pyo3/sync.rs
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//! Synchronization mechanisms based on the Python GIL.
//!
//! With the acceptance of [PEP 703] (aka a "freethreaded Python") for Python 3.13, these
//! are likely to undergo significant developments in the future.
//!
//! [PEP 703]: https://peps.python.org/pep-703/
use crate::{
gil::SuspendGIL,
sealed::Sealed,
types::{any::PyAnyMethods, PyAny, PyString},
Bound, Py, PyResult, PyTypeCheck, Python,
};
use std::{
cell::UnsafeCell,
marker::PhantomData,
mem::MaybeUninit,
sync::{Once, OnceState},
};
#[cfg(not(Py_GIL_DISABLED))]
use crate::PyVisit;
/// Value with concurrent access protected by the GIL.
///
/// This is a synchronization primitive based on Python's global interpreter lock (GIL).
/// It ensures that only one thread at a time can access the inner value via shared references.
/// It can be combined with interior mutability to obtain mutable references.
///
/// This type is not defined for extensions built against the free-threaded CPython ABI.
///
/// # Example
///
/// Combining `GILProtected` with `RefCell` enables mutable access to static data:
///
/// ```
/// # use pyo3::prelude::*;
/// use pyo3::sync::GILProtected;
/// use std::cell::RefCell;
///
/// static NUMBERS: GILProtected<RefCell<Vec<i32>>> = GILProtected::new(RefCell::new(Vec::new()));
///
/// Python::with_gil(|py| {
/// NUMBERS.get(py).borrow_mut().push(42);
/// });
/// ```
#[cfg(not(Py_GIL_DISABLED))]
pub struct GILProtected<T> {
value: T,
}
#[cfg(not(Py_GIL_DISABLED))]
impl<T> GILProtected<T> {
/// Place the given value under the protection of the GIL.
pub const fn new(value: T) -> Self {
Self { value }
}
/// Gain access to the inner value by giving proof of having acquired the GIL.
pub fn get<'py>(&'py self, _py: Python<'py>) -> &'py T {
&self.value
}
/// Gain access to the inner value by giving proof that garbage collection is happening.
pub fn traverse<'py>(&'py self, _visit: PyVisit<'py>) -> &'py T {
&self.value
}
}
#[cfg(not(Py_GIL_DISABLED))]
unsafe impl<T> Sync for GILProtected<T> where T: Send {}
/// A write-once primitive similar to [`std::sync::OnceLock<T>`].
///
/// Unlike `OnceLock<T>` which blocks threads to achieve thread safety, `GilOnceCell<T>`
/// allows calls to [`get_or_init`][GILOnceCell::get_or_init] and
/// [`get_or_try_init`][GILOnceCell::get_or_try_init] to race to create an initialized value.
/// (It is still guaranteed that only one thread will ever write to the cell.)
///
/// On Python versions that run with the Global Interpreter Lock (GIL), this helps to avoid
/// deadlocks between initialization and the GIL. For an example of such a deadlock, see
#[doc = concat!(
"[the FAQ section](https://pyo3.rs/v",
env!("CARGO_PKG_VERSION"),
"/faq.html#im-experiencing-deadlocks-using-pyo3-with-stdsynconcelock-stdsynclazylock-lazy_static-and-once_cell)"
)]
/// of the guide.
///
/// Note that because the GIL blocks concurrent execution, in practice the means that
/// [`get_or_init`][GILOnceCell::get_or_init] and
/// [`get_or_try_init`][GILOnceCell::get_or_try_init] may race if the initialization
/// function leads to the GIL being released and a thread context switch. This can
/// happen when importing or calling any Python code, as long as it releases the
/// GIL at some point. On free-threaded Python without any GIL, the race is
/// more likely since there is no GIL to prevent races. In the future, PyO3 may change
/// the semantics of GILOnceCell to behave more like the GIL build in the future.
///
/// # Re-entrant initialization
///
/// [`get_or_init`][GILOnceCell::get_or_init] and
/// [`get_or_try_init`][GILOnceCell::get_or_try_init] do not protect against infinite recursion
/// from reentrant initialization.
