Current File : //opt/hc_python/lib64/python3.8/site-packages/greenlet/TGreenlet.cpp
/* -*- indent-tabs-mode: nil; tab-width: 4; -*- */
/**
* Implementation of greenlet::Greenlet.
*
* 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"
*/
#ifndef TGREENLET_CPP
#define TGREENLET_CPP
#include "greenlet_internal.hpp"
#include "TGreenlet.hpp"
#include "TGreenletGlobals.cpp"
#include "TThreadStateDestroy.cpp"
namespace greenlet {
Greenlet::Greenlet(PyGreenlet* p)
: Greenlet(p, StackState())
{
}
Greenlet::Greenlet(PyGreenlet* p, const StackState& initial_stack)
: _self(p), stack_state(initial_stack)
{
assert(p->pimpl == nullptr);
p->pimpl = this;
}
Greenlet::~Greenlet()
{
// XXX: Can't do this. tp_clear is a virtual function, and by the
// time we're here, we've sliced off our child classes.
//this->tp_clear();
this->_self->pimpl = nullptr;
}
bool
Greenlet::force_slp_switch_error() const noexcept
{
return false;
}
void
Greenlet::release_args()
{
this->switch_args.CLEAR();
}
/**
* CAUTION: This will allocate memory and may trigger garbage
* collection and arbitrary Python code.
*/
OwnedObject
Greenlet::throw_GreenletExit_during_dealloc(const ThreadState& UNUSED(current_thread_state))
{
// If we're killed because we lost all references in the
// middle of a switch, that's ok. Don't reset the args/kwargs,
// we still want to pass them to the parent.
PyErr_SetString(mod_globs->PyExc_GreenletExit,
"Killing the greenlet because all references have vanished.");
// To get here it had to have run before
return this->g_switch();
}
inline void
Greenlet::slp_restore_state() noexcept
{
#ifdef SLP_BEFORE_RESTORE_STATE
SLP_BEFORE_RESTORE_STATE();
#endif
this->stack_state.copy_heap_to_stack(
this->thread_state()->borrow_current()->stack_state);
}
inline int
Greenlet::slp_save_state(char *const stackref) noexcept
{
// XXX: This used to happen in the middle, before saving, but
// after finding the next owner. Does that matter? This is
// only defined for Sparc/GCC where it flushes register
// windows to the stack (I think)
#ifdef SLP_BEFORE_SAVE_STATE
SLP_BEFORE_SAVE_STATE();
#endif
return this->stack_state.copy_stack_to_heap(stackref,
this->thread_state()->borrow_current()->stack_state);
}
/**
* CAUTION: This will allocate memory and may trigger garbage
* collection and arbitrary Python code.
*/
OwnedObject
Greenlet::on_switchstack_or_initialstub_failure(
Greenlet* target,
const Greenlet::switchstack_result_t& err,
const bool target_was_me,
const bool was_initial_stub)
{
// If we get here, either g_initialstub()
// failed, or g_switchstack() failed. Either one of those
// cases SHOULD leave us in the original greenlet with a valid stack.
if (!PyErr_Occurred()) {
PyErr_SetString(
PyExc_SystemError,
was_initial_stub
? "Failed to switch stacks into a greenlet for the first time."
: "Failed to switch stacks into a running greenlet.");
}
this->release_args();
if (target && !target_was_me) {
target->murder_in_place();
}
assert(!err.the_new_current_greenlet);
assert(!err.origin_greenlet);
return OwnedObject();
}
OwnedGreenlet
Greenlet::g_switchstack_success() noexcept
{
PyThreadState* tstate = PyThreadState_GET();
// restore the saved state
this->python_state >> tstate;
this->exception_state >> tstate;
// The thread state hasn't been changed yet.
ThreadState* thread_state = this->thread_state();
OwnedGreenlet result(thread_state->get_current());
thread_state->set_current(this->self());
//assert(thread_state->borrow_current().borrow() == this->_self);
return result;
}
Greenlet::switchstack_result_t
Greenlet::g_switchstack(void)
{
// if any of these assertions fail, it's likely because we
// switched away and tried to switch back to us. Early stages of
// switching are not reentrant because we re-use ``this->args()``.
// Switching away would happen if we trigger a garbage collection
// (by just using some Python APIs that happen to allocate Python
// objects) and some garbage had weakref callbacks or __del__ that
// switches (people don't write code like that by hand, but with
// gevent it's possible without realizing it)
assert(this->args() || PyErr_Occurred());
{ /* save state */
if (this->thread_state()->is_current(this->self())) {
// Hmm, nothing to do.
