https://github.com/python/cpython/commit/a95b1a56bbba76a382a5c676b71db025915e8695
commit: a95b1a56bbba76a382a5c676b71db025915e8695
branch: main
author: mpage <mp...@meta.com>
committer: colesbury <colesb...@gmail.com>
date: 2024-02-14T15:15:05-05:00
summary:
gh-115041: Add wrappers that are atomic only in free-threaded builds (#115046)
These are intended to be used in places where atomics are required in
free-threaded builds but not in the default build. We don't want to
introduce the potential performance overhead of an atomic operation in the
default build.
files:
A Include/internal/pycore_pyatomic_ft_wrappers.h
M Makefile.pre.in
M PCbuild/pythoncore.vcxproj
M PCbuild/pythoncore.vcxproj.filters
diff --git a/Include/internal/pycore_pyatomic_ft_wrappers.h
b/Include/internal/pycore_pyatomic_ft_wrappers.h
new file mode 100644
index 00000000000000..d1313976da1cfc
--- /dev/null
+++ b/Include/internal/pycore_pyatomic_ft_wrappers.h
@@ -0,0 +1,35 @@
+// This header file provides wrappers around the atomic operations found in
+// `pyatomic.h` that are only atomic in free-threaded builds.
+//
+// These are intended to be used in places where atomics are required in
+// free-threaded builds, but not in the default build, and we don't want to
+// introduce the potential performance overhead of an atomic operation in the
+// default build.
+//
+// All usages of these macros should be replaced with unconditionally atomic or
+// non-atomic versions, and this file should be removed, once the dust settles
+// on free threading.
+#ifndef Py_ATOMIC_FT_WRAPPERS_H
+#define Py_ATOMIC_FT_WRAPPERS_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#error "this header requires Py_BUILD_CORE define"
+#endif
+
+#ifdef Py_GIL_DISABLED
+#define FT_ATOMIC_LOAD_SSIZE_RELAXED(value) \
+ _Py_atomic_load_ssize_relaxed(&value)
+#define FT_ATOMIC_STORE_SSIZE_RELAXED(value, new_value) \
+ _Py_atomic_store_ssize_relaxed(&value, new_value)
+#else
+#define FT_ATOMIC_LOAD_SSIZE_RELAXED(value) value
+#define FT_ATOMIC_STORE_SSIZE_RELAXED(value, new_value) value = new_value
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_ATOMIC_FT_WRAPPERS_H */
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 96886adf309d81..8252e6631c5af5 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -1150,6 +1150,7 @@ PYTHON_HEADERS= \
$(srcdir)/Include/internal/pycore_parser.h \
$(srcdir)/Include/internal/pycore_pathconfig.h \
$(srcdir)/Include/internal/pycore_pyarena.h \
+ $(srcdir)/Include/internal/pycore_pyatomic_ft_wrappers.h \
$(srcdir)/Include/internal/pycore_pybuffer.h \
$(srcdir)/Include/internal/pycore_pyerrors.h \
$(srcdir)/Include/internal/pycore_pyhash.h \
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 4cc0ca4b9af8de..abfafbb2a32f45 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -266,6 +266,7 @@
<ClInclude Include="..\Include\internal\pycore_parking_lot.h" />
<ClInclude Include="..\Include\internal\pycore_pathconfig.h" />
<ClInclude Include="..\Include\internal\pycore_pyarena.h" />
+ <ClInclude Include="..\Include\internal\pycore_pyatomic_ft_wrappers.h" />
<ClInclude Include="..\Include\internal\pycore_pyerrors.h" />
<ClInclude Include="..\Include\internal\pycore_pyhash.h" />
<ClInclude Include="..\Include\internal\pycore_pylifecycle.h" />
diff --git a/PCbuild/pythoncore.vcxproj.filters
b/PCbuild/pythoncore.vcxproj.filters
index ceaa21217267cf..d14f5a6d7fb0fc 100644
--- a/PCbuild/pythoncore.vcxproj.filters
+++ b/PCbuild/pythoncore.vcxproj.filters
@@ -723,6 +723,9 @@
<ClInclude Include="..\Include\internal\pycore_pyarena.h">
<Filter>Include\internal</Filter>
</ClInclude>
+ <ClInclude Include="..\Include\internal\pycore_pyatomic_ft_wrappers.h">
+ <Filter>Include\internal</Filter>
+ </ClInclude>
<ClInclude Include="..\Include\internal\pycore_pyerrors.h">
<Filter>Include\internal</Filter>
</ClInclude>
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