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 struct kernel_cpustat kcpustat; 61 62 kcpustat_cpu_fetch(&kcpustat, i); 63 64 curr_used += kcpustat.cpustat[CPUTIME_USER] 65 + kcpustat.cpustat[CPUTIME_NICE] 66 + kcpustat.cpustat[CPUTIME_SYSTEM] 67 + kcpustat.cpustat[CPUTIME_SOFTIRQ] 68 + kcpustat.cpustat[CPUTIME_IRQ]; 69 cpus++; 70 } 71 72 /* We come here every 100ms in the worst case, so that's 100M ns of 73 * cumulated time. By dividing by 2^16, we get the time resolution 74 * down to 16us, ensuring we won't overflow 32-bit computations below 75 * even up to 3k CPUs, while keeping divides cheap on smaller systems. 76 */ 77 curr_boot = ktime_get_boottime_ns() * cpus; 78 diff_boot = (curr_boot - activity_data->last_boot) >> 16; 79 diff_used = (curr_used - activity_data->last_used) >> 16; 80 activity_data->last_boot = curr_boot; 81 activity_data->last_used = curr_used; 82 83 if (diff_boot <= 0 || diff_used < 0) 84 usage = 0; 85 else if (diff_used >= diff_boot) 86 usage = 100; 87 else 88 usage = 100 * diff_used / diff_boot; 89 90 /* 91 * Now we know the total boot_time multiplied by the number of CPUs, and 92 * the total idle+wait time for all CPUs. We'll compare how they evolved 93 * since last call. The % of overall CPU usage is : 94 * 95 * 1 - delta_idle / delta_boot 96 * 97 * What we want is that when the CPU usage is zero, the LED must blink 98 * slowly with very faint flashes that are detectable but not disturbing 99 * (typically 10ms every second, or 10ms ON, 990ms OFF). Then we want 100 * blinking frequency to increase up to the point where the load is 101 * enough to saturate one core in multi-core systems or 50% in single 102 * core systems. At this point it should reach 10 Hz with a 10/90 duty 103 * cycle (10ms ON, 90ms OFF). After this point, the blinking frequency 104 * remains stable (10 Hz) and only the duty cycle increases to report 105 * the activity, up to the point where we have 90ms ON, 10ms OFF when 106 * all cores are saturated. It's important that the LED never stays in 107 * a steady state so that it's easy to distinguish an idle or saturated 108 * machine from a hung one. 109 * 110 * This gives us : 111 * - a target CPU usage of min(50%, 100%/#CPU) for a 10% duty cycle 112 * (10ms ON, 90ms OFF) 113 * - below target : 114 * ON_ms = 10 115 * OFF_ms = 90 + (1 - usage/target) * 900 116 * - above target : 117 * ON_ms = 10 + (usage-target)/(100%-target) * 80 118 * OFF_ms = 90 - (usage-target)/(100%-target) * 80 119 * 120 * In order to keep a good responsiveness, we cap the sleep time to 121 * 100 ms and keep track of the sleep time left. This allows us to 122 * quickly change it if needed. 123 */ 124 125 activity_data->time_left -= 100; 126 if (activity_data->time_left <= 0) { 127 activity_data->time_left = 0; 128 activity_data->state = !activity_data->state; 129 led_set_brightness_nosleep(led_cdev, 130 (activity_data->state ^ activity_data->invert) ? 131 led_cdev->blink_brightness : LED_OFF); 132 } 133 134 target = (cpus > 1) ? (100 / cpus) : 50; 135 136 if (usage < target) 137 delay = activity_data->state ? 138 10 : /* ON */ 139 990 - 900 * usage / target; /* OFF */ 140 else 141 delay = activity_data->state ? 