bpo-39984: _PyThreadState_DeleteCurrent() takes tstate (GH-19051)

* _PyThreadState_DeleteCurrent() now takes tstate rather than
  runtime.
* Add ensure_tstate_not_null() helper to pystate.c.
* Add _PyEval_ReleaseLock() function.
* _PyThreadState_DeleteCurrent() now calls
  _PyEval_ReleaseLock(tstate) and frees PyThreadState memory after
  this call, not before.
* PyGILState_Release(): rename "tcur" variable to "tstate".

1 files changed, 9 insertions, 1 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index b055d61..d4c15f3 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -193,7 +193,8 @@ static void
 ensure_tstate_not_null(const char *func, PyThreadState *tstate)
 {
     if (tstate == NULL) {
-        _Py_FatalErrorFunc(func, "current thread state is NULL");
+        _Py_FatalErrorFunc(func,
+                           "current thread state is NULL (released GIL?)");
     }
 }
 
@@ -314,6 +315,13 @@ PyEval_ReleaseLock(void)
 }
 
 void
+_PyEval_ReleaseLock(PyThreadState *tstate)
+{
+    struct _ceval_runtime_state *ceval = &tstate->interp->runtime->ceval;
+    drop_gil(ceval, tstate);
+}
+
+void
 PyEval_AcquireThread(PyThreadState *tstate)
 {
     ensure_tstate_not_null(__func__, tstate);