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https://github.com/python/cpython/commit/de5ca0bf71760aad8f2b8449c89242498bff64c8
commit: de5ca0bf71760aad8f2b8449c89242498bff64c8
branch: main
author: Sam Gross <colesbury@gmail.com>
committer: colesbury <colesbury@gmail.com>
date: 2024-04-04T14:09:38-04:00
summary:

gh-117435: Make `SemLock` thread-safe in free-threaded build (#117436)

Use critical sections to make acquire, release, and _count thread-safe
without the GIL.

files:
M Modules/_multiprocessing/clinic/semaphore.c.h
M Modules/_multiprocessing/semaphore.c

diff --git a/Modules/_multiprocessing/clinic/semaphore.c.h b/Modules/_multiprocessing/clinic/semaphore.c.h
index 7c855113113c20..64e666b5af6f5b 100644
--- a/Modules/_multiprocessing/clinic/semaphore.c.h
+++ b/Modules/_multiprocessing/clinic/semaphore.c.h
@@ -6,6 +6,7 @@ preserve
# include "pycore_gc.h" // PyGC_Head
# include "pycore_runtime.h" // _Py_ID()
#endif
+#include "pycore_critical_section.h"// Py_BEGIN_CRITICAL_SECTION()
#include "pycore_modsupport.h" // _PyArg_UnpackKeywords()

#if defined(HAVE_MP_SEMAPHORE) && defined(MS_WINDOWS)
@@ -75,7 +76,9 @@ _multiprocessing_SemLock_acquire(SemLockObject *self, PyObject *const *args, Py_
}
timeout_obj = args[1];
skip_optional_pos:
+ Py_BEGIN_CRITICAL_SECTION(self);
return_value = _multiprocessing_SemLock_acquire_impl(self, blocking, timeout_obj);
+ Py_END_CRITICAL_SECTION();

exit:
return return_value;
@@ -100,7 +103,13 @@ _multiprocessing_SemLock_release_impl(SemLockObject *self);
static PyObject *
_multiprocessing_SemLock_release(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
- return _multiprocessing_SemLock_release_impl(self);
+ PyObject *return_value = NULL;
+
+ Py_BEGIN_CRITICAL_SECTION(self);
+ return_value = _multiprocessing_SemLock_release_impl(self);
+ Py_END_CRITICAL_SECTION();
+
+ return return_value;
}

#endif /* defined(HAVE_MP_SEMAPHORE) && defined(MS_WINDOWS) */
@@ -172,7 +181,9 @@ _multiprocessing_SemLock_acquire(SemLockObject *self, PyObject *const *args, Py_
}
timeout_obj = args[1];
skip_optional_pos:
+ Py_BEGIN_CRITICAL_SECTION(self);
return_value = _multiprocessing_SemLock_acquire_impl(self, blocking, timeout_obj);
+ Py_END_CRITICAL_SECTION();

exit:
return return_value;
@@ -197,7 +208,13 @@ _multiprocessing_SemLock_release_impl(SemLockObject *self);
static PyObject *
_multiprocessing_SemLock_release(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
- return _multiprocessing_SemLock_release_impl(self);
+ PyObject *return_value = NULL;
+
+ Py_BEGIN_CRITICAL_SECTION(self);
+ return_value = _multiprocessing_SemLock_release_impl(self);
+ Py_END_CRITICAL_SECTION();
+
+ return return_value;
}

#endif /* defined(HAVE_MP_SEMAPHORE) && !defined(MS_WINDOWS) */
@@ -340,7 +357,13 @@ _multiprocessing_SemLock__count_impl(SemLockObject *self);
static PyObject *
_multiprocessing_SemLock__count(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
- return _multiprocessing_SemLock__count_impl(self);
+ PyObject *return_value = NULL;
+
+ Py_BEGIN_CRITICAL_SECTION(self);
+ return_value = _multiprocessing_SemLock__count_impl(self);
+ Py_END_CRITICAL_SECTION();
+
+ return return_value;
}

