Update 2025-04-13_16:25:39

venv/lib/python3.11/site-packages/greenlet/TThreadState.hpp

@@ -0,0 +1,497 @@
+#ifndef GREENLET_THREAD_STATE_HPP
+#define GREENLET_THREAD_STATE_HPP
+
+#include <ctime>
+#include <stdexcept>
+
+#include "greenlet_internal.hpp"
+#include "greenlet_refs.hpp"
+#include "greenlet_thread_support.hpp"
+
+using greenlet::refs::BorrowedObject;
+using greenlet::refs::BorrowedGreenlet;
+using greenlet::refs::BorrowedMainGreenlet;
+using greenlet::refs::OwnedMainGreenlet;
+using greenlet::refs::OwnedObject;
+using greenlet::refs::OwnedGreenlet;
+using greenlet::refs::OwnedList;
+using greenlet::refs::PyErrFetchParam;
+using greenlet::refs::PyArgParseParam;
+using greenlet::refs::ImmortalString;
+using greenlet::refs::CreatedModule;
+using greenlet::refs::PyErrPieces;
+using greenlet::refs::NewReference;
+
+namespace greenlet {
+/**
+ * Thread-local state of greenlets.
+ *
+ * Each native thread will get exactly one of these objects,
+ * automatically accessed through the best available thread-local
+ * mechanism the compiler supports (``thread_local`` for C++11
+ * compilers or ``__thread``/``declspec(thread)`` for older GCC/clang
+ * or MSVC, respectively.)
+ *
+ * Previously, we kept thread-local state mostly in a bunch of
+ * ``static volatile`` variables in the main greenlet file.. This had
+ * the problem of requiring extra checks, loops, and great care
+ * accessing these variables if we potentially invoked any Python code
+ * that could release the GIL, because the state could change out from
+ * under us. Making the variables thread-local solves this problem.
+ *
+ * When we detected that a greenlet API accessing the current greenlet
+ * was invoked from a different thread than the greenlet belonged to,
+ * we stored a reference to the greenlet in the Python thread
+ * dictionary for the thread the greenlet belonged to. This could lead
+ * to memory leaks if the thread then exited (because of a reference
+ * cycle, as greenlets referred to the thread dictionary, and deleting
+ * non-current greenlets leaked their frame plus perhaps arguments on
+ * the C stack). If a thread exited while still having running
+ * greenlet objects (perhaps that had just switched back to the main
+ * greenlet), and did not invoke one of the greenlet APIs *in that
+ * thread, immediately before it exited, without some other thread
+ * then being invoked*, such a leak was guaranteed.
+ *
+ * This can be partly solved by using compiler thread-local variables
+ * instead of the Python thread dictionary, thus avoiding a cycle.
+ *
+ * To fully solve this problem, we need a reliable way to know that a
+ * thread is done and we should clean up the main greenlet. On POSIX,
+ * we can use the destructor function of ``pthread_key_create``, but
+ * there's nothing similar on Windows; a C++11 thread local object
+ * reliably invokes its destructor when the thread it belongs to exits
+ * (non-C++11 compilers offer ``__thread`` or ``declspec(thread)`` to
+ * create thread-local variables, but they can't hold C++ objects that
+ * invoke destructors; the C++11 version is the most portable solution
+ * I found). When the thread exits, we can drop references and
+ * otherwise manipulate greenlets and frames that we know can no
+ * longer be switched to. For compilers that don't support C++11
+ * thread locals, we have a solution that uses the python thread
+ * dictionary, though it may not collect everything as promptly as
+ * other compilers do, if some other library is using the thread
+ * dictionary and has a cycle or extra reference.
+ *
+ * There are two small wrinkles. The first is that when the thread
+ * exits, it is too late to actually invoke Python APIs: the Python
+ * thread state is gone, and the GIL is released. To solve *this*
+ * problem, our destructor uses ``Py_AddPendingCall`` to transfer the
+ * destruction work to the main thread. (This is not an issue for the
+ * dictionary solution.)
+ *
+ * The second is that once the thread exits, the thread local object
+ * is invalid and we can't even access a pointer to it, so we can't
+ * pass it to ``Py_AddPendingCall``. This is handled by actually using
+ * a second object that's thread local (ThreadStateCreator) and having
+ * it dynamically allocate this object so it can live until the
+ * pending call runs.
+ */
+
+
+
+class ThreadState {
+private:
+    // As of commit 08ad1dd7012b101db953f492e0021fb08634afad
+    // this class needed 56 bytes in o Py_DEBUG build
+    // on 64-bit macOS 11.
