1 /* 2 * Detect hard and soft lockups on a system 3 * 4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. 5 * 6 * this code detects hard lockups: incidents in where on a CPU 7 * the kernel does not respond to anything except NMI. 8 * 9 * Note: Most of this code is borrowed heavily from softlockup.c, 10 * so thanks to Ingo for the initial implementation. 11 * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks 12 * to those contributors as well. 13 */ 14 15 #include <linux/mm.h> 16 #include <linux/cpu.h> 17 #include <linux/nmi.h> 18 #include <linux/init.h> 19 #include <linux/delay.h> 20 #include <linux/freezer.h> 21 #include <linux/kthread.h> 22 #include <linux/lockdep.h> 23 #include <linux/notifier.h> 24 #include <linux/module.h> 25 #include <linux/sysctl.h> 26 27 #include <asm/irq_regs.h> 28 #include <linux/perf_event.h> 29 30 int watchdog_enabled; 31 int __read_mostly softlockup_thresh = 60; 32 33 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); 34 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog); 35 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer); 36 static DEFINE_PER_CPU(bool, softlockup_touch_sync); 37 static DEFINE_PER_CPU(bool, soft_watchdog_warn); 38 #ifdef CONFIG_HARDLOCKUP_DETECTOR 39 static DEFINE_PER_CPU(bool, hard_watchdog_warn); 40 static DEFINE_PER_CPU(bool, watchdog_nmi_touch); 41 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); 42 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); 43 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); 44 #endif 45 46 static int no_watchdog; 47 48 49 /* boot commands */ 50 /* 51 * Should we panic when a soft-lockup or hard-lockup occurs: 52 */ 53 #ifdef CONFIG_HARDLOCKUP_DETECTOR 54 static int hardlockup_panic; 55 56 static int __init hardlockup_panic_setup(char *str) 57 { 58 if (!strncmp(str, "panic", 5)) 59 hardlockup_panic = 1; 60 return 1; 61 } 62 __setup("nmi_watchdog=", hardlockup_panic_setup); 63 #endif 64 65 unsigned int __read_mostly softlockup_panic = 66 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE; 67 68 static int __init softlockup_panic_setup(char *str) 69 { 70 softlockup_panic = simple_strtoul(str, NULL, 0); 71 72 return 1; 73 } 74 __setup("softlockup_panic=", softlockup_panic_setup); 75 76 static int __init nowatchdog_setup(char *str) 77 { 78 no_watchdog = 1; 79 return 1; 80 } 81 __setup("nowatchdog", nowatchdog_setup); 82 83 /* deprecated */ 84 static int __init nosoftlockup_setup(char *str) 85 { 86 no_watchdog = 1; 87 return 1; 88 } 89 __setup("nosoftlockup", nosoftlockup_setup); 90 /* */ 91 92 93 /* 94 * Returns seconds, approximately. We don't need nanosecond 95 * resolution, and we don't need to waste time with a big divide when 96 * 2^30ns == 1.074s. 97 */ 98 static unsigned long get_timestamp(int this_cpu) 99 { 100 return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */ 101 } 102 103 static unsigned long get_sample_period(void) 104 { 105 /* 106 * convert softlockup_thresh from seconds to ns 107 * the divide by 5 is to give hrtimer 5 chances to 108 * increment before the hardlockup detector generates 109 * a warning 110 */ 111 return softlockup_thresh / 5 * NSEC_PER_SEC; 112 } 113 114 /* Commands for resetting the watchdog */ 115 static void __touch_watchdog(void) 116 { 117 int this_cpu = smp_processor_id(); 118 119 __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu); 120 } 121 122 void touch_softlockup_watchdog(void) 123 { 124 __raw_get_cpu_var(watchdog_touch_ts) = 0; 125 } 126 EXPORT_SYMBOL(touch_softlockup_watchdog); 127 128 void touch_all_softlockup_watchdogs(void) 129 { 130 int cpu; 131 132 /* 133 * this is done lockless 134 * do we care if a 0 races with a timestamp? 