drivers/leds/trigger/ledtrig-activity.c

   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/panic_notifier.h>
  15 #include <linux/reboot.h>
  16 #include <linux/sched.h>
  17 #include <linux/slab.h>
  18 #include <linux/timer.h>
  19 #include "../leds.h"
  20
  21 static int panic_detected;
  22
  23 struct activity_data {
  24         struct timer_list timer;
  25         struct led_classdev *led_cdev;
  26         u64 last_used;
  27         u64 last_boot;
  28         int time_left;
  29         int state;
  30         int invert;
  31 };
  32
  33 static void led_activity_function(struct timer_list *t)
  34 {
  35         struct activity_data *activity_data = from_timer(activity_data, t,
  36                                                          timer);
  37         struct led_classdev *led_cdev = activity_data->led_cdev;
  38         unsigned int target;
  39         unsigned int usage;
  40         int delay;
  41         u64 curr_used;
  42         u64 curr_boot;
  43         s32 diff_used;
  44         s32 diff_boot;
  45         int cpus;
  46         int i;
  47
  48         if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
  49                 led_cdev->blink_brightness = led_cdev->new_blink_brightness;
  50
  51         if (unlikely(panic_detected)) {
  52                 /* full brightness in case of panic */
  53                 led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
  54                 return;
  55         }
  56
  57         cpus = 0;
  58         curr_used = 0;
  59
  60         for_each_possible_cpu(i) {
  61                 struct kernel_cpustat kcpustat;
  62
  63                 kcpustat_cpu_fetch(&kcpustat, i);
  64
  65                 curr_used += kcpustat.cpustat[CPUTIME_USER]
  66                           +  kcpustat.cpustat[CPUTIME_NICE]
  67                           +  kcpustat.cpustat[CPUTIME_SYSTEM]
  68                           +  kcpustat.cpustat[CPUTIME_SOFTIRQ]
  69                           +  kcpustat.cpustat[CPUTIME_IRQ];
  70                 cpus++;
  71         }
  72
  73         /* We come here every 100ms in the worst case, so that's 100M ns of
  74          * cumulated time. By dividing by 2^16, we get the time resolution
  75          * down to 16us, ensuring we won't overflow 32-bit computations below
  76          * even up to 3k CPUs, while keeping divides cheap on smaller systems.
  77          */
  78         curr_boot = ktime_get_boottime_ns() * cpus;
  79         diff_boot = (curr_boot - activity_data->last_boot) >> 16;
  80         diff_used = (curr_used - activity_data->last_used) >> 16;
  81         activity_data->last_boot = curr_boot;
  82         activity_data->last_used = curr_used;
  83
  84         if (diff_boot <= 0 || diff_used < 0)
  85                 usage = 0;
  86         else if (diff_used >= diff_boot)
  87                 usage = 100;
  88         else
  89                 usage = 100 * diff_used / diff_boot;
  90
  91         /*
  92          * Now we know the total boot_time multiplied by the number of CPUs, and
  93          * the total idle+wait time for all CPUs. We'll compare how they evolved
  94          * since last call. The % of overall CPU usage is :
  95          *
  96          *      1 - delta_idle / delta_boot
  97          *
  98          * What we want is that when the CPU usage is zero, the LED must blink
  99          * slowly with very faint flashes that are detectable but not disturbing
 100          * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
 101          * blinking frequency to increase up to the point where the load is
 102          * enough to saturate one core in multi-core systems or 50% in single
 103          * core systems. At this point it should reach 10 Hz with a 10/90 duty
 104          * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
 105          * remains stable (10 Hz) and only the duty cycle increases to report
 106          * the activity, up to the point where we have 90ms ON, 10ms OFF when
 107          * all cores are saturated. It's important that the LED never stays in
 108          * a steady state so that it's easy to distinguish an idle or saturated
 109          * machine from a hung one.
 110          *
 111          * This gives us :
 112          *   - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
 113          *     (10ms ON, 90ms OFF)
 114          *   - below target :
 115          *      ON_ms  = 10
 116          *      OFF_ms = 90 + (1 - usage/target) * 900
 117          *   - above target :
 118          *      ON_ms  = 10 + (usage-target)/(100%-target) * 80
 119          *      OFF_ms = 90 - (usage-target)/(100%-target) * 80
 120          *
 121          * In order to keep a good responsiveness, we cap the sleep time to
 122          * 100 ms and keep track of the sleep time left. This allows us to
 123          * quickly change it if needed.
 124          */
 125
 126         activity_data->time_left -= 100;
 127         if (activity_data->time_left <= 0) {
 128                 activity_data->time_left = 0;
 129                 activity_data->state = !activity_data->state;
 130                 led_set_brightness_nosleep(led_cdev,
 131                         (activity_data->state ^ activity_data->invert) ?