#endif /* defined(HAVE_MP_SEMAPHORE) */
@@ -542,4 +565,4 @@ _multiprocessing_SemLock___exit__(SemLockObject *self, PyObject *const *args, Py
#ifndef _MULTIPROCESSING_SEMLOCK___EXIT___METHODDEF
#define _MULTIPROCESSING_SEMLOCK___EXIT___METHODDEF
#endif /* !defined(_MULTIPROCESSING_SEMLOCK___EXIT___METHODDEF) */
-/*[clinic end generated code: output=d57992037e6770b6 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=713b597256233716 input=a9049054013a1b77]*/
diff --git a/Modules/_multiprocessing/semaphore.c b/Modules/_multiprocessing/semaphore.c
index f8f2afda28d06d..5bb055f501e35b 100644
--- a/Modules/_multiprocessing/semaphore.c
+++ b/Modules/_multiprocessing/semaphore.c
@@ -81,6 +81,7 @@ _GetSemaphoreValue(HANDLE handle, long *value)
}

/*[clinic input]
+@critical_section
_multiprocessing.SemLock.acquire

block as blocking: bool = True
@@ -92,7 +93,7 @@ Acquire the semaphore/lock.
static PyObject *
_multiprocessing_SemLock_acquire_impl(SemLockObject *self, int blocking,
PyObject *timeout_obj)
-/*[clinic end generated code: output=f9998f0b6b0b0872 input=e5b45f5cbb775166]*/
+/*[clinic end generated code: output=f9998f0b6b0b0872 input=079ca779975f3ad6]*/
{
double timeout;
DWORD res, full_msecs, nhandles;
@@ -172,6 +173,7 @@ _multiprocessing_SemLock_acquire_impl(SemLockObject *self, int blocking,
}

/*[clinic input]
+@critical_section
_multiprocessing.SemLock.release

Release the semaphore/lock.
@@ -179,7 +181,7 @@ Release the semaphore/lock.

static PyObject *
_multiprocessing_SemLock_release_impl(SemLockObject *self)
-/*[clinic end generated code: output=b22f53ba96b0d1db input=ba7e63a961885d3d]*/
+/*[clinic end generated code: output=b22f53ba96b0d1db input=9bd62d3645e7a531]*/
{
if (self->kind == RECURSIVE_MUTEX) {
if (!ISMINE(self)) {
@@ -297,6 +299,7 @@ sem_timedwait_save(sem_t *sem, struct timespec *deadline, PyThreadState *_save)
#endif /* !HAVE_SEM_TIMEDWAIT */

/*[clinic input]
+@critical_section
_multiprocessing.SemLock.acquire

block as blocking: bool = True
@@ -308,7 +311,7 @@ Acquire the semaphore/lock.
static PyObject *
_multiprocessing_SemLock_acquire_impl(SemLockObject *self, int blocking,
PyObject *timeout_obj)
-/*[clinic end generated code: output=f9998f0b6b0b0872 input=e5b45f5cbb775166]*/
+/*[clinic end generated code: output=f9998f0b6b0b0872 input=079ca779975f3ad6]*/
{
int res, err = 0;
struct timespec deadline = {0};
@@ -382,6 +385,7 @@ _multiprocessing_SemLock_acquire_impl(SemLockObject *self, int blocking,
}

/*[clinic input]
+@critical_section
_multiprocessing.SemLock.release

Release the semaphore/lock.
@@ -389,7 +393,7 @@ Release the semaphore/lock.

static PyObject *
_multiprocessing_SemLock_release_impl(SemLockObject *self)
-/*[clinic end generated code: output=b22f53ba96b0d1db input=ba7e63a961885d3d]*/
+/*[clinic end generated code: output=b22f53ba96b0d1db input=9bd62d3645e7a531]*/
{
if (self->kind == RECURSIVE_MUTEX) {
if (!ISMINE(self)) {
@@ -583,6 +587,7 @@ semlock_dealloc(SemLockObject* self)
}

/*[clinic input]
+@critical_section
_multiprocessing.SemLock._count

Num of `acquire()`s minus num of `release()`s for this process.
@@ -590,7 +595,7 @@ Num of `acquire()`s minus num of `release()`s for this process.

static PyObject *
_multiprocessing_SemLock__count_impl(SemLockObject *self)
-/*[clinic end generated code: output=5ba8213900e517bb input=36fc59b1cd1025ab]*/
+/*[clinic end generated code: output=5ba8213900e517bb input=9fa6e0b321b16935]*/
{
return PyLong_FromLong((long)self->count);
}

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