///
/// # Examples
///
/// The following example shows how to use `GILOnceCell` to share a reference to a Python list
/// between threads:
///
/// ```
/// use pyo3::sync::GILOnceCell;
/// use pyo3::prelude::*;
/// use pyo3::types::PyList;
///
/// static LIST_CELL: GILOnceCell<Py<PyList>> = GILOnceCell::new();
///
/// pub fn get_shared_list(py: Python<'_>) -> &Bound<'_, PyList> {
/// LIST_CELL
/// .get_or_init(py, || PyList::empty(py).unbind())
/// .bind(py)
/// }
/// # Python::with_gil(|py| assert_eq!(get_shared_list(py).len(), 0));
/// ```
pub struct GILOnceCell<T> {
once: Once,
data: UnsafeCell<MaybeUninit<T>>,
/// (Copied from std::sync::OnceLock)
///
/// `PhantomData` to make sure dropck understands we're dropping T in our Drop impl.
///
/// ```compile_error,E0597
/// use pyo3::Python;
/// use pyo3::sync::GILOnceCell;
///
/// struct A<'a>(#[allow(dead_code)] &'a str);
///
/// impl<'a> Drop for A<'a> {
/// fn drop(&mut self) {}
/// }
///
/// let cell = GILOnceCell::new();
/// {
/// let s = String::new();
/// let _ = Python::with_gil(|py| cell.set(py,A(&s)));
/// }
/// ```
_marker: PhantomData<T>,
}
impl<T> Default for GILOnceCell<T> {
fn default() -> Self {
Self::new()
}
}
// T: Send is needed for Sync because the thread which drops the GILOnceCell can be different
// to the thread which fills it. (e.g. think scoped thread which fills the cell and then exits,
// leaving the cell to be dropped by the main thread).
unsafe impl<T: Send + Sync> Sync for GILOnceCell<T> {}
unsafe impl<T: Send> Send for GILOnceCell<T> {}
impl<T> GILOnceCell<T> {
/// Create a `GILOnceCell` which does not yet contain a value.
pub const fn new() -> Self {
Self {
once: Once::new(),
data: UnsafeCell::new(MaybeUninit::uninit()),
_marker: PhantomData,
}
}
/// Get a reference to the contained value, or `None` if the cell has not yet been written.
#[inline]
pub fn get(&self, _py: Python<'_>) -> Option<&T> {
if self.once.is_completed() {
// SAFETY: the cell has been written.
Some(unsafe { (*self.data.get()).assume_init_ref() })
} else {
None
}
}
/// Get a reference to the contained value, initializing it if needed using the provided
/// closure.
///
/// See the type-level documentation for detail on re-entrancy and concurrent initialization.
#[inline]
pub fn get_or_init<F>(&self, py: Python<'_>, f: F) -> &T
where
F: FnOnce() -> T,
{
if let Some(value) = self.get(py) {
return value;
}
// .unwrap() will never panic because the result is always Ok
self.init(py, || Ok::<T, std::convert::Infallible>(f()))
.unwrap()
}
/// Like `get_or_init`, but accepts a fallible initialization function. If it fails, the cell
/// is left uninitialized.
///
/// See the type-level documentation for detail on re-entrancy and concurrent initialization.
#[inline]
pub fn get_or_try_init<F, E>(&self, py: Python<'_>, f: F) -> Result<&T, E>
where
F: FnOnce() -> Result<T, E>,
{
if let Some(value) = self.get(py) {
return Ok(value);
}
self.init(py, f)
}
#[cold]
fn init<F, E>(&self, py: Python<'_>, f: F) -> Result<&T, E>
where
F: FnOnce() -> Result<T, E>,
{
// Note that f() could temporarily release the GIL, so it's possible that another thread
// writes to this GILOnceCell before f() finishes. That's fine; we'll just have to discard
// the value computed here and accept a bit of wasted computation.
// TODO: on the freethreaded build, consider wrapping this pair of operations in a
// critical section (requires a critical section API which can use a PyMutex without
// an object.)
let value = f()?;
let _ = self.set(py, value);
Ok(self.get(py).unwrap())
}
/// Get the contents of the cell mutably. This is only possible if the reference to the cell is
/// unique.
pub fn get_mut(&mut self) -> Option<&mut T> {
if self.once.is_completed() {
// SAFETY: the cell has been written.
Some(unsafe { (*self.data.get()).assume_init_mut() })
} else {
None
}
}
/// Set the value in the cell.