// TODO: Does this bypass trace events that are
// important?
return switchstack_result_t(0,
this, this->thread_state()->borrow_current());
}
BorrowedGreenlet current = this->thread_state()->borrow_current();
PyThreadState* tstate = PyThreadState_GET();
current->python_state << tstate;
current->exception_state << tstate;
this->python_state.will_switch_from(tstate);
switching_thread_state = this;
current->expose_frames();
}
assert(this->args() || PyErr_Occurred());
// If this is the first switch into a greenlet, this will
// return twice, once with 1 in the new greenlet, once with 0
// in the origin.
int err;
if (this->force_slp_switch_error()) {
err = -1;
}
else {
err = slp_switch();
}
if (err < 0) { /* error */
// Tested by
// test_greenlet.TestBrokenGreenlets.test_failed_to_slp_switch_into_running
//
// It's not clear if it's worth trying to clean up and
// continue here. Failing to switch stacks is a big deal which
// may not be recoverable (who knows what state the stack is in).
// Also, we've stolen references in preparation for calling
// ``g_switchstack_success()`` and we don't have a clean
// mechanism for backing that all out.
Py_FatalError("greenlet: Failed low-level slp_switch(). The stack is probably corrupt.");
}
// No stack-based variables are valid anymore.
// But the global is volatile so we can reload it without the
// compiler caching it from earlier.
Greenlet* greenlet_that_switched_in = switching_thread_state; // aka this
switching_thread_state = nullptr;
// except that no stack variables are valid, we would:
// assert(this == greenlet_that_switched_in);
// switchstack success is where we restore the exception state,
// etc. It returns the origin greenlet because its convenient.
OwnedGreenlet origin = greenlet_that_switched_in->g_switchstack_success();
assert(greenlet_that_switched_in->args() || PyErr_Occurred());
return switchstack_result_t(err, greenlet_that_switched_in, origin);
}
inline void
Greenlet::check_switch_allowed() const
{
// TODO: Make this take a parameter of the current greenlet,
// or current main greenlet, to make the check for
// cross-thread switching cheaper. Surely somewhere up the
// call stack we've already accessed the thread local variable.
// We expect to always have a main greenlet now; accessing the thread state
// created it. However, if we get here and cleanup has already
// begun because we're a greenlet that was running in a
// (now dead) thread, these invariants will not hold true. In
// fact, accessing `this->thread_state` may not even be possible.
// If the thread this greenlet was running in is dead,
// we'll still have a reference to a main greenlet, but the
// thread state pointer we have is bogus.
// TODO: Give the objects an API to determine if they belong
// to a dead thread.
const BorrowedMainGreenlet main_greenlet = this->find_main_greenlet_in_lineage();
if (!main_greenlet) {
throw PyErrOccurred(mod_globs->PyExc_GreenletError,
"cannot switch to a garbage collected greenlet");
}
if (!main_greenlet->thread_state()) {
throw PyErrOccurred(mod_globs->PyExc_GreenletError,
"cannot switch to a different thread (which happens to have exited)");
}
// The main greenlet we found was from the .parent lineage.
// That may or may not have any relationship to the main
// greenlet of the running thread. We can't actually access
// our this->thread_state members to try to check that,
// because it could be in the process of getting destroyed,
// but setting the main_greenlet->thread_state member to NULL
// may not be visible yet. So we need to check against the
// current thread state (once the cheaper checks are out of
// the way)
const BorrowedMainGreenlet current_main_greenlet = GET_THREAD_STATE().state().borrow_main_greenlet();
if (
// lineage main greenlet is not this thread's greenlet
current_main_greenlet != main_greenlet
|| (
// atteched to some thread
this->main_greenlet()
// XXX: Same condition as above. Was this supposed to be
// this->main_greenlet()?
&& current_main_greenlet != main_greenlet)
// switching into a known dead thread (XXX: which, if we get here,
// is bad, because we just accessed the thread state, which is
// gone!)
|| (!current_main_greenlet->thread_state())) {
// CAUTION: This may trigger memory allocations, gc, and
// arbitrary Python code.
