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Date: Thu, 12 Dec 2013 16:01:11 -0800
From: Zoran Markovic <zoran.markovic@...aro.org>
To: Eduardo Valentin <eduardo.valentin@...com>
Cc: lkml <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
Linux PM list <linux-pm@...r.kernel.org>,
Zhang Rui <rui.zhang@...el.com>, Rob Landley <rob@...dley.net>,
Amit Daniel Kachhap <amit.daniel@...sung.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Durgadoss R <durgadoss.r@...el.com>,
Christian Daudt <bcm@...thebug.org>,
James King <james.king@...aro.org>
Subject: Re: [RFC PATCH] thermal: add generic cpu hotplug cooling device
Hi Eduardo,
> Yeah, I would like to see it. But what I was more interested in seeing
> is how long does it take to offline a CPU?
>
I profiled this over 70 shutdown/startup cycles of CPU1 on Capri-AP
(Cortex-A9x2) board and I get:
shutdown: 1445usec (average), 3159usec (maximum), 834usec (minimum)
startup: 707usec (average), 3159usec (maximum), 327usec (minimum)
It's using a 32KHz clock so time resolution is ~30usec.
Regards, Zoran
>>>>> On 20 September 2013 15:15, Zoran Markovic <zoran.markovic@...aro.org> wrote:
>>>>>> This patch implements a generic CPU hotplug cooling device. The
>>>>>> implementation scales down the number of running CPUs when temperature
>>>>>> increases through a thermal trip point and prevents booting CPUs
>>>>>> until thermal conditions are restored. Upon restoration, the action
>>>>>> of starting up a CPU is left to another entity (e.g. CPU offline
>>>>>> governor, for which a patch is in the works).
>>>>>>
>>>>>> In the past two years, ARM considerably reduced the time required for
>>>>>> CPUs to boot and shutdown; this time is now measured in microseconds.
>>>>>> This patch is predominantly intended for ARM big.LITTLE architectures
>>>>>> where big cores are expected to have a much bigger impact on thermal
>>>>>> budget than little cores, resulting in fast temperature ramps to a trip
>>>>>> point, i.e. thermal runaways. Switching off the big core(s) may be one
>>>>>> of the recovery mechanisms to restore system temperature, but the actual
>>>>>> strategy is left to the thermal governor.
>>>>>>
>>>>>> The assumption is that CPU shutdown/startup is a rare event, so no
>>>>>> attempt was made to make the code atomic, i.e. the code evidently races
>>>>>> with CPU hotplug driver. The set_cur_state() function offlines CPUs
>>>>>> iteratively one at a time, checking the cooling state before each CPU
>>>>>> shutdown. A hotplug notifier callback validates any CPU boot requests
>>>>>> against current cooling state and approves/denies accordingly. This
>>>>>> mechanism guarantees that the desired cooling state could be reached in a
>>>>>> maximum of d-c iterations, where d and c are the "desired" and "current"
>>>>>> cooling states expressed in the number of offline CPUs.
>>>>>>
>>>>>> Credits to Amit Daniel Kachhap for initial attempt to upstream this feature.
>>>>>>
>>>>>> Cc: Zhang Rui <rui.zhang@...el.com>
>>>>>> Cc: Eduardo Valentin <eduardo.valentin@...com>
>>>>>> Cc: Rob Landley <rob@...dley.net>
>>>>>> Cc: Amit Daniel Kachhap <amit.daniel@...sung.com>
>>>>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>>>>> Cc: Durgadoss R <durgadoss.r@...el.com>
>>>>>> Cc: Christian Daudt <bcm@...thebug.org>
>>>>>> Cc: James King <james.king@...aro.org>
>>>>>> Signed-off-by: Zoran Markovic <zoran.markovic@...aro.org>
>>>>>> ---
>>>>>> Documentation/thermal/cpu-cooling-api.txt | 17 ++
>>>>>> drivers/thermal/Kconfig | 10 +
>>>>>> drivers/thermal/Makefile | 1 +
>>>>>> drivers/thermal/cpu_hotplug.c | 362 +++++++++++++++++++++++++++++
>>>>>> include/linux/cpuhp_cooling.h | 57 +++++
>>>>>> 5 files changed, 447 insertions(+)
>>>>>> create mode 100644 drivers/thermal/cpu_hotplug.c
>>>>>> create mode 100644 include/linux/cpuhp_cooling.h
>>>>>>
>>>>>> diff --git a/Documentation/thermal/cpu-cooling-api.txt b/Documentation/thermal/cpu-cooling-api.txt
>>>>>> index fca24c9..2f94f68 100644
>>>>>> --- a/Documentation/thermal/cpu-cooling-api.txt
>>>>>> +++ b/Documentation/thermal/cpu-cooling-api.txt
>>>>>> @@ -30,3 +30,20 @@ the user. The registration APIs returns the cooling device pointer.
