gh-128421: Avoid TSAN warnings in sys._current_frames()

This tells TSAN not to sanitize PyUnstable_InterpreterFrame_GetLine().
There's a possible data race on the access to the frame's instr_ptr
if the frame is currently executing. We don't really care about the
race. In theory, we could use relaxed atomics for every access to
`instr_ptr`, but that would create more code churn and current compilers
are overly conservative with optimizations around relaxed atomic
accesses.

We also don't sanitize _PyFrame_IsIncomplete() because it accesses
`instr_ptr` and is called from assertions within PyFrame_GetCode().

Author: colesbury

Include/internal/pycore_interpframe.h

@@ -228,8 +228,11 @@ _PyFrame_SetStackPointer(_PyInterpreterFrame *frame, _PyStackRef *stack_pointer)
  * Frames on the frame stack are incomplete until the
  * first RESUME instruction.
  * Frames owned by a generator are always complete.
+ *
+ * NOTE: We allow racy accesses to the instruction pointer
+ * from other threads for sys._current_frames() and similar APIs.
  */
-static inline bool
+static inline bool _Py_NO_SANITIZE_THREAD
 _PyFrame_IsIncomplete(_PyInterpreterFrame *frame)
 {
     if (frame->owner >= FRAME_OWNED_BY_INTERPRETER) {

Include/pyport.h

@@ -565,27 +565,45 @@ extern "C" {
 #  if __has_feature(memory_sanitizer)
 #    if !defined(_Py_MEMORY_SANITIZER)
 #      define _Py_MEMORY_SANITIZER
+#      define _Py_NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
 #    endif
 #  endif
 #  if __has_feature(address_sanitizer)
 #    if !defined(_Py_ADDRESS_SANITIZER)
 #      define _Py_ADDRESS_SANITIZER
+#      define _Py_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
 #    endif
 #  endif
 #  if __has_feature(thread_sanitizer)
 #    if !defined(_Py_THREAD_SANITIZER)
 #      define _Py_THREAD_SANITIZER
+#      define _Py_NO_SANITIZE_THREAD __attribute__((no_sanitize_thread))
 #    endif
 #  endif
 #elif defined(__GNUC__)
 #  if defined(__SANITIZE_ADDRESS__)
 #    define _Py_ADDRESS_SANITIZER
+#    define _Py_NO_SANITIZE_ADDRESS __attribute__((no_sanitize_address))
 #  endif
 #  if defined(__SANITIZE_THREAD__)
 #    define _Py_THREAD_SANITIZER
+#    define _Py_NO_SANITIZE_THREAD __attribute__((no_sanitize_thread))
+#  elif  __GNUC__ > 5 || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
+     // TSAN is supported since GCC 5.1, but __SANITIZE_THREAD__ macro
+     // is provided only since GCC 7.
+#    define _Py_NO_SANITIZE_THREAD __attribute__((no_sanitize_thread))
 #  endif
 #endif
 
+#ifndef _Py_NO_SANITIZE_ADDRESS
+#  define _Py_NO_SANITIZE_ADDRESS
+#endif
+#ifndef _Py_NO_SANITIZE_THREAD
+#  define _Py_NO_SANITIZE_THREAD
+#endif
+#ifndef _Py_NO_SANITIZE_MEMORY
+#  define _Py_NO_SANITIZE_MEMORY
+#endif
 
 /* AIX has __bool__ redefined in it's system header file. */
 #if defined(_AIX) && defined(__bool__)

Objects/obmalloc.c

@@ -470,40 +470,6 @@ _PyMem_ArenaFree(void *Py_UNUSED(ctx), void *ptr,
 /*******************************************/
 
 
-#if defined(__has_feature)  /* Clang */
-#  if __has_feature(address_sanitizer) /* is ASAN enabled? */
-#    define _Py_NO_SANITIZE_ADDRESS \
-        __attribute__((no_sanitize("address")))
-#  endif
-#  if __has_feature(thread_sanitizer)  /* is TSAN enabled? */
-#    define _Py_NO_SANITIZE_THREAD __attribute__((no_sanitize_thread))
-#  endif
-#  if __has_feature(memory_sanitizer)  /* is MSAN enabled? */
-#    define _Py_NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
-#  endif
-#elif defined(__GNUC__)
-#  if defined(__SANITIZE_ADDRESS__)    /* GCC 4.8+, is ASAN enabled? */
-#    define _Py_NO_SANITIZE_ADDRESS \
-        __attribute__((no_sanitize_address))
-#  endif
-   // TSAN is supported since GCC 5.1, but __SANITIZE_THREAD__ macro
-   // is provided only since GCC 7.
-#  if __GNUC__ > 5 || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
-#    define _Py_NO_SANITIZE_THREAD __attribute__((no_sanitize_thread))
-#  endif
-#endif
-
-#ifndef _Py_NO_SANITIZE_ADDRESS
-#  define _Py_NO_SANITIZE_ADDRESS
-#endif
-#ifndef _Py_NO_SANITIZE_THREAD
-#  define _Py_NO_SANITIZE_THREAD
-#endif
-#ifndef _Py_NO_SANITIZE_MEMORY
-#  define _Py_NO_SANITIZE_MEMORY
-#endif
-
-
 #define ALLOCATORS_MUTEX (_PyRuntime.allocators.mutex)
 #define _PyMem_Raw (_PyRuntime.allocators.standard.raw)
 #define _PyMem (_PyRuntime.allocators.standard.mem)

Python/frame.c

@@ -141,7 +141,9 @@ PyUnstable_InterpreterFrame_GetLasti(struct _PyInterpreterFrame *frame)
     return _PyInterpreterFrame_LASTI(frame) * sizeof(_Py_CODEUNIT);
 }
 
-int
+// NOTE: We allow racy accesses to the instruction pointer from other threads
+// for sys._current_frames() and similar APIs.
+int _Py_NO_SANITIZE_THREAD
 PyUnstable_InterpreterFrame_GetLine(_PyInterpreterFrame *frame)
 {
     int addr = _PyInterpreterFrame_LASTI(frame) * sizeof(_Py_CODEUNIT);