Fix _at_fork_reinit to write INIT directly instead of calling unlock() by youknowone · Pull Request #7312 · RustPython/RustPython

…() (RustPython#7312)

* Fix _at_fork_reinit to write INIT directly instead of calling unlock()

unlock() goes through unlock_slow() which accesses parking_lot's
global hash table to unpark waiters. After fork(), this hash table
contains stale entries from dead parent threads, making unlock_slow()
unsafe. Writing INIT directly bypasses parking_lot internals entirely.

* Add import lock (IMP_LOCK) reinit after fork

The import lock is a ReentrantMutex that was never reinit'd after
fork(). If a parent thread held it during fork, the child would
deadlock on any import. Only reset if the owner is a dead thread;
if the surviving thread held it, normal unlock still works.