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[3.10] bpo-44434: Don't call PyThread_exit_thread() explicitly (GH-26758) #26824

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merged 1 commit into from
Jun 21, 2021

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@miss-islington miss-islington commented Jun 21, 2021

_thread.start_new_thread() no longer calls PyThread_exit_thread()
explicitly at the thread exit, the call was redundant.

On Linux with the glibc, pthread_cancel() loads dynamically the
libgcc_s.so.1 library. dlopen() can fail if there is no more
available file descriptor to open the file. In this case, the process
aborts with the error message:

"libgcc_s.so.1 must be installed for pthread_cancel to work"

pthread_cancel() unwinds back to the thread's wrapping function that
calls the thread entry point.

The unwind function is dynamically loaded from the libgcc_s library
since it is tightly coupled to the C compiler (GCC). The unwinder
depends on DWARF, the compiler generates DWARF, so the unwinder
belongs to the compiler.

Thanks Florian Weimer and Carlos O'Donell for their help on
investigating this issue.
(cherry picked from commit 45a78f9)

Co-authored-by: Victor Stinner vstinner@python.org

https://bugs.python.org/issue44434

_thread.start_new_thread() no longer calls PyThread_exit_thread()
explicitly at the thread exit, the call was redundant.

On Linux with the glibc, pthread_cancel() loads dynamically the
libgcc_s.so.1 library. dlopen() can fail if there is no more
available file descriptor to open the file. In this case, the process
aborts with the error message:

"libgcc_s.so.1 must be installed for pthread_cancel to work"

pthread_cancel() unwinds back to the thread's wrapping function that
calls the thread entry point.

The unwind function is dynamically loaded from the libgcc_s library
since it is tightly coupled to the C compiler (GCC). The unwinder
depends on DWARF, the compiler generates DWARF, so the unwinder
belongs to the compiler.

Thanks Florian Weimer and Carlos O'Donell for their help on
investigating this issue.
(cherry picked from commit 45a78f9)

Co-authored-by: Victor Stinner <vstinner@python.org>
@miss-islington
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@vstinner: Status check is done, and it's a success ✅ .

@miss-islington
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@vstinner: Status check is done, and it's a success ✅ .

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LGTM, good bot.

@vstinner vstinner merged commit 6614eac into python:3.10 Jun 21, 2021
@miss-islington miss-islington deleted the backport-45a78f9-3.10 branch June 21, 2021 12:29
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4 participants