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bpo-39877: _PyRuntimeState.finalizing becomes atomic #18816

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Merged
vstinner merged 2 commits into from
Mar 6, 2020
Merged

bpo-39877: _PyRuntimeState.finalizing becomes atomic #18816

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699e914
bpo-39877: _PyRuntimeState.finalizing becomes atomic
vstinner Mar 6, 2020
c5926d9
Fix Windows build
vstinner Mar 6, 2020
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bpo-39877: _PyRuntimeState.finalizing becomes atomic 
Convert _PyRuntimeState.finalizing field to an atomic variable:

* Rename it to _finalizing
* Change its type to _Py_atomic_address
* Add _PyRuntimeState_GetFinalizing() and _PyRuntimeState_SetFinalizing()
  functions
* Remove _Py_CURRENTLY_FINALIZING() function: replace it with testing
  directly _PyRuntimeState_GetFinalizing() value

Convert _PyRuntimeState_GetThreadState() to static inline function.
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@vstinner
vstinner committed Mar 6, 2020
commit 699e914cddce7c0dc5d5b6f1a750f345d78f64a9
23 changes: 17 additions & 6 deletions Include/internal/pycore_pystate.h
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Expand Up @@ -223,8 +223,11 @@ typedef struct pyruntimestate {
int initialized;

/* Set by Py_FinalizeEx(). Only reset to NULL if Py_Initialize()
is called again. */
PyThreadState *finalizing;
is called again.

Use _PyRuntimeState_GetFinalizing() and _PyRuntimeState_SetFinalizing()
to access it, don't access it directly. */
_Py_atomic_address _finalizing;

struct pyinterpreters {
PyThread_type_lock mutex;
Expand Down Expand Up @@ -279,17 +282,25 @@ PyAPI_FUNC(PyStatus) _PyRuntime_Initialize(void);

PyAPI_FUNC(void) _PyRuntime_Finalize(void);

#define _Py_CURRENTLY_FINALIZING(runtime, tstate) \
(runtime->finalizing == tstate)
static inline PyThreadState*
_PyRuntimeState_GetFinalizing(_PyRuntimeState *runtime) {
return (PyThreadState*)_Py_atomic_load_relaxed(&runtime->_finalizing);
}

static inline void
_PyRuntimeState_SetFinalizing(_PyRuntimeState *runtime, PyThreadState *tstate) {
return _Py_atomic_store_relaxed(&runtime->_finalizing, (uintptr_t)tstate);

@pitrou pitrou Mar 6, 2020

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I think the return is confusing MSVC (see CI failures).

}

PyAPI_FUNC(int) _Py_IsMainInterpreter(PyThreadState* tstate);


/* Variable and macro for in-line access to current thread
and interpreter state */

#define _PyRuntimeState_GetThreadState(runtime) \
((PyThreadState*)_Py_atomic_load_relaxed(&(runtime)->gilstate.tstate_current))
static inline PyThreadState* _PyRuntimeState_GetThreadState(_PyRuntimeState *runtime) {
return (PyThreadState*)_Py_atomic_load_relaxed(&runtime->gilstate.tstate_current);
}

/* Get the current Python thread state.

Expand Down
3 changes: 2 additions & 1 deletion Python/ceval.c
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Expand Up @@ -240,7 +240,8 @@ exit_thread_if_finalizing(PyThreadState *tstate)
{
_PyRuntimeState *runtime = tstate->interp->runtime;
/* _Py_Finalizing is protected by the GIL */
if (runtime->finalizing != NULL && !_Py_CURRENTLY_FINALIZING(runtime, tstate)) {
PyThreadState *finalizing = _PyRuntimeState_GetFinalizing(runtime);
if (finalizing != NULL && finalizing != tstate) {
drop_gil(&runtime->ceval, tstate);
PyThread_exit_thread();
}
Expand Down
11 changes: 6 additions & 5 deletions Python/pylifecycle.c
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Expand Up @@ -103,7 +103,7 @@ _PyRuntime_Finalize(void)
int
_Py_IsFinalizing(void)
{
return _PyRuntime.finalizing != NULL;
return _PyRuntimeState_GetFinalizing(&_PyRuntime) != NULL;
}

/* Hack to force loading of object files */
Expand Down Expand Up @@ -507,7 +507,7 @@ pycore_init_runtime(_PyRuntimeState *runtime,
* threads still hanging around from a previous Py_Initialize/Finalize
* pair :(
*/
runtime->finalizing = NULL;
_PyRuntimeState_SetFinalizing(runtime, NULL);

PyStatus status = _Py_HashRandomization_Init(config);
if (_PyStatus_EXCEPTION(status)) {
Expand Down Expand Up @@ -1366,7 +1366,7 @@ Py_FinalizeEx(void)

/* Remaining threads (e.g. daemon threads) will automatically exit
after taking the GIL (in PyEval_RestoreThread()). */
runtime->finalizing = tstate;
_PyRuntimeState_SetFinalizing(runtime, tstate);
runtime->initialized = 0;
runtime->core_initialized = 0;

Expand Down Expand Up @@ -2131,8 +2131,9 @@ static void
fatal_error_dump_runtime(FILE *stream, _PyRuntimeState *runtime)
{
fprintf(stream, "Python runtime state: ");
if (runtime->finalizing) {
fprintf(stream, "finalizing (tstate=%p)", runtime->finalizing);
PyThreadState *finalizing = _PyRuntimeState_GetFinalizing(runtime);
if (finalizing) {
fprintf(stream, "finalizing (tstate=%p)", finalizing);
}
else if (runtime->initialized) {
fprintf(stream, "initialized");
Expand Down
2 changes: 1 addition & 1 deletion Python/pystate.c
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Expand Up @@ -292,7 +292,7 @@ PyInterpreterState_Clear(PyInterpreterState *interp)
Py_CLEAR(interp->after_forkers_parent);
Py_CLEAR(interp->after_forkers_child);
#endif
if (runtime->finalizing == NULL) {
if (_PyRuntimeState_GetFinalizing(runtime) == NULL) {
_PyWarnings_Fini(interp);
}
// XXX Once we have one allocator per interpreter (i.e.
Expand Down
5 changes: 3 additions & 2 deletions Python/sysmodule.c
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Expand Up @@ -289,8 +289,9 @@ _PySys_ClearAuditHooks(void)
/* Must be finalizing to clear hooks */
_PyRuntimeState *runtime = &_PyRuntime;
PyThreadState *ts = _PyRuntimeState_GetThreadState(runtime);
assert(!ts || _Py_CURRENTLY_FINALIZING(runtime, ts));
if (!ts || !_Py_CURRENTLY_FINALIZING(runtime, ts)) {
PyThreadState *finalizing = _PyRuntimeState_GetFinalizing(runtime);
assert(!ts || finalizing == ts);
if (!ts || finalizing != ts) {
return;
}

Expand Down