced this issue Aug 22, 2024
@colesbury @Fidget-Spinner @blhsing
pythongh-118926: Spill deferred references to stack in cases generator (
6431127 
python#122748)

This automatically spills the results from `_PyStackRef_FromPyObjectNew`
to the in-memory stack so that the deferred references are visible to
the GC before we make any possibly escaping call.

Co-authored-by: Ken Jin <kenjin@python.org>
@JacobCoffee JacobCoffee added type-bug An unexpected behavior, bug, or error interpreter-core (Objects, Python, Grammar, and Parser dirs) labels Oct 1, 2024
@JacobCoffee
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hey @Fidget-Spinner is this good to close since the ref'd PRs are merged?

@Fidget-Spinner
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Yup

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GH-120024: Refactor code generators to uses classes for emitting code. faster-cpython/cpython
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@colesbury @Fidget-Spinner @JacobCoffee