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More fork safety by youknowone · Pull Request #7380 · RustPython/RustPython

coderabbitai[bot]

coderabbitai[bot]

coderabbitai[bot]

coderabbitai[bot]

coderabbitai[bot]

- Fix park_detached_threads: successful CAS no longer sets
  all_suspended=false, avoiding unnecessary polling rounds
- Replace park_timeout(50µs) with park() in wait_while_suspended
- Remove redundant self-suspension in attach_thread and detach_thread;
  the STW controller handles DETACHED→SUSPENDED via park_detached_threads
- Add double-check under mutex before condvar wait to prevent lost wakes
- Remove dead stats_detach_wait_yields field and add_detach_wait_yields
Like CPython's ThreadHandle_start, set RUNNING state in the parent
thread immediately after spawn() succeeds, rather than in the child.
This eliminates a race where join() could see Starting state if called
before the child thread executes.

Also reverts the macOS skip for test_start_new_thread_failed since the
root cause is fixed.
Add lock_wrapped to ThreadMutex for detaching thread state
while waiting on contended locks. Use it for buffered and
text IO locks. Wrap FileIO read/write in allow_threads via
crt_fd to prevent STW hangs on blocking file operations.
Replace parking_lot Mutex/Condvar with std::sync (pthread-based)
for started_event and handle_ready_event. This prevents hangs
in forked children where parking_lot's global HASHTABLE may be
corrupted.

youknowone added a commit to youknowone/RustPython that referenced this pull request

Mar 8, 2026
* apply more allow_threads

* Simplify STW thread state transitions

- Fix park_detached_threads: successful CAS no longer sets
  all_suspended=false, avoiding unnecessary polling rounds
- Replace park_timeout(50µs) with park() in wait_while_suspended
- Remove redundant self-suspension in attach_thread and detach_thread;
  the STW controller handles DETACHED→SUSPENDED via park_detached_threads
- Add double-check under mutex before condvar wait to prevent lost wakes
- Remove dead stats_detach_wait_yields field and add_detach_wait_yields

* Representable for ThreadHandle

* Set ThreadHandle state to Running in parent thread after spawn

Like CPython's ThreadHandle_start, set RUNNING state in the parent
thread immediately after spawn() succeeds, rather than in the child.
This eliminates a race where join() could see Starting state if called
before the child thread executes.

Also reverts the macOS skip for test_start_new_thread_failed since the
root cause is fixed.

* Set ThreadHandle state to Running in parent thread after spawn

* Add debug_assert for thread state in start_the_world

* Unskip now-passing test_get_event_loop_thread and test_start_new_thread_at_finalization

* Wrap IO locks and file ops in allow_threads

Add lock_wrapped to ThreadMutex for detaching thread state
while waiting on contended locks. Use it for buffered and
text IO locks. Wrap FileIO read/write in allow_threads via
crt_fd to prevent STW hangs on blocking file operations.

* Use std::sync for thread start/ready events

Replace parking_lot Mutex/Condvar with std::sync (pthread-based)
for started_event and handle_ready_event. This prevents hangs
in forked children where parking_lot's global HASHTABLE may be
corrupted.

youknowone added a commit to youknowone/RustPython that referenced this pull request

Mar 22, 2026
* apply more allow_threads

* Simplify STW thread state transitions

- Fix park_detached_threads: successful CAS no longer sets
  all_suspended=false, avoiding unnecessary polling rounds
- Replace park_timeout(50µs) with park() in wait_while_suspended
- Remove redundant self-suspension in attach_thread and detach_thread;
  the STW controller handles DETACHED→SUSPENDED via park_detached_threads
- Add double-check under mutex before condvar wait to prevent lost wakes
- Remove dead stats_detach_wait_yields field and add_detach_wait_yields

* Representable for ThreadHandle

* Set ThreadHandle state to Running in parent thread after spawn

Like CPython's ThreadHandle_start, set RUNNING state in the parent
thread immediately after spawn() succeeds, rather than in the child.
This eliminates a race where join() could see Starting state if called
before the child thread executes.

Also reverts the macOS skip for test_start_new_thread_failed since the
root cause is fixed.

* Set ThreadHandle state to Running in parent thread after spawn

* Add debug_assert for thread state in start_the_world

* Unskip now-passing test_get_event_loop_thread and test_start_new_thread_at_finalization

* Wrap IO locks and file ops in allow_threads

Add lock_wrapped to ThreadMutex for detaching thread state
while waiting on contended locks. Use it for buffered and
text IO locks. Wrap FileIO read/write in allow_threads via
crt_fd to prevent STW hangs on blocking file operations.

* Use std::sync for thread start/ready events

Replace parking_lot Mutex/Condvar with std::sync (pthread-based)
for started_event and handle_ready_event. This prevents hangs
in forked children where parking_lot's global HASHTABLE may be
corrupted.