Open
Description
os.fork needs certain support functions to work properly, namely _at_fork_reinit
Basic idea is that whenever child is forked from parent, it shouldn't own locks held by its parent (parent's problem is not children's problem right?).
So whenever child gets initialized, lock object should get reallocated.
cpython code
int
_PyThread_at_fork_reinit(PyThread_type_lock *lock)
{
PyThread_type_lock new_lock = PyThread_allocate_lock();
if (new_lock == NULL) {
return -1;
}
/* bpo-6721, bpo-40089: The old lock can be in an inconsistent state.
fork() can be called in the middle of an operation on the lock done by
another thread. So don't call PyThread_free_lock(*lock).
Leak memory on purpose. Don't release the memory either since the
address of a mutex is relevant. Putting two mutexes at the same address
can lead to problems. */
*lock = new_lock;
return 0;
}
Notice, it doesn't bother cleanup up old lock object.
cpython's Add _at_fork_reinit() method to locks gives relevant details
Unknowns: LockType object is alias for Lock, but there is file called Lib/_dummy_thread.py in rustpython which I don't see in cpython.
Implementation strategy:
- Add _at_fork_reinit in Lock and RLock in vm/src/stdlib/thread.rs
- Realloc self.mu.
For this, I can not possibly do this
#[pymethod]
fn _at_fork_reinit(&mut self, vm: &VirtualMachine) -> PyResult<()> {
self.mu = RawMutex::INIT;
Ok(())
}
It complains about
error[E0277]: the trait bound `for<'a, 'b> fn(&'a mut RLock, &'b vm::VirtualMachine) -> Result<(), object::core::PyRef<exceptions::types::PyBaseException>> {RLock::_at_fork_reinit}: PyNativeFnInternal<_, _, _>` is not satisfied
--> vm/src/stdlib/thread.rs:186:5
|
186 | #[pyclass(with(Representable))]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `PyNativeFnInternal<_, _, _>` is not implemented for fn item `for<'a, 'b> fn(&'a mut RLock, &'b vm::VirtualMachine) -> Result<(), object::core::PyRef<exceptions::types::PyBaseException>> {RLock::_at_fork_reinit}`
|
note: required for `for<'a, 'b> fn(&'a mut RLock, &'b vm::VirtualMachine) -> Result<(), object::core::PyRef<exceptions::types::PyBaseException>> {RLock::_at_fork_reinit}` to implement `IntoPyNativeFn<(_, _, _)>`
--> vm/src/function/builtin.rs:44:19
|
44 | impl<F, T, R, VM> IntoPyNativeFn<(T, R, VM)> for F
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ ^
45 | where
46 | F: PyNativeFnInternal<T, R, VM>,
| ---------------------------- unsatisfied trait bound introduced here
= note: this error originates in the attribute macro `pyclass` (in Nightly builds, run with -Z macro-backtrace for more info)
For more information about this error, try `rustc --explain E0277`.
error: could not compile `rustpython-vm` due to 2 previous errors
which is unfortunate.