///
/// If the cell has already been written, `Err(value)` will be returned containing the new
/// value which was not written.
pub fn set(&self, _py: Python<'_>, value: T) -> Result<(), T> {
let mut value = Some(value);
// NB this can block, but since this is only writing a single value and
// does not call arbitrary python code, we don't need to worry about
// deadlocks with the GIL.
self.once.call_once_force(|_| {
// SAFETY: no other threads can be writing this value, because we are
// inside the `call_once_force` closure.
unsafe {
// `.take().unwrap()` will never panic
(*self.data.get()).write(value.take().unwrap());
}
});
match value {
// Some other thread wrote to the cell first
Some(value) => Err(value),
None => Ok(()),
}
}
/// Takes the value out of the cell, moving it back to an uninitialized state.
///
/// Has no effect and returns None if the cell has not yet been written.
pub fn take(&mut self) -> Option<T> {
if self.once.is_completed() {
// Reset the cell to its default state so that it won't try to
// drop the value again.
self.once = Once::new();
// SAFETY: the cell has been written. `self.once` has been reset,
// so when `self` is dropped the value won't be read again.
Some(unsafe { self.data.get_mut().assume_init_read() })
} else {
None
}
}
/// Consumes the cell, returning the wrapped value.
///
/// Returns None if the cell has not yet been written.
pub fn into_inner(mut self) -> Option<T> {
self.take()
}
}
impl<T> GILOnceCell<Py<T>> {
/// Creates a new cell that contains a new Python reference to the same contained object.
///
/// Returns an uninitialized cell if `self` has not yet been initialized.
pub fn clone_ref(&self, py: Python<'_>) -> Self {
let cloned = Self {
once: Once::new(),
data: UnsafeCell::new(MaybeUninit::uninit()),
_marker: PhantomData,
};
if let Some(value) = self.get(py) {
let _ = cloned.set(py, value.clone_ref(py));
}
cloned
}
}
impl<T> GILOnceCell<Py<T>>
where
T: PyTypeCheck,
{
/// Get a reference to the contained Python type, initializing the cell if needed.
///
/// This is a shorthand method for `get_or_init` which imports the type from Python on init.
///
/// # Example: Using `GILOnceCell` to store a class in a static variable.
///
/// `GILOnceCell` can be used to avoid importing a class multiple times:
/// ```
/// # use pyo3::prelude::*;
/// # use pyo3::sync::GILOnceCell;
/// # use pyo3::types::{PyDict, PyType};
/// # use pyo3::intern;
/// #
/// #[pyfunction]
/// fn create_ordered_dict<'py>(py: Python<'py>, dict: Bound<'py, PyDict>) -> PyResult<Bound<'py, PyAny>> {
/// // Even if this function is called multiple times,
/// // the `OrderedDict` class will be imported only once.
/// static ORDERED_DICT: GILOnceCell<Py<PyType>> = GILOnceCell::new();
/// ORDERED_DICT
/// .import(py, "collections", "OrderedDict")?
/// .call1((dict,))
/// }
///
/// # Python::with_gil(|py| {
/// # let dict = PyDict::new(py);
/// # dict.set_item(intern!(py, "foo"), 42).unwrap();
/// # let fun = wrap_pyfunction!(create_ordered_dict, py).unwrap();
/// # let ordered_dict = fun.call1((&dict,)).unwrap();
/// # assert!(dict.eq(ordered_dict).unwrap());
/// # });
/// ```
pub fn import<'py>(
&self,
py: Python<'py>,
module_name: &str,
attr_name: &str,
) -> PyResult<&Bound<'py, T>> {
self.get_or_try_init(py, || {
let type_object = py
.import(module_name)?
.getattr(attr_name)?
.downcast_into()?;
Ok(type_object.unbind())
})
.map(|ty| ty.bind(py))
}
}
impl<T> Drop for GILOnceCell<T> {
fn drop(&mut self) {
if self.once.is_completed() {
// SAFETY: the cell has been written.
unsafe { MaybeUninit::assume_init_drop(self.data.get_mut()) }
}
}
}
/// Interns `text` as a Python string and stores a reference to it in static storage.
///
/// A reference to the same Python string is returned on each invocation.
///
/// # Example: Using `intern!` to avoid needlessly recreating the same Python string
///
/// ```
/// use pyo3::intern;
/// # use pyo3::{prelude::*, types::PyDict};
///
/// #[pyfunction]
/// fn create_dict(py: Python<'_>) -> PyResult<Bound<'_, PyDict>> {
/// let dict = PyDict::new(py);
/// // 👇 A new `PyString` is created
/// // for every call of this function.
