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_field(&kcpustat_cpu(i), CPUTIME_SYSTEM, i) 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"); 266