+    // Adding the vector takes us up to 80 bytes ()
+
+    /* Strong reference to the main greenlet */
+    OwnedMainGreenlet main_greenlet;
+
+    /* Strong reference to the current greenlet. */
+    OwnedGreenlet current_greenlet;
+
+    /* Strong reference to the trace function, if any. */
+    OwnedObject tracefunc;
+
+    typedef std::vector<PyGreenlet*, PythonAllocator<PyGreenlet*> > deleteme_t;
+    /* A vector of raw PyGreenlet pointers representing things that need
+       deleted when this thread is running. The vector owns the
+       references, but you need to manually INCREF/DECREF as you use
+       them. We don't use a vector<refs::OwnedGreenlet> because we
+       make copy of this vector, and that would become O(n) as all the
+       refcounts are incremented in the copy.
+    */
+    deleteme_t deleteme;
+
+#ifdef GREENLET_NEEDS_EXCEPTION_STATE_SAVED
+    void* exception_state;
+#endif
+
+    static std::clock_t _clocks_used_doing_gc;
+    static ImmortalString get_referrers_name;
+    static PythonAllocator<ThreadState> allocator;
+
+    G_NO_COPIES_OF_CLS(ThreadState);
+
+
+    // Allocates a main greenlet for the thread state. If this fails,
+    // exits the process. Called only during constructing a ThreadState.
+    MainGreenlet* alloc_main()
+    {
+        PyGreenlet* gmain;
+
+        /* create the main greenlet for this thread */
+        gmain = reinterpret_cast<PyGreenlet*>(PyType_GenericAlloc(&PyGreenlet_Type, 0));
+        if (gmain == NULL) {
+            throw PyFatalError("alloc_main failed to alloc"); //exits the process
+        }
+
+        MainGreenlet* const main = new MainGreenlet(gmain, this);
+
+        assert(Py_REFCNT(gmain) == 1);
+        assert(gmain->pimpl == main);
+        return main;
+    }
+
+
+public:
+    static void* operator new(size_t UNUSED(count))
+    {
+        return ThreadState::allocator.allocate(1);
+    }
+
+    static void operator delete(void* ptr)
+    {
+        return ThreadState::allocator.deallocate(static_cast<ThreadState*>(ptr),
+                                                 1);
+    }
+
+    static void init()
+    {
+        ThreadState::get_referrers_name = "get_referrers";
+        ThreadState::_clocks_used_doing_gc = 0;
+    }
+
+    ThreadState()
+    {
+
+#ifdef GREENLET_NEEDS_EXCEPTION_STATE_SAVED
+        this->exception_state = slp_get_exception_state();
+#endif
+
+        // XXX: Potentially dangerous, exposing a not fully
+        // constructed object.
+        MainGreenlet* const main = this->alloc_main();
+        this->main_greenlet = OwnedMainGreenlet::consuming(
+            main->self()
+        );
+        assert(this->main_greenlet);
+        this->current_greenlet = main->self();
+        // The main greenlet starts with 1 refs: The returned one. We
+        // then copied it to the current greenlet.
+        assert(this->main_greenlet.REFCNT() == 2);
+    }
+
+    inline void restore_exception_state()
+    {
+#ifdef GREENLET_NEEDS_EXCEPTION_STATE_SAVED
+        // It's probably important this be inlined and only call C
+        // functions to avoid adding an SEH frame.
+        slp_set_exception_state(this->exception_state);
+#endif
+    }
+
+    inline bool has_main_greenlet() const noexcept
+    {
+        return bool(this->main_greenlet);
+    }
+
+    // Called from the ThreadStateCreator when we're in non-standard
+    // threading mode. In that case, there is an object in the Python
+    // thread state dictionary that points to us. The main greenlet
+    // also traverses into us, in which case it's crucial not to
+    // traverse back into the main greenlet.
+    int tp_traverse(visitproc visit, void* arg, bool traverse_main=true)
+    {
+        if (traverse_main) {
+            Py_VISIT(main_greenlet.borrow_o());
+        }
+        if (traverse_main || current_greenlet != main_greenlet) {
+            Py_VISIT(current_greenlet.borrow_o());
+        }
+        Py_VISIT(tracefunc.borrow());
+        return 0;
+    }
+
+    inline BorrowedMainGreenlet borrow_main_greenlet() const noexcept
+    {
+        assert(this->main_greenlet);
+        assert(this->main_greenlet.REFCNT() >= 2);
+        return this->main_greenlet;
+    };
+
+    inline OwnedMainGreenlet get_main_greenlet() const noexcept
+    {
+        return this->main_greenlet;
+    }
+
+    /**
+     * In addition to returning a new reference to the currunt
+     * greenlet, this performs any maintenance needed.
