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Diffstat (limited to 'venv/lib/python3.11/site-packages/greenlet/TPythonState.cpp')
| -rw-r--r-- | venv/lib/python3.11/site-packages/greenlet/TPythonState.cpp | 375 |
1 files changed, 375 insertions, 0 deletions
diff --git a/venv/lib/python3.11/site-packages/greenlet/TPythonState.cpp b/venv/lib/python3.11/site-packages/greenlet/TPythonState.cpp new file mode 100644 index 0000000..465d417 --- /dev/null +++ b/venv/lib/python3.11/site-packages/greenlet/TPythonState.cpp @@ -0,0 +1,375 @@ +#ifndef GREENLET_PYTHON_STATE_CPP +#define GREENLET_PYTHON_STATE_CPP + +#include <Python.h> +#include "greenlet_greenlet.hpp" + +namespace greenlet { + +PythonState::PythonState() + : _top_frame() +#if GREENLET_USE_CFRAME + ,cframe(nullptr) + ,use_tracing(0) +#endif +#if GREENLET_PY312 + ,py_recursion_depth(0) + ,c_recursion_depth(0) +#else + ,recursion_depth(0) +#endif + ,trash_delete_nesting(0) +#if GREENLET_PY311 + ,current_frame(nullptr) + ,datastack_chunk(nullptr) + ,datastack_top(nullptr) + ,datastack_limit(nullptr) +#endif +{ +#if GREENLET_USE_CFRAME + /* + The PyThreadState->cframe pointer usually points to memory on + the stack, alloceted in a call into PyEval_EvalFrameDefault. + + Initially, before any evaluation begins, it points to the + initial PyThreadState object's ``root_cframe`` object, which is + statically allocated for the lifetime of the thread. + + A greenlet can last for longer than a call to + PyEval_EvalFrameDefault, so we can't set its ``cframe`` pointer + to be the current ``PyThreadState->cframe``; nor could we use + one from the greenlet parent for the same reason. Yet a further + no: we can't allocate one scoped to the greenlet and then + destroy it when the greenlet is deallocated, because inside the + interpreter the _PyCFrame objects form a linked list, and that too + can result in accessing memory beyond its dynamic lifetime (if + the greenlet doesn't actually finish before it dies, its entry + could still be in the list). + + Using the ``root_cframe`` is problematic, though, because its + members are never modified by the interpreter and are set to 0, + meaning that its ``use_tracing`` flag is never updated. We don't + want to modify that value in the ``root_cframe`` ourself: it + *shouldn't* matter much because we should probably never get + back to the point where that's the only cframe on the stack; + even if it did matter, the major consequence of an incorrect + value for ``use_tracing`` is that if its true the interpreter + does some extra work --- however, it's just good code hygiene. + + Our solution: before a greenlet runs, after its initial + creation, it uses the ``root_cframe`` just to have something to + put there. However, once the greenlet is actually switched to + for the first time, ``g_initialstub`` (which doesn't actually + "return" while the greenlet is running) stores a new _PyCFrame on + its local stack, and copies the appropriate values from the + currently running _PyCFrame; this is then made the _PyCFrame for the + newly-minted greenlet. ``g_initialstub`` then proceeds to call + ``glet.run()``, which results in ``PyEval_...`` adding the + _PyCFrame to the list. Switches continue as normal. Finally, when + the greenlet finishes, the call to ``glet.run()`` returns and + the _PyCFrame is taken out of the linked list and the stack value + is now unused and free to expire. + + XXX: I think we can do better. If we're deallocing in the same + thread, can't we traverse the list and unlink our frame? + Can we just keep a reference to the thread state in case we + dealloc in another thread? (Is that even possible if we're still + running and haven't returned from g_initialstub?) + */ + this->cframe = &PyThreadState_GET()->root_cframe; +#endif +} + + +inline void PythonState::may_switch_away() noexcept +{ +#if GREENLET_PY311 + // PyThreadState_GetFrame is probably going to have to allocate a + // new frame object. That may trigger garbage collection. Because + // we call this during the early phases of a switch (it doesn't + // matter to which greenlet, as this has a global effect), if a GC + // triggers a switch away, two things can happen, both bad: + // - We might not get switched back to, halting forward progress. + // this is pathological, but possible. + // - We might get switched back to with a different set of + // arguments or a throw instead of a switch. That would corrupt + // our state (specifically, PyErr_Occurred() and this->args() + // would no longer agree). + // + // Thus, when we call this API, we need to have GC disabled. + // This method serves as a bottleneck we call when maybe beginning + // a switch. In this way, it is always safe -- no risk of GC -- to + // use ``_GetFrame()`` whenever we need to, just as it was in + // <=3.10 (because subsequent calls will be cached and not + // allocate memory). + + GCDisabledGuard