root/drivers/leds/trigger/ledtrig-activity.c

DEFINITIONS

1. led_activity_function
2. led_invert_show
3. led_invert_store
4. activity_activate
5. activity_deactivate
6. activity_reboot_notifier
7. activity_panic_notifier
8. activity_init
9. activity_exit

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Activity LED trigger
   4  *
   5  * Copyright (C) 2017 Willy Tarreau <w@1wt.eu>
   6  * Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
   7  */
   8 
   9 #include <linux/init.h>
  10 #include <linux/kernel.h>
  11 #include <linux/kernel_stat.h>
  12 #include <linux/leds.h>
  13 #include <linux/module.h>
  14 #include <linux/reboot.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/timer.h>
  18 #include "../leds.h"
  19 
  20 static int panic_detected;
  21 
  22 struct activity_data {
  23         struct timer_list timer;
  24         struct led_classdev *led_cdev;
  25         u64 last_used;
  26         u64 last_boot;
  27         int time_left;
  28         int state;
  29         int invert;
  30 };
  31 
  32 static void led_activity_function(struct timer_list *t)
  33 {
  34         struct activity_data *activity_data = from_timer(activity_data, t,
  35                                                          timer);
  36         struct led_classdev *led_cdev = activity_data->led_cdev;
  37         unsigned int target;
  38         unsigned int usage;
  39         int delay;
  40         u64 curr_used;
  41         u64 curr_boot;
  42         s32 diff_used;
  43         s32 diff_boot;
  44         int cpus;
  45         int i;
  46 
  47         if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
  48                 led_cdev->blink_brightness = led_cdev->new_blink_brightness;
  49 
  50         if (unlikely(panic_detected)) {
  51                 /* full brightness in case of panic */
  52                 led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
  53                 return;
  54         }
  55 
  56         cpus = 0;
  57         curr_used = 0;
  58 
  59         for_each_possible_cpu(i) {
  60                 curr_used += kcpustat_cpu(i).cpustat[CPUTIME_USER]
  61                           +  kcpustat_cpu(i).cpustat[CPUTIME_NICE]
  62                           +  kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]
  63                           +  kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]
  64                           +  kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
  65                 cpus++;
  66         }
  67 
  68         /* We come here every 100ms in the worst case, so that's 100M ns of
  69          * cumulated time. By dividing by 2^16, we get the time resolution
  70          * down to 16us, ensuring we won't overflow 32-bit computations below
  71          * even up to 3k CPUs, while keeping divides cheap on smaller systems.
  72          */
  73         curr_boot = ktime_get_boottime_ns() * cpus;
  74         diff_boot = (curr_boot - activity_data->last_boot) >> 16;
  75         diff_used = (curr_used - activity_data->last_used) >> 16;
  76         activity_data->last_boot = curr_boot;
  77         activity_data->last_used = curr_used;
  78 
  79         if (diff_boot <= 0 || diff_used < 0)
  80                 usage = 0;
  81         else if (diff_used >= diff_boot)
  82                 usage = 100;
  83         else
  84                 usage = 100 * diff_used / diff_boot;
  85 
  86         /*
  87          * Now we know the total boot_time multiplied by the number of CPUs, and
  88          * the total idle+wait time for all CPUs. We'll compare how they evolved
  89          * since last call. The % of overall CPU usage is :
  90          *
  91          *      1 - delta_idle / delta_boot
  92          *
  93          * What we want is that when the CPU usage is zero, the LED must blink
  94          * slowly with very faint flashes that are detectable but not disturbing
  95          * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
  96          * blinking frequency to increase up to the point where the load is
  97          * enough to saturate one core in multi-core systems or 50% in single
  98          * core systems. At this point it should reach 10 Hz with a 10/90 duty
  99          * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
 100          * remains stable (10 Hz) and only the duty cycle increases to report
 101          * the activity, up to the point where we have 90ms ON, 10ms OFF when
 102          * all cores are saturated. It's important that the LED never stays in
 103          * a steady state so that it's easy to distinguish an idle or saturated
 104          * machine from a hung one.
 105          *
 106          * This gives us :
 107          *   - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
 108          *     (10ms ON, 90ms OFF)
 109          *   - below target :
 110          *      ON_ms  = 10
 111          *      OFF_ms = 90 + (1 - usage/target) * 900
 112          *   - above target :
 113          *      ON_ms  = 10 + (usage-target)/(100%-target) * 80
 114          *      OFF_ms = 90 - (usage-target)/(100%-target) * 80
 115          *
 116          * In order to keep a good responsiveness, we cap the sleep time to
 117          * 100 ms and keep track of the sleep time left. This allows us to
 118          * quickly change it if needed.
