1/*
   2 * Detect hard and soft lockups on a system
   3 *
   4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
   5 *
   6 * Note: Most of this code is borrowed heavily from the original softlockup
   7 * detector, so thanks to Ingo for the initial implementation.
   8 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
 
 
 
   9 * to those contributors as well.
  10 */
  11
  12#define pr_fmt(fmt) "NMI watchdog: " fmt
  13
  14#include <linux/mm.h>
  15#include <linux/cpu.h>
  16#include <linux/nmi.h>
  17#include <linux/init.h>
 
 
 
 
 
  18#include <linux/module.h>
  19#include <linux/sysctl.h>
  20#include <linux/smpboot.h>
  21#include <linux/sched/rt.h>
  22#include <linux/tick.h>
  23#include <linux/workqueue.h>
  24
  25#include <asm/irq_regs.h>
  26#include <linux/kvm_para.h>
  27#include <linux/perf_event.h>
  28#include <linux/kthread.h>
  29
  30/*
  31 * The run state of the lockup detectors is controlled by the content of the
  32 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
  33 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
  34 *
  35 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
  36 * are variables that are only used as an 'interface' between the parameters
  37 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
  38 * 'watchdog_thresh' variable is handled differently because its value is not
  39 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
  40 * is equal zero.
  41 */
  42#define NMI_WATCHDOG_ENABLED_BIT   0
  43#define SOFT_WATCHDOG_ENABLED_BIT  1
  44#define NMI_WATCHDOG_ENABLED      (1 << NMI_WATCHDOG_ENABLED_BIT)
  45#define SOFT_WATCHDOG_ENABLED     (1 << SOFT_WATCHDOG_ENABLED_BIT)
  46
  47static DEFINE_MUTEX(watchdog_proc_mutex);
  48
  49#ifdef CONFIG_HARDLOCKUP_DETECTOR
  50static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
  51#else
  52static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
  53#endif
  54int __read_mostly nmi_watchdog_enabled;
  55int __read_mostly soft_watchdog_enabled;
  56int __read_mostly watchdog_user_enabled;
  57int __read_mostly watchdog_thresh = 10;
  58
  59#ifdef CONFIG_SMP
  60int __read_mostly sysctl_softlockup_all_cpu_backtrace;
  61int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
  62#else
  63#define sysctl_softlockup_all_cpu_backtrace 0
  64#define sysctl_hardlockup_all_cpu_backtrace 0
  65#endif
  66static struct cpumask watchdog_cpumask __read_mostly;
  67unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
  68
  69/* Helper for online, unparked cpus. */
  70#define for_each_watchdog_cpu(cpu) \
  71	for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
  72
  73/*
  74 * The 'watchdog_running' variable is set to 1 when the watchdog threads
  75 * are registered/started and is set to 0 when the watchdog threads are
  76 * unregistered/stopped, so it is an indicator whether the threads exist.
  77 */
  78static int __read_mostly watchdog_running;
  79/*
  80 * If a subsystem has a need to deactivate the watchdog temporarily, it
  81 * can use the suspend/resume interface to achieve this. The content of
  82 * the 'watchdog_suspended' variable reflects this state. Existing threads
  83 * are parked/unparked by the lockup_detector_{suspend|resume} functions
  84 * (see comment blocks pertaining to those functions for further details).
  85 *
  86 * 'watchdog_suspended' also prevents threads from being registered/started
  87 * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
  88 * of 'watchdog_running' cannot change while the watchdog is deactivated
  89 * temporarily (see related code in 'proc' handlers).
  90 */
  91static int __read_mostly watchdog_suspended;
  92
  93static u64 __read_mostly sample_period;
  94
  95static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
  96static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
  97static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
  98static DEFINE_PER_CPU(bool, softlockup_touch_sync);
  99static DEFINE_PER_CPU(bool, soft_watchdog_warn);
 100static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 101static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
 102static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
 103#ifdef CONFIG_HARDLOCKUP_DETECTOR
 104static DEFINE_PER_CPU(bool, hard_watchdog_warn);
 105static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
 
