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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Activity LED trigger
4 *
5 * Copyright (C) 2017 Willy Tarreau <[email protected]>
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
21static int panic_detected;
22
23struct 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
33static void led_activity_function(struct timer_list *t)
34{
35 struct activity_data *activity_data = timer_container_of(activity_data,
36 t, 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
154static 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, "%d\n", activity_data->invert);
160}
161
162static 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
179static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
180
181static struct attribute *activity_led_attrs[] = {
182 &dev_attr_invert.attr,
183 NULL
184};
185ATTRIBUTE_GROUPS(activity_led);
186
187static int activity_activate(struct led_classdev *led_cdev)
188{
189 struct activity_data *activity_data;
190
191 activity_data = kzalloc_obj(*activity_data);
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
207static 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
216static struct led_trigger activity_led_trigger = {
217 .name = "activity",
218 .activate = activity_activate,
219 .deactivate = activity_deactivate,
220 .groups = activity_led_groups,
221};
222
223static 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
230static 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
237static struct notifier_block activity_reboot_nb = {
238 .notifier_call = activity_reboot_notifier,
239};
240
241static struct notifier_block activity_panic_nb = {
242 .notifier_call = activity_panic_notifier,
243};
244
245static 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
257static 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
265module_init(activity_init);
266module_exit(activity_exit);
267
268MODULE_AUTHOR("Willy Tarreau <[email protected]>");
269MODULE_DESCRIPTION("Activity LED trigger");
270MODULE_LICENSE("GPL v2");