 119          */
 120 
 121         activity_data->time_left -= 100;
 122         if (activity_data->time_left <= 0) {
 123                 activity_data->time_left = 0;
 124                 activity_data->state = !activity_data->state;
 125                 led_set_brightness_nosleep(led_cdev,
 126                         (activity_data->state ^ activity_data->invert) ?
 127                         led_cdev->blink_brightness : LED_OFF);
 128         }
 129 
 130         target = (cpus > 1) ? (100 / cpus) : 50;
 131 
 132         if (usage < target)
 133                 delay = activity_data->state ?
 134                         10 :                        /* ON  */
 135                         990 - 900 * usage / target; /* OFF */
 136         else
 137                 delay = activity_data->state ?
 138                         10 + 80 * (usage - target) / (100 - target) : /* ON  */
 139                         90 - 80 * (usage - target) / (100 - target);  /* OFF */
 140 
 141 
 142         if (!activity_data->time_left || delay <= activity_data->time_left)
 143                 activity_data->time_left = delay;
 144 
 145         delay = min_t(int, activity_data->time_left, 100);
 146         mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
 147 }
 148 
 149 static ssize_t led_invert_show(struct device *dev,
 150                                struct device_attribute *attr, char *buf)
 151 {
 152         struct activity_data *activity_data = led_trigger_get_drvdata(dev);
 153 
 154         return sprintf(buf, "%u\n", activity_data->invert);
 155 }
 156 
 157 static ssize_t led_invert_store(struct device *dev,
 158                                 struct device_attribute *attr,
 159                                 const char *buf, size_t size)
 160 {
 161         struct activity_data *activity_data = led_trigger_get_drvdata(dev);
 162         unsigned long state;
 163         int ret;
 164 
 165         ret = kstrtoul(buf, 0, &state);
 166         if (ret)
 167                 return ret;
 168 
 169         activity_data->invert = !!state;
 170 
 171         return size;
 172 }
 173 
 174 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
 175 
 176 static struct attribute *activity_led_attrs[] = {
 177         &dev_attr_invert.attr,
 178         NULL
 179 };
 180 ATTRIBUTE_GROUPS(activity_led);
 181 
 182 static int activity_activate(struct led_classdev *led_cdev)
 183 {
 184         struct activity_data *activity_data;
 185 
 186         activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
 187         if (!activity_data)
 188                 return -ENOMEM;
 189 
 190         led_set_trigger_data(led_cdev, activity_data);
 191 
 192         activity_data->led_cdev = led_cdev;
 193         timer_setup(&activity_data->timer, led_activity_function, 0);
 194         if (!led_cdev->blink_brightness)
 195                 led_cdev->blink_brightness = led_cdev->max_brightness;
 196         led_activity_function(&activity_data->timer);
 197         set_bit(LED_BLINK_SW, &led_cdev->work_flags);
 198 
 199         return 0;
 200 }
 201 
 202 static void activity_deactivate(struct led_classdev *led_cdev)
 203 {
 204         struct activity_data *activity_data = led_get_trigger_data(led_cdev);
 205 
 206         del_timer_sync(&activity_data->timer);
 207         kfree(activity_data);
 208         clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
 209 }
 210 
 211 static struct led_trigger activity_led_trigger = {
 212         .name       = "activity",
 213         .activate   = activity_activate,
 214         .deactivate = activity_deactivate,
 215         .groups     = activity_led_groups,
 216 };
 217 
 218 static int activity_reboot_notifier(struct notifier_block *nb,
 219                                     unsigned long code, void *unused)
 220 {
 221         led_trigger_unregister(&activity_led_trigger);
 222         return NOTIFY_DONE;
 223 }
 224 
 225 static int activity_panic_notifier(struct notifier_block *nb,
 226                                    unsigned long code, void *unused)
 227 {
 228         panic_detected = 1;
 229         return NOTIFY_DONE;
 230 }
 231 
 232 static struct notifier_block activity_reboot_nb = {
 233         .notifier_call = activity_reboot_notifier,
 234 };
 235 
 236 static struct notifier_block activity_panic_nb = {
 237         .notifier_call = activity_panic_notifier,
 238 };
 239 
 240 static int __init activity_init(void)
 241 {
 242         int rc = led_trigger_register(&activity_led_trigger);
 243 
 244         if (!rc) {
 245                 atomic_notifier_chain_register(&panic_notifier_list,
 246                                                &activity_panic_nb);
 247                 register_reboot_notifier(&activity_reboot_nb);
 248         }
 249         return rc;
 250 }
 251 
 252 static void __exit activity_exit(void)
 253 {
 254         unregister_reboot_notifier(&activity_reboot_nb);
 255         atomic_notifier_chain_unregister(&panic_notifier_list,
 256                                          &activity_panic_nb);
 257         led_trigger_unregister(&activity_led_trigger);
 258 }
 259 
 260 module_init(activity_init);
 261 module_exit(activity_exit);
 262 
 263 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>");
 264 MODULE_DESCRIPTION("Activity LED trigger");
 265 MODULE_LICENSE("GPL v2");