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Add Clone for PyObject / Py<T>

This commit is contained in:
David Hewitt 2020-05-06 09:04:57 +01:00
parent 8e84721438
commit 86af474a95
5 changed files with 181 additions and 62 deletions
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1
CHANGELOG.md
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@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
- `_PyDict_NewPresized`. [#849](https://github.com/PyO3/pyo3/pull/849)
- `IntoPy<PyObject>` for `HashSet` and `BTreeSet`. [#864](https://github.com/PyO3/pyo3/pull/864)
- `PyAny::dir`. [#886](https://github.com/PyO3/pyo3/pull/886)
- `impl Clone` for `PyObject` and `Py<T>`. [#908](https://github.com/PyO3/pyo3/pull/908)
- All builtin types (`PyList`, `PyTuple`, `PyDict`) etc. now implement `Deref<Target = PyAny>`. [#911](https://github.com/PyO3/pyo3/pull/911)
- `PyCell<T>` now implements `Deref<Target = PyAny>`. [#911](https://github.com/PyO3/pyo3/pull/911)
- Methods and associated constants can now be annotated with `#[classattr]` to define class attributes. [#905](https://github.com/PyO3/pyo3/pull/905) [#914](https://github.com/PyO3/pyo3/pull/914)

185
src/gil.rs
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@ -166,10 +166,11 @@ impl Drop for GILGuard {
}
}
/// Thread-safe storage for objects which were dropped while the GIL was not held.
struct ReleasePool {
/// Thread-safe storage for objects which were inc_ref / dec_ref while the GIL was not held.
struct ReferencePool {
locked: AtomicBool,
pointers_to_drop: UnsafeCell<Vec<NonNull<ffi::PyObject>>>,
pointers_to_incref: UnsafeCell<Vec<NonNull<ffi::PyObject>>>,
pointers_to_decref: UnsafeCell<Vec<NonNull<ffi::PyObject>>>,
}
struct Lock<'a> {
@ -191,35 +192,58 @@ impl<'a> Drop for Lock<'a> {
}
}
impl ReleasePool {
impl ReferencePool {
const fn new() -> Self {
Self {
locked: AtomicBool::new(false),
pointers_to_drop: UnsafeCell::new(Vec::new()),
pointers_to_incref: UnsafeCell::new(Vec::new()),
pointers_to_decref: UnsafeCell::new(Vec::new()),
}
}
fn register_pointer(&self, obj: NonNull<ffi::PyObject>) {
fn register_incref(&self, obj: NonNull<ffi::PyObject>) {
let _lock = Lock::new(&self.locked);
let v = self.pointers_to_drop.get();
let v = self.pointers_to_incref.get();
unsafe { (*v).push(obj) };
}
fn release_pointers(&self, _py: Python) {
fn register_decref(&self, obj: NonNull<ffi::PyObject>) {
let _lock = Lock::new(&self.locked);
let v = self.pointers_to_drop.get();
unsafe {
for ptr in &(*v) {
ffi::Py_DECREF(ptr.as_ptr());
let v = self.pointers_to_decref.get();
unsafe { (*v).push(obj) };
}
fn update_counts(&self, _py: Python) {
let _lock = Lock::new(&self.locked);
// Always increase reference counts first - as otherwise objects which have a
// nonzero total reference count might be incorrectly dropped by Python during
// this update.
{
let v = self.pointers_to_incref.get();
unsafe {
for ptr in &(*v) {
ffi::Py_INCREF(ptr.as_ptr());
}
(*v).clear();
}
}
{
let v = self.pointers_to_decref.get();
unsafe {
for ptr in &(*v) {
ffi::Py_DECREF(ptr.as_ptr());
}
(*v).clear();
}
(*v).clear();
}
}
}
unsafe impl Sync for ReleasePool {}
unsafe impl Sync for ReferencePool {}
static POOL: ReleasePool = ReleasePool::new();
static POOL: ReferencePool = ReferencePool::new();
/// A RAII pool which PyO3 uses to store owned Python references.
pub struct GILPool {
@ -240,8 +264,8 @@ impl GILPool {
#[inline]
pub unsafe fn new() -> GILPool {
increment_gil_count();
// Release objects that were dropped since last GIL acquisition
POOL.release_pointers(Python::assume_gil_acquired());
// 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()),
@ -279,16 +303,35 @@ impl Drop for GILPool {
}
}
/// Register a Python object pointer inside the release pool, to have reference count decreased
/// Register a Python object pointer inside the release pool, to have reference count increased
/// next time the GIL is acquired in pyo3.
///
/// If the GIL is held, the reference count will be increased immediately instead of being queued
/// for later.
///
/// # Safety
/// The object must be an owned Python reference.
pub unsafe fn register_pointer(obj: NonNull<ffi::PyObject>) {
pub unsafe fn register_incref(obj: NonNull<ffi::PyObject>) {