 106static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 107static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
 108#endif
 109static unsigned long soft_lockup_nmi_warn;
 110
 111/* boot commands */
 112/*
 113 * Should we panic when a soft-lockup or hard-lockup occurs:
 114 */
 115#ifdef CONFIG_HARDLOCKUP_DETECTOR
 116unsigned int __read_mostly hardlockup_panic =
 117			CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
 118static unsigned long hardlockup_allcpu_dumped;
 119/*
 120 * We may not want to enable hard lockup detection by default in all cases,
 121 * for example when running the kernel as a guest on a hypervisor. In these
 122 * cases this function can be called to disable hard lockup detection. This
 123 * function should only be executed once by the boot processor before the
 124 * kernel command line parameters are parsed, because otherwise it is not
 125 * possible to override this in hardlockup_panic_setup().
 126 */
 127void hardlockup_detector_disable(void)
 128{
 129	watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
 130}
 131
 132static int __init hardlockup_panic_setup(char *str)
 133{
 134	if (!strncmp(str, "panic", 5))
 135		hardlockup_panic = 1;
 136	else if (!strncmp(str, "nopanic", 7))
 137		hardlockup_panic = 0;
 138	else if (!strncmp(str, "0", 1))
 139		watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
 140	else if (!strncmp(str, "1", 1))
 141		watchdog_enabled |= NMI_WATCHDOG_ENABLED;
 142	return 1;
 143}
 144__setup("nmi_watchdog=", hardlockup_panic_setup);
 145#endif
 146
 147unsigned int __read_mostly softlockup_panic =
 148			CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
 149
 150static int __init softlockup_panic_setup(char *str)
 151{
 152	softlockup_panic = simple_strtoul(str, NULL, 0);
 153
 154	return 1;
 155}
 156__setup("softlockup_panic=", softlockup_panic_setup);
 157
 158static int __init nowatchdog_setup(char *str)
 159{
 160	watchdog_enabled = 0;
 161	return 1;
 162}
 163__setup("nowatchdog", nowatchdog_setup);
 164
 