/// dict.set_item("foo", 42)?;
/// Ok(dict)
/// }
///
/// #[pyfunction]
/// fn create_dict_faster(py: Python<'_>) -> PyResult<Bound<'_, PyDict>> {
/// let dict = PyDict::new(py);
/// // 👇 A `PyString` is created once and reused
/// // for the lifetime of the program.
/// dict.set_item(intern!(py, "foo"), 42)?;
/// Ok(dict)
/// }
/// #
/// # Python::with_gil(|py| {
/// # let fun_slow = wrap_pyfunction!(create_dict, py).unwrap();
/// # let dict = fun_slow.call0().unwrap();
/// # assert!(dict.contains("foo").unwrap());
/// # let fun = wrap_pyfunction!(create_dict_faster, py).unwrap();
/// # let dict = fun.call0().unwrap();
/// # assert!(dict.contains("foo").unwrap());
/// # });
/// ```
#[macro_export]
macro_rules! intern {
($py: expr, $text: expr) => {{
static INTERNED: $crate::sync::Interned = $crate::sync::Interned::new($text);
INTERNED.get($py)
}};
}
/// Implementation detail for `intern!` macro.
#[doc(hidden)]
pub struct Interned(&'static str, GILOnceCell<Py<PyString>>);
impl Interned {
/// Creates an empty holder for an interned `str`.
pub const fn new(value: &'static str) -> Self {
Interned(value, GILOnceCell::new())
}
/// Gets or creates the interned `str` value.
#[inline]
pub fn get<'py>(&self, py: Python<'py>) -> &Bound<'py, PyString> {
self.1
.get_or_init(py, || PyString::intern(py, self.0).into())
.bind(py)
}
}
/// Executes a closure with a Python critical section held on an object.
///
/// Acquires the per-object lock for the object `op` that is held
/// until the closure `f` is finished.
///
/// This is structurally equivalent to the use of the paired
/// Py_BEGIN_CRITICAL_SECTION and Py_END_CRITICAL_SECTION C-API macros.
///
/// A no-op on GIL-enabled builds, where the critical section API is exposed as
/// a no-op by the Python C API.
///
/// Provides weaker locking guarantees than traditional locks, but can in some
/// cases be used to provide guarantees similar to the GIL without the risk of
/// deadlocks associated with traditional locks.
///
/// Many CPython C API functions do not acquire the per-object lock on objects
/// passed to Python. You should not expect critical sections applied to
/// built-in types to prevent concurrent modification. This API is most useful
/// for user-defined types with full control over how the internal state for the
/// type is managed.
#[cfg_attr(not(Py_GIL_DISABLED), allow(unused_variables))]
pub fn with_critical_section<F, R>(object: &Bound<'_, PyAny>, f: F) -> R
where
F: FnOnce() -> R,
{
#[cfg(Py_GIL_DISABLED)]
{
struct Guard(crate::ffi::PyCriticalSection);
impl Drop for Guard {
fn drop(&mut self) {
unsafe {
crate::ffi::PyCriticalSection_End(&mut self.0);
}
}
}
let mut guard = Guard(unsafe { std::mem::zeroed() });
unsafe { crate::ffi::PyCriticalSection_Begin(&mut guard.0, object.as_ptr()) };
f()
}
#[cfg(not(Py_GIL_DISABLED))]
{
f()
}
}
/// Executes a closure with a Python critical section held on two objects.
///
/// Acquires the per-object lock for the objects `a` and `b` that are held
/// until the closure `f` is finished.
///
/// This is structurally equivalent to the use of the paired
/// Py_BEGIN_CRITICAL_SECTION2 and Py_END_CRITICAL_SECTION2 C-API macros.
///
/// A no-op on GIL-enabled builds, where the critical section API is exposed as
/// a no-op by the Python C API.
///
/// Provides weaker locking guarantees than traditional locks, but can in some
/// cases be used to provide guarantees similar to the GIL without the risk of
/// deadlocks associated with traditional locks.
///
/// Many CPython C API functions do not acquire the per-object lock on objects
/// passed to Python. You should not expect critical sections applied to
/// built-in types to prevent concurrent modification. This API is most useful
/// for user-defined types with full control over how the internal state for the
/// type is managed.
