// SPDX-License-Identifier: GPL-2.0-only
/*
* Activity LED trigger
*
* Copyright (C) 2017 Willy Tarreau <[email protected]>
* Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/panic_notifier.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/timer.h>
#include "../leds.h"
static int panic_detected;
struct activity_data {
struct timer_list timer;
struct led_classdev *led_cdev;
u64 last_used;
u64 last_boot;
int time_left;
int state;
int invert;
};
static void led_activity_function(struct timer_list *t)
{
struct activity_data *activity_data = from_timer(activity_data, t,
timer);
struct led_classdev *led_cdev = activity_data->led_cdev;
unsigned int target;
unsigned int usage;
int delay;
u64 curr_used;
u64 curr_boot;
s32 diff_used;
s32 diff_boot;
int cpus;
int i;
if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
led_cdev->blink_brightness = led_cdev->new_blink_brightness;
if (unlikely(panic_detected)) {
/* full brightness in case of panic */
led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
return;
}
cpus = 0;
curr_used = 0;
for_each_possible_cpu(i) {
struct kernel_cpustat kcpustat;
kcpustat_cpu_fetch(&kcpustat, i);
curr_used += kcpustat.cpustat[CPUTIME_USER]
+ kcpustat.cpustat[CPUTIME_NICE]
+ kcpustat.cpustat[CPUTIME_SYSTEM]
+ kcpustat.cpustat[CPUTIME_SOFTIRQ]
+ kcpustat.cpustat[CPUTIME_IRQ];
cpus++;
}
/* We come here every 100ms in the worst case, so that's 100M ns of
* cumulated time. By dividing by 2^16, we get the time resolution
* down to 16us, ensuring we won't overflow 32-bit computations below
* even up to 3k CPUs, while keeping divides cheap on smaller systems.
*/
curr_boot = ktime_get_boottime_ns() * cpus;
diff_boot = (curr_boot - activity_data->last_boot) >> 16;
diff_used = (curr_used - activity_data->last_used) >> 16;
activity_data->last_boot = curr_boot;
activity_data->last_used = curr_used;
if (diff_boot <= 0 || diff_used < 0)
usage = 0;
else if (diff_used >= diff_boot)
usage = 100;
else
usage = 100 * diff_used / diff_boot;
/*
* Now we know the total boot_time multiplied by the number of CPUs, and
* the total idle+wait time for all CPUs. We'll compare how they evolved
* since last call. The % of overall CPU usage is :
*
* 1 - delta_idle / delta_boot
*
* What we want is that when the CPU usage is zero, the LED must blink
* slowly with very faint flashes that are detectable but not disturbing
* (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
* blinking frequency to increase up to the point where the load is
* enough to saturate one core in multi-core systems or 50% in single
* core systems. At this point it should reach 10 Hz with a 10/90 duty
* cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
* remains stable (10 Hz) and only the duty cycle increases to report
* the activity, up to the point where we have 90ms ON, 10ms OFF when
* all cores are saturated. It's important that the LED never stays in
* a steady state so that it's easy to distinguish an idle or saturated
* machine from a hung one.
*
* This gives us :
* - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
* (10ms ON, 90ms OFF)
* - below target :
* ON_ms = 10
* OFF_ms = 90 + (1 - usage/target) * 900
* - above target :
* ON_ms = 10 + (usage-target)/(100%-target) * 80
* OFF_ms = 90 - (usage-target)/(100%-target) * 80
*
* In order to keep a good responsiveness, we cap the sleep time to
* 100 ms and keep track of the sleep time left. This allows us to
* quickly change it if needed.
*/
activity_data->time_left -= 100;
if (activity_data->time_left <= 0) {
activity_data->time_left = 0;
activity_data->state = !activity_data->state;
led_set_brightness_nosleep(led_cdev,
(activity_data->state ^ activity_data->invert) ?
led_cdev->blink_brightness : LED_OFF);
}
target = (cpus > 1) ? (100 / cpus) : 50;
if (usage < target)
delay = activity_data->state ?
10 : /* ON */
990 - 900 * usage / target; /* OFF */
else
delay = activity_data->state ?
10 + 80 * (usage - target) / (100 - target) : /* ON */
90 - 80 * (usage - target) / (100 - target); /* OFF */
if (!activity_data->time_left || delay <= activity_data->time_left)
activity_data->time_left = delay;
delay = min_t(int, activity_data->time_left, 100);
mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
}
static ssize_t led_invert_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct activity_data *activity_data = led_trigger_get_drvdata(dev);
return sprintf(buf, "%u\n", activity_data->invert);
}
static ssize_t led_invert_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t size)
{
struct activity_data *activity_data = led_trigger_get_drvdata(dev);
unsigned long state;
int ret;
ret = kstrtoul(buf, 0, &state);
if (ret)
return ret;
activity_data->invert = !!state;
return size;
}
static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
static struct attribute *activity_led_attrs[] = {
&dev_attr_invert.attr,
NULL
};
ATTRIBUTE_GROUPS(activity_led);
static int activity_activate(struct led_classdev *led_cdev)
{
struct activity_data *activity_data;
activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
if (!activity_data)
return -ENOMEM;
led_set_trigger_data(led_cdev, activity_data);
activity_data->led_cdev = led_cdev;
timer_setup(&activity_data->timer, led_activity_function, 0);
if (!led_cdev->blink_brightness)
led_cdev->blink_brightness = led_cdev->max_brightness;
led_activity_function(&activity_data->timer);
set_bit(LED_BLINK_SW, &led_cdev->work_flags);
return 0;
}
static void activity_deactivate(struct led_classdev *led_cdev)
{
struct activity_data *activity_data = led_get_trigger_data(led_cdev);
timer_shutdown_sync(&activity_data->timer);
kfree(activity_data);
clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
}
static struct led_trigger activity_led_trigger = {
.name = "activity",
.activate = activity_activate,
.deactivate = activity_deactivate,
.groups = activity_led_groups,
};
static int activity_reboot_notifier(struct notifier_block *nb,
unsigned long code, void *unused)
{
led_trigger_unregister(&activity_led_trigger);
return NOTIFY_DONE;
}
static int activity_panic_notifier(struct notifier_block *nb,
unsigned long code, void *unused)
{
panic_detected = 1;
return NOTIFY_DONE;
}
static struct notifier_block activity_reboot_nb = {
.notifier_call = activity_reboot_notifier,
};
static struct notifier_block activity_panic_nb = {
.notifier_call = activity_panic_notifier,
};
static int __init activity_init(void)
{
int rc = led_trigger_register(&activity_led_trigger);
if (!rc) {
atomic_notifier_chain_register(&panic_notifier_list,
&activity_panic_nb);
register_reboot_notifier(&activity_reboot_nb);
}
return rc;
}
static void __exit activity_exit(void)
{
unregister_reboot_notifier(&activity_reboot_nb);
atomic_notifier_chain_unregister(&panic_notifier_list,
&activity_panic_nb);
led_trigger_unregister(&activity_led_trigger);
}
module_init(activity_init);
module_exit(activity_exit);
MODULE_AUTHOR("Willy Tarreau <[email protected]>");
MODULE_DESCRIPTION("Activity LED trigger");
MODULE_LICENSE("GPL v2");
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