 165static int __init nosoftlockup_setup(char *str)
 166{
 167	watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
 168	return 1;
 169}
 170__setup("nosoftlockup", nosoftlockup_setup);
 171
 172#ifdef CONFIG_SMP
 173static int __init softlockup_all_cpu_backtrace_setup(char *str)
 174{
 175	sysctl_softlockup_all_cpu_backtrace =
 176		!!simple_strtol(str, NULL, 0);
 177	return 1;
 178}
 179__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
 180static int __init hardlockup_all_cpu_backtrace_setup(char *str)
 181{
 182	sysctl_hardlockup_all_cpu_backtrace =
 183		!!simple_strtol(str, NULL, 0);
 184	return 1;
 185}
 186__setup("hardlockup_all_cpu_backtrace=", hardlockup_all_cpu_backtrace_setup);
 187#endif
 188
 189/*
 190 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
 191 * lockups can have false positives under extreme conditions. So we generally
 192 * want a higher threshold for soft lockups than for hard lockups. So we couple
 193 * the thresholds with a factor: we make the soft threshold twice the amount of
 194 * time the hard threshold is.
 195 */
 196static int get_softlockup_thresh(void)
 197{
 198	return watchdog_thresh * 2;
 199}
 200
 201/*
 202 * Returns seconds, approximately.  We don't need nanosecond
 203 * resolution, and we don't need to waste time with a big divide when
 204 * 2^30ns == 1.074s.
 205 */
 206static unsigned long get_timestamp(void)
 207{
 208	return running_clock() >> 30LL;  /* 2^30 ~= 10^9 */
 209}
 210
 211static void set_sample_period(void)
 212{
 213	/*
 214	 * convert watchdog_thresh from seconds to ns
 215	 * the divide by 5 is to give hrtimer several chances (two
 216	 * or three with the current relation between the soft
 217	 * and hard thresholds) to increment before the
 218	 * hardlockup detector generates a warning
 219	 */
 220	sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
 221}
 222
 223/* Commands for resetting the watchdog */
 224static void __touch_watchdog(void)
 225{
 226	__this_cpu_write(watchdog_touch_ts, get_timestamp());
 227}
 228
 229/**
 230 * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
 231 *
 232 * Call when the scheduler may have stalled for legitimate reasons
 233 * preventing the watchdog task from executing - e.g. the scheduler
 234 * entering idle state.  This should only be used for scheduler events.
 235 * Use touch_softlockup_watchdog() for everything else.
 236 */
 237void touch_softlockup_watchdog_sched(void)
 238{
 239	/*
 240	 * Preemption can be enabled.  It doesn't matter which CPU's timestamp
 241	 * gets zeroed here, so use the raw_ operation.
 242	 */
 243	raw_cpu_write(watchdog_touch_ts, 0);
 244}
 245
 246void touch_softlockup_watchdog(void)
 247{
 248	touch_softlockup_watchdog_sched();
 249	wq_watchdog_touch(raw_smp_processor_id());
 250}
 251EXPORT_SYMBOL(touch_softlockup_watchdog);
 252
 253void touch_all_softlockup_watchdogs(void)
 254{
 255	int cpu;
 256
 257	/*
 258	 * this is done lockless
 259	 * do we care if a 0 races with a timestamp?
 260	 * all it means is the softlock check starts one cycle later
 261	 */
 262	for_each_watchdog_cpu(cpu)
 263		per_cpu(watchdog_touch_ts, cpu) = 0;
 264	wq_watchdog_touch(-1);
 265}
 266
 267#ifdef CONFIG_HARDLOCKUP_DETECTOR
 268void touch_nmi_watchdog(void)
 269{
 270	/*
 271	 * Using __raw here because some code paths have
 272	 * preemption enabled.  If preemption is enabled
 273	 * then interrupts should be enabled too, in which
 274	 * case we shouldn't have to worry about the watchdog
 275	 * going off.
 276	 */
 277	raw_cpu_write(watchdog_nmi_touch, true);
 278	touch_softlockup_watchdog();
 279}
 280EXPORT_SYMBOL(touch_nmi_watchdog);
 281
 282#endif
 283
 284void touch_softlockup_watchdog_sync(void)
 285{
 286	__this_cpu_write(softlockup_touch_sync, true);
 287	__this_cpu_write(watchdog_touch_ts, 0);
 288}
 289
 290#ifdef CONFIG_HARDLOCKUP_DETECTOR
 291/* watchdog detector functions */
 292static bool is_hardlockup(void)
 293{
 294	unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
 295
 296	if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
 297		return true;
 298
 299	__this_cpu_write(hrtimer_interrupts_saved, hrint);
 300	return false;
 301}
 302#endif
 303
 304static int is_softlockup(unsigned long touch_ts)
 305{
 306	unsigned long now = get_timestamp();
 
 
 
 
 307
 308	if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
 309		/* Warn about unreasonable delays. */
 310		if (time_after(now, touch_ts + get_softlockup_thresh()))
 311			return now - touch_ts;
 312	}
 313	return 0;
 314}
 315
 316#ifdef CONFIG_HARDLOCKUP_DETECTOR
 317
 318static struct perf_event_attr wd_hw_attr = {
 319	.type		= PERF_TYPE_HARDWARE,
 320	.config		= PERF_COUNT_HW_CPU_CYCLES,
 321	.size		= sizeof(struct perf_event_attr),
 322	.pinned		= 1,
 323	.disabled	= 1,
 324};
 325
 326/* Callback function for perf event subsystem */
 327static void watchdog_overflow_callback(struct perf_event *event,
 328		 struct perf_sample_data *data,
 329		 struct pt_regs *regs)
 330{
 331	/* Ensure the watchdog never gets throttled */
 332	event->hw.interrupts = 0;
 333
 334	if (__this_cpu_read(watchdog_nmi_touch) == true) {
 335		__this_cpu_write(watchdog_nmi_touch, false);
 336		return;
 337	}
 338
 339	/* check for a hardlockup
 340	 * This is done by making sure our timer interrupt
 341	 * is incrementing.  The timer interrupt should have
 342	 * fired multiple times before we overflow'd.  If it hasn't
 343	 * then this is a good indication the cpu is stuck
 344	 */
 345	if (is_hardlockup()) {
 346		int this_cpu = smp_processor_id();
 347		struct pt_regs *regs = get_irq_regs();
 348
 349		/* only print hardlockups once */
 350		if (__this_cpu_read(hard_watchdog_warn) == true)
 351			return;
 352
 353		pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
 354		print_modules();
 355		print_irqtrace_events(current);
 356		if (regs)
 357			show_regs(regs);
 358		else
 359			dump_stack();
 360
 361		/*
 362		 * Perform all-CPU dump only once to avoid multiple hardlockups
 363		 * generating interleaving traces
 364		 */
 365		if (sysctl_hardlockup_all_cpu_backtrace &&
 366				!test_and_set_bit(0, &hardlockup_allcpu_dumped))
 367			trigger_allbutself_cpu_backtrace();
 368
 369		if (hardlockup_panic)
 370			nmi_panic(regs, "Hard LOCKUP");
 
