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
/*
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* linux/drivers/clocksource/dummy_timer.c
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*
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* Copyright (C) 2013 ARM Ltd.
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/clockchips.h>
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#include <linux/cpu.h>
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#include <linux/init.h>
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#include <linux/percpu.h>
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#include <linux/cpumask.h>
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static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);
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static void dummy_timer_set_mode(enum clock_event_mode mode,
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struct clock_event_device *evt)
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{
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/*
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* Core clockevents code will call this when exchanging timer devices.
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* We don't need to do anything here.
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*/
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}
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static void dummy_timer_setup(void)
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{
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int cpu = smp_processor_id();
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struct clock_event_device *evt = __this_cpu_ptr(&dummy_timer_evt);
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evt->name = "dummy_timer";
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evt->features = CLOCK_EVT_FEAT_PERIODIC |
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CLOCK_EVT_FEAT_ONESHOT |
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CLOCK_EVT_FEAT_DUMMY;
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evt->rating = 100;
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evt->set_mode = dummy_timer_set_mode;
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evt->cpumask = cpumask_of(cpu);
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clockevents_register_device(evt);
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}
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static int dummy_timer_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
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dummy_timer_setup();
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return NOTIFY_OK;
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}
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static struct notifier_block dummy_timer_cpu_nb = {
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.notifier_call = dummy_timer_cpu_notify,
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};
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static int __init dummy_timer_register(void)
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{
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int err = 0;
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cpu_notifier_register_begin();
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err = __register_cpu_notifier(&dummy_timer_cpu_nb);
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if (err)
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goto out;
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/* We won't get a call on the boot CPU, so register immediately */
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if (num_possible_cpus() > 1)
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dummy_timer_setup();
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out:
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cpu_notifier_register_done();
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return err;
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}
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early_initcall(dummy_timer_register);
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