Reinit IO buffer locks after fork to prevent deadlocks by youknowone · Pull Request #7339 · RustPython/RustPython

BufferedReader/Writer/TextIOWrapper use PyThreadMutex internally.
If a parent thread held one of these locks during fork(), the child
would deadlock on any IO operation.

Add reinit_after_fork() to RawThreadMutex and call it on sys.stdin/
stdout/stderr in the child process fork handler, analogous to
CPython's _PyIO_Reinit().

- Mark reinit_std_streams_after_fork as unsafe fn to encode
  fork-only precondition, update call site in posix.rs
- Reinit IncrementalNewlineDecoder's PyThreadMutex via
  TextIOWrapper's decoder field to prevent child deadlocks

* Reinit IO buffer locks after fork to prevent deadlocks

BufferedReader/Writer/TextIOWrapper use PyThreadMutex internally.
If a parent thread held one of these locks during fork(), the child
would deadlock on any IO operation.

Add reinit_after_fork() to RawThreadMutex and call it on sys.stdin/
stdout/stderr in the child process fork handler, analogous to
CPython's _PyIO_Reinit().

* Address review: unsafe fn + decoder lock reinit

- Mark reinit_std_streams_after_fork as unsafe fn to encode
  fork-only precondition, update call site in posix.rs
- Reinit IncrementalNewlineDecoder's PyThreadMutex via
  TextIOWrapper's decoder field to prevent child deadlocks

* Auto-format: cargo fmt --all

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>