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gh-59956: Clarify GILState-related Code #101161

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Merged
ericsnowcurrently merged 11 commits into from
Jan 19, 2023
Merged

gh-59956: Clarify GILState-related Code #101161

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c35aee5
Add some TODO comments.
ericsnowcurrently Jan 18, 2023
bb86c59
Factor out "current_tss" helpers.
ericsnowcurrently Jan 18, 2023
5903b39
Inline the current_tss helpers.
ericsnowcurrently Jan 19, 2023
a5eb3d8
Factor out "current_fast" helpers.
ericsnowcurrently Jan 18, 2023
6281edb
Move tstate_current out of _PyRuntimeState.gilstate.
ericsnowcurrently Jan 18, 2023
2f8aaec
Do not use _PyThreadState_GET() in pystate.c.
ericsnowcurrently Jan 18, 2023
4af2ecb
Move autoTSSkey out of _PyRuntimeState.gilstate.
ericsnowcurrently Jan 19, 2023
7bdf5a4
Initialize autoTSSkey earlier.
ericsnowcurrently Jan 19, 2023
4b952e0
Factor out bind_tstate() and unbind_tstate().
ericsnowcurrently Jan 19, 2023
5e7283c
PyThreadState_IsCurrent() -> holds_gil().
ericsnowcurrently Jan 19, 2023
57bd92e
Do not set PyThreadState.thread_id to a negative value.
ericsnowcurrently Jan 19, 2023
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Factor out "current_fast" helpers.
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@ericsnowcurrently
ericsnowcurrently committed Jan 19, 2023
commit a5eb3d86fc0e9153fe6693ff96ee84edf861c1e1
62 changes: 41 additions & 21 deletions Python/pystate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -44,11 +44,30 @@ static void _PyThreadState_Delete(PyThreadState *tstate, int check_current);

/* the current thread state */

#define _PyRuntimeGILState_GetThreadState(gilstate) \
((PyThreadState*)_Py_atomic_load_relaxed(&(gilstate)->tstate_current))
#define _PyRuntimeGILState_SetThreadState(gilstate, value) \
_Py_atomic_store_relaxed(&(gilstate)->tstate_current, \
(uintptr_t)(value))
static inline PyThreadState *
current_fast_get(_PyRuntimeState *runtime)
{
// The GIL must be held by the current thread.
return (PyThreadState*)_Py_atomic_load_relaxed(
&runtime->gilstate.tstate_current);
}

static inline void
current_fast_set(_PyRuntimeState *runtime, PyThreadState *tstate)
{
// The GIL must be held by the current thread.
assert(tstate != NULL);
_Py_atomic_store_relaxed(&runtime->gilstate.tstate_current,
(uintptr_t)tstate);
}

static inline void
current_fast_clear(_PyRuntimeState *runtime)
{
// The GIL must be held by the current thread.
_Py_atomic_store_relaxed(&runtime->gilstate.tstate_current,
(uintptr_t)NULL);
}


static int
Expand Down Expand Up @@ -1145,8 +1164,7 @@ PyThreadState_Clear(PyThreadState *tstate)

/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
static void
tstate_delete_common(PyThreadState *tstate,
struct _gilstate_runtime_state *gilstate)
tstate_delete_common(PyThreadState *tstate)
{
_Py_EnsureTstateNotNULL(tstate);
PyInterpreterState *interp = tstate->interp;
Expand Down Expand Up @@ -1187,13 +1205,12 @@ tstate_delete_common(PyThreadState *tstate,
static void
_PyThreadState_Delete(PyThreadState *tstate, int check_current)
{
struct _gilstate_runtime_state *gilstate = &tstate->interp->runtime->gilstate;
if (check_current) {
if (tstate == _PyRuntimeGILState_GetThreadState(gilstate)) {
if (tstate == current_fast_get(tstate->interp->runtime)) {
_Py_FatalErrorFormat(__func__, "tstate %p is still current", tstate);
}
}
tstate_delete_common(tstate, gilstate);
tstate_delete_common(tstate);
free_threadstate(tstate);
}

Expand All @@ -1209,18 +1226,16 @@ void
_PyThreadState_DeleteCurrent(PyThreadState *tstate)
{
_Py_EnsureTstateNotNULL(tstate);
struct _gilstate_runtime_state *gilstate = &tstate->interp->runtime->gilstate;
tstate_delete_common(tstate, gilstate);
_PyRuntimeGILState_SetThreadState(gilstate, NULL);
tstate_delete_common(tstate);
current_fast_clear(tstate->interp->runtime);
_PyEval_ReleaseLock(tstate);
free_threadstate(tstate);
}

void
PyThreadState_DeleteCurrent(void)
{
struct _gilstate_runtime_state *gilstate = &_PyRuntime.gilstate;
PyThreadState *tstate = _PyRuntimeGILState_GetThreadState(gilstate);
PyThreadState *tstate = current_fast_get(&_PyRuntime);
_PyThreadState_DeleteCurrent(tstate);
}

Expand Down Expand Up @@ -1286,9 +1301,14 @@ PyThreadState_Get(void)
PyThreadState *
_PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
{
PyThreadState *oldts = _PyRuntimeGILState_GetThreadState(&runtime->gilstate);
PyThreadState *oldts = current_fast_get(runtime);

_PyRuntimeGILState_SetThreadState(&runtime->gilstate, newts);
if (newts == NULL) {
current_fast_clear(runtime);
}
else {
current_fast_set(runtime, newts);
}
/* It should not be possible for more than one thread state
to be used for a thread. Check this the best we can in debug
builds.
Expand Down Expand Up @@ -1590,7 +1610,7 @@ PyThreadState_IsCurrent(PyThreadState *tstate)
_PyRuntimeState *runtime = tstate->interp->runtime;
/* Must be the tstate for this thread */
assert(tstate == current_tss_get(runtime));
return tstate == _PyRuntimeGILState_GetThreadState(&runtime->gilstate);
return tstate == current_fast_get(runtime);
}

/* Internal initialization/finalization functions called by
Expand Down Expand Up @@ -1738,7 +1758,7 @@ PyGILState_Check(void)
return 1;
}

PyThreadState *tstate = _PyRuntimeGILState_GetThreadState(&runtime->gilstate);
PyThreadState *tstate = current_fast_get(runtime);
if (tstate == NULL) {
return 0;
}
Expand Down Expand Up @@ -1830,7 +1850,7 @@ PyGILState_Release(PyGILState_STATE oldstate)
* races; see bugs 225673 and 1061968 (that nasty bug has a
* habit of coming back).
*/
assert(_PyRuntimeGILState_GetThreadState(&runtime->gilstate) == tstate);
assert(current_fast_get(runtime) == tstate);
_PyThreadState_DeleteCurrent(tstate);
}
/* Release the lock if necessary */
Expand Down Expand Up @@ -2017,7 +2037,7 @@ _call_in_interpreter(PyInterpreterState *interp, releasefunc func, void *arg)
*/
_PyRuntimeState *runtime = interp->runtime;
PyThreadState *save_tstate = NULL;
if (interp != _PyRuntimeGILState_GetThreadState(&runtime->gilstate)->interp) {
if (interp != current_fast_get(runtime)->interp) {
// XXX Using the "head" thread isn't strictly correct.
PyThreadState *tstate = PyInterpreterState_ThreadHead(interp);
// XXX Possible GILState issues?
Expand Down