135 * all it means is the softlock check starts one cycle later 136 */ 137 for_each_online_cpu(cpu) 138 per_cpu(watchdog_touch_ts, cpu) = 0; 139 } 140 141 #ifdef CONFIG_HARDLOCKUP_DETECTOR 142 void touch_nmi_watchdog(void) 143 { 144 if (watchdog_enabled) { 145 unsigned cpu; 146 147 for_each_present_cpu(cpu) { 148 if (per_cpu(watchdog_nmi_touch, cpu) != true) 149 per_cpu(watchdog_nmi_touch, cpu) = true; 150 } 151 } 152 touch_softlockup_watchdog(); 153 } 154 EXPORT_SYMBOL(touch_nmi_watchdog); 155 156 #endif 157 158 void touch_softlockup_watchdog_sync(void) 159 { 160 __raw_get_cpu_var(softlockup_touch_sync) = true; 161 __raw_get_cpu_var(watchdog_touch_ts) = 0; 162 } 163 164 #ifdef CONFIG_HARDLOCKUP_DETECTOR 165 /* watchdog detector functions */ 166 static int is_hardlockup(void) 167 { 168 unsigned long hrint = __get_cpu_var(hrtimer_interrupts); 169 170 if (__get_cpu_var(hrtimer_interrupts_saved) == hrint) 171 return 1; 172 173 __get_cpu_var(hrtimer_interrupts_saved) = hrint; 174 return 0; 175 } 176 #endif 177 178 static int is_softlockup(unsigned long touch_ts) 179 { 180 unsigned long now = get_timestamp(smp_processor_id()); 181 182 /* Warn about unreasonable delays: */ 183 if (time_after(now, touch_ts + softlockup_thresh)) 184 return now - touch_ts; 185 186 return 0; 187 } 188 189 #ifdef CONFIG_HARDLOCKUP_DETECTOR 190 static struct perf_event_attr wd_hw_attr = { 191 .type = PERF_TYPE_HARDWARE, 192 .config = PERF_COUNT_HW_CPU_CYCLES, 193 .size = sizeof(struct perf_event_attr), 194 .pinned = 1, 195 .disabled = 1, 196 }; 197 198 /* Callback function for perf event subsystem */ 199 static void watchdog_overflow_callback(struct perf_event *event, int nmi, 200 struct perf_sample_data *data, 201 struct pt_regs *regs) 202 { 203 /* Ensure the watchdog never gets throttled */ 204 event->hw.interrupts = 0; 205 206 if (__get_cpu_var(watchdog_nmi_touch) == true) { 207 __get_cpu_var(watchdog_nmi_touch) = false; 208 return; 209 } 210 211 /* check for a hardlockup 212 * This is done by making sure our timer interrupt 213 * is incrementing. The timer interrupt should have 214 * fired multiple times before we overflow'd. If it hasn't 215 * then this is a good indication the cpu is stuck 216 */ 217 if (is_hardlockup()) { 218 int this_cpu = smp_processor_id(); 219 220 /* only print hardlockups once */ 221 if (__get_cpu_var(hard_watchdog_warn) == true) 222 return; 223 224 if (hardlockup_panic) 225 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu); 226 else 227 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu); 228 229 __get_cpu_var(hard_watchdog_warn) = true; 230 return; 231 } 232 233 __get_cpu_var(hard_watchdog_warn) = false; 234 return; 235 } 236 static void watchdog_interrupt_count(void) 237 { 238 __get_cpu_var(hrtimer_interrupts)++; 239 } 240 #else 241 static inline void watchdog_interrupt_count(void) { return; } 242 #endif /* CONFIG_HARDLOCKUP_DETECTOR */ 243 244 /* watchdog kicker functions */ 245 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) 246 { 247 unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts); 248 struct pt_regs *regs = get_irq_regs(); 249 int duration; 250 251 /* kick the hardlockup detector */ 252 watchdog_interrupt_count(); 253 254 /* kick the softlockup detector */ 255 wake_up_process(__get_cpu_var(softlockup_watchdog)); 256 257 /* .. and repeat */ 258 hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period())); 259 260 if (touch_ts == 0) { 261 if (unlikely(__get_cpu_var(softlockup_touch_sync))) { 262 /* 263 * If the time stamp was touched atomically 264 * make sure the scheduler tick is up to date. 265 */ 266 __get_cpu_var(softlockup_touch_sync) = false; 267 sched_clock_tick(); 268 } 269 __touch_watchdog(); 270 return HRTIMER_RESTART; 271 } 272 273 /* check for a softlockup 274 * This is done by making sure a high