if gil_is_acquired() {
ffi::Py_INCREF(obj.as_ptr())
} else {
POOL.register_incref(obj);
}
}
/// Register a Python object pointer inside the release pool, to have reference count decreased
/// next time the GIL is acquired in pyo3.
///
/// If the GIL is held, the reference count will be decreased immediately instead of being queued
/// for later.
///
/// # Safety
/// The object must be an owned Python reference.
pub unsafe fn register_decref(obj: NonNull<ffi::PyObject>) {
if gil_is_acquired() {
ffi::Py_DECREF(obj.as_ptr())
} else {
POOL.register_pointer(obj);
POOL.register_decref(obj);
}
}
@ -341,7 +384,7 @@ fn decrement_gil_count() {
#[cfg(test)]
mod test {
use super::{GILPool, GIL_COUNT, OWNED_OBJECTS, POOL};
use super::{gil_is_acquired, GILPool, GIL_COUNT, OWNED_OBJECTS, POOL};
use crate::{ffi, gil, AsPyPointer, IntoPyPointer, PyObject, Python, ToPyObject};
use std::ptr::NonNull;
@ -501,32 +544,23 @@ mod test {
#[test]
fn test_allow_threads() {
// allow_threads should temporarily release GIL in Py03's internal tracking too.
let gil = Python::acquire_gil();
let py = gil.python();
let object = get_object(py);
assert!(gil_is_acquired());
py.allow_threads(move || {
// Should be no pointers to drop
assert!(unsafe { (*POOL.pointers_to_drop.get()).is_empty() });
assert!(!gil_is_acquired());
// Dropping object without the GIL should put the pointer in the pool
drop(object);
let obj_count = unsafe { (*POOL.pointers_to_drop.get()).len() };
assert_eq!(obj_count, 1);
// Now repeat dropping an object, with the GIL.
let gil = Python::acquire_gil();
assert!(gil_is_acquired());
// (Acquiring the GIL should have cleared the pool).
assert!(unsafe { (*POOL.pointers_to_drop.get()).is_empty() });
let object = get_object(gil.python());
drop(object);
drop(gil);
assert!(!gil_is_acquired());
});
// Previous drop should have decreased count immediately instead of put in pool
assert!(unsafe { (*POOL.pointers_to_drop.get()).is_empty() });
})
assert!(gil_is_acquired());
}
#[test]
@ -541,6 +575,79 @@ mod test {
drop(gil2);
// After gil2 drops, obj should still have a reference count of one
assert_eq!(unsafe { ffi::Py_REFCNT(obj.as_ptr()) }, 1);
assert_eq!(obj.get_refcnt(), 1);
}
#[test]
fn test_clone_with_gil() {
let gil = Python::acquire_gil();
let obj = get_object(gil.python());
let count = obj.get_refcnt();
// Cloning with the GIL should increase reference count immediately
#[allow(clippy::redundant_clone)]
let c = obj.clone();
assert_eq!(count + 1, c.get_refcnt());
}
#[test]
fn test_clone_without_gil() {
let gil = Python::acquire_gil();
let py = gil.python();
let obj = get_object(py);
let count = obj.get_refcnt();
// Cloning without GIL should not update reference count
drop(gil);
let c = obj.clone();
assert_eq!(count, obj.get_refcnt());
// Acquring GIL will clear this pending change
let gil = Python::acquire_gil();
// Total reference count should be one higher
assert_eq!(count + 1, obj.get_refcnt());
// Clone dropped then GIL released
drop(c);
drop(gil);
// Overall count is now back to the original, and should be no pending change
assert_eq!(count, obj.get_refcnt());
}
#[test]
fn test_clone_in_other_thread() {
let gil = Python::acquire_gil();
let obj = get_object(gil.python());
let count = obj.get_refcnt();
// Move obj to a thread which does not have the GIL, and clone it
let t = std::thread::spawn(move || {
// Cloning without GIL should not update reference count
let _ = obj.clone();
assert_eq!(count, obj.get_refcnt());
// Return obj so original thread can continue to use
obj
});
let obj = t.join().unwrap();
let ptr = NonNull::new(obj.as_ptr()).unwrap();
// The pointer should appear once in the incref pool, and once in the
// decref pool (for the clone being created and also dropped)
assert_eq!(unsafe { &*POOL.pointers_to_incref.get() }, &vec![ptr]);
assert_eq!(unsafe { &*POOL.pointers_to_decref.get() }, &vec![ptr]);
// Re-acquring GIL will clear these pending changes
drop(gil);
let _gil = Python::acquire_gil();
assert!(unsafe { (*POOL.pointers_to_incref.get()).is_empty() });
assert!(unsafe { (*POOL.pointers_to_decref.get()).is_empty() });
// Overall count is still unchanged
assert_eq!(count, obj.get_refcnt());
}
}