throw PyErrOccurred(
mod_globs->PyExc_GreenletError,
"Cannot switch to a different thread\n\tCurrent: %R\n\tExpected: %R",
current_main_greenlet, main_greenlet);
}
}
const OwnedObject
Greenlet::context() const
{
using greenlet::PythonStateContext;
OwnedObject result;
if (this->is_currently_running_in_some_thread()) {
/* Currently running greenlet: context is stored in the thread state,
not the greenlet object. */
if (GET_THREAD_STATE().state().is_current(this->self())) {
result = PythonStateContext::context(PyThreadState_GET());
}
else {
throw ValueError(
"cannot get context of a "
"greenlet that is running in a different thread");
}
}
else {
/* Greenlet is not running: just return context. */
result = this->python_state.context();
}
if (!result) {
result = OwnedObject::None();
}
return result;
}
void
Greenlet::context(BorrowedObject given)
{
using greenlet::PythonStateContext;
if (!given) {
throw AttributeError("can't delete context attribute");
}
if (given.is_None()) {
/* "Empty context" is stored as NULL, not None. */
given = nullptr;
}
//checks type, incrs refcnt
greenlet::refs::OwnedContext context(given);
PyThreadState* tstate = PyThreadState_GET();
if (this->is_currently_running_in_some_thread()) {
if (!GET_THREAD_STATE().state().is_current(this->self())) {
throw ValueError("cannot set context of a greenlet"
" that is running in a different thread");
}
/* Currently running greenlet: context is stored in the thread state,
not the greenlet object. */
OwnedObject octx = OwnedObject::consuming(PythonStateContext::context(tstate));
PythonStateContext::context(tstate, context.relinquish_ownership());
}
else {
/* Greenlet is not running: just set context. Note that the
greenlet may be dead.*/
this->python_state.context() = context;
}
}
/**
* CAUTION: May invoke arbitrary Python code.
*
* Figure out what the result of ``greenlet.switch(arg, kwargs)``
* should be and transfers ownership of it to the left-hand-side.
*
* If switch() was just passed an arg tuple, then we'll just return that.
* If only keyword arguments were passed, then we'll pass the keyword
* argument dict. Otherwise, we'll create a tuple of (args, kwargs) and
* return both.
*
* CAUTION: This may allocate a new tuple object, which may
* cause the Python garbage collector to run, which in turn may
* run arbitrary Python code that switches.
*/
OwnedObject& operator<<=(OwnedObject& lhs, greenlet::SwitchingArgs& rhs) noexcept
{
// Because this may invoke arbitrary Python code, which could
// result in switching back to us, we need to get the
// arguments locally on the stack.
assert(rhs);
OwnedObject args = rhs.args();
OwnedObject kwargs = rhs.kwargs();
rhs.CLEAR();
// We shouldn't be called twice for the same switch.
assert(args || kwargs);
assert(!rhs);
if (!kwargs) {
lhs = args;
}
else if (!PyDict_Size(kwargs.borrow())) {
lhs = args;
}
else if (!PySequence_Length(args.borrow())) {
lhs = kwargs;
}
else {
// PyTuple_Pack allocates memory, may GC, may run arbitrary
// Python code.
lhs = OwnedObject::consuming(PyTuple_Pack(2, args.borrow(), kwargs.borrow()));
}
return lhs;
}
static OwnedObject
g_handle_exit(const OwnedObject& greenlet_result)
{
if (!greenlet_result && mod_globs->PyExc_GreenletExit.PyExceptionMatches()) {
/* catch and ignore GreenletExit */
PyErrFetchParam val;
PyErr_Fetch(PyErrFetchParam(), val, PyErrFetchParam());
if (!val) {
return OwnedObject::None();
}
return OwnedObject(val);
}
if (greenlet_result) {
// package the result into a 1-tuple
// PyTuple_Pack increments the reference of its arguments,
// so we always need to decref the greenlet result;
// the owner will do that.
return OwnedObject::consuming(PyTuple_Pack(1, greenlet_result.borrow()));
}
return OwnedObject();
}
/**
* May run arbitrary Python code.
*/
OwnedObject
Greenlet::g_switch_finish(const switchstack_result_t& err)
{
assert(err.the_new_current_greenlet == this);
ThreadState& state = *this->thread_state();
// Because calling the trace function could do arbitrary things,
// including switching away from this greenlet and then maybe
// switching back, we need to capture the arguments now so that
// they don't change.
OwnedObject result;
if (this->args()) {
result <<= this->args();
}
else {
assert(PyErr_Occurred());
}
assert(!this->args());
try {
// Our only caller handles the bad error case
assert(err.status >= 0);
assert(state.borrow_current() == this->self());
if (OwnedObject tracefunc = state.get_tracefunc()) {
assert(result || PyErr_Occurred());
g_calltrace(tracefunc,
result ? mod_globs->event_switch : mod_globs->event_throw,
err.origin_greenlet,
this->self());
}
// The above could have invoked arbitrary Python code, but
// it couldn't switch back to this object and *also*
// throw an exception, so the args won't have changed.
if (PyErr_Occurred()) {
// We get here if we fell of the end of the run() function
// raising an exception. The switch itself was
// successful, but the function raised.