priority task is 275 * being scheduled. The task touches the watchdog to 276 * indicate it is getting cpu time. If it hasn't then 277 * this is a good indication some task is hogging the cpu 278 */ 279 duration = is_softlockup(touch_ts); 280 if (unlikely(duration)) { 281 /* only warn once */ 282 if (__get_cpu_var(soft_watchdog_warn) == true) 283 return HRTIMER_RESTART; 284 285 printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", 286 smp_processor_id(), duration, 287 current->comm, task_pid_nr(current)); 288 print_modules(); 289 print_irqtrace_events(current); 290 if (regs) 291 show_regs(regs); 292 else 293 dump_stack(); 294 295 if (softlockup_panic) 296 panic("softlockup: hung tasks"); 297 __get_cpu_var(soft_watchdog_warn) = true; 298 } else 299 __get_cpu_var(soft_watchdog_warn) = false; 300 301 return HRTIMER_RESTART; 302 } 303 304 305 /* 306 * The watchdog thread - touches the timestamp. 307 */ 308 static int watchdog(void *unused) 309 { 310 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; 311 struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer); 312 313 sched_setscheduler(current, SCHED_FIFO, ¶m); 314 315 /* initialize timestamp */ 316 __touch_watchdog(); 317 318 /* kick off the timer for the hardlockup detector */ 319 /* done here because hrtimer_start can only pin to smp_processor_id() */ 320 hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()), 321 HRTIMER_MODE_REL_PINNED); 322 323 set_current_state(TASK_INTERRUPTIBLE); 324 /* 325 * Run briefly once per second to reset the softlockup timestamp. 326 * If this gets delayed for more than 60 seconds then the 327 * debug-printout triggers in watchdog_timer_fn(). 328 */ 329 while (!kthread_should_stop()) { 330 __touch_watchdog(); 331 schedule(); 332 333 if (kthread_should_stop()) 334 break; 335 336 set_current_state(TASK_INTERRUPTIBLE); 337 } 338 __set_current_state(TASK_RUNNING); 339 340 return 0; 341 } 342 343 344 #ifdef CONFIG_HARDLOCKUP_DETECTOR 345 static int watchdog_nmi_enable(int cpu) 346 { 347 struct perf_event_attr *wd_attr; 348 struct perf_event *event = per_cpu(watchdog_ev, cpu); 349 350 /* is it already setup and enabled? */ 351 if (event && event->state > PERF_EVENT_STATE_OFF) 352 goto out; 353 354 /* it is setup but not enabled */ 355 if (event != NULL) 356 goto out_enable; 357 358 /* Try to register using hardware perf events */ 359 wd_attr = &wd_hw_attr; 360 wd_attr->sample_period = hw_nmi_get_sample_period(); 361 event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback); 362 if (!IS_ERR(event)) { 363 printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n"); 364 goto out_save; 365 } 366 367 printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event); 368 return PTR_ERR(event); 369 370 /* success path */ 371 out_save: 372 per_cpu(watchdog_ev, cpu) = event; 373 out_enable: 374 perf_event_enable(per_cpu(watchdog_ev, cpu)); 375 out: 376 return 0; 377 } 378 379 static void watchdog_nmi_disable(int cpu) 380 { 381 struct perf_event *event = per_cpu(watchdog_ev, cpu); 382 383 if (event) { 384 perf_event_disable(event); 385 per_cpu(watchdog_ev, cpu) = NULL; 386 387 /* should be in cleanup, but blocks oprofile */ 388 perf_event_release_kernel(event); 389 } 390 return; 391 } 392 #else 393 static int watchdog_nmi_enable(int cpu) { return 0; } 394 static void watchdog_nmi_disable(int cpu) { return; } 395 #endif /* CONFIG_HARDLOCKUP_DETECTOR */ 396 397 /* prepare/enable/disable routines */ 398 static int watchdog_prepare_cpu(int cpu) 399 { 400 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu); 401 402 WARN_ON(per_cpu(softlockup_watchdog, cpu)); 403 hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 404 hrtimer->function = watchdog_timer_fn; 405 406 return 0; 407 } 408 409 static