 132                         led_cdev->blink_brightness : LED_OFF);
 133         }
 134
 135         target = (cpus > 1) ? (100 / cpus) : 50;
 136
 137         if (usage < target)
 138                 delay = activity_data->state ?
 139                         10 :                        /* ON  */
 140                         990 - 900 * usage / target; /* OFF */
 141         else
 142                 delay = activity_data->state ?
 143                         10 + 80 * (usage - target) / (100 - target) : /* ON  */
 144                         90 - 80 * (usage - target) / (100 - target);  /* OFF */
 145
 146
 147         if (!activity_data->time_left || delay <= activity_data->time_left)
 148                 activity_data->time_left = delay;
 149
 150         delay = min_t(int, activity_data->time_left, 100);
 151         mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
 152 }
 153
 154 static ssize_t led_invert_show(struct device *dev,
 155                                struct device_attribute *attr, char *buf)
 156 {
 157         struct activity_data *activity_data = led_trigger_get_drvdata(dev);
 158
 159         return sprintf(buf, "%u\n", activity_data->invert);
 160 }
 161
 162 static ssize_t led_invert_store(struct device *dev,
 163                                 struct device_attribute *attr,
 164                                 const char *buf, size_t size)
 165 {
 166         struct activity_data *activity_data = led_trigger_get_drvdata(dev);
 167         unsigned long state;
 168         int ret;
 169
 170         ret = kstrtoul(buf, 0, &state);
 171         if (ret)
 172                 return ret;
 173
 174         activity_data->invert = !!state;
 175
 176         return size;
 177 }
 178
 179 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
 180
 181 static struct attribute *activity_led_attrs[] = {
 182         &dev_attr_invert.attr,
 183         NULL
 184 };
 185 ATTRIBUTE_GROUPS(activity_led);
 186
 187 static int activity_activate(struct led_classdev *led_cdev)
 188 {
 189         struct activity_data *activity_data;
 190
 191         activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
 192         if (!activity_data)
 193                 return -ENOMEM;
 194
 195         led_set_trigger_data(led_cdev, activity_data);
 196
 197         activity_data->led_cdev = led_cdev;
 198         timer_setup(&activity_data->timer, led_activity_function, 0);
 199         if (!led_cdev->blink_brightness)
 200                 led_cdev->blink_brightness = led_cdev->max_brightness;
 201         led_activity_function(&activity_data->timer);
 202         set_bit(LED_BLINK_SW, &led_cdev->work_flags);
 203
 204         return 0;
 205 }
 206
 207 static void activity_deactivate(struct led_classdev *led_cdev)
 208 {
 209         struct activity_data *activity_data = led_get_trigger_data(led_cdev);
 210
 211         timer_shutdown_sync(&activity_data->timer);
 212         kfree(activity_data);
 213         clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
 214 }
 215
 216 static struct led_trigger activity_led_trigger = {
 217         .name       = "activity",
 218         .activate   = activity_activate,
 219         .deactivate = activity_deactivate,
 220         .groups     = activity_led_groups,
 221 };
 222
 223 static int activity_reboot_notifier(struct notifier_block *nb,
 224                                     unsigned long code, void *unused)
 225 {
 226         led_trigger_unregister(&activity_led_trigger);
 227         return NOTIFY_DONE;
 228 }
 229
 230 static int activity_panic_notifier(struct notifier_block *nb,
 231                                    unsigned long code, void *unused)
 232 {
 233         panic_detected = 1;
 234         return NOTIFY_DONE;
 235 }
 236
 237 static struct notifier_block activity_reboot_nb = {
 238         .notifier_call = activity_reboot_notifier,
 239 };
 240
 241 static struct notifier_block activity_panic_nb = {
 242         .notifier_call = activity_panic_notifier,
 243 };
 244
 245 static int __init activity_init(void)
 246 {
 247         int rc = led_trigger_register(&activity_led_trigger);
 248
 249         if (!rc) {
 250                 atomic_notifier_chain_register(&panic_notifier_list,
 251                                                &activity_panic_nb);
 252                 register_reboot_notifier(&activity_reboot_nb);
 253         }
 254         return rc;
 255 }
 256
 257 static void __exit activity_exit(void)
 258 {
 259         unregister_reboot_notifier(&activity_reboot_nb);
 260         atomic_notifier_chain_unregister(&panic_notifier_list,
 261                                          &activity_panic_nb);
 262         led_trigger_unregister(&activity_led_trigger);
 263 }
 264
 265 module_init(activity_init);
 266 module_exit(activity_exit);
 267
 268 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>");
 269 MODULE_DESCRIPTION("Activity LED trigger");
 270 MODULE_LICENSE("GPL v2");