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Message-ID: <52A5D3F1.9040301@ti.com>
Date: Mon, 9 Dec 2013 10:30:09 -0400
From: Eduardo Valentin <eduardo.valentin@...com>
To: Zoran Markovic <zoran.markovic@...aro.org>
CC: Eduardo Valentin <eduardo.valentin@...com>,
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
On 02-12-2013 19:05, Zoran Markovic wrote:
> Hi Eduardo,
> I have some graphs created for Broadcom's Capri (Cortex-A9x2) device.
> I do a full temperature ramp using ARM-proprietary test, which heats
> it up to ~48C. By hot-unplugging CPU1 I can cool it down to ~40C
> within seconds. Let me know if you'd like to see the graphs.
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?
> Regards, Zoran
>
> On 29 November 2013 06:08, Eduardo Valentin <eduardo.valentin@...com> wrote:
>> Hello Zoran,
>>
>> On 27-11-2013 17:56, Zoran Markovic wrote:
>>> Pinging again... Does anyone have any opinion on this feature?
>>
>> Sorry for not answering you. Yes there is interest in such work.
>> Besides, your patch is not the very first attempt to do so. If I
>> remember correctly, when Amit D. K was originally sending the current
>> cpu cooling device, it included a hotplug part. That is why it was named
>> cpucooling and not cpufreqcooling. Anyways, the major concerns by that
>> time was the latencies to off line a CPU, mainly due to task and
>> structure migration.
>>
>> Thus the question is, have you measure the behavior of your system when
>> using this cooling device? Does it present any cooling effectiveness
>> during high system load scenarios for instance? In case you have data,
>> would you be able to share them?
>>
>>
>>> Thanks,
>>> Zoran
>>>
>>> On 4 October 2013 15:52, Zoran Markovic <zoran.markovic@...aro.org> wrote:
>>>> Any comments on this proposed feature and implementation? Apparently
>>>> it's also useful for server systems.
>>
>>
>>
>>
>>>> Thanks,
>>>> 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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