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gh-109549: Add new states to PyThreadState to support PEP 703 (gh-109915)
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.
This commit is contained in:
Sam Gross
GitHub
parent
9eb2489266
commit
6e97a9647a
6 changed files with 141 additions and 92 deletions
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@ -462,24 +462,22 @@ PyStatus
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_PyEval_InitGIL(PyThreadState *tstate, int own_gil)
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{
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assert(tstate->interp->ceval.gil == NULL);
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int locked;
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if (!own_gil) {
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/* The interpreter will share the main interpreter's instead. */
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PyInterpreterState *main_interp = _PyInterpreterState_Main();
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assert(tstate->interp != main_interp);
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struct _gil_runtime_state *gil = main_interp->ceval.gil;
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init_shared_gil(tstate->interp, gil);
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locked = current_thread_holds_gil(gil, tstate);
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assert(!current_thread_holds_gil(gil, tstate));
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}
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else {
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PyThread_init_thread();
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init_own_gil(tstate->interp, &tstate->interp->_gil);
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locked = 0;
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}
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if (!locked) {
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take_gil(tstate);
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}
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// Lock the GIL and mark the current thread as attached.
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_PyThreadState_Attach(tstate);
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return _PyStatus_OK();
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}
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@ -569,24 +567,14 @@ void
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PyEval_AcquireThread(PyThreadState *tstate)
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{
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_Py_EnsureTstateNotNULL(tstate);
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take_gil(tstate);
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if (_PyThreadState_SwapNoGIL(tstate) != NULL) {
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Py_FatalError("non-NULL old thread state");
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}
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_PyThreadState_Attach(tstate);
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}
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void
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PyEval_ReleaseThread(PyThreadState *tstate)
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{
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assert(_PyThreadState_CheckConsistency(tstate));
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PyThreadState *new_tstate = _PyThreadState_SwapNoGIL(NULL);
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if (new_tstate != tstate) {
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Py_FatalError("wrong thread state");
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}
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drop_gil(tstate->interp, tstate);
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_PyThreadState_Detach(tstate);
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}
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#ifdef HAVE_FORK
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@ -629,11 +617,8 @@ _PyEval_SignalAsyncExc(PyInterpreterState *interp)
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PyThreadState *
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PyEval_SaveThread(void)
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{
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PyThreadState *tstate = _PyThreadState_SwapNoGIL(NULL);
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_Py_EnsureTstateNotNULL(tstate);
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assert(gil_created(tstate->interp->ceval.gil));
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drop_gil(tstate->interp, tstate);
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PyThreadState *tstate = _PyThreadState_GET();
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_PyThreadState_Detach(tstate);
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return tstate;
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}
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@ -641,10 +626,7 @@ void
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PyEval_RestoreThread(PyThreadState *tstate)
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{
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_Py_EnsureTstateNotNULL(tstate);
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take_gil(tstate);
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_PyThreadState_SwapNoGIL(tstate);
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_PyThreadState_Attach(tstate);
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}
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@ -1015,18 +997,11 @@ _Py_HandlePending(PyThreadState *tstate)
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/* GIL drop request */
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if (_Py_eval_breaker_bit_is_set(interp, _PY_GIL_DROP_REQUEST_BIT)) {
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/* Give another thread a chance */
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if (_PyThreadState_SwapNoGIL(NULL) != tstate) {
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Py_FatalError("tstate mix-up");
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}
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drop_gil(interp, tstate);
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_PyThreadState_Detach(tstate);
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/* Other threads may run now */
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take_gil(tstate);
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if (_PyThreadState_SwapNoGIL(tstate) != NULL) {
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Py_FatalError("orphan tstate");
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}
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_PyThreadState_Attach(tstate);
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}
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/* Check for asynchronous exception. */
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@ -661,8 +661,6 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
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return _PyStatus_ERR("can't make first thread");
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}
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_PyThreadState_Bind(tstate);
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// XXX For now we do this before the GIL is created.
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(void) _PyThreadState_SwapNoGIL(tstate);
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status = init_interp_create_gil(tstate, config.gil);
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if (_PyStatus_EXCEPTION(status)) {
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@ -2060,8 +2058,7 @@ new_interpreter(PyThreadState **tstate_p, const PyInterpreterConfig *config)
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}
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_PyThreadState_Bind(tstate);
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// XXX For now we do this before the GIL is created.
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PyThreadState *save_tstate = _PyThreadState_SwapNoGIL(tstate);
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PyThreadState *save_tstate = _PyThreadState_GET();
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int has_gil = 0;
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/* From this point until the init_interp_create_gil() call,
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@ -2073,7 +2070,7 @@ new_interpreter(PyThreadState **tstate_p, const PyInterpreterConfig *config)
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const PyConfig *src_config;
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if (save_tstate != NULL) {
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// XXX Might new_interpreter() have been called without the GIL held?
