1#!/usr/bin/env drgn
2# SPDX-License-Identifier: GPL-2.0+
3#
4# Dump out the number of RCU callbacks outstanding.
5#
6# On older kernels having multiple flavors of RCU, this dumps out the
7# number of callbacks for the most heavily used flavor.
8#
9# Usage: sudo drgn rcu-cbs.py
10#
11# Copyright (C) 2021 Facebook, Inc.
12#
13# Authors: Paul E. McKenney <paulmck@kernel.org>
14
15import sys
16import drgn
17from drgn import NULL, Object
18from drgn.helpers.linux import *
19
20def get_rdp0(prog):
21	try:
22		rdp0 = prog.variable('rcu_preempt_data', 'kernel/rcu/tree.c');
23	except LookupError:
24		rdp0 = NULL;
25
26	if rdp0 == NULL:
27		try:
28			rdp0 = prog.variable('rcu_sched_data',
29					     'kernel/rcu/tree.c');
30		except LookupError:
31			rdp0 = NULL;
32
33	if rdp0 == NULL:
34		rdp0 = prog.variable('rcu_data', 'kernel/rcu/tree.c');
35	return rdp0.address_of_();
36
37rdp0 = get_rdp0(prog);
38
39# Sum up RCU callbacks.
40sum = 0;
41for cpu in for_each_possible_cpu(prog):
42	rdp = per_cpu_ptr(rdp0, cpu);
43	len = rdp.cblist.len.value_();
44	# print("CPU " + str(cpu) + " RCU callbacks: " + str(len));
45	sum += len;
46print("Number of RCU callbacks in flight: " + str(sum));
47