// valgrind reports that memory allocated here can still
// be reached after a test run.
throw PyErrOccurred::from_current();
}
return result;
}
catch (const PyErrOccurred&) {
/* Turn switch errors into switch throws */
/* Turn trace errors into switch throws */
this->release_args();
throw;
}
}
void
Greenlet::g_calltrace(const OwnedObject& tracefunc,
const greenlet::refs::ImmortalEventName& event,
const BorrowedGreenlet& origin,
const BorrowedGreenlet& target)
{
PyErrPieces saved_exc;
try {
TracingGuard tracing_guard;
// TODO: We have saved the active exception (if any) that's
// about to be raised. In the 'throw' case, we could provide
// the exception to the tracefunction, which seems very helpful.
tracing_guard.CallTraceFunction(tracefunc, event, origin, target);
}
catch (const PyErrOccurred&) {
// In case of exceptions trace function is removed,
// and any existing exception is replaced with the tracing
// exception.
GET_THREAD_STATE().state().set_tracefunc(Py_None);
throw;
}
saved_exc.PyErrRestore();
assert(
(event == mod_globs->event_throw && PyErr_Occurred())
|| (event == mod_globs->event_switch && !PyErr_Occurred())
);
}
void
Greenlet::murder_in_place()
{
if (this->active()) {
assert(!this->is_currently_running_in_some_thread());
this->deactivate_and_free();
}
}
inline void
Greenlet::deactivate_and_free()
{
if (!this->active()) {
return;
}
// Throw away any saved stack.
this->stack_state = StackState();
assert(!this->stack_state.active());
// Throw away any Python references.
// We're holding a borrowed reference to the last
// frame we executed. Since we borrowed it, the
// normal traversal, clear, and dealloc functions
// ignore it, meaning it leaks. (The thread state
// object can't find it to clear it when that's
// deallocated either, because by definition if we
// got an object on this list, it wasn't
// running and the thread state doesn't have
// this frame.)
// So here, we *do* clear it.
this->python_state.tp_clear(true);
}
bool
Greenlet::belongs_to_thread(const ThreadState* thread_state) const
{
if (!this->thread_state() // not running anywhere, or thread
// exited
|| !thread_state) { // same, or there is no thread state.
return false;
}
return true;
}
void
Greenlet::deallocing_greenlet_in_thread(const ThreadState* current_thread_state)
{
/* Cannot raise an exception to kill the greenlet if
it is not running in the same thread! */
if (this->belongs_to_thread(current_thread_state)) {
assert(current_thread_state);
// To get here it had to have run before
/* Send the greenlet a GreenletExit exception. */
// We don't care about the return value, only whether an
// exception happened.
this->throw_GreenletExit_during_dealloc(*current_thread_state);
return;
}
// Not the same thread! Temporarily save the greenlet
// into its thread's deleteme list, *if* it exists.
// If that thread has already exited, and processed its pending
// cleanup, we'll never be able to clean everything up: we won't
// be able to raise an exception.
// That's mostly OK! Since we can't add it to a list, our refcount
// won't increase, and we'll go ahead with the DECREFs later.
ThreadState *const thread_state = this->thread_state();
if (thread_state) {
thread_state->delete_when_thread_running(this->self());
}
else {
// The thread is dead, we can't raise an exception.
// We need to make it look non-active, though, so that dealloc
// finishes killing it.
this->deactivate_and_free();
}
return;
}
int
Greenlet::tp_traverse(visitproc visit, void* arg)
{
int result;
if ((result = this->exception_state.tp_traverse(visit, arg)) != 0) {
return result;
}
//XXX: This is ugly. But so is handling everything having to do
//with the top frame.
bool visit_top_frame = this->was_running_in_dead_thread();
// When true, the thread is dead. Our implicit weak reference to the
// frame is now all that's left; we consider ourselves to
// strongly own it now.
if ((result = this->python_state.tp_traverse(visit, arg, visit_top_frame)) != 0) {
return result;
}
return 0;
}
int
Greenlet::tp_clear()
{
bool own_top_frame = this->was_running_in_dead_thread();
this->exception_state.tp_clear();
this->python_state.tp_clear(own_top_frame);
return 0;
}
bool Greenlet::is_currently_running_in_some_thread() const
{
return this->stack_state.active() && !this->python_state.top_frame();
}
#if GREENLET_PY312
void GREENLET_NOINLINE(Greenlet::expose_frames)()
{
if (!this->python_state.top_frame()) {
return;
}
_PyInterpreterFrame* last_complete_iframe = nullptr;
_PyInterpreterFrame* iframe = this->python_state.top_frame()->f_frame;
while (iframe) {
// We must make a copy before looking at the iframe contents,
// since iframe might point to a portion of the greenlet's C stack
// that was spilled when switching greenlets.
