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/* -*- indent-tabs-mode: nil; tab-width: 4; -*- */ /* Format with: * clang-format -i --style=file src/greenlet/greenlet.c * * * Fix missing braces with: * clang-tidy src/greenlet/greenlet.c -fix -checks="readability-braces-around-statements" */ #define GREENLET_MODULE #include "greenlet.h" #include "structmember.h" #ifdef __clang__ # pragma clang diagnostic push # pragma clang diagnostic ignored "-Wunused-parameter" # pragma clang diagnostic ignored "-Wmissing-field-initializers" #endif /*********************************************************** A PyGreenlet is a range of C stack addresses that must be saved and restored in such a way that the full range of the stack contains valid data when we switch to it. Stack layout for a greenlet: | ^^^ | | older data | | | stack_stop . |_______________| . | | . | greenlet data | . | in stack | . * |_______________| . . _____________ stack_copy + stack_saved . | | | | . | data | |greenlet data| . | unrelated | | saved | . | to | | in heap | stack_start . | this | . . |_____________| stack_copy | greenlet | | | | newer data | | vvv | Note that a greenlet's stack data is typically partly at its correct place in the stack, and partly saved away in the heap, but always in the above configuration: two blocks, the more recent one in the heap and the older one still in the stack (either block may be empty). Greenlets are chained: each points to the previous greenlet, which is the one that owns the data currently in the C stack above my stack_stop. The currently running greenlet is the first element of this chain. The main (initial) greenlet is the last one. Greenlets whose stack is entirely in the heap can be skipped from the chain. The chain is not related to execution order, but only to the order in which bits of C stack happen to belong to greenlets at a particular point in time. The main greenlet doesn't have a stack_stop: it is responsible for the complete rest of the C stack, and we don't know where it begins. We use (char*) -1, the largest possible address. States: stack_stop == NULL && stack_start == NULL: did not start yet stack_stop != NULL && stack_start == NULL: already finished stack_stop != NULL && stack_start != NULL: active The running greenlet's stack_start is undefined but not NULL. ***********************************************************/ /*** global state ***/ /* In the presence of multithreading, this is a bit tricky: - ts_current always store a reference to a greenlet, but it is not really the current greenlet after a thread switch occurred. - each *running* greenlet uses its run_info field to know which thread it is attached to. A greenlet can only run in the thread where it was created. This run_info is a ref to tstate->dict. - the thread state dict is used to save and restore ts_current, using the dictionary key 'ts_curkey'. */ extern PyTypeObject PyGreenlet_Type; #if PY_VERSION_HEX >= 0x030700A3 # define GREENLET_PY37 1 #else # define GREENLET_PY37 0 #endif #if PY_VERSION_HEX >= 0x30A00B1 /* Python 3.10 beta 1 changed tstate->use_tracing to a nested cframe member. See https://github.com/python/cpython/pull/25276 We have to save and restore this as well. */ #define TSTATE_USE_TRACING(tstate) (tstate->cframe->use_tracing) #define GREENLET_USE_CFRAME 1 #else #define TSTATE_USE_TRACING(tstate) (tstate->use_tracing) #define GREENLET_USE_CFRAME 0 #endif #ifndef Py_SET_REFCNT /* Py_REFCNT and Py_SIZE macros are converted to functions https://bugs.python.org/issue39573 */ # define Py_SET_REFCNT(obj, refcnt) Py_REFCNT(obj) = (refcnt) #endif #ifndef _Py_DEC_REFTOTAL /* _Py_DEC_REFTOTAL macro has been removed from Python 3.9 by: https://github.com/python/cpython/commit/49932fec62c616ec88da52642339d83ae719e924 */ # ifdef Py_REF_DEBUG # define _Py_DEC_REFTOTAL _Py_RefTotal-- # else # define _Py_DEC_REFTOTAL # endif #endif /* Weak reference to the switching-to greenlet during the slp switch */ static PyGreenlet* volatile ts_target = NULL; /* Strong reference to the switching from greenlet after the switch */ static PyGreenlet* volatile ts_origin = NULL; /* Strong reference to the current greenlet in this thread state */ static PyGreenlet* volatile ts_current = NULL; /* NULL if error, otherwise args tuple to pass around during slp switch */ static PyObject* volatile ts_passaround_args = NULL; static PyObject* volatile ts_passaround_kwargs = NULL; /* Used internally in ``g_switchstack()`` */ #if GREENLET_USE_CFRAME static int volatile ts__g_switchstack_use_tracing = 0; #endif /***********************************************************/ /* Thread-aware routines, switching global variables when needed */ #define STATE_OK \ (ts_current->run_info == PyThreadState_GET()->dict || \ !green_updatecurrent()) static PyObject* ts_curkey; static PyObject* ts_delkey; static PyObject* ts_tracekey; static PyObject* ts_event_switch; static PyObject* ts_event_throw; static PyObject* PyExc_GreenletError; static PyObject* PyExc_GreenletExit; static PyObject* ts_empty_tuple; static PyObject* ts_empty_dict; #define GREENLET_GC_FLAGS Py_TPFLAGS_HAVE_GC #define GREENLET_tp_alloc PyType_GenericAlloc #define GREENLET_tp_free PyObject_GC_Del #define GREENLET_tp_traverse green_traverse #define GREENLET_tp_clear green_clear #define GREENLET_tp_is_gc green_is_gc static void green_clear_exc(PyGreenlet* g) { #if GREENLET_PY37 g->exc_info = NULL; g->exc_state.exc_type = NULL; g->exc_state.exc_value = NULL; g->exc_state.exc_traceback = NULL; g->exc_state.previous_item = NULL; #else g->exc_type = NULL; g->exc_value = NULL; g->exc_traceback = NULL; #endif } static PyGreenlet* green_create_main(void) { PyGreenlet* gmain; PyObject* dict = PyThreadState_GetDict(); if (dict == NULL) { if (!PyErr_Occurred()) { PyErr_NoMemory(); } return NULL; } /* create the main greenlet for this thread */ gmain = (PyGreenlet*)PyType_GenericAlloc(&PyGreenlet_Type, 0); if (gmain == NULL) { return NULL; } gmain->stack_start = (char*)1; gmain->stack_stop = (char*)-1; /* GetDict() returns a borrowed reference. Make it strong. */ gmain->run_info = dict; Py_INCREF(dict); return gmain; } static int green_updatecurrent(void) { PyObject *exc, *val, *tb; PyThreadState* tstate; PyGreenlet* current; PyGreenlet* previous; PyObject* deleteme; green_updatecurrent_restart: /* save current exception */ PyErr_Fetch(&exc, &val, &tb); /* get ts_current from the active tstate */ tstate = PyThreadState_GET(); if (tstate->dict && (current = (PyGreenlet*)PyDict_GetItem(tstate->dict, ts_curkey))) { /* found -- remove it, to avoid keeping a ref */ Py_INCREF(current); PyDict_DelItem(tstate->dict, ts_curkey); } else { /* first time we see this tstate */ current = green_create_main(); if (current == NULL) { Py_XDECREF(exc); Py_XDECREF(val); Py_XDECREF(tb); return -1; } } assert(current->run_info == tstate->dict); green_updatecurrent_retry: /* update ts_current as soon as possible, in case of nested switches */ Py_INCREF(current); previous = ts_current; ts_current = current; /* save ts_current as the current greenlet of its own thread */ if (PyDict_SetItem(previous->run_info, ts_curkey, (PyObject*)previous)) { P