#[cfg_attr(not(Py_GIL_DISABLED), allow(unused_variables))]
pub fn with_critical_section2<F, R>(a: &Bound<'_, PyAny>, b: &Bound<'_, PyAny>, f: F) -> R
where
F: FnOnce() -> R,
{
#[cfg(Py_GIL_DISABLED)]
{
struct Guard(crate::ffi::PyCriticalSection2);
impl Drop for Guard {
fn drop(&mut self) {
unsafe {
crate::ffi::PyCriticalSection2_End(&mut self.0);
}
}
}
let mut guard = Guard(unsafe { std::mem::zeroed() });
unsafe { crate::ffi::PyCriticalSection2_Begin(&mut guard.0, a.as_ptr(), b.as_ptr()) };
f()
}
#[cfg(not(Py_GIL_DISABLED))]
{
f()
}
}
#[cfg(rustc_has_once_lock)]
mod once_lock_ext_sealed {
pub trait Sealed {}
impl<T> Sealed for std::sync::OnceLock<T> {}
}
/// Helper trait for `Once` to help avoid deadlocking when using a `Once` when attached to a
/// Python thread.
pub trait OnceExt: Sealed {
/// Similar to [`call_once`][Once::call_once], but releases the Python GIL temporarily
/// if blocking on another thread currently calling this `Once`.
fn call_once_py_attached(&self, py: Python<'_>, f: impl FnOnce());
/// Similar to [`call_once_force`][Once::call_once_force], but releases the Python GIL
/// temporarily if blocking on another thread currently calling this `Once`.
fn call_once_force_py_attached(&self, py: Python<'_>, f: impl FnOnce(&OnceState));
}
/// Extension trait for [`std::sync::OnceLock`] which helps avoid deadlocks between the Python
/// interpreter and initialization with the `OnceLock`.
#[cfg(rustc_has_once_lock)]
pub trait OnceLockExt<T>: once_lock_ext_sealed::Sealed {
/// Initializes this `OnceLock` with the given closure if it has not been initialized yet.
///
/// If this function would block, this function detaches from the Python interpreter and
/// reattaches before calling `f`. This avoids deadlocks between the Python interpreter and
/// the `OnceLock` in cases where `f` can call arbitrary Python code, as calling arbitrary
/// Python code can lead to `f` itself blocking on the Python interpreter.
///
/// By detaching from the Python interpreter before blocking, this ensures that if `f` blocks
/// then the Python interpreter cannot be blocked by `f` itself.
fn get_or_init_py_attached<F>(&self, py: Python<'_>, f: F) -> &T
where
F: FnOnce() -> T;
}
/// Extension trait for [`std::sync::Mutex`] which helps avoid deadlocks between
/// the Python interpreter and acquiring the `Mutex`.
pub trait MutexExt<T>: Sealed {
/// Lock this `Mutex` in a manner that cannot deadlock with the Python interpreter.
///
/// Before attempting to lock the mutex, this function detaches from the
/// Python runtime. When the lock is acquired, it re-attaches to the Python
/// runtime before returning the `LockResult`. This avoids deadlocks between
/// the GIL and other global synchronization events triggered by the Python
/// interpreter.
fn lock_py_attached(
&self,
py: Python<'_>,
) -> std::sync::LockResult<std::sync::MutexGuard<'_, T>>;
}
impl OnceExt for Once {
fn call_once_py_attached(&self, py: Python<'_>, f: impl FnOnce()) {
if self.is_completed() {
return;
}
init_once_py_attached(self, py, f)
}
fn call_once_force_py_attached(&self, py: Python<'_>, f: impl FnOnce(&OnceState)) {
if self.is_completed() {
return;
}
init_once_force_py_attached(self, py, f);
}
}
#[cfg(rustc_has_once_lock)]
impl<T> OnceLockExt<T> for std::sync::OnceLock<T> {
fn get_or_init_py_attached<F>(&self, py: Python<'_>, f: F) -> &T
where
F: FnOnce() -> T,
{
// this trait is guarded by a rustc version config
// so clippy's MSRV check is wrong
#[allow(clippy::incompatible_msrv)]
// Use self.get() first to create a fast path when initialized
self.get()
.unwrap_or_else(|| init_once_lock_py_attached(self, py, f))
}
}
impl<T> MutexExt<T> for std::sync::Mutex<T> {
fn lock_py_attached(
&self,
_py: Python<'_>,
) -> std::sync::LockResult<std::sync::MutexGuard<'_, T>> {
// If try_lock is successful or returns a poisoned mutex, return them so
// the caller can deal with them. Otherwise we need to use blocking
// lock, which requires detaching from the Python runtime to avoid
// possible deadlocks.
