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gh-99113: Make Sure the GIL is Acquired at the Right Places (gh-104208)

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This is a pre-requisite for a per-interpreter GIL.  Without it this change isn't strictly necessary.  However, there is no real downside otherwise.
This commit is contained in:
Eric Snow 2023-05-06 15:59:30 -06:00 • committed by GitHub
parent fff193bbfe
commit 92d8bfffbf
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4 changed files with 113 additions and 40 deletions
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84
Python/ceval_gil.c
View file

@ -499,42 +499,66 @@ PyEval_ThreadsInitialized(void)
return _PyEval_ThreadsInitialized();
}
static inline int
current_thread_holds_gil(struct _gil_runtime_state *gil, PyThreadState *tstate)
{
if (((PyThreadState*)_Py_atomic_load_relaxed(&gil->last_holder)) != tstate) {
return 0;
}
return _Py_atomic_load_relaxed(&gil->locked);
}
static void
init_shared_gil(PyInterpreterState *interp, struct _gil_runtime_state *gil)
{
assert(gil_created(gil));
interp->ceval.gil = gil;
interp->ceval.own_gil = 0;
}
static void
init_own_gil(PyInterpreterState *interp, struct _gil_runtime_state *gil)
{
assert(!gil_created(gil));
create_gil(gil);
assert(gil_created(gil));
interp->ceval.gil = gil;
interp->ceval.own_gil = 1;
}
PyStatus
_PyEval_InitGIL(PyThreadState *tstate, int own_gil)
{
assert(tstate->interp->ceval.gil == NULL);
int locked;
if (!own_gil) {
PyInterpreterState *main_interp = _PyInterpreterState_Main();
assert(tstate->interp != main_interp);
struct _gil_runtime_state *gil = main_interp->ceval.gil;
assert(gil_created(gil));
tstate->interp->ceval.gil = gil;
tstate->interp->ceval.own_gil = 0;
return _PyStatus_OK();
init_shared_gil(tstate->interp, gil);
locked = current_thread_holds_gil(gil, tstate);
}
/* XXX per-interpreter GIL */
struct _gil_runtime_state *gil = &tstate->interp->runtime->ceval.gil;
if (!_Py_IsMainInterpreter(tstate->interp)) {
else if (!_Py_IsMainInterpreter(tstate->interp)) {
/* Currently, the GIL is shared by all interpreters,
and only the main interpreter is responsible to create
and destroy it. */
assert(gil_created(gil));
tstate->interp->ceval.gil = gil;
struct _gil_runtime_state *main_gil = _PyInterpreterState_Main()->ceval.gil;
init_shared_gil(tstate->interp, main_gil);
// XXX For now we lie.
tstate->interp->ceval.own_gil = 1;
return _PyStatus_OK();
locked = current_thread_holds_gil(main_gil, tstate);
}
else {
PyThread_init_thread();
// XXX per-interpreter GIL: switch to interp->_gil.
init_own_gil(tstate->interp, &tstate->interp->runtime->ceval.gil);
locked = 0;
}
if (!locked) {
take_gil(tstate);
}
assert(own_gil);
assert(!gil_created(gil));
PyThread_init_thread();
create_gil(gil);
assert(gil_created(gil));
tstate->interp->ceval.gil = gil;
tstate->interp->ceval.own_gil = 1;
take_gil(tstate);
return _PyStatus_OK();
}
@ -611,9 +635,17 @@ PyEval_ReleaseLock(void)
drop_gil(ceval, tstate);
}
void
_PyEval_AcquireLock(PyThreadState *tstate)
{
_Py_EnsureTstateNotNULL(tstate);
take_gil(tstate);
}
void
_PyEval_ReleaseLock(PyThreadState *tstate)
{
_Py_EnsureTstateNotNULL(tstate);
struct _ceval_state *ceval = &tstate->interp->ceval;
drop_gil(ceval, tstate);
}
@ -625,7 +657,7 @@ PyEval_AcquireThread(PyThreadState *tstate)
take_gil(tstate);
if (_PyThreadState_Swap(tstate->interp->runtime, tstate) != NULL) {
if (_PyThreadState_SwapNoGIL(tstate) != NULL) {
Py_FatalError("non-NULL old thread state");
}
}
@ -635,8 +667,7 @@ PyEval_ReleaseThread(PyThreadState *tstate)
{
assert(is_tstate_valid(tstate));
_PyRuntimeState *runtime = tstate->interp->runtime;
PyThreadState *new_tstate = _PyThreadState_Swap(runtime, NULL);
PyThreadState *new_tstate = _PyThreadState_SwapNoGIL(NULL);
if (new_tstate != tstate) {
Py_FatalError("wrong thread state");
}
@ -684,8 +715,7 @@ _PyEval_SignalAsyncExc(PyInterpreterState *interp)
PyThreadState *
PyEval_SaveThread(void)
{
_PyRuntimeState *runtime = &_PyRuntime;
PyThreadState *tstate = _PyThreadState_Swap(runtime, NULL);
PyThreadState *tstate = _PyThreadState_SwapNoGIL(NULL);
_Py_EnsureTstateNotNULL(tstate);
struct _ceval_state *ceval = &tstate->interp->ceval;
@ -701,7 +731,7 @@ PyEval_RestoreThread(PyThreadState *tstate)
take_gil(tstate);
_PyThreadState_Swap(tstate->interp->runtime, tstate);
_PyThreadState_SwapNoGIL(tstate);
}
@ -1005,7 +1035,7 @@ _Py_HandlePending(PyThreadState *tstate)
/* GIL drop request */
if (_Py_atomic_load_relaxed_int32(&interp_ceval_state->gil_drop_request)) {
/* Give another thread a chance */
if (_PyThreadState_Swap(runtime, NULL) != tstate) {
if (_PyThreadState_SwapNoGIL(NULL) != tstate) {
Py_FatalError("tstate mix-up");
}
drop_gil(interp_ceval_state, tstate);
@ -1014,7 +1044,7 @@ _Py_HandlePending(PyThreadState *tstate)
take_gil(tstate);
if (_PyThreadState_Swap(runtime, tstate) != NULL) {
if (_PyThreadState_SwapNoGIL(tstate) != NULL) {
Py_FatalError("orphan tstate");
}
}