no_gc; + Py_XDECREF(PyThreadState_GetFrame(PyThreadState_GET())); +#endif +} + +void PythonState::operator<<(const PyThreadState *const tstate) noexcept +{ + this->_context.steal(tstate->context); +#if GREENLET_USE_CFRAME + /* + IMPORTANT: ``cframe`` is a pointer into the STACK. Thus, because + the call to ``slp_switch()`` changes the contents of the stack, + you cannot read from ``ts_current->cframe`` after that call and + necessarily get the same values you get from reading it here. + Anything you need to restore from now to then must be saved in a + global/threadlocal variable (because we can't use stack + variables here either). For things that need to persist across + the switch, use `will_switch_from`. + */ + this->cframe = tstate->cframe; + #if !GREENLET_PY312 + this->use_tracing = tstate->cframe->use_tracing; + #endif +#endif // GREENLET_USE_CFRAME +#if GREENLET_PY311 + #if GREENLET_PY312 + this->py_recursion_depth = tstate->py_recursion_limit - tstate->py_recursion_remaining; + this->c_recursion_depth = C_RECURSION_LIMIT - tstate->c_recursion_remaining; + #else // not 312 + this->recursion_depth = tstate->recursion_limit - tstate->recursion_remaining; + #endif // GREENLET_PY312 + this->current_frame = tstate->cframe->current_frame; + this->datastack_chunk = tstate->datastack_chunk; + this->datastack_top = tstate->datastack_top; + this->datastack_limit = tstate->datastack_limit; + + PyFrameObject *frame = PyThreadState_GetFrame((PyThreadState *)tstate); + Py_XDECREF(frame); // PyThreadState_GetFrame gives us a new + // reference. + this->_top_frame.steal(frame); + #if GREENLET_PY312 + this->trash_delete_nesting = tstate->trash.delete_nesting; + #else // not 312 + this->trash_delete_nesting = tstate->trash_delete_nesting; + #endif // GREENLET_PY312 +#else // Not 311 + this->recursion_depth = tstate->recursion_depth; + this->_top_frame.steal(tstate->frame); + this->trash_delete_nesting = tstate->trash_delete_nesting; +#endif // GREENLET_PY311 +} + +#if GREENLET_PY312 +void GREENLET_NOINLINE(PythonState::unexpose_frames)() +{ + if (!this->top_frame()) { + return; + } + + // See GreenletState::expose_frames() and the comment on frames_were_exposed + // for more information about this logic. + _PyInterpreterFrame *iframe = this->_top_frame->f_frame; + while (iframe != nullptr) { + _PyInterpreterFrame *prev_exposed = iframe->previous; + assert(iframe->frame_obj); + memcpy(&iframe->previous, &iframe->frame_obj->_f_frame_data[0], + sizeof(void *)); + iframe = prev_exposed; + } +} +#else +void PythonState::unexpose_frames() +{} +#endif + +void PythonState::operator>>(PyThreadState *const tstate) noexcept +{ + tstate->context = this->_context.relinquish_ownership(); + /* Incrementing this value invalidates the contextvars cache, + which would otherwise remain valid across switches */ + tstate->context_ver++; +#if GREENLET_USE_CFRAME + tstate->cframe = this->cframe; + /* + If we were tracing, we need to keep tracing. + There should never be the possibility of hitting the + root_cframe here. See note above about why we can't + just copy this from ``origin->cframe->use_tracing``. + */ + #if !GREENLET_PY312 + tstate->cframe->use_tracing = this->use_tracing; + #endif +#endif // GREENLET_USE_CFRAME +#if GREENLET_PY311 + #if GREENLET_PY312 + tstate->py_recursion_remaining = tstate->py_recursion_limit - this->py_recursion_depth; + tstate->c_recursion_remaining = C_RECURSION_LIMIT - this->c_recursion_depth; + this->unexpose_frames(); + #else // \/ 3.11 + tstate->recursion_remaining = tstate->recursion_limit - this->recursion_depth; + #endif // GREENLET_PY312 + tstate->cframe->current_frame = this->current_frame; + tstate->datastack_chunk = this->datastack_chunk; + tstate->datastack_top = this->datastack_top; + tstate->datastack_limit = this->datastack_limit; + this->_top_frame.relinquish_ownership(); + #if GREENLET_PY312 + tstate->trash.delete_nesting = this->trash_delete_nesting; + #else // not 3.12 + tstate->trash_delete_nesting = this->trash_delete_nesting; + #endif // GREENLET_PY312 +#else // not 3.11 + tstate->frame = this->_top_frame.relinquish_ownership(); + tstate->recursion_depth = this->recursion_depth; + tstate->trash_delete_nesting = this->trash_delete_nesting; +#endif // GREENLET_PY311 +} + +inline void PythonState::will_switch_from(PyThreadState *const origin_tstate) noexcept +{ +#if GREENLET_USE_CFRAME && !GREENLET_PY312 + // The weird thing is, we don't actually save this for an + // effect on the current greenlet, it's saved for an + // effect on the target greenlet. That is, we want + // continuity of this setting across the greenlet switch. + this->use_tracing = origin_tstate->cframe->use_tracing; +#endif +} + +void PythonState::set_initial_state(const PyThreadState* const tstate) noexcept +{ + this->_top_frame = nullptr; +#if GREENLET_PY312 + this->py_recursion_depth = tstate->py_recursion_limit - tstate->py_recursion_remaining; + // XXX: TODO: Comment from a reviewer: + // Should this be ``C_RECURSION_LIMIT - tstate->c_recursion_remaining``? + // But to me it looks more like that might not be the right + // initialization either? + this->c_recursion_depth = tstate->py_recursion_limit - tstate->py_recursion_remaining; +#elif GREENLET_PY311 + this->recursion_depth = tstate->recursion_limit - tstate->recursion_remaining; +#else + this->recursion_depth = tstate->recursion_depth; +#endif +} +// TODO: Better state management about when we own the top frame. +int PythonState::tp_traverse(visitproc visit, void* arg, bool own_top_frame) noexcept +{ + Py_VISIT(this->_context.borrow()); + if (own_top_frame) { + Py_VISIT(this->_top_frame.borrow()); + } + return 0; +} + +void PythonState::tp_clear(bool own_top_frame) noexcept +{ + PythonStateContext::tp_clear(); + // If we get here owning a frame, + // we got dealloc'd without being finished. We may or may not be + // in the same thread. + if (own_top_frame) { + this->_top_frame.CLEAR(); + } +} + +#if GREENLET_USE_CFRAME +void PythonState::set_new_cframe(_PyCFrame& frame) noexcept +{ + frame = *PyThreadState_GET()->cframe; + /* Make the target greenlet refer to the stack value. */ + this->cframe = &frame; + /* + And restore the link to the previous frame so this one gets + unliked appropriately. + */ + this->cframe->previous = &PyThreadState_GET()->root_cframe; +} +#endif + +const PythonState::OwnedFrame& PythonState::top_frame() const noexcept +{ + return this->_top_frame; +} + +void PythonState::did_finish(PyThreadState* tstate) noexcept +{ +#if GREENLET_PY311 + // See https://github.com/gevent/gevent/issues/1924 and + // https://github.com/python-greenlet/greenlet/issues/328. In + // short, Python 3.11 allocates memory for frames as a sort of + // linked list that's kept as part of PyThreadState in the + // ``datastack_chunk`` member and friends. These are saved and + // restored as part of switching greenlets. + // + // When we initially switch to a greenlet, we set those to NULL. + // That causes the frame management code to treat this like a + // brand new thread and start a fresh list of chunks, beginning + // with a new "root" chunk. As we make calls in this greenlet, + // those chunks get added, and as calls return, they get popped. + // But the frame code (pystate.c) is careful to make sure that the + // root chunk never gets popped. + // + // Thus, when a greenlet exits for the last time, there will be at + // least a single root chunk that we must be responsible for + // deallocating. + // + // The complex part is that these chunks are allocated and freed + // using ``_PyObject_VirtualAlloc``/``Free``. Those aren't public + // functions, and they aren't exported for linking. It so happens + // that we know they are just thin wrappers around the Arena + // allocator, so we can use that directly to deallocate in a + // compatible way. + // + // CAUTION: Check this implementation detail on every major version. + // + // It might be nice to be able to do this in our destructor, but + // can we be sure that no one else is using that memory? Plus, as + // described below, our pointers may not even be valid anymore. As + // a special case, there is one time that we know we can do this, + // and that's from the destructor of the associated UserGreenlet + // (NOT main greenlet) + PyObjectArenaAllocator alloc; + _PyStackChunk* chunk = nullptr; + if (tstate) { + // We really did finish, we can never be switched to again. + chunk = tstate->datastack_chunk; + // Unfortunately, we can't do much sanity checking. Our + // this->datastack_chunk pointer is out of date (evaluation may + // have popped down through it already) so we can't verify that + // we deallocate it. I don't think we can even check datastack_top + // for the same reason. + + PyObject_GetArenaAllocator(&alloc); + tstate->datastack_chunk = nullptr; + tstate->datastack_limit = nullptr; + tstate->datastack_top = nullptr; + + } + else if (this->datastack_chunk) { + // The UserGreenlet (NOT the main greenlet!) is being deallocated. If we're + // still holding a stack chunk, it's garbage because we know + // we can never switch back to let cPython clean it up. + // Because the last time we got switched away from, and we + // haven't run since then, we know our chain is valid and can + // be dealloced. + chunk = this->datastack_chunk; + PyObject_GetArenaAllocator(&alloc); + } + + if (alloc.free && chunk) { + // In case the arena mechanism has been torn down already. + while (chunk) { + _PyStackChunk *prev = chunk->previous; + chunk->previous = nullptr; + alloc.free(alloc.ctx, chunk, chunk->size); + chunk = prev; + } + } + + this->datastack_chunk = nullptr; + this->datastack_limit = nullptr; + this->datastack_top = nullptr; +#endif +} + + +}; // namespace greenlet + +#endif // GREENLET_PYTHON_STATE_CPP |