match self.try_lock() {
Ok(inner) => return Ok(inner),
Err(std::sync::TryLockError::Poisoned(inner)) => {
return std::sync::LockResult::Err(inner)
}
Err(std::sync::TryLockError::WouldBlock) => {}
}
// SAFETY: detach from the runtime right before a possibly blocking call
// then reattach when the blocking call completes and before calling
// into the C API.
let ts_guard = unsafe { SuspendGIL::new() };
let res = self.lock();
drop(ts_guard);
res
}
}
#[cold]
fn init_once_py_attached<F, T>(once: &Once, _py: Python<'_>, f: F)
where
F: FnOnce() -> T,
{
// SAFETY: detach from the runtime right before a possibly blocking call
// then reattach when the blocking call completes and before calling
// into the C API.
let ts_guard = unsafe { SuspendGIL::new() };
once.call_once(move || {
drop(ts_guard);
f();
});
}
#[cold]
fn init_once_force_py_attached<F, T>(once: &Once, _py: Python<'_>, f: F)
where
F: FnOnce(&OnceState) -> T,
{
// SAFETY: detach from the runtime right before a possibly blocking call
// then reattach when the blocking call completes and before calling
// into the C API.
let ts_guard = unsafe { SuspendGIL::new() };
once.call_once_force(move |state| {
drop(ts_guard);
f(state);
});
}
#[cfg(rustc_has_once_lock)]
#[cold]
fn init_once_lock_py_attached<'a, F, T>(
lock: &'a std::sync::OnceLock<T>,
_py: Python<'_>,
f: F,
) -> &'a T
where
F: FnOnce() -> T,
{
// SAFETY: detach from the runtime right before a possibly blocking call
// then reattach when the blocking call completes and before calling
// into the C API.
let ts_guard = unsafe { SuspendGIL::new() };
// this trait is guarded by a rustc version config
// so clippy's MSRV check is wrong
#[allow(clippy::incompatible_msrv)]
// By having detached here, we guarantee that `.get_or_init` cannot deadlock with
// the Python interpreter
let value = lock.get_or_init(move || {
drop(ts_guard);
f()
});
value
}
#[cfg(test)]
mod tests {
use super::*;
use crate::types::{PyDict, PyDictMethods};
#[cfg(not(target_arch = "wasm32"))]
use std::sync::Mutex;
#[cfg(not(target_arch = "wasm32"))]
#[cfg(feature = "macros")]
use std::sync::{
atomic::{AtomicBool, Ordering},
Barrier,
};
#[cfg(not(target_arch = "wasm32"))]
#[cfg(feature = "macros")]
#[crate::pyclass(crate = "crate")]
struct BoolWrapper(AtomicBool);
#[cfg(not(target_arch = "wasm32"))]
#[cfg(feature = "macros")]
#[crate::pyclass(crate = "crate")]
struct VecWrapper(Vec<isize>);
#[test]
fn test_intern() {
Python::with_gil(|py| {
let foo1 = "foo";
let foo2 = intern!(py, "foo");
let foo3 = intern!(py, stringify!(foo));
let dict = PyDict::new(py);
dict.set_item(foo1, 42_usize).unwrap();
assert!(dict.contains(foo2).unwrap());
assert_eq!(
dict.get_item(foo3)
.unwrap()
.unwrap()
.extract::<usize>()
.unwrap(),
42
);
});
}
#[test]
fn test_once_cell() {
Python::with_gil(|py| {
let mut cell = GILOnceCell::new();
assert!(cell.get(py).is_none());
assert_eq!(cell.get_or_try_init(py, || Err(5)), Err(5));
assert!(cell.get(py).is_none());
assert_eq!(cell.get_or_try_init(py, || Ok::<_, ()>(2)), Ok(&2));
assert_eq!(cell.get(py), Some(&2));
assert_eq!(cell.get_or_try_init(py, || Err(5)), Ok(&2));
assert_eq!(cell.take(), Some(2));
assert_eq!(cell.into_inner(), None);
let cell_py = GILOnceCell::new();
assert!(cell_py.clone_ref(py).get(py).is_none());
cell_py.get_or_init(py, || py.None());
assert!(cell_py.clone_ref(py).get(py).unwrap().is_none(py));
})
}
#[test]
fn test_once_cell_drop() {
