https://github.com/python/cpython/commit/ad4f909e0e7890e027c4ae7fea74586667242ad3
commit: ad4f909e0e7890e027c4ae7fea74586667242ad3
branch: main
author: Sam Gross <[email protected]>
committer: colesbury <[email protected]>
date: 2024-02-15T08:37:54-05:00
summary:
gh-115432: Add critical section variant that handles a NULL object (#115433)
This adds `Py_XBEGIN_CRITICAL_SECTION` and
`Py_XEND_CRITICAL_SECTION`, which accept a possibly NULL object as an
argument. If the argument is NULL, then nothing is locked or unlocked.
Otherwise, they behave like `Py_BEGIN/END_CRITICAL_SECTION`.
files:
M Include/internal/pycore_critical_section.h
M Modules/_testinternalcapi/test_critical_sections.c
diff --git a/Include/internal/pycore_critical_section.h
b/Include/internal/pycore_critical_section.h
index 38ed8cd69804ba..30820a24f5bb64 100644
--- a/Include/internal/pycore_critical_section.h
+++ b/Include/internal/pycore_critical_section.h
@@ -96,6 +96,15 @@ extern "C" {
_PyCriticalSection_End(&_cs); \
}
+# define Py_XBEGIN_CRITICAL_SECTION(op) \
+ { \
+ _PyCriticalSection _cs_opt = {0}; \
+ _PyCriticalSection_XBegin(&_cs_opt, _PyObject_CAST(op))
+
+# define Py_XEND_CRITICAL_SECTION() \
+ _PyCriticalSection_XEnd(&_cs_opt); \
+ }
+
# define Py_BEGIN_CRITICAL_SECTION2(a, b) \
{ \
_PyCriticalSection2 _cs2; \
@@ -131,6 +140,8 @@ extern "C" {
// The critical section APIs are no-ops with the GIL.
# define Py_BEGIN_CRITICAL_SECTION(op)
# define Py_END_CRITICAL_SECTION()
+# define Py_XBEGIN_CRITICAL_SECTION(op)
+# define Py_XEND_CRITICAL_SECTION()
# define Py_BEGIN_CRITICAL_SECTION2(a, b)
# define Py_END_CRITICAL_SECTION2()
# define _Py_CRITICAL_SECTION_ASSERT_MUTEX_LOCKED(mutex)
@@ -187,6 +198,16 @@ _PyCriticalSection_Begin(_PyCriticalSection *c, PyMutex *m)
}
}
+static inline void
+_PyCriticalSection_XBegin(_PyCriticalSection *c, PyObject *op)
+{
+#ifdef Py_GIL_DISABLED
+ if (op != NULL) {
+ _PyCriticalSection_Begin(c, &_PyObject_CAST(op)->ob_mutex);
+ }
+#endif
+}
+
// Removes the top-most critical section from the thread's stack of critical
// sections. If the new top-most critical section is inactive, then it is
// resumed.
@@ -209,6 +230,14 @@ _PyCriticalSection_End(_PyCriticalSection *c)
_PyCriticalSection_Pop(c);
}
+static inline void
+_PyCriticalSection_XEnd(_PyCriticalSection *c)
+{
+ if (c->mutex) {
+ _PyCriticalSection_End(c);
+ }
+}
+
static inline void
_PyCriticalSection2_Begin(_PyCriticalSection2 *c, PyMutex *m1, PyMutex *m2)
{
diff --git a/Modules/_testinternalcapi/test_critical_sections.c
b/Modules/_testinternalcapi/test_critical_sections.c
index 1f7e311558b27c..94da0468fcf149 100644
--- a/Modules/_testinternalcapi/test_critical_sections.c
+++ b/Modules/_testinternalcapi/test_critical_sections.c
@@ -49,6 +49,15 @@ test_critical_sections(PyObject *self, PyObject
*Py_UNUSED(args))
Py_END_CRITICAL_SECTION2();
assert_nogil(!PyMutex_IsLocked(&d2->ob_mutex));
+ // Optional variant behaves the same if the object is non-NULL
+ Py_XBEGIN_CRITICAL_SECTION(d1);
+ assert_nogil(PyMutex_IsLocked(&d1->ob_mutex));
+ Py_XEND_CRITICAL_SECTION();
+
+ // No-op
+ Py_XBEGIN_CRITICAL_SECTION(NULL);
+ Py_XEND_CRITICAL_SECTION();
+
Py_DECREF(d2);
Py_DECREF(d1);
Py_RETURN_NONE;
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