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Merge pull request #1004 from kngwyu/tls-destructed

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Ensure GILPool don't panic even after thread_locals are destructed
This commit is contained in:
Yuji Kanagawa 2020-06-27 15:46:05 +09:00 committed by GitHub
parent e114f637c5 7ce0c36b2f
commit bb782d7f83
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 60 additions and 47 deletions
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105
src/gil.rs
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@ -9,6 +9,26 @@ use std::{any, mem::ManuallyDrop, ptr::NonNull, sync};
static START: sync::Once = sync::Once::new();
/// Holds temporally owned objects.
struct ObjectHolder {
/// Objects owned by the current thread
obj: Vec<NonNull<ffi::PyObject>>,
/// Non-python objects(e.g., String) owned by the current thread
any: Vec<Box<dyn any::Any>>,
}
impl ObjectHolder {
fn new() -> Self {
Self {
obj: Vec::with_capacity(256),
any: Vec::with_capacity(4),
}
}
fn len(&self) -> (usize, usize) {
(self.obj.len(), self.any.len())
}
}
thread_local! {
/// This is a internal counter in pyo3 monitoring whether this thread has the GIL.
///
@ -20,12 +40,8 @@ thread_local! {
/// pub(crate) because it is manipulated temporarily by Python::allow_threads
pub(crate) static GIL_COUNT: Cell<u32> = Cell::new(0);
/// These are objects owned by the current thread, to be released when the GILPool drops.
static OWNED_OBJECTS: RefCell<Vec<NonNull<ffi::PyObject>>> = RefCell::new(Vec::with_capacity(256));
/// These are non-python objects such as (String) owned by the current thread, to be released
/// when the GILPool drops.
static OWNED_ANYS: RefCell<Vec<Box<dyn any::Any>>> = RefCell::new(Vec::with_capacity(256));
/// Temporally hold objects that will be released when the GILPool drops.
static OWNED_OBJECTS: RefCell<ObjectHolder> = RefCell::new(ObjectHolder::new());
}
/// Check whether the GIL is acquired.
@ -87,6 +103,14 @@ pub fn prepare_freethreaded_python() {
ffi::Py_InitializeEx(0);
// Make sure Py_Finalize will be called before exiting.
extern "C" fn finalize() {
unsafe {
if ffi::Py_IsInitialized() != 0 {
ffi::PyGILState_Ensure();
ffi::Py_Finalize();
}
}
}
libc::atexit(finalize);
}
@ -226,9 +250,9 @@ static POOL: ReferencePool = ReferencePool::new();
/// A RAII pool which PyO3 uses to store owned Python references.
pub struct GILPool {
owned_objects_start: usize,
owned_anys_start: usize,
// Stable solution for impl !Send
/// Initial length of owned objects and anys.
/// `Option` is used since TSL can be broken when `new` is called from `atexit`.
start: Option<(usize, usize)>,
no_send: Unsendable,
}
@ -246,8 +270,7 @@ impl GILPool {
// Update counts of PyObjects / Py that have been cloned or dropped since last acquisition
POOL.update_counts(Python::assume_gil_acquired());
GILPool {
owned_objects_start: OWNED_OBJECTS.with(|o| o.borrow().len()),
owned_anys_start: OWNED_ANYS.with(|o| o.borrow().len()),
start: OWNED_OBJECTS.try_with(|o| o.borrow().len()).ok(),
no_send: Unsendable::default(),
}
}
@ -261,22 +284,22 @@ impl GILPool {
impl Drop for GILPool {
fn drop(&mut self) {
unsafe {
OWNED_OBJECTS.with(|owned_objects| {
// Note: inside this closure we must be careful to not hold a borrow too long, because
// while calling Py_DECREF we may cause other callbacks to run which will need to
// register objects into the GILPool.
let len = owned_objects.borrow().len();
if self.owned_objects_start < len {
let rest = owned_objects
.borrow_mut()
.split_off(self.owned_objects_start);
for obj in rest {
if let Some((obj_len_start, any_len_start)) = self.start {
let dropping_obj = OWNED_OBJECTS.with(|holder| {
// `holder` must be dropped before calling Py_DECREF, or Py_DECREF may call
// `GILPool::drop` recursively, resulting in invalid borrowing.
let mut holder = holder.borrow_mut();
holder.any.truncate(any_len_start);
if obj_len_start < holder.obj.len() {
holder.obj.split_off(obj_len_start)
} else {
Vec::new()
}
});
for obj in dropping_obj {
ffi::Py_DECREF(obj.as_ptr());
}
}
});
OWNED_ANYS.with(|owned_anys| owned_anys.borrow_mut().truncate(self.owned_anys_start));
}
decrement_gil_count();
}
@ -320,7 +343,8 @@ pub unsafe fn register_decref(obj: NonNull<ffi::PyObject>) {
/// The object must be an owned Python reference.
pub unsafe fn register_owned(_py: Python, obj: NonNull<ffi::PyObject>) {
debug_assert!(gil_is_acquired());
OWNED_OBJECTS.with(|objs| objs.borrow_mut().push(obj));
// Ignoring the error means we do nothing if the TLS is broken.
let _ = OWNED_OBJECTS.try_with(|holder| holder.borrow_mut().obj.push(obj));
}
/// Register any value inside the GILPool.
@ -330,44 +354,33 @@ pub unsafe fn register_owned(_py: Python, obj: NonNull<ffi::PyObject>) {
/// the Rust compiler to outlast the current GILPool.
pub unsafe fn register_any<'p, T: 'static>(obj: T) -> &'p T {
debug_assert!(gil_is_acquired());
OWNED_ANYS.with(|owned_anys| {
OWNED_OBJECTS.with(|holder| {
let boxed = Box::new(obj);
let value_ref: &T = &*boxed;
// Sneaky - extend the lifetime of the reference so that the box can be moved
let value_ref_extended_lifetime = std::mem::transmute(value_ref);
owned_anys.borrow_mut().push(boxed);
value_ref_extended_lifetime
let value_ref: *const T = &*boxed;
holder.borrow_mut().any.push(boxed);
&*value_ref
})
}
/// Increment pyo3's internal GIL count - to be called whenever GILPool or GILGuard is created.
// Ignores the error in case this function called from `atexit`.
#[inline(always)]
fn increment_gil_count() {
GIL_COUNT.with(|c| c.set(c.get() + 1))
let _ = GIL_COUNT.with(|c| c.set(c.get() + 1));
}
/// Decrement pyo3's internal GIL count - to be called whenever GILPool or GILGuard is dropped.
// Ignores the error in case this function called from `atexit`.
#[inline(always)]
fn decrement_gil_count() {
GIL_COUNT.with(|c| {
let _ = GIL_COUNT.try_with(|c| {
let current = c.get();
debug_assert!(
current > 0,
"Negative GIL count detected. Please report this error to the PyO3 repo as a bug."
);
c.set(current - 1);
})
}
extern "C" fn finalize() {
unsafe {
if ffi::Py_IsInitialized() != 0 {
ffi::PyGILState_Ensure();
ffi::Py_Finalize();
}
}
});
}
/// Ensure the GIL is held, useful in implementation of APIs like PyErr::new where it's
@ -418,7 +431,7 @@ mod test {
}
fn owned_object_count() -> usize {
OWNED_OBJECTS.with(|objs| objs.borrow().len())
OWNED_OBJECTS.with(|holder| holder.borrow().obj.len())
}
#[test]