+     */
+    inline OwnedGreenlet get_current()
+    {
+        /* green_dealloc() cannot delete greenlets from other threads, so
+           it stores them in the thread dict; delete them now. */
+        this->clear_deleteme_list();
+        //assert(this->current_greenlet->main_greenlet == this->main_greenlet);
+        //assert(this->main_greenlet->main_greenlet == this->main_greenlet);
+        return this->current_greenlet;
+    }
+
+    /**
+     * As for non-const get_current();
+     */
+    inline BorrowedGreenlet borrow_current()
+    {
+        this->clear_deleteme_list();
+        return this->current_greenlet;
+    }
+
+    /**
+     * Does no maintenance.
+     */
+    inline OwnedGreenlet get_current() const
+    {
+        return this->current_greenlet;
+    }
+
+    template<typename T, refs::TypeChecker TC>
+    inline bool is_current(const refs::PyObjectPointer<T, TC>& obj) const
+    {
+        return this->current_greenlet.borrow_o() == obj.borrow_o();
+    }
+
+    inline void set_current(const OwnedGreenlet& target)
+    {
+        this->current_greenlet = target;
+    }
+
+private:
+    /**
+     * Deref and remove the greenlets from the deleteme list. Must be
+     * holding the GIL.
+     *
+     * If *murder* is true, then we must be called from a different
+     * thread than the one that these greenlets were running in.
+     * In that case, if the greenlet was actually running, we destroy
+     * the frame reference and otherwise make it appear dead before
+     * proceeding; otherwise, we would try (and fail) to raise an
+     * exception in it and wind up right back in this list.
+     */
+    inline void clear_deleteme_list(const bool murder=false)
+    {
+        if (!this->deleteme.empty()) {
+            // It's possible we could add items to this list while
+            // running Python code if there's a thread switch, so we
+            // need to defensively copy it before that can happen.
+            deleteme_t copy = this->deleteme;
+            this->deleteme.clear(); // in case things come back on the list
+            for(deleteme_t::iterator it = copy.begin(), end = copy.end();
+                it != end;
+                ++it ) {
+                PyGreenlet* to_del = *it;
+                if (murder) {
+                    // Force each greenlet to appear dead; we can't raise an
+                    // exception into it anymore anyway.
+                    to_del->pimpl->murder_in_place();
+                }
+
+                // The only reference to these greenlets should be in
+                // this list, decreffing them should let them be
+                // deleted again, triggering calls to green_dealloc()
+                // in the correct thread (if we're not murdering).
+                // This may run arbitrary Python code and switch
+                // threads or greenlets!
+                Py_DECREF(to_del);
+                if (PyErr_Occurred()) {
+                    PyErr_WriteUnraisable(nullptr);
+                    PyErr_Clear();
+                }
+            }
+        }
+    }
+
+public:
+
+    /**
+     * Returns a new reference, or a false object.
+     */
+    inline OwnedObject get_tracefunc() const
+    {
+        return tracefunc;
+    };
+
+
+    inline void set_tracefunc(BorrowedObject tracefunc)
+    {
+        assert(tracefunc);
+        if (tracefunc == BorrowedObject(Py_None)) {
+            this->tracefunc.CLEAR();
+        }
+        else {
+            this->tracefunc = tracefunc;
+        }
+    }
+
+    /**
+     * Given a reference to a greenlet that some other thread
+     * attempted to delete (has a refcount of 0) store it for later
+     * deletion when the thread this state belongs to is current.
+     */
+    inline void delete_when_thread_running(PyGreenlet* to_del)
+    {
+        Py_INCREF(to_del);
+        this->deleteme.push_back(to_del);
+    }
+
+    /**
+     * Set to std::clock_t(-1) to disable.
+     */
+    inline static std::clock_t& clocks_used_doing_gc()
+    {
+        return ThreadState::_clocks_used_doing_gc;
+    }
+
+    ~ThreadState()
+    {
+        if (!PyInterpreterState_Head()) {
+            // We shouldn't get here (our callers protect us)
+            // but if we do, all we can do is bail early.
+            return;
+        }
+
+        // We should not have an "origin" greenlet; that only exists
+        // for the temporary time during a switch, which should not
+        // be in progress as the thread dies.
+        //assert(!this->switching_state.origin);
+
+        this->tracefunc.CLEAR();
+
+        // Forcibly GC as much as we can.
+        this->clear_deleteme_list(true);
+
+        // The pending call did this.
+        assert(this->main_greenlet->thread_state() == nullptr);
+
+        // If the main greenlet is the current greenlet,
+        // then we "fell off the end" and the thread died.
+        // It's possible that there is some other greenlet that
+        // switched to us, leaving a reference to the main greenlet
+        // on the stack, somewhere uncollectible. Try to detect that.
