python: Fix GC isn't working correctly.

The uftrace_python_symbol keeps code PyObject in rb tree so GC can
not run correctly in the trace process. Fixed the problem by
dropping it. and change rb compare from code PyObject to func_name

Fixed: namhyung#1886
Signed-off-by: Yi Hong <zouzou0208@gmail.com>
Signed-off-by: Honggyu Kim <honggyu.kp@gmail.com>

python/trace-python.c

@@ -102,7 +102,6 @@ static union uftrace_python_symtab *dbg_info;
 /* symbol table entry to maintain mappings from code to addr */
 struct uftrace_python_symbol {
 	struct rb_node node;
-	PyObject *code;
 	char *name;
 	uint32_t addr;
 	uint32_t flag;
@@ -653,42 +652,14 @@ static void init_uftrace(void)
 /* this is called during GC traversal */
 static int uftrace_py_traverse(PyObject *m, visitproc visit, void *arg)
 {
-	struct uftrace_py_state *state;
-	struct rb_node *node;
-	struct uftrace_python_symbol *sym;
-
-	state = PyModule_GetState(m);
-
-	Py_VISIT(state->trace_func);
-
-	node = rb_first(&code_tree);
-	while (node) {
-		sym = rb_entry(node, struct uftrace_python_symbol, node);
-		Py_VISIT(sym->code);
-
-		node = rb_next(node);
-	}
+	/* do nothing for now */
 	return 0;
 }
 
 /* this is called before the module is deallocated */
 static int uftrace_py_clear(PyObject *m)
 {
-	struct uftrace_py_state *state;
-	struct rb_node *node;
-	struct uftrace_python_symbol *sym;
-
-	state = PyModule_GetState(m);
-
-	Py_CLEAR(state->trace_func);
-
-	node = rb_first(&code_tree);
-	while (node) {
-		sym = rb_entry(node, struct uftrace_python_symbol, node);
-		Py_CLEAR(sym->code);
-
-		node = rb_next(node);
-	}
+	/* do nothing for now */
 	return 0;
 }
 
@@ -878,6 +849,7 @@ static struct uftrace_python_symbol *convert_function_addr(PyObject *frame, PyOb
 	const char *file_name = NULL;
 	char *func_name;
 	bool is_main = false;
+	int cmp;
 
 	if (is_pyfunc) {
 		code = PyObject_GetAttrString(frame, "f_code");
@@ -889,30 +861,33 @@ static struct uftrace_python_symbol *convert_function_addr(PyObject *frame, PyOb
 		Py_INCREF(code);
 	}
 
+	if (is_pyfunc)
+		func_name = get_python_funcname(frame, code, &is_main);
+	else
+		func_name = get_c_funcname(frame, code);
+
+	/* code is not used anymore */
+	Py_DECREF(code);
+
+	if (func_name == NULL)
+		return NULL;
+
 	while (*p) {
 		parent = *p;
 		iter = rb_entry(parent, struct uftrace_python_symbol, node);
 
-		/* just compare pointers of the code object */
-		if (iter->code == code) {
-			Py_DECREF(code);
+		/* compare func_name */
+		cmp = strcmp(iter->name, func_name);
+		if (cmp == 0) {
+			free(func_name);
 			return iter;
 		}
-
-		if (iter->code < code)
+		if (cmp < 0)
 			p = &parent->rb_left;
 		else
 			p = &parent->rb_right;
 	}
 
-	if (is_pyfunc)
-		func_name = get_python_funcname(frame, code, &is_main);
-	else
-		func_name = get_c_funcname(frame, code);
-
-	if (func_name == NULL)
-		return NULL;
-
 	if (main_dir && PyObject_HasAttrString(code, "co_filename")) {
 		PyObject *obj;
 
@@ -926,7 +901,6 @@ static struct uftrace_python_symbol *convert_function_addr(PyObject *frame, PyOb
 	}
 
 	new_sym = xmalloc(sizeof(*new_sym));
-	new_sym->code = code;
 	new_sym->addr = get_new_sym_addr(func_name, !is_main);
 	new_sym->name = func_name;
 	new_sym->flag = is_main ? 0 : UFT_PYSYM_F_LIBCALL;