_PyInterpreterFrame iframe_copy;
this->stack_state.copy_from_stack(&iframe_copy, iframe, sizeof(*iframe));
if (!_PyFrame_IsIncomplete(&iframe_copy)) {
// If the iframe were OWNED_BY_CSTACK then it would always be
// incomplete. Since it's not incomplete, it's not on the C stack
// and we can access it through the original `iframe` pointer
// directly. This is important since GetFrameObject might
// lazily _create_ the frame object and we don't want the
// interpreter to lose track of it.
assert(iframe_copy.owner != FRAME_OWNED_BY_CSTACK);
// We really want to just write:
// PyFrameObject* frame = _PyFrame_GetFrameObject(iframe);
// but _PyFrame_GetFrameObject calls _PyFrame_MakeAndSetFrameObject
// which is not a visible symbol in libpython. The easiest
// way to get a public function to call it is using
// PyFrame_GetBack, which is defined as follows:
// assert(frame != NULL);
// assert(!_PyFrame_IsIncomplete(frame->f_frame));
// PyFrameObject *back = frame->f_back;
// if (back == NULL) {
// _PyInterpreterFrame *prev = frame->f_frame->previous;
// prev = _PyFrame_GetFirstComplete(prev);
// if (prev) {
// back = _PyFrame_GetFrameObject(prev);
// }
// }
// return (PyFrameObject*)Py_XNewRef(back);
if (!iframe->frame_obj) {
PyFrameObject dummy_frame;
_PyInterpreterFrame dummy_iframe;
dummy_frame.f_back = nullptr;
dummy_frame.f_frame = &dummy_iframe;
// force the iframe to be considered complete without
// needing to check its code object:
dummy_iframe.owner = FRAME_OWNED_BY_GENERATOR;
dummy_iframe.previous = iframe;
assert(!_PyFrame_IsIncomplete(&dummy_iframe));
// Drop the returned reference immediately; the iframe
// continues to hold a strong reference
Py_XDECREF(PyFrame_GetBack(&dummy_frame));
assert(iframe->frame_obj);
}
// This is a complete frame, so make the last one of those we saw
// point at it, bypassing any incomplete frames (which may have
// been on the C stack) in between the two. We're overwriting
// last_complete_iframe->previous and need that to be reversible,
// so we store the original previous ptr in the frame object
// (which we must have created on a previous iteration through
// this loop). The frame object has a bunch of storage that is
// only used when its iframe is OWNED_BY_FRAME_OBJECT, which only
// occurs when the frame object outlives the frame's execution,
// which can't have happened yet because the frame is currently
// executing as far as the interpreter is concerned. So, we can
// reuse it for our own purposes.
assert(iframe->owner == FRAME_OWNED_BY_THREAD
|| iframe->owner == FRAME_OWNED_BY_GENERATOR);
if (last_complete_iframe) {
assert(last_complete_iframe->frame_obj);
memcpy(&last_complete_iframe->frame_obj->_f_frame_data[0],
&last_complete_iframe->previous, sizeof(void *));
last_complete_iframe->previous = iframe;
}
last_complete_iframe = iframe;
}
// Frames that are OWNED_BY_FRAME_OBJECT are linked via the
// frame's f_back while all others are linked via the iframe's
// previous ptr. Since all the frames we traverse are running
// as far as the interpreter is concerned, we don't have to
// worry about the OWNED_BY_FRAME_OBJECT case.
iframe = iframe_copy.previous;
}
// Give the outermost complete iframe a null previous pointer to
// account for any potential incomplete/C-stack iframes between it
// and the actual top-of-stack
if (last_complete_iframe) {
assert(last_complete_iframe->frame_obj);
memcpy(&last_complete_iframe->frame_obj->_f_frame_data[0],
&last_complete_iframe->previous, sizeof(void *));
last_complete_iframe->previous = nullptr;
}
}
#else
void Greenlet::expose_frames()
{
}
#endif
}; // namespace greenlet
#endif
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