gh-138122: Don't sample partial frame chains with suspended generators

Author: pablogsal

Modules/_remote_debugging_module.c

@@ -2254,15 +2254,22 @@ is_frame_valid(
     }
 
     void* frame = (void*)frame_addr;
+    char owner = GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner);
 
-    if (GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) == FRAME_OWNED_BY_INTERPRETER) {
+    if (owner == FRAME_OWNED_BY_INTERPRETER) {
         return 0;  // C frame
     }
 
-    if (GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) != FRAME_OWNED_BY_GENERATOR
-        && GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) != FRAME_OWNED_BY_THREAD) {
-        PyErr_Format(PyExc_RuntimeError, "Unhandled frame owner %d.\n",
-                    GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner));
+    // Reject generator frames with NULL previous pointer - can't unwind past them
+    if (owner == FRAME_OWNED_BY_GENERATOR) {
+        uintptr_t previous = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.previous);
+        if (previous == 0) {
+            return 0;  // Generator frame with no caller - skip it
+        }
+    }
+
+    if (owner != FRAME_OWNED_BY_GENERATOR && owner != FRAME_OWNED_BY_THREAD) {
+        PyErr_Format(PyExc_RuntimeError, "Unhandled frame owner %d.\n", owner);
         set_exception_cause(unwinder, PyExc_RuntimeError, "Unhandled frame owner type in async frame");
         return -1;
     }