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gh-117657: Make Py_TYPE and Py_SET_TYPE thread safe - #120165
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colesbury
commented
Jun 6, 2024
Contributor
Do you have a test / stack trace of the reported race? I don't think we should be modifying an object's type ( |
MemberAuthor
Example code: classFoo:
passclassBar:
passimportthreadingimportosX=Foo()
defwork():
foo=Xfor_inrange(10000):
foo.__class__=Bartype(foo)
foo.__class__=Footype(foo)
threads= []
foriinrange(os.cpu_count() -1):
thread=threading.Thread(target=work)
thread.start()
threads.append(thread)
work()
forthreadinthreads:
thread.join()TSAN output: Py_SET_TYPE: |
Fidget-Spinner
commented
Jun 7, 2024
MemberAuthor
Wow... the test case actually causes a segfault even with the fixes, not just a tsan warning. |
vstinner
commented
Jun 7, 2024
Member
Well, Py_TYPE() returns a borrow reference which is a bad thing :-/ But it shouldn't matter in this case, since the type is not deleted by the test. |
Fidget-Spinner
commented
Jun 7, 2024
MemberAuthor
Can't merge this until we fix the actual crasher code #120198. It seems even default build is affected. |
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picnixz
reviewed
Jun 9, 2024
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Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
| } | ||
| Py_BEGIN_CRITICAL_SECTION(self); | ||
| if (newto->tp_flags & Py_TPFLAGS_HEAPTYPE) { | ||
| Py_INCREF(newto); |
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Is it important to do the INCREF(newto) and DECREF(oldto) inside the critical section?
Or it it possible to restrict the critical section to the following code?
oldto=Py_TYPE(self);
Py_SET_TYPE(self, newto);MemberAuthor
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You're right. I can shrink it!
Co-Authored-By: Nadeshiko Manju <me@manjusaka.me>
vstinner
approved these changes
Jun 12, 2024
vstinner
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LGTM.
Since my previous review, object_set_class() got a critical section and it LGTM.
Fidget-Spinner
commented
Jun 12, 2024
MemberAuthor
Thanks for the review Victor! |
Thanks @Fidget-Spinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13. |
miss-islington pushed a commit
to miss-islington/cpython
that referenced
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Jun 12, 2024
GH-120403 is a backport of this pull request to the 3.13 branch. |
colesbury
commented
Jun 17, 2024
Contributor
I think we should address
The thread-safety guarantees should be something like:
@Fidget-Spinner, would you like to work on this? |
Fidget-Spinner
commented
Jun 17, 2024
MemberAuthor
@colesbury yeah I can revert the atomics in Py_TYPE and PY_SET_TYPE and stop the world instead. |
mrahtz pushed a commit
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Jun 30, 2024
…20165) Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com> Co-authored-by: Nadeshiko Manju <me@manjusaka.me>
noahbkim pushed a commit
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Jul 11, 2024
…20165) Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com> Co-authored-by: Nadeshiko Manju <me@manjusaka.me>
estyxx pushed a commit
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Jul 17, 2024
…20165) Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com> Co-authored-by: Nadeshiko Manju <me@manjusaka.me>
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