>>>>>> This interface function unregisters the "thermal-cpufreq-%x" cooling device.
>>>>>>
>>>>>> cdev: Cooling device pointer which has to be unregistered.
>>>>>> +
>>>>>> +1.2 cpu hotplug registration/unregistration APIs
>>>>>> +1.2.1 struct thermal_cooling_device *cpuhp_cooling_register(
>>>>>> + struct cpumask *cpus, const char *ext)
>>>>>> +
>>>>>> + This function creates and registers a cpu hotplug cooling device with
>>>>>> + the name "cpu-hotplug-%s".
>>>>>> +
>>>>>> + cpus: cpumask of cpu cores participating in cooling.
>>>>>> + ext: instance-specific name of device
>>>>>> +
>>>>>> +1.2.2 void cpuhotplug_cooling_unregister(struct thermal_cooling_device *cdev)
>>>>>> +
>>>>>> + This function unregisters and frees the cpu hotplug cooling device cdev.
>>>>>> +
>>>>>> + cdev: Pointer to cooling device to unregister.
>>>>>> +
>>>>>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>>>>>> index 52b6ed7..3509100 100644
>>>>>> --- a/drivers/thermal/Kconfig
>>>>>> +++ b/drivers/thermal/Kconfig
>>>>>> @@ -79,6 +79,16 @@ config CPU_THERMAL
>>>>>>
>>>>>> If you want this support, you should say Y here.
>>>>>>
>>>>>> +config CPU_THERMAL_HOTPLUG
>>>>>> + bool "Generic CPU hotplug cooling"
>>>>>> + depends on HOTPLUG_CPU
>>>>>> + help
>>>>>> + Shutdown CPUs to prevent the device from overheating. This feature
>>>>>> + uses generic CPU hot-unplug capabilities to control device
>>>>>> + temperature. When the temperature increases over a trip point, a
>>>>>> + random subset of CPUs is shut down to reach the desired cooling
>>>>>> + state.
>>>>>> +
>>>>>> config THERMAL_EMULATION
>>>>>> bool "Thermal emulation mode support"
>>>>>> help
>>>>>> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
>>>>>> index 5ee0db0..0bd08be 100644
>>>>>> --- a/drivers/thermal/Makefile
>>>>>> +++ b/drivers/thermal/Makefile
>>>>>> @@ -12,6 +12,7 @@ thermal_sys-$(CONFIG_THERMAL_GOV_USER_SPACE) += user_space.o
>>>>>>
>>>>>> # cpufreq cooling
>>>>>> thermal_sys-$(CONFIG_CPU_THERMAL) += cpu_cooling.o
>>>>>> +thermal_sys-$(CONFIG_CPU_THERMAL_HOTPLUG) += cpu_hotplug.o
>>>>>>
>>>>>> # platform thermal drivers
>>>>>> obj-$(CONFIG_SPEAR_THERMAL) += spear_thermal.o
>>>>>> diff --git a/drivers/thermal/cpu_hotplug.c b/drivers/thermal/cpu_hotplug.c
>>>>>> new file mode 100644
>>>>>> index 0000000..8c3021e
>>>>>> --- /dev/null
>>>>>> +++ b/drivers/thermal/cpu_hotplug.c
>>>>>> @@ -0,0 +1,362 @@
>>>>>> +/*
>>>>>> + * drivers/thermal/cpu_hotplug.c
>>>>>> + *
>>>>>> + * Copyright (C) 2013 Broadcom Corporation Ltd.
