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bpo-39465: Add pycore_atomic_funcs.h header (GH-20766)

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Add pycore_atomic_funcs.h internal header file: similar to
pycore_atomic.h but don't require to declare variables as atomic.

Add _Py_atomic_size_get() and _Py_atomic_size_set() functions.
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Victor Stinner 2020-12-23 03:41:08 +01:00 • committed by GitHub
parent 46b5c6be29
commit 52a327c1cb
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9 changed files with 132 additions and 17 deletions
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6
Include/internal/pycore_atomic.h
View file

@ -11,8 +11,8 @@ extern "C" {
#include "dynamic_annotations.h" /* _Py_ANNOTATE_MEMORY_ORDER */
#include "pyconfig.h"
#if defined(HAVE_STD_ATOMIC)
#include <stdatomic.h>
#ifdef HAVE_STD_ATOMIC
# include <stdatomic.h>
#endif
@ -62,7 +62,7 @@ typedef struct _Py_atomic_int {
#define _Py_atomic_load_explicit(ATOMIC_VAL, ORDER) \
atomic_load_explicit(&((ATOMIC_VAL)->_value), ORDER)
/* Use builtin atomic operations in GCC >= 4.7 */
// Use builtin atomic operations in GCC >= 4.7 and clang
#elif defined(HAVE_BUILTIN_ATOMIC)
typedef enum _Py_memory_order {

94
Include/internal/pycore_atomic_funcs.h Normal file
View file

@ -0,0 +1,94 @@
/* Atomic functions: similar to pycore_atomic.h, but don't need
to declare variables as atomic.
Py_ssize_t type:
* value = _Py_atomic_size_get(&var)
* _Py_atomic_size_set(&var, value)
Use sequentially-consistent ordering (__ATOMIC_SEQ_CST memory order):
enforce total ordering with all other atomic functions.
*/
#ifndef Py_ATOMIC_FUNC_H
#define Py_ATOMIC_FUNC_H
#ifdef __cplusplus
extern "C" {
#endif
#ifndef Py_BUILD_CORE
# error "this header requires Py_BUILD_CORE define"
#endif
#if defined(_MSC_VER)
# include <intrin.h> // _InterlockedExchange()
#endif
// Use builtin atomic operations in GCC >= 4.7 and clang
#ifdef HAVE_BUILTIN_ATOMIC
static inline Py_ssize_t _Py_atomic_size_get(Py_ssize_t *var)
{
return __atomic_load_n(var, __ATOMIC_SEQ_CST);
}
static inline void _Py_atomic_size_set(Py_ssize_t *var, Py_ssize_t value)
{
__atomic_store_n(var, value, __ATOMIC_SEQ_CST);
}
#elif defined(_MSC_VER)
static inline Py_ssize_t _Py_atomic_size_get(Py_ssize_t *var)
{
#if SIZEOF_VOID_P == 8
Py_BUILD_ASSERT(sizeof(__int64) == sizeof(*var));
volatile __int64 *volatile_var = (volatile __int64 *)var;
__int64 old;
do {
old = *volatile_var;
} while(_InterlockedCompareExchange64(volatile_var, old, old) != old);
#else
Py_BUILD_ASSERT(sizeof(long) == sizeof(*var));
volatile long *volatile_var = (volatile long *)var;
long old;
do {
old = *volatile_var;
} while(_InterlockedCompareExchange(volatile_var, old, old) != old);
#endif
return old;
}
static inline void _Py_atomic_size_set(Py_ssize_t *var, Py_ssize_t value)
{
#if SIZEOF_VOID_P == 8
Py_BUILD_ASSERT(sizeof(__int64) == sizeof(*var));
volatile __int64 *volatile_var = (volatile __int64 *)var;
_InterlockedExchange64(volatile_var, value);
#else
Py_BUILD_ASSERT(sizeof(long) == sizeof(*var));
volatile long *volatile_var = (volatile long *)var;
_InterlockedExchange(volatile_var, value);
#endif
}
#else
// Fallback implementation using volatile
static inline Py_ssize_t _Py_atomic_size_get(Py_ssize_t *var)
{
volatile Py_ssize_t *volatile_var = (volatile Py_ssize_t *)var;
return *volatile_var;
}
static inline void _Py_atomic_size_set(Py_ssize_t *var, Py_ssize_t value)
{
volatile Py_ssize_t *volatile_var = (volatile Py_ssize_t *)var;
*volatile_var = value;
}
#endif
#ifdef __cplusplus
}
#endif
#endif /* Py_ATOMIC_FUNC_H */