142 10 + 80 * (usage - target) / (100 - target) : /* ON */ 143 90 - 80 * (usage - target) / (100 - target); /* OFF */ 144 145 146 if (!activity_data->time_left || delay <= activity_data->time_left) 147 activity_data->time_left = delay; 148 149 delay = min_t(int, activity_data->time_left, 100); 150 mod_timer(&activity_data->timer, jiffies + msecs_to_jiffies(delay)); 151 } 152 153 static ssize_t led_invert_show(struct device *dev, 154 struct device_attribute *attr, char *buf) 155 { 156 struct activity_data *activity_data = led_trigger_get_drvdata(dev); 157 158 return sprintf(buf, "%u\n", activity_data->invert); 159 } 160 161 static ssize_t led_invert_store(struct device *dev, 162 struct device_attribute *attr, 163 const char *buf, size_t size) 164 { 165 struct activity_data *activity_data = led_trigger_get_drvdata(dev); 166 unsigned long state; 167 int ret; 168 169 ret = kstrtoul(buf, 0, &state); 170 if (ret) 171 return ret; 172 173 activity_data->invert = !!state; 174 175 return size; 176 } 177 178 static DEVICE_ATTR(invert, 0644, led_invert_show, led_invert_store); 179 180 static struct attribute *activity_led_attrs[] = { 181 &dev_attr_invert.attr, 182 NULL 183 }; 184 ATTRIBUTE_GROUPS(activity_led); 185 186 static int activity_activate(struct led_classdev *led_cdev) 187 { 188 struct activity_data *activity_data; 189 190 activity_data = kzalloc(sizeof(*activity_data), GFP_KERNEL); 191 if (!activity_data) 192 return -ENOMEM; 193 194 led_set_trigger_data(led_cdev, activity_data); 195 196 activity_data->led_cdev = led_cdev; 197 timer_setup(&activity_data->timer, led_activity_function, 0); 198 if (!led_cdev->blink_brightness) 199 led_cdev->blink_brightness = led_cdev->max_brightness; 200 led_activity_function(&activity_data->timer); 201 set_bit(LED_BLINK_SW, &led_cdev->work_flags); 202 203 return 0; 204 } 205 206 static void activity_deactivate(struct led_classdev *led_cdev) 207 { 208 struct activity_data *activity_data = led_get_trigger_data(led_cdev); 209 210 del_timer_sync(&activity_data->timer); 211 kfree(activity_data); 212 clear_bit(LED_BLINK_SW, &led_cdev->work_flags); 213 } 214 215 static struct led_trigger activity_led_trigger = { 216 .name = "activity", 217 .activate = activity_activate, 218 .deactivate = activity_deactivate, 219 .groups = activity_led_groups, 220 }; 221 222 static int activity_reboot_notifier(struct notifier_block *nb, 223 unsigned long code, void *unused) 224 { 225 led_trigger_unregister(&activity_led_trigger); 226 return NOTIFY_DONE; 227 } 228 229 static int activity_panic_notifier(struct notifier_block *nb, 230 unsigned long code, void *unused) 231 { 232 panic_detected = 1; 233 return NOTIFY_DONE; 234 } 235 236 static struct notifier_block activity_reboot_nb = { 237 .notifier_call = activity_reboot_notifier, 238 }; 239 240 static struct notifier_block activity_panic_nb = { 241 .notifier_call = activity_panic_notifier, 242 }; 243 244 static int __init activity_init(void) 245 { 246 int rc = led_trigger_register(&activity_led_trigger); 247 248 if (!rc) { 249 atomic_notifier_chain_register(&panic_notifier_list, 250 &activity_panic_nb); 251 register_reboot_notifier(&activity_reboot_nb); 252 } 253 return rc; 254 } 255 256 static void __exit activity_exit(void) 257 { 258 unregister_reboot_notifier(&activity_reboot_nb); 259 atomic_notifier_chain_unregister(&panic_notifier_list, 260 &activity_panic_nb); 261 led_trigger_unregister(&activity_led_trigger); 262 } 263 264 module_init(activity_init); 265 module_exit(activity_exit); 266 267 MODULE_AUTHOR("Willy Tarreau <w@1wt.eu>"); 268 MODULE_DESCRIPTION("Activity LED trigger"); 269 MODULE_LICENSE("GPL v2"); 270