int watchdog_enable(int cpu) 410 { 411 struct task_struct *p = per_cpu(softlockup_watchdog, cpu); 412 int err; 413 414 /* enable the perf event */ 415 err = watchdog_nmi_enable(cpu); 416 if (err) 417 return err; 418 419 /* create the watchdog thread */ 420 if (!p) { 421 p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu); 422 if (IS_ERR(p)) { 423 printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu); 424 return PTR_ERR(p); 425 } 426 kthread_bind(p, cpu); 427 per_cpu(watchdog_touch_ts, cpu) = 0; 428 per_cpu(softlockup_watchdog, cpu) = p; 429 wake_up_process(p); 430 } 431 432 /* if any cpu succeeds, watchdog is considered enabled for the system */ 433 watchdog_enabled = 1; 434 435 return 0; 436 } 437 438 static void watchdog_disable(int cpu) 439 { 440 struct task_struct *p = per_cpu(softlockup_watchdog, cpu); 441 struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu); 442 443 /* 444 * cancel the timer first to stop incrementing the stats 445 * and waking up the kthread 446 */ 447 hrtimer_cancel(hrtimer); 448 449 /* disable the perf event */ 450 watchdog_nmi_disable(cpu); 451 452 /* stop the watchdog thread */ 453 if (p) { 454 per_cpu(softlockup_watchdog, cpu) = NULL; 455 kthread_stop(p); 456 } 457 } 458 459 static void watchdog_enable_all_cpus(void) 460 { 461 int cpu; 462 int result = 0; 463 464 for_each_online_cpu(cpu) 465 result += watchdog_enable(cpu); 466 467 if (result) 468 printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n"); 469 470 } 471 472 static void watchdog_disable_all_cpus(void) 473 { 474 int cpu; 475 476 if (no_watchdog) 477 return; 478 479 for_each_online_cpu(cpu) 480 watchdog_disable(cpu); 481 482 /* if all watchdogs are disabled, then they are disabled for the system */ 483 watchdog_enabled = 0; 484 } 485 486 487 /* sysctl functions */ 488 #ifdef CONFIG_SYSCTL 489 /* 490 * proc handler for /proc/sys/kernel/nmi_watchdog 491 */ 492 493 int proc_dowatchdog_enabled(struct ctl_table *table, int write, 494 void __user *buffer, size_t *length, loff_t *ppos) 495 { 496 proc_dointvec(table, write, buffer, length, ppos); 497 498 if (watchdog_enabled) 499 watchdog_enable_all_cpus(); 500 else 501 watchdog_disable_all_cpus(); 502 return 0; 503 } 504 505 int proc_dowatchdog_thresh(struct ctl_table *table, int write, 506 void __user *buffer, 507 size_t *lenp, loff_t *ppos) 508 { 509 return proc_dointvec_minmax(table, write, buffer, lenp, ppos); 510 } 511 #endif /* CONFIG_SYSCTL */ 512 513 514 /* 515 * Create/destroy watchdog threads as CPUs come and go: 516 */ 517 static int __cpuinit 518 cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) 519 { 520 int hotcpu = (unsigned long)hcpu; 521 int err = 0; 522 523 switch (action) { 524 case CPU_UP_PREPARE: 525 case CPU_UP_PREPARE_FROZEN: 526 err = watchdog_prepare_cpu(hotcpu); 527 break; 528 case CPU_ONLINE: 529 case CPU_ONLINE_FROZEN: 530 err = watchdog_enable(hotcpu); 531 break; 532 #ifdef CONFIG_HOTPLUG_CPU 533 case CPU_UP_CANCELED: 534 case CPU_UP_CANCELED_FROZEN: 535 watchdog_disable(hotcpu); 536 break; 537 case CPU_DEAD: 538 case CPU_DEAD_FROZEN: 539 watchdog_disable(hotcpu); 540 break; 541 #endif /* CONFIG_HOTPLUG_CPU */ 542 } 543 return notifier_from_errno(err); 544 } 545 546 static struct notifier_block __cpuinitdata cpu_nfb = { 547 .notifier_call = cpu_callback 548 }; 549 550 static int __init spawn_watchdog_task(void) 551 { 552 void *cpu = (void *)(long)smp_processor_id(); 553 int err; 554 555 if (no_watchdog) 556 return 0; 557 558 err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); 559 WARN_ON(notifier_to_errno(err)); 560 561 cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); 562 register_cpu_notifier(&cpu_nfb); 563 564 return 0; 565 } 566 early_initcall(spawn_watchdog_task); 567