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_PyEval_ReleaseLock(save_tstate->interp, save_tstate);
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_PyThreadState_Detach(save_tstate);
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src_config = _PyInterpreterState_GetConfig(save_tstate->interp);
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}
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else
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@ -2120,12 +2117,11 @@ error:
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*tstate_p = NULL;
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/* Oops, it didn't work. Undo it all. */
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PyErr_PrintEx(0);
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if (has_gil) {
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PyThreadState_Swap(save_tstate);
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_PyThreadState_Detach(tstate);
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}
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else {
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_PyThreadState_SwapNoGIL(save_tstate);
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if (save_tstate != NULL) {
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_PyThreadState_Attach(save_tstate);
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}
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PyThreadState_Clear(tstate);
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PyThreadState_Delete(tstate);
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125
Python/pystate.c
125
Python/pystate.c
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@ -998,6 +998,7 @@ _PyInterpreterState_Clear(PyThreadState *tstate)
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static inline void tstate_deactivate(PyThreadState *tstate);
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static void tstate_set_detached(PyThreadState *tstate);
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static void zapthreads(PyInterpreterState *interp);
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void
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@ -1011,9 +1012,7 @@ PyInterpreterState_Delete(PyInterpreterState *interp)
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PyThreadState *tcur = current_fast_get(runtime);
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if (tcur != NULL && interp == tcur->interp) {
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/* Unset current thread. After this, many C API calls become crashy. */
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current_fast_clear(runtime);
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tstate_deactivate(tcur);
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_PyEval_ReleaseLock(interp, NULL);
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_PyThreadState_Detach(tcur);
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}
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zapthreads(interp);
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@ -1651,6 +1650,7 @@ static void
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tstate_delete_common(PyThreadState *tstate)
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{
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assert(tstate->_status.cleared && !tstate->_status.finalized);
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assert(tstate->state != _Py_THREAD_ATTACHED);
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PyInterpreterState *interp = tstate->interp;
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if (interp == NULL) {
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@ -1711,6 +1711,7 @@ void
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_PyThreadState_DeleteCurrent(PyThreadState *tstate)
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{
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_Py_EnsureTstateNotNULL(tstate);
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tstate_set_detached(tstate);
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tstate_delete_common(tstate);
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current_fast_clear(tstate->interp->runtime);
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_PyEval_ReleaseLock(tstate->interp, NULL);
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@ -1867,6 +1868,79 @@ tstate_deactivate(PyThreadState *tstate)
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// It will still be used in PyGILState_Ensure().
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}
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static int
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tstate_try_attach(PyThreadState *tstate)
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{
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#ifdef Py_NOGIL
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int expected = _Py_THREAD_DETACHED;
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if (_Py_atomic_compare_exchange_int(
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&tstate->state,
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&expected,
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_Py_THREAD_ATTACHED)) {
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return 1;
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}
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return 0;
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#else
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assert(tstate->state == _Py_THREAD_DETACHED);
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tstate->state = _Py_THREAD_ATTACHED;
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return 1;
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#endif
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}
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static void
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tstate_set_detached(PyThreadState *tstate)
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{
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assert(tstate->state == _Py_THREAD_ATTACHED);
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#ifdef Py_NOGIL
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_Py_atomic_store_int(&tstate->state, _Py_THREAD_DETACHED);
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#else
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tstate->state = _Py_THREAD_DETACHED;
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#endif
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}
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void
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_PyThreadState_Attach(PyThreadState *tstate)
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{
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#if defined(Py_DEBUG)
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// This is called from PyEval_RestoreThread(). Similar
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// to it, we need to ensure errno doesn't change.
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int err = errno;
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#endif
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_Py_EnsureTstateNotNULL(tstate);
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if (current_fast_get(&_PyRuntime) != NULL) {
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Py_FatalError("non-NULL old thread state");
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}
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_PyEval_AcquireLock(tstate);
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// XXX assert(tstate_is_alive(tstate));
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current_fast_set(&_PyRuntime, tstate);
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tstate_activate(tstate);
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if (!tstate_try_attach(tstate)) {
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// TODO: Once stop-the-world GC is implemented for --disable-gil builds
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// this will need to wait until the GC completes. For now, this case
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// should never happen.
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Py_FatalError("thread attach failed");
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}
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#if defined(Py_DEBUG)
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errno = err;
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#endif
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}
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void
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_PyThreadState_Detach(PyThreadState *tstate)
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{
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// XXX assert(tstate_is_alive(tstate) && tstate_is_bound(tstate));
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assert(tstate->state == _Py_THREAD_ATTACHED);
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assert(tstate == current_fast_get(&_PyRuntime));
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tstate_set_detached(tstate);
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tstate_deactivate(tstate);
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current_fast_clear(&_PyRuntime);
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_PyEval_ReleaseLock(tstate->interp, tstate);
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}
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//----------
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// other API
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@ -1939,56 +2013,15 @@ PyThreadState_Get(void)
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return tstate;
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}
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static void
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_swap_thread_states(_PyRuntimeState *runtime,
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PyThreadState *oldts, PyThreadState *newts)
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{
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// XXX Do this only if oldts != NULL?
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current_fast_clear(runtime);
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if (oldts != NULL) {
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// XXX assert(tstate_is_alive(oldts) && tstate_is_bound(oldts));
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tstate_deactivate(oldts);
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}
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if (newts != NULL) {
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// XXX assert(tstate_is_alive(newts));
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assert(tstate_is_bound(newts));
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current_fast_set(runtime, newts);
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tstate_activate(newts);
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}
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}
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PyThreadState *
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_PyThreadState_SwapNoGIL(PyThreadState *newts)
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{
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#if defined(Py_DEBUG)
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/* This can be called from PyEval_RestoreThread(). Similar
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to it, we need to ensure errno doesn't change.
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*/
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int err = errno;
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#endif
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PyThreadState *oldts = current_fast_get(&_PyRuntime);
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_swap_thread_states(&_PyRuntime, oldts, newts);
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#if defined(Py_DEBUG)
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errno = err;
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#endif
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return oldts;
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}
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PyThreadState *
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_PyThreadState_Swap(_PyRuntimeState *runtime, PyThreadState *newts)
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{
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PyThreadState *oldts = current_fast_get(runtime);
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if (oldts != NULL) {
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_PyEval_ReleaseLock(oldts->interp, oldts);
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_PyThreadState_Detach(oldts);
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}
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_swap_thread_states(runtime, oldts, newts);
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if (newts != NULL) {
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_PyEval_AcquireLock(newts);
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_PyThreadState_Attach(newts);
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}
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return oldts;
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}
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