11
src/instance.rs
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@ -265,11 +265,20 @@ impl<T> PartialEq for Py<T> {
}
}
impl<T> Clone for Py<T> {
fn clone(&self) -> Self {
unsafe {
gil::register_incref(self.0);
}
Self(self.0, PhantomData)
}
}
/// Dropping a `Py` instance decrements the reference count on the object by 1.
impl<T> Drop for Py<T> {
fn drop(&mut self) {
unsafe {
gil::register_pointer(self.0);
gil::register_decref(self.0);
}
}
}

11
src/object.rs
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@ -308,11 +308,20 @@ impl<'a> FromPyObject<'a> for PyObject {
}
}
impl Clone for PyObject {
fn clone(&self) -> Self {
unsafe {
gil::register_incref(self.0);
}
Self(self.0)
}
}
/// Dropping a `PyObject` instance decrements the reference count on the object by 1.
impl Drop for PyObject {
fn drop(&mut self) {
unsafe {
gil::register_pointer(self.0);
gil::register_decref(self.0);
}
}
}

35
src/types/string.rs
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@ -1,13 +1,13 @@
// Copyright (c) 2017-present PyO3 Project and Contributors
use crate::types::PyBytes;
use crate::{
ffi, gil, AsPyPointer, FromPy, FromPyObject, IntoPy, PyAny, PyErr, PyNativeType, PyObject,
PyResult, PyTryFrom, Python, ToPyObject,
ffi, AsPyPointer, FromPy, FromPyObject, IntoPy, PyAny, PyErr, PyNativeType, PyObject, PyResult,
PyTryFrom, Python, ToPyObject,
};
use std::borrow::Cow;
use std::ffi::CStr;
use std::os::raw::c_char;
use std::ptr::NonNull;
use std::str;
/// Represents a Python `string` (a Unicode string object).
@ -71,24 +71,17 @@ impl PyString {
match self.to_string() {
Ok(s) => s,
Err(_) => {
unsafe {
let py_bytes = ffi::PyUnicode_AsEncodedString(
self.as_ptr(),
CStr::from_bytes_with_nul(b"utf-8\0").unwrap().as_ptr(),
CStr::from_bytes_with_nul(b"surrogatepass\0")
.unwrap()
.as_ptr(),
);
// Since we have a valid PyString and replace any surrogates, assume success.
debug_assert!(!py_bytes.is_null());
// ensure DECREF will be called
gil::register_pointer(NonNull::new(py_bytes).unwrap());
let buffer = ffi::PyBytes_AsString(py_bytes) as *const u8;
debug_assert!(!buffer.is_null());
let length = ffi::PyBytes_Size(py_bytes) as usize;
let bytes = std::slice::from_raw_parts(buffer, length);
String::from_utf8_lossy(bytes)
}
let bytes = unsafe {
self.py()
.from_owned_ptr::<PyBytes>(ffi::PyUnicode_AsEncodedString(
self.as_ptr(),
CStr::from_bytes_with_nul(b"utf-8\0").unwrap().as_ptr(),
CStr::from_bytes_with_nul(b"surrogatepass\0")
.unwrap()
.as_ptr(),
))
};
String::from_utf8_lossy(bytes.as_bytes())
}
}
}