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");
271