1 /*
2  * Activity LED trigger
3  *
4  * Copyright (C) 2017 Willy Tarreau <w@1wt.eu>
5  * Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  */
12 #include <linux/init.h>
13 #include <linux/kernel.h>
14 #include <linux/kernel_stat.h>
15 #include <linux/leds.h>
16 #include <linux/module.h>
17 #include <linux/reboot.h>
18 #include <linux/sched.h>
19 #include <linux/slab.h>
20 #include <linux/timer.h>
21 #include "../leds.h"
22 
23 static int panic_detected;
24 
25 struct activity_data {
26 	struct timer_list timer;
27 	struct led_classdev *led_cdev;
28 	u64 last_used;
29 	u64 last_boot;
30 	int time_left;
31 	int state;
32 	int invert;
33 };
34 
35 static void led_activity_function(struct timer_list *t)
36 {
37 	struct activity_data *activity_data = from_timer(activity_data, t,
38 							 timer);
39 	struct led_classdev *led_cdev = activity_data->led_cdev;
40 	struct timespec boot_time;
41 	unsigned int target;
42 	unsigned int usage;
43 	int delay;
44 	u64 curr_used;
45 	u64 curr_boot;
46 	s32 diff_used;
47 	s32 diff_boot;
48 	int cpus;
49 	int i;
50 
51 	if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
52 		led_cdev->blink_brightness = led_cdev->new_blink_brightness;
53 
54 	if (unlikely(panic_detected)) {
55 		/* full brightness in case of panic */
56 		led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
57 		return;
58 	}
59 
60 	get_monotonic_boottime(&boot_time);
61 
62 	cpus = 0;
63 	curr_used = 0;
64 
65 	for_each_possible_cpu(i) {
66 		curr_used += kcpustat_cpu(i).cpustat[CPUTIME_USER]
67 			  +  kcpustat_cpu(i).cpustat[CPUTIME_NICE]
68 			  +  kcpustat_cpu(i).cpustat[CPUTIME_SYSTEM]
69 			  +  kcpustat_cpu(i).cpustat[CPUTIME_SOFTIRQ]
70 			  +  kcpustat_cpu(i).cpustat[CPUTIME_IRQ];
71 		cpus++;
72 	}
73 
74 	/* We come here every 100ms in the worst case, so that's 100M ns of
75 	 * cumulated time. By dividing by 2^16, we get the time resolution
76 	 * down to 16us, ensuring we won't overflow 32-bit computations below
77 	 * even up to 3k CPUs, while keeping divides cheap on smaller systems.
78 	 */
79 	curr_boot = timespec_to_ns(&boot_time) * cpus;
80 	diff_boot = (curr_boot - activity_data->last_boot) >> 16;
81 	diff_used = (curr_used - activity_data->last_used) >> 16;
82 	activity_data->last_boot = curr_boot;
83 	activity_data->last_used = curr_used;
84 
85 	if (diff_boot <= 0 || diff_used < 0)
86 		usage = 0;
87 	else if (diff_used >= diff_boot)
88 		usage = 100;
89 	else
90 		usage = 100 * diff_used / diff_boot;
91 
92 	/*
93 	 * Now we know the total boot_time multiplied by the number of CPUs, and
94 	 * the total idle+wait time for all CPUs. We'll compare how they evolved
95 	 * since last call. The % of overall CPU usage is :
96 	 *
97 	 *      1 - delta_idle / delta_boot
98 	 *
99 	 * What we want is that when the CPU usage is zero, the LED must blink
100 	 * slowly with very faint flashes that are detectable but not disturbing
101 	 * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want
102 	 * blinking frequency to increase up to the point where the load is
103 	 * enough to saturate one core in multi-core systems or 50% in single
104 	 * core systems. At this point it should reach 10 Hz with a 10/90 duty
105 	 * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency
106 	 * remains stable (10 Hz) and only the duty cycle increases to report
107 	 * the activity, up to the point where we have 90ms ON, 10ms OFF when
108 	 * all cores are saturated. It's important that the LED never stays in
109 	 * a steady state so that it's easy to distinguish an idle or saturated
110 	 * machine from a hung one.
111 	 *
112 	 * This gives us :
113 	 *   - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle
114 	 *     (10ms ON, 90ms OFF)
115 	 *   - below target :
116 	 *      ON_ms  = 10
117 	 *      OFF_ms = 90 + (1 - usage/target) * 900
118 	 *   - above target :
119 	 *      ON_ms  = 10 + (usage-target)/(100%-target) * 80
120 	 *      OFF_ms = 90 - (usage-target)/(100%-target) * 80
121 	 *
122 	 * In order to keep a good responsiveness, we cap the sleep time to
123 	 * 100 ms and keep track of the sleep time left. This allows us to
124 	 * quickly change it if needed.