+        if (this->current_greenlet == this->main_greenlet && this->current_greenlet) {
+            assert(this->current_greenlet->is_currently_running_in_some_thread());
+            // Drop one reference we hold.
+            this->current_greenlet.CLEAR();
+            assert(!this->current_greenlet);
+            // Only our reference to the main greenlet should be left,
+            // But hold onto the pointer in case we need to do extra cleanup.
+            PyGreenlet* old_main_greenlet = this->main_greenlet.borrow();
+            Py_ssize_t cnt = this->main_greenlet.REFCNT();
+            this->main_greenlet.CLEAR();
+            if (ThreadState::_clocks_used_doing_gc != std::clock_t(-1)
+                && cnt == 2 && Py_REFCNT(old_main_greenlet) == 1) {
+                // Highly likely that the reference is somewhere on
+                // the stack, not reachable by GC. Verify.
+                // XXX: This is O(n) in the total number of objects.
+                // TODO: Add a way to disable this at runtime, and
+                // another way to report on it.
+                std::clock_t begin = std::clock();
+                NewReference gc(PyImport_ImportModule("gc"));
+                if (gc) {
+                    OwnedObject get_referrers = gc.PyRequireAttr(ThreadState::get_referrers_name);
+                    OwnedList refs(get_referrers.PyCall(old_main_greenlet));
+                    if (refs && refs.empty()) {
+                        assert(refs.REFCNT() == 1);
+                        // We found nothing! So we left a dangling
+                        // reference: Probably the last thing some
+                        // other greenlet did was call
+                        // 'getcurrent().parent.switch()' to switch
+                        // back to us. Clean it up. This will be the
+                        // case on CPython 3.7 and newer, as they use
+                        // an internal calling conversion that avoids
+                        // creating method objects and storing them on
+                        // the stack.
+                        Py_DECREF(old_main_greenlet);
+                    }
+                    else if (refs
+                             && refs.size() == 1
+                             && PyCFunction_Check(refs.at(0))
+                             && Py_REFCNT(refs.at(0)) == 2) {
+                        assert(refs.REFCNT() == 1);
+                        // Ok, we found a C method that refers to the
+                        // main greenlet, and its only referenced
+                        // twice, once in the list we just created,
+                        // once from...somewhere else. If we can't
+                        // find where else, then this is a leak.
+                        // This happens in older versions of CPython
+                        // that create a bound method object somewhere
+                        // on the stack that we'll never get back to.
+                        if (PyCFunction_GetFunction(refs.at(0).borrow()) == (PyCFunction)green_switch) {
+                            BorrowedObject function_w = refs.at(0);
+                            refs.clear(); // destroy the reference
+                                          // from the list.
+                            // back to one reference. Can *it* be
+                            // found?
+                            assert(function_w.REFCNT() == 1);
+                            refs = get_referrers.PyCall(function_w);
+                            if (refs && refs.empty()) {
+                                // Nope, it can't be found so it won't
+                                // ever be GC'd. Drop it.
+                                Py_CLEAR(function_w);
+                            }
+                        }
+                    }
+                    std::clock_t end = std::clock();
+                    ThreadState::_clocks_used_doing_gc += (end - begin);
+                }
+            }
+        }
+
+        // We need to make sure this greenlet appears to be dead,
+        // because otherwise deallocing it would fail to raise an
+        // exception in it (the thread is dead) and put it back in our
+        // deleteme list.
+        if (this->current_greenlet) {
+            this->current_greenlet->murder_in_place();
+            this->current_greenlet.CLEAR();
+        }
+
+        if (this->main_greenlet) {
+            // Couldn't have been the main greenlet that was running
+            // when the thread exited (because we already cleared this
+            // pointer if it was). This shouldn't be possible?
+
+            // If the main greenlet was current when the thread died (it
+            // should be, right?) then we cleared its self pointer above
+            // when we cleared the current greenlet's main greenlet pointer.
+            // assert(this->main_greenlet->main_greenlet == this->main_greenlet
+            //        || !this->main_greenlet->main_greenlet);
+            // // self reference, probably gone
+            // this->main_greenlet->main_greenlet.CLEAR();
+
+            // This will actually go away when the ivar is destructed.
+            this->main_greenlet.CLEAR();
+        }
+
+        if (PyErr_Occurred()) {
+            PyErr_WriteUnraisable(NULL);
+            PyErr_Clear();
+        }
+
+    }
+
+};
+
+ImmortalString ThreadState::get_referrers_name(nullptr);
+PythonAllocator<ThreadState> ThreadState::allocator;
+std::clock_t ThreadState::_clocks_used_doing_gc(0);
+
+
+
+
+
+}; // namespace greenlet
+
+#endif