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gh-109549: Add new states to PyThreadState to support PEP 703 (gh-109915)

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This adds a new field 'state' to PyThreadState that can take on one of three values: _Py_THREAD_ATTACHED, _Py_THREAD_DETACHED, or _Py_THREAD_GC.  The "attached" and "detached" states correspond closely to acquiring and releasing the GIL.  The "gc" state is current unused, but will be used to implement stop-the-world GC for --disable-gil builds in the near future.
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Sam Gross 2023-10-05 15:46:33 +00:00 • committed by GitHub
parent 9eb2489266
commit 6e97a9647a
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GPG key ID: 4AEE18F83AFDEB23
6 changed files with 141 additions and 92 deletions
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125
Python/pystate.c
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@ -998,6 +998,7 @@ _PyInterpreterState_Clear(PyThreadState *tstate)
static inline void tstate_deactivate(PyThreadState *tstate);
static void tstate_set_detached(PyThreadState *tstate);
static void zapthreads(PyInterpreterState *interp);
void
@ -1011,9 +1012,7 @@ PyInterpreterState_Delete(PyInterpreterState *interp)
PyThreadState *tcur = current_fast_get(runtime);
if (tcur != NULL && interp == tcur->interp) {
/* Unset current thread. After this, many C API calls become crashy. */
current_fast_clear(runtime);
tstate_deactivate(tcur);
_PyEval_ReleaseLock(interp, NULL);
_PyThreadState_Detach(tcur);
}
zapthreads(interp);
@ -1651,6 +1650,7 @@ static void
tstate_delete_common(PyThreadState *tstate)
{
assert(tstate->_status.cleared && !tstate->_status.finalized);
assert(tstate->state != _Py_THREAD_ATTACHED);
PyInterpreterState *interp = tstate->interp;
if (interp == NULL) {
@ -1711,6 +1711,7 @@ void
_PyThreadState_DeleteCurrent(PyThreadState *tstate)
{
_Py_EnsureTstateNotNULL(tstate);
tstate_set_detached(tstate);
tstate_delete_common(tstate);
current_fast_clear(tstate->interp->runtime);
_PyEval_ReleaseLock(tstate->interp, NULL);
@ -1867,6 +1868,79 @@ tstate_deactivate(PyThreadState *tstate)
// It will still be used in PyGILState_Ensure().
}
static int
tstate_try_attach(PyThreadState *tstate)
{
#ifdef Py_NOGIL
int expected = _Py_THREAD_DETACHED;
if (_Py_atomic_compare_exchange_int(
&tstate->state,
&expected,
_Py_THREAD_ATTACHED)) {
return 1;
}
return 0;
#else
assert(tstate->state == _Py_THREAD_DETACHED);
tstate->state = _Py_THREAD_ATTACHED;
return 1;
#endif
}
static void
tstate_set_detached(PyThreadState *tstate)
{
assert(tstate->state == _Py_THREAD_ATTACHED);
#ifdef Py_NOGIL
_Py_atomic_store_int(&tstate->state, _Py_THREAD_DETACHED);
#else
tstate->state = _Py_THREAD_DETACHED;
#endif
}
void
_PyThreadState_Attach(PyThreadState *tstate)
{
#if defined(Py_DEBUG)
// This is called from PyEval_RestoreThread(). Similar
// to it, we need to ensure errno doesn't change.
int err = errno;
#endif
_Py_EnsureTstateNotNULL(tstate);
if (current_fast_get(&_PyRuntime) != NULL) {
Py_FatalError("non-NULL old thread state");
}
_PyEval_AcquireLock(tstate);
// XXX assert(tstate_is_alive(tstate));
current_fast_set(&_PyRuntime, tstate);
tstate_activate(tstate);
if (!tstate_try_attach(tstate)) {
// TODO: Once stop-the-world GC is implemented for --disable-gil builds
// this will need to wait until the GC completes. For now, this case
// should never happen.
Py_FatalError("thread attach failed");
}
#if defined(Py_DEBUG)
errno = err;
#endif
}
void
_PyThreadState_Detach(PyThreadState *tstate)
{
// XXX assert(tstate_is_alive(tstate) && tstate_is_bound(tstate));
assert(tstate->state == _Py_THREAD_ATTACHED);
assert(tstate == current_fast_get(&_PyRuntime));
tstate_set_detached(tstate);
tstate_deactivate(tstate);
current_fast_clear(&_PyRuntime);
_PyEval_ReleaseLock(tstate->interp, tstate);
}
//----------
// other API
@ -1939,56 +2013,15 @@ PyThreadState_Get(void)
return tstate;
}
static void
_swap_thread_states(_PyRuntimeState *runtime,
PyThreadState *oldts, PyThreadState *newts)
{
// XXX Do this only if oldts != NULL?
current_fast_clear(runtime);
if (oldts != NULL) {
// XXX assert(tstate_is_alive(oldts) && tstate_is_bound(oldts));
tstate_deactivate(oldts);
}
if (newts != NULL) {
// XXX assert(tstate_is_alive(newts));
assert(tstate_is_bound(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;
#endif
return oldts;
}
PyThreadState *
_PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
{
PyThreadState *oldts = current_fast_get(runtime);
if (oldts != NULL) {
_PyEval_ReleaseLock(oldts->interp, oldts);
_PyThreadState_Detach(oldts);
}
_swap_thread_states(runtime, oldts, newts);
if (newts != NULL) {
_PyEval_AcquireLock(newts);
_PyThreadState_Attach(newts);
}
return oldts;
}