25
Python/pylifecycle.c
View file

@ -591,6 +591,7 @@ init_interp_create_gil(PyThreadState *tstate, int own_gil)
/* finalize_interp_delete() comment explains why _PyEval_FiniGIL() is
only called here. */
// XXX This is broken with a per-interpreter GIL.
_PyEval_FiniGIL(tstate->interp);
/* Auto-thread-state API */
@ -645,7 +646,8 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
return _PyStatus_ERR("can't make first thread");
}
_PyThreadState_Bind(tstate);
(void) PyThreadState_Swap(tstate);
// XXX For now we do this before the GIL is created.
(void) _PyThreadState_SwapNoGIL(tstate);
status = init_interp_create_gil(tstate, config.own_gil);
if (_PyStatus_EXCEPTION(status)) {
@ -2025,11 +2027,20 @@ new_interpreter(PyThreadState **tstate_p, const PyInterpreterConfig *config)
}
_PyThreadState_Bind(tstate);
PyThreadState *save_tstate = PyThreadState_Swap(tstate);
// XXX For now we do this before the GIL is created.
PyThreadState *save_tstate = _PyThreadState_SwapNoGIL(tstate);
int has_gil = 0;
/* From this point until the init_interp_create_gil() call,
we must not do anything that requires that the GIL be held
(or otherwise exist). That applies whether or not the new
interpreter has its own GIL (e.g. the main interpreter). */
/* Copy the current interpreter config into the new interpreter */
const PyConfig *src_config;
if (save_tstate != NULL) {
// XXX Might new_interpreter() have been called without the GIL held?
_PyEval_ReleaseLock(save_tstate);
src_config = _PyInterpreterState_GetConfig(save_tstate->interp);
}
else
@ -2039,11 +2050,13 @@ new_interpreter(PyThreadState **tstate_p, const PyInterpreterConfig *config)
src_config = _PyInterpreterState_GetConfig(main_interp);
}
/* This does not require that the GIL be held. */
status = _PyConfig_Copy(&interp->config, src_config);
if (_PyStatus_EXCEPTION(status)) {
goto error;
}
/* This does not require that the GIL be held. */
status = init_interp_settings(interp, config);
if (_PyStatus_EXCEPTION(status)) {
goto error;
@ -2053,6 +2066,7 @@ new_interpreter(PyThreadState **tstate_p, const PyInterpreterConfig *config)
if (_PyStatus_EXCEPTION(status)) {
goto error;
}
has_gil = 1;
status = pycore_interp_init(tstate);
if (_PyStatus_EXCEPTION(status)) {
@ -2072,7 +2086,12 @@ error:
/* Oops, it didn't work. Undo it all. */
PyErr_PrintEx(0);
PyThreadState_Swap(save_tstate);
if (has_gil) {
PyThreadState_Swap(save_tstate);
}
else {
_PyThreadState_SwapNoGIL(save_tstate);
}
PyThreadState_Clear(tstate);
PyThreadState_Delete(tstate);
PyInterpreterState_Delete(interp);

42
Python/pystate.c
View file

@ -1863,17 +1863,11 @@ PyThreadState_Get(void)
}
PyThreadState *
_PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
static void
_swap_thread_states(_PyRuntimeState *runtime,
PyThreadState *oldts, PyThreadState *newts)
{
#if defined(Py_DEBUG)
/* This can be called from PyEval_RestoreThread(). Similar
to it, we need to ensure errno doesn't change.
*/
int err = errno;
#endif
PyThreadState *oldts = current_fast_get(runtime);
// XXX Do this only if oldts != NULL?
current_fast_clear(runtime);
if (oldts != NULL) {
@ -1887,6 +1881,20 @@ _PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
current_fast_set(runtime, newts);
tstate_activate(newts);
}
}
PyThreadState *
_PyThreadState_SwapNoGIL(PyThreadState *newts)
{
#if defined(Py_DEBUG)
/* This can be called from PyEval_RestoreThread(). Similar
to it, we need to ensure errno doesn't change.
*/
int err = errno;
#endif
PyThreadState *oldts = current_fast_get(&_PyRuntime);
_swap_thread_states(&_PyRuntime, oldts, newts);
#if defined(Py_DEBUG)
errno = err;
@ -1894,6 +1902,20 @@ _PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
return oldts;
}
PyThreadState *
_PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
{
PyThreadState *oldts = current_fast_get(runtime);
if (oldts != NULL) {
_PyEval_ReleaseLock(oldts);
}
_swap_thread_states(runtime, oldts, newts);
if (newts != NULL) {
_PyEval_AcquireLock(newts);
}
return oldts;
}
PyThreadState *
PyThreadState_Swap(PyThreadState *newts)
{