125 	 */
126 
127 	activity_data->time_left -= 100;
128 	if (activity_data->time_left <= 0) {
129 		activity_data->time_left = 0;
130 		activity_data->state = !activity_data->state;
131 		led_set_brightness_nosleep(led_cdev,
132 			(activity_data->state ^ activity_data->invert) ?
133 			led_cdev->blink_brightness : LED_OFF);
134 	}
135 
136 	target = (cpus > 1) ? (100 / cpus) : 50;
137 
138 	if (usage < target)
139 		delay = activity_data->state ?
140 			10 :                        /* ON  */
141 			990 - 900 * usage / target; /* OFF */
142 	else
143 		delay = activity_data->state ?
144 			10 + 80 * (usage - target) / (100 - target) : /* ON  */
145 			90 - 80 * (usage - target) / (100 - target);  /* OFF */
146 
147 
148 	if (!activity_data->time_left || delay <= activity_data->time_left)
149 		activity_data->time_left = delay;
150 
151 	delay = min_t(int, activity_data->time_left, 100);
152 	mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay));
153 }
154 
155 static ssize_t led_invert_show(struct device *dev,
156                                struct device_attribute *attr, char *buf)
157 {
158 	struct led_classdev *led_cdev = dev_get_drvdata(dev);
159 	struct activity_data *activity_data = led_cdev->trigger_data;
160 
161 	return sprintf(buf, "%u\n", activity_data->invert);
162 }
163 
164 static ssize_t led_invert_store(struct device *dev,
165                                 struct device_attribute *attr,
166                                 const char *buf, size_t size)
167 {
168 	struct led_classdev *led_cdev = dev_get_drvdata(dev);
169 	struct activity_data *activity_data = led_cdev->trigger_data;
170 	unsigned long state;
171 	int ret;
172 
173 	ret = kstrtoul(buf, 0, &state);
174 	if (ret)
175 		return ret;
176 
177 	activity_data->invert = !!state;
178 
179 	return size;
180 }
181 
182 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store);
183 
184 static void activity_activate(struct led_classdev *led_cdev)
185 {
186 	struct activity_data *activity_data;
187 	int rc;
188 
189 	activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL);
190 	if (!activity_data)
191 		return;
192 
193 	led_cdev->trigger_data = activity_data;
194 	rc = device_create_file(led_cdev->dev, &dev_attr_invert);
195 	if (rc) {
196 		kfree(led_cdev->trigger_data);
197 		return;
198 	}
199 
200 	activity_data->led_cdev = led_cdev;
201 	timer_setup(&activity_data->timer, led_activity_function, 0);
202 	if (!led_cdev->blink_brightness)
203 		led_cdev->blink_brightness = led_cdev->max_brightness;
204 	led_activity_function(&activity_data->timer);
205 	set_bit(LED_BLINK_SW, &led_cdev->work_flags);
206 	led_cdev->activated = true;
207 }
208 
209 static void activity_deactivate(struct led_classdev *led_cdev)
210 {
211 	struct activity_data *activity_data = led_cdev->trigger_data;
212 
213 	if (led_cdev->activated) {
214 		del_timer_sync(&activity_data->timer);
215 		device_remove_file(led_cdev->dev, &dev_attr_invert);
216 		kfree(activity_data);
217 		clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
218 		led_cdev->activated = false;
219 	}
220 }
221 
222 static struct led_trigger activity_led_trigger = {
223 	.name       = "activity",
224 	.activate   = activity_activate,
225 	.deactivate = activity_deactivate,
226 };
227 
228 static int activity_reboot_notifier(struct notifier_block *nb,
229                                     unsigned long code, void *unused)
230 {
231 	led_trigger_unregister(&activity_led_trigger);
232 	return NOTIFY_DONE;
233 }
234 
235 static int activity_panic_notifier(struct notifier_block *nb,
236                                    unsigned long code, void *unused)
237 {
238 	panic_detected = 1;
239 	return NOTIFY_DONE;
240 }
241 
242 static struct notifier_block activity_reboot_nb = {
243 	.notifier_call = activity_reboot_notifier,
244 };
245 
246 static struct notifier_block activity_panic_nb = {
247 	.notifier_call = activity_panic_notifier,
248 };
249 
250 static int __init activity_init(void)
251 {
252 	int rc = led_trigger_register(&activity_led_trigger);
253 
254 	if (!rc) {
255 		atomic_notifier_chain_register(&panic_notifier_list,
256 					       &activity_panic_nb);
257 		register_reboot_notifier(&activity_reboot_nb);
258 	}
259 	return rc;
260 }
261 
262 static void __exit activity_exit(void)
263 {
264 	unregister_reboot_notifier(&activity_reboot_nb);
265 	atomic_notifier_chain_unregister(&panic_notifier_list,
266 					 &activity_panic_nb);
267 	led_trigger_unregister(&activity_led_trigger);
268 }
269 
270 module_init(activity_init);
271 module_exit(activity_exit);
272 
273 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>");
274 MODULE_DESCRIPTION("Activity LED trigger");
275 MODULE_LICENSE("GPL");
276