#[derive(Debug)]
struct RecordDrop<'a>(&'a mut bool);
impl Drop for RecordDrop<'_> {
fn drop(&mut self) {
*self.0 = true;
}
}
Python::with_gil(|py| {
let mut dropped = false;
let cell = GILOnceCell::new();
cell.set(py, RecordDrop(&mut dropped)).unwrap();
let drop_container = cell.get(py).unwrap();
assert!(!*drop_container.0);
drop(cell);
assert!(dropped);
});
}
#[cfg(feature = "macros")]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_critical_section() {
let barrier = Barrier::new(2);
let bool_wrapper = Python::with_gil(|py| -> Py<BoolWrapper> {
Py::new(py, BoolWrapper(AtomicBool::new(false))).unwrap()
});
std::thread::scope(|s| {
s.spawn(|| {
Python::with_gil(|py| {
let b = bool_wrapper.bind(py);
with_critical_section(b, || {
barrier.wait();
std::thread::sleep(std::time::Duration::from_millis(10));
b.borrow().0.store(true, Ordering::Release);
})
});
});
s.spawn(|| {
barrier.wait();
Python::with_gil(|py| {
let b = bool_wrapper.bind(py);
// this blocks until the other thread's critical section finishes
with_critical_section(b, || {
assert!(b.borrow().0.load(Ordering::Acquire));
});
});
});
});
}
#[cfg(feature = "macros")]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_critical_section2() {
let barrier = Barrier::new(3);
let (bool_wrapper1, bool_wrapper2) = Python::with_gil(|py| {
(
Py::new(py, BoolWrapper(AtomicBool::new(false))).unwrap(),
Py::new(py, BoolWrapper(AtomicBool::new(false))).unwrap(),
)
});
std::thread::scope(|s| {
s.spawn(|| {
Python::with_gil(|py| {
let b1 = bool_wrapper1.bind(py);
let b2 = bool_wrapper2.bind(py);
with_critical_section2(b1, b2, || {
barrier.wait();
std::thread::sleep(std::time::Duration::from_millis(10));
b1.borrow().0.store(true, Ordering::Release);
b2.borrow().0.store(true, Ordering::Release);
})
});
});
s.spawn(|| {
barrier.wait();
Python::with_gil(|py| {
let b1 = bool_wrapper1.bind(py);
// this blocks until the other thread's critical section finishes
with_critical_section(b1, || {
assert!(b1.borrow().0.load(Ordering::Acquire));
});
});
});
s.spawn(|| {
barrier.wait();
Python::with_gil(|py| {
let b2 = bool_wrapper2.bind(py);
// this blocks until the other thread's critical section finishes
with_critical_section(b2, || {
assert!(b2.borrow().0.load(Ordering::Acquire));
});
});
});
});
}
#[cfg(feature = "macros")]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_critical_section2_same_object_no_deadlock() {
let barrier = Barrier::new(2);
let bool_wrapper = Python::with_gil(|py| -> Py<BoolWrapper> {
Py::new(py, BoolWrapper(AtomicBool::new(false))).unwrap()
});
std::thread::scope(|s| {
s.spawn(|| {
Python::with_gil(|py| {
let b = bool_wrapper.bind(py);
with_critical_section2(b, b, || {
barrier.wait();
std::thread::sleep(std::time::Duration::from_millis(10));
b.borrow().0.store(true, Ordering::Release);
})
});
});
s.spawn(|| {
barrier.wait();
Python::with_gil(|py| {
let b = bool_wrapper.bind(py);
// this blocks until the other thread's critical section finishes
with_critical_section(b, || {
assert!(b.borrow().0.load(Ordering::Acquire));
});
});
});
});
}
#[cfg(feature = "macros")]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_critical_section2_two_containers() {
let (vec1, vec2) = Python::with_gil(|py| {
(
Py::new(py, VecWrapper(vec![1, 2, 3])).unwrap(),
Py::new(py, VecWrapper(vec![4, 5])).unwrap(),
)
});
std::thread::scope(|s| {
s.spawn(|| {
Python::with_gil(|py| {
let v1 = vec1.bind(py);
let v2 = vec2.bind(py);
