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 del_timer_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