Fix stack getter segfault caused by is_shutting_down and gil (#9681)

Fixes https://github.com/Oneflow-Inc/OneTeam/issues/1861 ，在
TryCloseDefaultSession 之前设置 is_shutting_down 为
true（#9502 这个 PR 在
TryCloseDefaultSession 里引入了 Sync 操作），并把 python c 对象的指针保存在 PyFrame
对象里，GetCurrentFrame 里不再需要重复获取，修复因为没有拿到 gil 锁导致的 segfault

Signed-off-by: daquexian <daquexian566@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

oneflow/extension/stack/python/stack_getter.cpp

@@ -34,29 +34,35 @@ namespace py = pybind11;
 namespace oneflow {
 
 namespace {
-std::string RawPyUnicodeToStdString(const PyObject* py_str) {
+std::string PyUnicodeToStdString(const PyObject* py_str) {
   return PyBytes_AsString(PyUnicode_AsEncodedString(const_cast<PyObject*>(py_str), "utf-8", "~E~"));
 }
-static constexpr auto* PyUnicodeToStdString =
-    DECORATE(&RawPyUnicodeToStdString, ThreadLocalCachedCopiable);
 }  // namespace
 
 class PyFrame final
     : public Frame,
       public intrusive::EnableObjectPool<PyFrame, intrusive::kThreadUnsafeAndDisableDestruct> {
  public:
-  PyFrame() : EnableObjectPool(), lineno(0) {}
-  void __Init__(PyCodeObject* code, int lineno, intrusive::shared_ptr<PyFrame> back) {
-    this->filename = PyUnicodeToStdString(code->co_filename);
-    this->funcname = PyUnicodeToStdString(code->co_name);
-    this->lineno = lineno;
+  PyFrame()
+      : EnableObjectPool(),
+        filename(nullptr),
+        funcname(nullptr),
+        cpython_frame(nullptr),
+        lineno(0) {}
+  void __Init__(PyFrameObject* frame, intrusive::shared_ptr<PyFrame> back) {
+    // There is no need to increase the reference count of these cpython objects
+    // because they must be alive during the lifetime of `PyFrame`.
+    this->filename = frame->f_code->co_filename;
+    this->funcname = frame->f_code->co_name;
+    this->cpython_frame = frame;
     this->back = std::move(back);
   }
   OF_DISALLOW_COPY_AND_MOVE(PyFrame);
   ~PyFrame() = default;
 
-  std::string filename;
-  std::string funcname;
+  PyObject* filename;
+  PyObject* funcname;
+  PyFrameObject* cpython_frame;
   int lineno;
   intrusive::shared_ptr<PyFrame> back;
 };
@@ -67,16 +73,17 @@ class PyStackGetter final : public ForeignStackGetter {
     auto* frame = PyEval_GetFrame();
     // Get the first frame. It assumes `import oneflow` is called in global scope,
     while (frame->f_back != nullptr) { frame = frame->f_back; }
-    current_frame_ = object_pool_.make_shared(frame->f_code, 0, nullptr);
+    current_frame_ = object_pool_.make_shared(frame, nullptr);
   }
   // indended to be called in main thread.
   intrusive::shared_ptr<Frame> GetCurrentFrame() const override {
     if (IsShuttingDown() || !current_frame_) { return nullptr; }
     // See `RecordAndEvalFrame` for documentation.
-    current_frame_->lineno = PyFrame_GetLineNumber(PyEval_GetFrame());
+    current_frame_->lineno = PyFrame_GetLineNumber(current_frame_->cpython_frame);
     return intrusive::shared_ptr<Frame>(current_frame_.get());
   }
 
+  // bad path, performance is not a concern.
   std::string GetFormattedStack(intrusive::shared_ptr<Frame> frame) const override {
     if (frame == nullptr) { return "  <unknown>\n"; }
     std::string buffer;
@@ -86,7 +93,7 @@ class PyStackGetter final : public ForeignStackGetter {
       const auto& lineno = py_frame->lineno;
       const std::string line_text = [&]() -> std::string {
         std::string line_text;
-        std::ifstream ifs(py_frame->filename);
+        std::ifstream ifs(PyUnicodeToStdString(py_frame->filename));
         if (!ifs.is_open()) { return "<unknown>"; }
         for (int j = 0; j < lineno; ++j) { std::getline(ifs, line_text); }
         line_text.erase(line_text.find_last_not_of(' ') + 1);  // suffixing spaces
@@ -95,7 +102,8 @@ class PyStackGetter final : public ForeignStackGetter {
       }();
       // immitate python's stack trace format
       fmt::format_to(std::back_inserter(buffer), "  File \"{}\", line {}, in {}\n    {}\n",
-                     py_frame->filename, lineno, py_frame->funcname, line_text);
+                     PyUnicodeToStdString(py_frame->filename), lineno,
+                     PyUnicodeToStdString(py_frame->funcname), line_text);
       py_frame = py_frame->back.get();
     }
     return buffer;
@@ -134,7 +142,7 @@ class PyStackGetter final : public ForeignStackGetter {
 
   void PushFrame(PyFrameObject* frame) {
     if (auto* f = frame->f_back) { current_frame_->lineno = PyFrame_GetLineNumber(f); }
-    current_frame_ = object_pool_.make_shared(frame->f_code, 0, current_frame_);
+    current_frame_ = object_pool_.make_shared(frame, current_frame_);
   }
   void PopFrame() {
     CHECK_NOTNULL(current_frame_);

python/oneflow/__init__.py

@@ -298,8 +298,8 @@ def is_normal_exit(self):
 
 
 def atexit_hook(hook):
-    oneflow.framework.session_context.TryCloseDefaultSession()
     __oneflow_global_unique_env.switch_to_shutting_down(hook.is_normal_exit())
+    oneflow.framework.session_context.TryCloseDefaultSession()
 
 
 atexit.register(atexit_hook, hook)