with_critical_section2(v1, v2, || {
// v2.extend(v1)
v2.borrow_mut().0.extend(v1.borrow().0.iter());
})
});
});
s.spawn(|| {
Python::with_gil(|py| {
let v1 = vec1.bind(py);
let v2 = vec2.bind(py);
with_critical_section2(v1, v2, || {
// v1.extend(v2)
v1.borrow_mut().0.extend(v2.borrow().0.iter());
})
});
});
});
Python::with_gil(|py| {
let v1 = vec1.bind(py);
let v2 = vec2.bind(py);
// execution order is not guaranteed, so we need to check both
// NB: extend should be atomic, items must not be interleaved
// v1.extend(v2)
// v2.extend(v1)
let expected1_vec1 = vec![1, 2, 3, 4, 5];
let expected1_vec2 = vec![4, 5, 1, 2, 3, 4, 5];
// v2.extend(v1)
// v1.extend(v2)
let expected2_vec1 = vec![1, 2, 3, 4, 5, 1, 2, 3];
let expected2_vec2 = vec![4, 5, 1, 2, 3];
assert!(
(v1.borrow().0.eq(&expected1_vec1) && v2.borrow().0.eq(&expected1_vec2))
|| (v1.borrow().0.eq(&expected2_vec1) && v2.borrow().0.eq(&expected2_vec2))
);
});
}
#[test]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
fn test_once_ext() {
// adapted from the example in the docs for Once::try_once_force
let init = Once::new();
std::thread::scope(|s| {
// poison the once
let handle = s.spawn(|| {
Python::with_gil(|py| {
init.call_once_py_attached(py, || panic!());
})
});
assert!(handle.join().is_err());
// poisoning propagates
let handle = s.spawn(|| {
Python::with_gil(|py| {
init.call_once_py_attached(py, || {});
});
});
assert!(handle.join().is_err());
// call_once_force will still run and reset the poisoned state
Python::with_gil(|py| {
init.call_once_force_py_attached(py, |state| {
assert!(state.is_poisoned());
});
// once any success happens, we stop propagating the poison
init.call_once_py_attached(py, || {});
});
});
}
#[cfg(rustc_has_once_lock)]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_once_lock_ext() {
let cell = std::sync::OnceLock::new();
std::thread::scope(|s| {
assert!(cell.get().is_none());
s.spawn(|| {
Python::with_gil(|py| {
assert_eq!(*cell.get_or_init_py_attached(py, || 12345), 12345);
});
});
});
assert_eq!(cell.get(), Some(&12345));
}
#[cfg(feature = "macros")]
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_mutex_ext() {
let barrier = Barrier::new(2);
let mutex = Python::with_gil(|py| -> Mutex<Py<BoolWrapper>> {
Mutex::new(Py::new(py, BoolWrapper(AtomicBool::new(false))).unwrap())
});
std::thread::scope(|s| {
s.spawn(|| {
Python::with_gil(|py| {
let b = mutex.lock_py_attached(py).unwrap();
barrier.wait();
// sleep to ensure the other thread actually blocks
std::thread::sleep(std::time::Duration::from_millis(10));
(*b).bind(py).borrow().0.store(true, Ordering::Release);
drop(b);
});
});
s.spawn(|| {
barrier.wait();
Python::with_gil(|py| {
// blocks until the other thread releases the lock
let b = mutex.lock_py_attached(py).unwrap();
assert!((*b).bind(py).borrow().0.load(Ordering::Acquire));
});
});
});
}
#[cfg(not(target_arch = "wasm32"))] // We are building wasm Python with pthreads disabled
#[test]
fn test_mutex_ext_poison() {
let mutex = Mutex::new(42);
std::thread::scope(|s| {
let lock_result = s.spawn(|| {
Python::with_gil(|py| {
let _unused = mutex.lock_py_attached(py);
panic!();
});
});
assert!(lock_result.join().is_err());
assert!(mutex.is_poisoned());
});
let guard = Python::with_gil(|py| {
// recover from the poisoning
match mutex.lock_py_attached(py) {
Ok(guard) => guard,
Err(poisoned) => poisoned.into_inner(),
}
});
assert!(*guard == 42);
}
}