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#!/usr/bin/env drgn
# SPDX-License-Identifier: GPL-2.0+
#
# Dump out the number of RCU callbacks outstanding.
#
# On older kernels having multiple flavors of RCU, this dumps out the
# number of callbacks for the most heavily used flavor.
#
# Usage: sudo drgn rcu-cbs.py
#
# Copyright (C) 2021 Facebook, Inc.
#
# Authors: Paul E. McKenney <paulmck@kernel.org>
import sys
import drgn
from drgn import NULL, Object
from drgn.helpers.linux import *
def get_rdp0(prog):
try:
rdp0 = prog.variable('rcu_preempt_data', 'kernel/rcu/tree.c');
except LookupError:
rdp0 = NULL;
if rdp0 == NULL:
try:
rdp0 = prog.variable('rcu_sched_data',
'kernel/rcu/tree.c');
except LookupError:
rdp0 = NULL;
if rdp0 == NULL:
rdp0 = prog.variable('rcu_data', 'kernel/rcu/tree.c');
return rdp0.address_of_();
rdp0 = get_rdp0(prog);
# Sum up RCU callbacks.
sum = 0;
for cpu in for_each_possible_cpu(prog):
rdp = per_cpu_ptr(rdp0, cpu);
len = rdp.cblist.len.value_();
# print("CPU " + str(cpu) + " RCU callbacks: " + str(len));
sum += len;
print("Number of RCU callbacks in flight: " + str(sum));
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