mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-25 22:20:55 +07:00
8daa127f4e
Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the clocksource dummy-timer code by using this latter form of callback registration. Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
75 lines
1.8 KiB
C
75 lines
1.8 KiB
C
/*
|
|
* linux/drivers/clocksource/dummy_timer.c
|
|
*
|
|
* Copyright (C) 2013 ARM Ltd.
|
|
* All Rights Reserved
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
#include <linux/clockchips.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/init.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/cpumask.h>
|
|
|
|
static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);
|
|
|
|
static void dummy_timer_set_mode(enum clock_event_mode mode,
|
|
struct clock_event_device *evt)
|
|
{
|
|
/*
|
|
* Core clockevents code will call this when exchanging timer devices.
|
|
* We don't need to do anything here.
|
|
*/
|
|
}
|
|
|
|
static void dummy_timer_setup(void)
|
|
{
|
|
int cpu = smp_processor_id();
|
|
struct clock_event_device *evt = __this_cpu_ptr(&dummy_timer_evt);
|
|
|
|
evt->name = "dummy_timer";
|
|
evt->features = CLOCK_EVT_FEAT_PERIODIC |
|
|
CLOCK_EVT_FEAT_ONESHOT |
|
|
CLOCK_EVT_FEAT_DUMMY;
|
|
evt->rating = 100;
|
|
evt->set_mode = dummy_timer_set_mode;
|
|
evt->cpumask = cpumask_of(cpu);
|
|
|
|
clockevents_register_device(evt);
|
|
}
|
|
|
|
static int dummy_timer_cpu_notify(struct notifier_block *self,
|
|
unsigned long action, void *hcpu)
|
|
{
|
|
if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
|
|
dummy_timer_setup();
|
|
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static struct notifier_block dummy_timer_cpu_nb = {
|
|
.notifier_call = dummy_timer_cpu_notify,
|
|
};
|
|
|
|
static int __init dummy_timer_register(void)
|
|
{
|
|
int err = 0;
|
|
|
|
cpu_notifier_register_begin();
|
|
err = __register_cpu_notifier(&dummy_timer_cpu_nb);
|
|
if (err)
|
|
goto out;
|
|
|
|
/* We won't get a call on the boot CPU, so register immediately */
|
|
if (num_possible_cpus() > 1)
|
|
dummy_timer_setup();
|
|
|
|
out:
|
|
cpu_notifier_register_done();
|
|
return err;
|
|
}
|
|
early_initcall(dummy_timer_register);
|