>>>>>> + * Copyright (C) 2013 Zoran Markovic <zoran.markovic@...aro.org>
>>>>>> + *
>>>>>> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>> + * This program is free software; you can redistribute it and/or modify
>>>>>> + * it under the terms of the GNU General Public License as published by
>>>>>> + * the Free Software Foundation; version 2 of the License.
>>>>>> + *
>>>>>> + * This program is distributed in the hope that it will be useful, but
>>>>>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>>>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>>>>>> + * General Public License for more details.
>>>>>> + *
>>>>>> + * You should have received a copy of the GNU General Public License along
>>>>>> + * with this program; if not, write to the Free Software Foundation, Inc.,
>>>>>> + * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
>>>>>> + *
>>>>>> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>> + */
>>>>>> +#include <linux/module.h>
>>>>>> +#include <linux/thermal.h>
>>>>>> +#include <linux/workqueue.h>
>>>>>> +#include <linux/cpu.h>
>>>>>> +#include <linux/err.h>
>>>>>> +#include <linux/slab.h>
>>>>>> +#include <linux/cpuhp_cooling.h>
>>>>>> +
>>>>>> +/**
>>>>>> + * struct cpuhotplug_cooling_device - cpu hotplug cooling device data
>>>>>> + * @cpus: cpu mask representing cpus that can be hot-unplugged for cooling
>>>>>> + * @cdev: pointer to generic cooling device
>>>>>> + */
>>>>>> +struct cpuhotplug_cooling_device {
>>>>>> + unsigned int target;
>>>>>> + struct cpumask cpus;
>>>>>> + struct thermal_cooling_device *cdev;
>>>>>> + struct list_head list;
>>>>>> +};
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_list - list of all cpu hotplug cooling devices. Traversed
>>>>>> + * by cpu hotplug notifier to check constraints on booting cpus. Locked
>>>>>> + * by cpuhotplug_cooling_lock mutex.
>>>>>> + */
>>>>>> +static LIST_HEAD(cpuhotplug_list);
>>>>>> +static DEFINE_MUTEX(cpuhotplug_cooling_lock);
>>>>>> +
>>>>>> +/**
>>>>>> + * boot_cpu - return index of boot CPU; same criteria as in
>>>>>> + * disable_nonboot_cpus()
>>>>>> + */
>>>>>> +static inline int boot_cpu(void)
>>>>>> +{
>>>>>> + int cpu;
>>>>>> + get_online_cpus();
>>>>>> + cpu = cpumask_first(cpu_online_mask);
>>>>>> + put_online_cpus();
>>>>>> + return cpu;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * random_online_cpu - pick any online hot-unpluggable cpu
>>>>>> + * @d: pointer to cpuhotplug_cooling_device containing hot-pluggable cpu mask
>>>>>> + */
>>>>>> +static inline int random_online_cpu(struct cpuhotplug_cooling_device *d)
>>>>>> +{
>>>>>> + int cpu;
>>>>>> +
>>>>>> + get_online_cpus();
>>>>>> + cpu = any_online_cpu(d->cpus);
>>>>>> + put_online_cpus();
>>>>>> +
>>>>>> + return cpu;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * _num_offline_cpus - number of hot-pluggable cpus currently offline
>>>>>> + * @d: pointer to cpuhotplug_cooling_device containing hot-pluggable cpu mask
>>>>>> + */
>>>>>> +static inline int _num_offline_cpus(struct cpuhotplug_cooling_device *d)
>>>>>> +{
>>>>>> + struct cpumask offline;
>>>>>> +
>>>>>> + cpumask_andnot(&offline, &(d->cpus), cpu_online_mask);
>>>>>> + return cpumask_weight(&offline);
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * num_offline_cpus - same as _num_offline_cpus, but safe from background
>>>>>> + * hotplug events.
