@@ -801,6 +801,8 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
         }
         if (_PyOpcode_Caches[original_opcode]) {
             _PyBinaryOpCache *cache = (_PyBinaryOpCache *)(next_instr+1);
+            /* Prevent the underlying instruction from specializing
+             * and overwriting the instrumentation. */
             INCREMENT_ADAPTIVE_COUNTER(cache->counter);
         }
         opcode = original_opcode;
 
@@ -1108,6 +1108,9 @@ _Py_call_instrumentation_line(PyThreadState *tstate, _PyInterpreterFrame* frame,
     int prev_line = _Py_Instrumentation_GetLine(code, prev_index);
     if (prev_line == line) {
         int prev_opcode = _PyCode_CODE(code)[prev_index].op.code;
+        /* RESUME and INSTRUMENTED_RESUME are needed for the operation of
+         * instrumentation, so must never be hidden by an INSTRUMENTED_LINE.
+         */
         if (prev_opcode != RESUME && prev_opcode != INSTRUMENTED_RESUME) {
             goto done;
         }
Original file line number	Diff line number	Diff line change
@@ -801,6 +801,8 @@ _PyEval_EvalFrameDefault(PyThreadState tstate, _PyInterpreterFrame frame, int
801	801	}
802	802	if (_PyOpcode_Caches[original_opcode]) {
803	803	_PyBinaryOpCache cache = (_PyBinaryOpCache )(next_instr+1);
	804	+ /* Prevent the underlying instruction from specializing
	805	+ * and overwriting the instrumentation. */
804	806	INCREMENT_ADAPTIVE_COUNTER(cache->counter);
805	807	}
806	808	opcode = original_opcode;