therm_throt.c

/*
 * linux/arch/i386/kerne/cpu/mcheck/therm_throt.c
 *
 * Thermal throttle event support code (such as syslog messaging and rate
 * limiting) that was factored out from x86_64 (mce_intel.c) and i386 (p4.c).
 * This allows consistent reporting of CPU thermal throttle events.
 *
 * Maintains a counter in /sys that keeps track of the number of thermal
 * events, such that the user knows how bad the thermal problem might be
 * (since the logging to syslog and mcelog is rate limited).
 *
 * Author: Dmitriy Zavin (dmitriyz@google.com)
 *
 * Credits: Adapted from Zwane Mwaikambo's original code in mce_intel.c.
 *          Inspired by Ross Biro's and Al Borchers' counter code.
 */

#include <linux/percpu.h>
#include <linux/sysdev.h>
#include <linux/cpu.h>
#include <asm/cpu.h>
#include <linux/notifier.h>
#include <linux/jiffies.h>
#include <asm/therm_throt.h>

/* How long to wait between reporting thermal events */
#define CHECK_INTERVAL              (300 * HZ)

static DEFINE_PER_CPU(__u64, next_check) = INITIAL_JIFFIES;
static DEFINE_PER_CPU(unsigned long, thermal_throttle_count);
atomic_t therm_throt_en = ATOMIC_INIT(0);

#ifdef CONFIG_SYSFS
#define define_therm_throt_sysdev_one_ro(_name)                              \
        static SYSDEV_ATTR(_name, 0444, therm_throt_sysdev_show_##_name, NULL)

#define define_therm_throt_sysdev_show_func(name)                            \
static ssize_t therm_throt_sysdev_show_##name(struct sys_device *dev,        \
                                              char *buf)                     \
{                                                                            \
	unsigned int cpu = dev->id;                                          \
	ssize_t ret;                                                         \
                                                                             \
	preempt_disable();              /* CPU hotplug */                    \
	if (cpu_online(cpu))                                                 \
		ret = sprintf(buf, "%lu\n",                                  \
			      per_cpu(thermal_throttle_##name, cpu));        \
	else                                                                 \
		ret = 0;                                                     \
	preempt_enable();                                                    \
                                                                             \
	return ret;                                                          \
}

define_therm_throt_sysdev_show_func(count);
define_therm_throt_sysdev_one_ro(count);

static struct attribute *thermal_throttle_attrs[] = {
	&attr_count.attr,
	NULL
};

static struct attribute_group thermal_throttle_attr_group = {
	.attrs = thermal_throttle_attrs,
	.name = "thermal_throttle"
};
#endif /* CONFIG_SYSFS */

/***
 * therm_throt_process - Process thermal throttling event from interrupt
 * @curr: Whether the condition is current or not (boolean), since the
 *        thermal interrupt normally gets called both when the thermal
 *        event begins and once the event has ended.
 *
 * This function is called by the thermal interrupt after the
 * IRQ has been acknowledged.
 *
 * It will take care of rate limiting and printing messages to the syslog.
 *
 * Returns: 0 : Event should NOT be further logged, i.e. still in
 *              "timeout" from previous log message.
 *          1 : Event should be logged further, and a message has been
 *              printed to the syslog.
 */
int therm_throt_process(int curr)
{
	unsigned int cpu = smp_processor_id();
	__u64 tmp_jiffs = get_jiffies_64();

	if (curr)
		__get_cpu_var(thermal_throttle_count)++;

	if (time_before64(tmp_jiffs, __get_cpu_var(next_check)))
		return 0;

	__get_cpu_var(next_check) = tmp_jiffs + CHECK_INTERVAL;

	/* if we just entered the thermal event */
	if (curr) {
		printk(KERN_CRIT "CPU%d: Temperature above threshold, "
		       "cpu clock throttled (total events = %lu)\n", cpu,
		       __get_cpu_var(thermal_throttle_count));

		add_taint(TAINT_MACHINE_CHECK);
	} else {
		printk(KERN_CRIT "CPU%d: Temperature/speed normal\n", cpu);
	}

	return 1;
}

#ifdef CONFIG_SYSFS
/* Add/Remove thermal_throttle interface for CPU device */
static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev)
{
	return sysfs_create_group(&sys_dev->kobj, &thermal_throttle_attr_group);
}

static __cpuinit void thermal_throttle_remove_dev(struct sys_device *sys_dev)
{
	return sysfs_remove_group(&sys_dev->kobj, &thermal_throttle_attr_group);
}

/* Mutex protecting device creation against CPU hotplug */
static DEFINE_MUTEX(therm_cpu_lock);

/* Get notified when a cpu comes on/off. Be hotplug friendly. */
static __cpuinit int thermal_throttle_cpu_callback(struct notifier_block *nfb,
						   unsigned long action,
						   void *hcpu)
{
	unsigned int cpu = (unsigned long)hcpu;
	struct sys_device *sys_dev;
	int err;

	sys_dev = get_cpu_sysdev(cpu);
	mutex_lock(&therm_cpu_lock);
	switch (action) {
	case CPU_ONLINE:
		err = thermal_throttle_add_dev(sys_dev);
		WARN_ON(err);
		break;
	case CPU_DEAD:
		thermal_throttle_remove_dev(sys_dev);
		break;
	}
	mutex_unlock(&therm_cpu_lock);
	return NOTIFY_OK;
}

static struct notifier_block thermal_throttle_cpu_notifier =
{
	.notifier_call = thermal_throttle_cpu_callback,
};

static __init int thermal_throttle_init_device(void)
{
	unsigned int cpu = 0;
	int err;

	if (!atomic_read(&therm_throt_en))
		return 0;

	register_hotcpu_notifier(&thermal_throttle_cpu_notifier);

#ifdef CONFIG_HOTPLUG_CPU
	mutex_lock(&therm_cpu_lock);
#endif
	/* connect live CPUs to sysfs */
	for_each_online_cpu(cpu) {
		err = thermal_throttle_add_dev(get_cpu_sysdev(cpu));
		WARN_ON(err);
	}
#ifdef CONFIG_HOTPLUG_CPU
	mutex_unlock(&therm_cpu_lock);
#endif

	return 0;
}

device_initcall(thermal_throttle_init_device);
#endif /* CONFIG_SYSFS */