>>>>>> + * @d: pointer to cpuhotplug_cooling_device containing hot-pluggable cpu mask
>>>>>> + */
>>>>>> +static inline int num_offline_cpus(struct cpuhotplug_cooling_device *d)
>>>>>> +{
>>>>>> + int num;
>>>>>> +
>>>>>> + get_online_cpus();
>>>>>> + num = _num_offline_cpus(d);
>>>>>> + put_online_cpus();
>>>>>> +
>>>>>> + return num;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_get_max_state - get maximum cooling state of device
>>>>>> + * @cdev: pointer to generic cooling device
>>>>>> + * @state: returned maximum cooling state
>>>>>> + *
>>>>>> + * Thermal framework callback to get the maximum cooling state of cpu
>>>>>> + * hotplug cooling device.
>>>>>> + *
>>>>>> + * Return: always 0.
>>>>>> + */
>>>>>> +static int cpuhotplug_get_max_state(struct thermal_cooling_device *cdev,
>>>>>> + unsigned long *state)
>>>>>> +{
>>>>>> + struct cpuhotplug_cooling_device *d = cdev->devdata;
>>>>>> +
>>>>>> + /* defined as number of CPUs in hot-pluggable mask: this is invariant */
>>>>>> + *state = cpumask_weight(&(d->cpus));
>>>>>> +
>>>>>> + return 0;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_get_cur_state - get current cooling state of device
>>>>>> + * @cdev: pointer to generic cooling device
>>>>>> + * @state: current cooling state
>>>>>> + *
>>>>>> + * Thermal framework callback to get the current cooling state of cpu
>>>>>> + * hotplug cooling device.
>>>>>> + *
>>>>>> + * Return: always 0.
>>>>>> + */
>>>>>> +static int cpuhotplug_get_cur_state(struct thermal_cooling_device *cdev,
>>>>>> + unsigned long *state)
>>>>>> +{
>>>>>> + struct cpuhotplug_cooling_device *d = cdev->devdata;
>>>>>> +
>>>>>> + *state = d->target;
>>>>>> +
>>>>>> + return 0;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_get_cur_state - set cooling state of device
>>>>>> + * @cdev: pointer to generic cooling device
>>>>>> + * @state: cooling state
>>>>>> + *
>>>>>> + * Thermal framework callback to set/change cooling state of cpu hotplug
>>>>>> + * cooling device.
>>>>>> + *
>>>>>> + * Return: 0 on success, or error code otherwise
>>>>>> + */
>>>>>> +static int cpuhotplug_set_cur_state(struct thermal_cooling_device *cdev,
>>>>>> + unsigned long state)
>>>>>> +{
>>>>>> + struct cpuhotplug_cooling_device *d = cdev->devdata;
>>>>>> + unsigned long cstate;
>>>>>> + unsigned int cpu;
>>>>>> + int err = 0;
>>>>>> +
>>>>>> + if (state > cpumask_weight(&(d->cpus)))
>>>>>> + return -EINVAL; /* out of allowed range */
>>>>>> +
>>>>>> + /*
>>>>>> + * Set target state here; hot-unplug CPUs if we are too hot, but
>>>>>> + * don't attempt to hot-plug CPUs if we're cold. Starting CPUs
>>>>>> + * should be left to CPUOffline governor.
>>>>>> + *
>>>>>> + * There is a chance that CPU hotplug driver is racing with this
>>>>>> + * code. Rather than trying to make the procedure atomic, iterate
>>>>>> + * until we reach the desired state, or signal error if the state
>>>>>> + * cannot be reached.
>>>>>> + *
>>>>>> + * Neither CPU hotplug nor this code is expected to run too often.
>>>>>> + */
>>>>>> + d->target = state;
>>>>>> +
>>>>>> + /* compare desired cooling state to current cooling state */
>>>>>> + while ((cstate = num_offline_cpus(d)) < state && !err) {
>>>>>> + /* cstate < cstate: we're too hot, unplug any cpu */
>>>>>> + cpu = random_online_cpu(d);
>>>>>> + if (cpu < nr_cpu_ids)
>>>>>> + err = work_on_cpu(boot_cpu(),
>>>>>> + (long(*)(void *))cpu_down,
>>>>>> + (void *)cpu);
>>>>>> + /* on error, message would come from cpu_down() */
>>>>>> + else {
>>>>>> + pr_warn("cpuhotplug: CPUs already down\n");
>>>>>> + err = -EAGAIN;
>>>>>> + }
>>>>>> + }
>>>>>> +
>>>>>> + return err;
>>>>>> +}
>>>>>> +
>>>>>> +/* cpu hotplug cooling device ops */
>>>>>> +static struct thermal_cooling_device_ops const cpuhotplug_cooling_ops = {
>>>>>> + .get_max_state = cpuhotplug_get_max_state,
>>>>>> + .get_cur_state = cpuhotplug_get_cur_state,
>>>>>> + .set_cur_state = cpuhotplug_set_cur_state,
>>>>>> +};
>>>>>> +
>>>>>> +/**
>>>>>> + * _cpu_startup_allowed - traverse list of hotplug cooling devices to
>>>>>> + * check if startup of cpu violates thermal constraints
>>>>>> + */
>>>>>> +static inline int _cpu_startup_allowed(int cpu)
>>>>>> +{
>>>>>> + struct cpuhotplug_cooling_device *d;
>>>>>> + int ret = 1;
>>>>>> +
>>>>>> + /*
>>>>>> + * Prevent starting CPU if it violates any cooling
>>>>>> + * device's constraint. Called from hotplug notifier, so
>>>>>> + * cpu_up()/cpu_down() already holds a lock on hotplug
>>>>>> + * events.
>>>>>> + */
>>>>>> + mutex_lock(&cpuhotplug_cooling_lock);
>>>>>> + list_for_each_entry(d, &cpuhotplug_list, list) {
>>>>>> + if (cpumask_test_cpu(cpu, &(d->cpus)) &&
>>>>>> + d->target >= _num_offline_cpus(d)) {
>>>>>> + pr_warn("%s: CPU%d startup prevented\n",
>>>>>> + dev_name(&(d->cdev->device)), cpu);
>>>>>> + ret = 0;
>>>>>> + break;
>>>>>> + }
>>>>>> + }
>>>>>> + mutex_unlock(&cpuhotplug_cooling_lock);
>>>>>> + return ret;
>>>>>> +}
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_thermal_notifier - notifier callback for CPU hotplug events.
>>>>>> + * @nb: struct notifier_block
>>>>>> + * @event: cpu hotplug event for which callback is invoked.
>>>>>> + * @data: context data, in this particular case CPU index.
>>>>>> + *
>>>>>> + * Callback intercepting CPU hotplug events. Compares CPU hotplug action
>>>>>> + * with current thermal state and allows/denies accordingly.
>>>>>> + *
>>>>>> + * Return: 0 (allow) or error (deny).
>>>>>> + */
>>>>>> +static int cpuhotplug_thermal_notifier(struct notifier_block *nb,
>>>>>> + unsigned long event, void *data)
>>>>>> +{
>>>>>> + int cpu = (int)data;
>>>>>> +
>>>>>> + switch (event) {
>>>>>> + case CPU_UP_PREPARE:
>>>>>> + case CPU_UP_PREPARE_FROZEN:
>>>>>> + /* _cpu_up() only cares about result from CPU_UP_PREPAREs */
>>>>>> + if (!_cpu_startup_allowed(cpu))
>>>>>> + return notifier_from_errno(-EAGAIN);
>>>>>> + break;
>>>>>> + default:
>>>>>> + /* allow all other actions */
>>>>>> + break;
>>>>>> + }
>>>>>> + return 0;
>>>>>> +}
>>>>>> +
>>>>>> +static struct notifier_block cpuhotplug_thermal_notifier_block = {
>>>>>> + .notifier_call = cpuhotplug_thermal_notifier,
>>>>>> +};
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_cooling_register - create cpu hotplug cooling device
>>>>>> + * @cpus: cpumask of cpu cores participating in cooling
>>>>>> + * @ext: instance-specific name of device
>>>>>> + *
>>>>>> + * Creates and registers a cpu hotplug cooling device with the name
>>>>>> + * "cpu-hotplug-<ext>".
>>>>>> + *
>>>>>> + * Return: valid pointer to cpuhotplug_cooling_device struct on success,
>>>>>> + * corresponding ERR_PTR() on failure.
>>>>>> + */
>>>>>> +struct thermal_cooling_device *
>>>>>> +cpuhotplug_cooling_register(const struct cpumask *cpus, const char *ext)
>>>>>> +{
>>>>>> + struct thermal_cooling_device *cdev;
>>>>>> + struct cpuhotplug_cooling_device *cpuhotplug_cdev;
>>>>>> + struct cpumask test;
>>>>>> + char name[THERMAL_NAME_LENGTH];
>>>>>> + int err;
>>>>>> +
>>>>>> + /* test if we passed in a good cpumask */
>>>>>> + cpu_maps_update_begin();
>>>>>> + cpumask_and(&test, cpus, cpu_possible_mask);
>>>>>> + cpu_maps_update_done();
>>>>>> +
>>>>>> + if (cpumask_test_cpu(boot_cpu(), &test)) {
>>>>>> + pr_warn("cannot hot-plug boot CPU%d\n", boot_cpu());
>>>>>> + cpumask_clear_cpu(boot_cpu(), &test);
>>>>>> + }
>>>>>> + if (cpumask_empty(&test)) {
>>>>>> + pr_err("CPUs unavailable for hot-plug cooling\n");
>>>>>> + err = -EINVAL;
>>>>>> + goto out;
>>>>>> + }
>>>>>> +
>>>>>> + cpuhotplug_cdev = kzalloc(sizeof(struct cpuhotplug_cooling_device),
>>>>>> + GFP_KERNEL);
>>>>>> + if (!cpuhotplug_cdev) {
>>>>>> + err = -ENOMEM;
>>>>>> + goto out;
>>>>>> + }
>>>>>> +
>>>>>> + cpumask_copy(&cpuhotplug_cdev->cpus, &test);
>>>>>> +
>>>>>> + snprintf(name, sizeof(name), "cpu-hotplug-%s", ext);
>>>>>> +
>>>>>> + cpuhotplug_cdev->target = 0;
>>>>>> + cdev = thermal_cooling_device_register(name, cpuhotplug_cdev,
>>>>>> + &cpuhotplug_cooling_ops);
>>>>>> + if (!cdev) {
>>>>>> + pr_err("%s: cooling device registration failed.\n", name);
>>>>>> + err = -EINVAL;
>>>>>> + goto out_free;
>>>>>> + }
>>>>>> + cpuhotplug_cdev->cdev = cdev;
>>>>>> +
>>>>>> + mutex_lock(&cpuhotplug_cooling_lock);
>>>>>> + if (list_empty(&cpuhotplug_list))
>>>>>> + register_cpu_notifier(&cpuhotplug_thermal_notifier_block);
>>>>>> + list_add(&(cpuhotplug_cdev->list), &cpuhotplug_list);
>>>>>> + mutex_unlock(&cpuhotplug_cooling_lock);
>>>>>> +
>>>>>> + return cdev;
>>>>>> +
>>>>>> +out_free:
>>>>>> + kfree(cpuhotplug_cdev);
>>>>>> +out:
>>>>>> + return ERR_PTR(err);
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(cpuhotplug_cooling_register);
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_cooling_unregister - remove cpu hotplug cooling device
>>>>>> + * @cdev: cooling device to remove
>>>>>> + *
>>>>>> + * Unregisters and frees the cpu hotplug cooling device.
>>>>>> + */
>>>>>> +void cpuhotplug_cooling_unregister(struct thermal_cooling_device *cdev)
>>>>>> +{
>>>>>> + struct cpuhotplug_cooling_device *cpuhotplug_cdev = cdev->devdata;
>>>>>> +
>>>>>> + mutex_lock(&cpuhotplug_cooling_lock);
>>>>>> + list_del(&(cpuhotplug_cdev->list));
>>>>>> + if (list_empty(&cpuhotplug_list))
>>>>>> + unregister_cpu_notifier(&cpuhotplug_thermal_notifier_block);
>>>>>> + mutex_unlock(&cpuhotplug_cooling_lock);
>>>>>> +
>>>>>> + thermal_cooling_device_unregister(cpuhotplug_cdev->cdev);
>>>>>> + kfree(cpuhotplug_cdev);
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(cpuhotplug_cooling_unregister);
>>>>>> +
>>>>>> diff --git a/include/linux/cpuhp_cooling.h b/include/linux/cpuhp_cooling.h
>>>>>> new file mode 100644
>>>>>> index 0000000..ace1d5b
>>>>>> --- /dev/null
>>>>>> +++ b/include/linux/cpuhp_cooling.h
>>>>>> @@ -0,0 +1,57 @@
>>>>>> +/*
>>>>>> + * linux/include/linux/cpuhp_cooling.h
>>>>>> + *
>>>>>> + * Copyright (C) 2013 Broadcom Corporation Ltd.
>>>>>> + * Copyright (C) 2013 Zoran Markovic <zoran.markovic@...aro.org>
>>>>>> + *
>>>>>> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>> + * This program is free software; you can redistribute it and/or modify
>>>>>> + * it under the terms of the GNU General Public License as published by
>>>>>> + * the Free Software Foundation; version 2 of the License.
>>>>>> + *
>>>>>> + * This program is distributed in the hope that it will be useful, but
>>>>>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>>>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>>>>>> + * General Public License for more details.
>>>>>> + *
>>>>>> + * You should have received a copy of the GNU General Public License along
>>>>>> + * with this program; if not, write to the Free Software Foundation, Inc.,
>>>>>> + * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
>>>>>> + *
>>>>>> + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>> + */
>>>>>> +
>>>>>> +#ifndef __CPUHP_COOLING_H__
>>>>>> +#define __CPUHP_COOLING_H__
>>>>>> +
>>>>>> +#include <linux/thermal.h>
>>>>>> +#include <linux/cpumask.h>
>>>>>> +
>>>>>> +#ifdef CONFIG_CPU_THERMAL_HOTPLUG
>>>>>> +/**
>>>>>> + * cpuhotplug_cooling_register - create cpu hotplug cooling device.
>>>>>> + * @cpus: cpumask of hot-pluggable cpus
>>>>>> + * @ext: instance-specific device name
>>>>>> + */
>>>>>> +struct thermal_cooling_device *
>>>>>> +cpuhotplug_cooling_register(const struct cpumask *cpus, const char *ext);
>>>>>> +
>>>>>> +/**
>>>>>> + * cpuhotplug_cooling_unregister - remove cpu hoptlug cooling device.
>>>>>> + * @cdev: thermal cooling device pointer.
>>>>>> + */
>>>>>> +void cpuhotplug_cooling_unregister(struct thermal_cooling_device *cdev);
>>>>>> +#else /* !CONFIG_CPU_THERMAL_HOTPLUG */
>>>>>> +static inline struct thermal_cooling_device *
>>>>>> +cpuhotplug_cooling_register(const struct cpumask *cpus, const char *ext)
>>>>>> +{
>>>>>> + return NULL;
>>>>>> +}
>>>>>> +static inline
>>>>>> +void cpuhotplug_cooling_unregister(struct thermal_cooling_device *cdev)
>>>>>> +{
>>>>>> + return;
>>>>>> +}
>>>>>> +#endif /* CONFIG_CPU_THERMAL_HOTPLUG */
>>>>>> +
>>>>>> +#endif /* __CPU_COOLING_H__ */
>>>>>> --
>>>>>> 1.7.9.5
>>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> You have got to be excited about what you are doing. (L. Lamport)
>>>
>>> Eduardo Valentin
>>>
>>
>>
>
>
> --
> You have got to be excited about what you are doing. (L. Lamport)
>
> Eduardo Valentin
>
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