float race

Author: dpdani

Include/cpython/pyatomic.h

@@ -336,6 +336,9 @@ _Py_atomic_load_ushort_relaxed(const unsigned short *obj);
 static inline long
 _Py_atomic_load_long_relaxed(const long *obj);
 
+static inline float
+_Py_atomic_load_float_relaxed(const float *obj);
+
 static inline int8_t
 _Py_atomic_load_int8_relaxed(const int8_t *obj);
 
@@ -514,6 +517,9 @@ _Py_atomic_store_uint_release(unsigned int *obj, unsigned int value);
 static inline void
 _Py_atomic_store_long_release(long *obj, long value);
 
+static inline void
+_Py_atomic_store_float_release(float *obj, float value);
+
 static inline int
 _Py_atomic_load_int_acquire(const int *obj);
 

Include/cpython/pyatomic_gcc.h

@@ -326,6 +326,10 @@ static inline long
 _Py_atomic_load_long_relaxed(const long *obj)
 { return __atomic_load_n(obj, __ATOMIC_RELAXED); }
 
+static inline float
+_Py_atomic_load_float_relaxed(const float *obj)
+{ float ret; __atomic_load(obj, &ret, __ATOMIC_RELAXED); return ret; }
+
 static inline int8_t
 _Py_atomic_load_int8_relaxed(const int8_t *obj)
 { return __atomic_load_n(obj, __ATOMIC_RELAXED); }
@@ -552,6 +556,10 @@ static inline void
 _Py_atomic_store_long_release(long *obj, long value)
 { __atomic_store_n(obj, value, __ATOMIC_RELEASE); }
 
+static inline void
+_Py_atomic_store_float_release(float *obj, float value)
+{ __atomic_store(obj, &value, __ATOMIC_RELEASE); }
+
 static inline void
 _Py_atomic_store_ssize_release(Py_ssize_t *obj, Py_ssize_t value)
 { __atomic_store_n(obj, value, __ATOMIC_RELEASE); }

Include/cpython/pyatomic_msc.h

@@ -664,6 +664,12 @@ _Py_atomic_load_long_relaxed(const long *obj)
     return *(volatile long *)obj;
 }
 
+static inline float
+_Py_atomic_load_float_relaxed(const float *obj)
+{
+    return *(volatile float *)obj;
+}
+
 static inline int8_t
 _Py_atomic_load_int8_relaxed(const int8_t *obj)
 {
@@ -1072,6 +1078,19 @@ _Py_atomic_store_long_release(long *obj, long value)
 #endif
 }
 
+static inline void
+_Py_atomic_store_float_release(float *obj, float value)
+{
+#if defined(_M_X64) || defined(_M_IX86)
+    *(float volatile *)obj = value;
+#elif defined(_M_ARM64)
+    _Py_atomic_ASSERT_ARG_TYPE(unsigned __int32);
+    __stlr64((unsigned __int32 volatile *)obj, (unsigned __int32)value);
+#else
+#  error "no implementation of _Py_atomic_store_float_release"
+#endif
+}
+
 static inline void
 _Py_atomic_store_ssize_release(Py_ssize_t *obj, Py_ssize_t value)
 {

Include/cpython/pyatomic_std.h

@@ -555,6 +555,14 @@ _Py_atomic_load_long_relaxed(const long *obj)
                                 memory_order_relaxed);
 }
 
+static inline float
+_Py_atomic_load_float_relaxed(const float *obj)
+{
+    _Py_USING_STD;
+    return atomic_load_explicit((const _Atomic(float)*)obj,
+                                memory_order_relaxed);
+}
+
 static inline int8_t
 _Py_atomic_load_int8_relaxed(const int8_t *obj)
 {
@@ -983,6 +991,14 @@ _Py_atomic_store_long_release(long *obj, long value)
                           memory_order_release);
 }
 
+static inline void
+_Py_atomic_store_float_release(float *obj, float value)
+{
+    _Py_USING_STD;
+    atomic_store_explicit((_Atomic(float)*)obj, value,
+                          memory_order_release);
+}
+
 static inline void
 _Py_atomic_store_ssize_release(Py_ssize_t *obj, Py_ssize_t value)
 {

Include/internal/pycore_pyatomic_ft_wrappers.h

@@ -93,6 +93,10 @@ extern "C" {
     _Py_atomic_store_ulong(&value, new_value)
 #define FT_ATOMIC_STORE_SSIZE_RELEASE(value, new_value) \
     _Py_atomic_store_ssize_release(&value, new_value)
+#define FT_ATOMIC_STORE_FLOAT_RELEASE(value, new_value) \
+    _Py_atomic_store_float_release(&value, new_value)
+#define FT_ATOMIC_LOAD_FLOAT_RELAXED(value) \
+    _Py_atomic_load_float_relaxed(&value)
 
 #else
 #define FT_ATOMIC_LOAD_PTR(value) value
@@ -132,6 +136,8 @@ extern "C" {
 #define FT_ATOMIC_STORE_LONG_RELEASE(value, new_value) value = new_value
 #define FT_ATOMIC_STORE_ULONG(value, new_value) value = new_value
 #define FT_ATOMIC_STORE_SSIZE_RELEASE(value, new_value) value = new_value
+#define FT_ATOMIC_LOAD_FLOAT_RELAXED(value) value
+#define FT_ATOMIC_STORE_FLOAT_RELEASE(value, new_value) value = new_value
 
 #endif
 

Python/structmember.c

@@ -64,7 +64,7 @@ PyMember_GetOne(const char *obj_addr, PyMemberDef *l)
         v = PyLong_FromSsize_t(FT_ATOMIC_LOAD_SSIZE_RELAXED(*(Py_ssize_t*)addr));
         break;
     case Py_T_FLOAT:
-        v = PyFloat_FromDouble((double)*(float*)addr);
+        v = PyFloat_FromDouble((double)FT_ATOMIC_LOAD_FLOAT_RELAXED(*(float*)addr));
         break;
     case Py_T_DOUBLE:
         v = PyFloat_FromDouble(*(double*)addr);
@@ -293,7 +293,7 @@ PyMember_SetOne(char *addr, PyMemberDef *l, PyObject *v)
         double double_val = PyFloat_AsDouble(v);
         if ((double_val == -1) && PyErr_Occurred())
             return -1;
-        *(float*)addr = (float)double_val;
+        FT_ATOMIC_STORE_FLOAT_RELEASE(*(float*)addr, (float)double_val);
         break;
         }
     case Py_T_DOUBLE: