From bfd316e750bc3040c08d1b5872e2de188e8c1e5f Mon Sep 17 00:00:00 2001 From: Victor Stinner Date: Wed, 20 Jan 2016 11:12:38 +0100 Subject: [PATCH] Add _PyThreadState_UncheckedGet() Issue #26154: Add a new private _PyThreadState_UncheckedGet() function which gets the current thread state, but don't call Py_FatalError() if it is NULL. Python 3.5.1 removed the _PyThreadState_Current symbol from the Python C API to no more expose complex and private atomic types. Atomic types depends on the compiler or can even depend on compiler options. The new function _PyThreadState_UncheckedGet() allows to get the variable value without having to care of the exact implementation of atomic types. Changes: * Replace direct usage of the _PyThreadState_Current variable with a call to _PyThreadState_UncheckedGet(). * In pystate.c, replace direct usage of the _PyThreadState_Current variable with the PyThreadState_GET() macro for readability. * Document also PyThreadState_Get() in pystate.h --- Include/pystate.h | 10 ++++++++++ Misc/NEWS | 7 +++++++ Modules/faulthandler.c | 2 +- Objects/dictobject.c | 6 ++---- Python/errors.c | 8 +------- Python/pystate.c | 33 ++++++++++++++++++++------------- Python/sysmodule.c | 2 +- 7 files changed, 42 insertions(+), 26 deletions(-) diff --git a/Include/pystate.h b/Include/pystate.h index 6000b81ae4..b50b16b39c 100644 --- a/Include/pystate.h +++ b/Include/pystate.h @@ -168,7 +168,17 @@ PyAPI_FUNC(void) PyThreadState_DeleteCurrent(void); PyAPI_FUNC(void) _PyGILState_Reinit(void); #endif +/* Return the current thread state. The global interpreter lock must be held. + * When the current thread state is NULL, this issues a fatal error (so that + * the caller needn't check for NULL). */ PyAPI_FUNC(PyThreadState *) PyThreadState_Get(void); + +#ifdef WITH_THREAD +/* Similar to PyThreadState_Get(), but don't issue a fatal error + * if it is NULL. */ +PyAPI_FUNC(PyThreadState *) _PyThreadState_UncheckedGet(void); +#endif + PyAPI_FUNC(PyThreadState *) PyThreadState_Swap(PyThreadState *); PyAPI_FUNC(PyObject *) PyThreadState_GetDict(void); PyAPI_FUNC(int) PyThreadState_SetAsyncExc(long, PyObject *); diff --git a/Misc/NEWS b/Misc/NEWS index 3fe9bd0d26..4baf757b5f 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -10,6 +10,13 @@ Release date: tba Core and Builtins ----------------- +- Issue #26154: Add a new private _PyThreadState_UncheckedGet() function to get + the current Python thread state, but don't issue a fatal error if it is NULL. + This new function must be used instead of accessing directly the + _PyThreadState_Current variable. The variable is no more exposed since + Python 3.5.1 to hide the exact implementation of atomic C types, to avoid + compiler issues. + - Issue #25731: Fix set and deleting __new__ on a class. - Issue #22995: [UPDATE] Comment out the one of the pickleability tests in diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c index 1ed22bf8bc..14384b5d1c 100644 --- a/Modules/faulthandler.c +++ b/Modules/faulthandler.c @@ -490,7 +490,7 @@ faulthandler_thread(void *unused) assert(st == PY_LOCK_FAILURE); /* get the thread holding the GIL, NULL if no thread hold the GIL */ - current = (PyThreadState*)_Py_atomic_load_relaxed(&_PyThreadState_Current); + current = _PyThreadState_UncheckedGet(); _Py_write_noraise(thread.fd, thread.header, (int)thread.header_len); diff --git a/Objects/dictobject.c b/Objects/dictobject.c index 9a30fa8897..8523511d3a 100644 --- a/Objects/dictobject.c +++ b/Objects/dictobject.c @@ -1064,8 +1064,7 @@ PyDict_GetItem(PyObject *op, PyObject *key) Let's just hope that no exception occurs then... This must be _PyThreadState_Current and not PyThreadState_GET() because in debug mode, the latter complains if tstate is NULL. */ - tstate = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + tstate = _PyThreadState_UncheckedGet(); if (tstate != NULL && tstate->curexc_type != NULL) { /* preserve the existing exception */ PyObject *err_type, *err_value, *err_tb; @@ -1102,8 +1101,7 @@ _PyDict_GetItem_KnownHash(PyObject *op, PyObject *key, Py_hash_t hash) Let's just hope that no exception occurs then... This must be _PyThreadState_Current and not PyThreadState_GET() because in debug mode, the latter complains if tstate is NULL. */ - tstate = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + tstate = _PyThreadState_UncheckedGet(); if (tstate != NULL && tstate->curexc_type != NULL) { /* preserve the existing exception */ PyObject *err_type, *err_value, *err_tb; diff --git a/Python/errors.c b/Python/errors.c index 7b67566727..5ff1e4c81a 100644 --- a/Python/errors.c +++ b/Python/errors.c @@ -152,13 +152,7 @@ PyErr_SetString(PyObject *exception, const char *string) PyObject * PyErr_Occurred(void) { - /* If there is no thread state, PyThreadState_GET calls - Py_FatalError, which calls PyErr_Occurred. To avoid the - resulting infinite loop, we inline PyThreadState_GET here and - treat no thread as no error. */ - PyThreadState *tstate = - ((PyThreadState*)_Py_atomic_load_relaxed(&_PyThreadState_Current)); - + PyThreadState *tstate = _PyThreadState_UncheckedGet(); return tstate == NULL ? NULL : tstate->curexc_type; } diff --git a/Python/pystate.c b/Python/pystate.c index 7e0267ae1d..83f15fd671 100644 --- a/Python/pystate.c +++ b/Python/pystate.c @@ -3,6 +3,12 @@ #include "Python.h" +#ifndef Py_BUILD_CORE +/* ensure that PyThreadState_GET() is a macro, not an alias to + * PyThreadState_Get() */ +# error "pystate.c must be compiled with Py_BUILD_CORE defined" +#endif + /* -------------------------------------------------------------------------- CAUTION @@ -423,7 +429,7 @@ tstate_delete_common(PyThreadState *tstate) void PyThreadState_Delete(PyThreadState *tstate) { - if (tstate == (PyThreadState*)_Py_atomic_load_relaxed(&_PyThreadState_Current)) + if (tstate == PyThreadState_GET()) Py_FatalError("PyThreadState_Delete: tstate is still current"); #ifdef WITH_THREAD if (autoInterpreterState && PyThread_get_key_value(autoTLSkey) == tstate) @@ -437,8 +443,7 @@ PyThreadState_Delete(PyThreadState *tstate) void PyThreadState_DeleteCurrent() { - PyThreadState *tstate = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + PyThreadState *tstate = PyThreadState_GET(); if (tstate == NULL) Py_FatalError( "PyThreadState_DeleteCurrent: no current tstate"); @@ -488,11 +493,17 @@ _PyThreadState_DeleteExcept(PyThreadState *tstate) } +PyThreadState * +_PyThreadState_UncheckedGet(void) +{ + return PyThreadState_GET(); +} + + PyThreadState * PyThreadState_Get(void) { - PyThreadState *tstate = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + PyThreadState *tstate = PyThreadState_GET(); if (tstate == NULL) Py_FatalError("PyThreadState_Get: no current thread"); @@ -503,8 +514,7 @@ PyThreadState_Get(void) PyThreadState * PyThreadState_Swap(PyThreadState *newts) { - PyThreadState *oldts = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + PyThreadState *oldts = PyThreadState_GET(); _Py_atomic_store_relaxed(&_PyThreadState_Current, newts); /* It should not be possible for more than one thread state @@ -535,8 +545,7 @@ PyThreadState_Swap(PyThreadState *newts) PyObject * PyThreadState_GetDict(void) { - PyThreadState *tstate = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + PyThreadState *tstate = PyThreadState_GET(); if (tstate == NULL) return NULL; @@ -682,7 +691,7 @@ PyThreadState_IsCurrent(PyThreadState *tstate) { /* Must be the tstate for this thread */ assert(PyGILState_GetThisThreadState()==tstate); - return tstate == (PyThreadState*)_Py_atomic_load_relaxed(&_PyThreadState_Current); + return tstate == PyThreadState_GET(); } /* Internal initialization/finalization functions called by @@ -774,9 +783,7 @@ PyGILState_GetThisThreadState(void) int PyGILState_Check(void) { - /* can't use PyThreadState_Get() since it will assert that it has the GIL */ - PyThreadState *tstate = (PyThreadState*)_Py_atomic_load_relaxed( - &_PyThreadState_Current); + PyThreadState *tstate = PyThreadState_GET(); return tstate && (tstate == PyGILState_GetThisThreadState()); } diff --git a/Python/sysmodule.c b/Python/sysmodule.c index 334f5d0c8e..8d7e05a465 100644 --- a/Python/sysmodule.c +++ b/Python/sysmodule.c @@ -1397,7 +1397,7 @@ error: Py_XDECREF(name); Py_XDECREF(value); /* No return value, therefore clear error state if possible */ - if (_Py_atomic_load_relaxed(&_PyThreadState_Current)) + if (_PyThreadState_UncheckedGet()) PyErr_Clear(); } -- 2.40.0