 
 371
 372		__this_cpu_write(hard_watchdog_warn, true);
 373		return;
 374	}
 375
 376	__this_cpu_write(hard_watchdog_warn, false);
 377	return;
 378}
 379#endif /* CONFIG_HARDLOCKUP_DETECTOR */
 380
 381static void watchdog_interrupt_count(void)
 382{
 383	__this_cpu_inc(hrtimer_interrupts);
 384}
 385
 386static int watchdog_nmi_enable(unsigned int cpu);
 387static void watchdog_nmi_disable(unsigned int cpu);
 388
 389static int watchdog_enable_all_cpus(void);
 390static void watchdog_disable_all_cpus(void);
 391
 392/* watchdog kicker functions */
 393static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 394{
 395	unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
 396	struct pt_regs *regs = get_irq_regs();
 397	int duration;
 398	int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
 399
 400	/* kick the hardlockup detector */
 401	watchdog_interrupt_count();
 402
 403	/* kick the softlockup detector */
 404	wake_up_process(__this_cpu_read(softlockup_watchdog));
 405
 406	/* .. and repeat */
 407	hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
 408
 409	if (touch_ts == 0) {
 410		if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
 411			/*
 412			 * If the time stamp was touched atomically
 413			 * make sure the scheduler tick is up to date.
 414			 */
 415			__this_cpu_write(softlockup_touch_sync, false);
 416			sched_clock_tick();
 417		}
 418
 419		/* Clear the guest paused flag on watchdog reset */
 420		kvm_check_and_clear_guest_paused();
 421		__touch_watchdog();
 422		return HRTIMER_RESTART;
 423	}
 424
 425	/* check for a softlockup
 426	 * This is done by making sure a high priority task is
 427	 * being scheduled.  The task touches the watchdog to
 428	 * indicate it is getting cpu time.  If it hasn't then
 429	 * this is a good indication some task is hogging the cpu
 430	 */
 431	duration = is_softlockup(touch_ts);
 432	if (unlikely(duration)) {
 433		/*
 434		 * If a virtual machine is stopped by the host it can look to
 435		 * the watchdog like a soft lockup, check to see if the host
 436		 * stopped the vm before we issue the warning
 437		 */
 438		if (kvm_check_and_clear_guest_paused())
 439			return HRTIMER_RESTART;
 440
 441		/* only warn once */
 442		if (__this_cpu_read(soft_watchdog_warn) == true) {
 443			/*
 444			 * When multiple processes are causing softlockups the
 445			 * softlockup detector only warns on the first one
 446			 * because the code relies on a full quiet cycle to
 447			 * re-arm.  The second process prevents the quiet cycle
 448			 * and never gets reported.  Use task pointers to detect
 449			 * this.
 450			 */
 451			if (__this_cpu_read(softlockup_task_ptr_saved) !=
 452			    current) {
 453				__this_cpu_write(soft_watchdog_warn, false);
 454				__touch_watchdog();
 455			}
 456			return HRTIMER_RESTART;
 457		}
 458
 459		if (softlockup_all_cpu_backtrace) {
 460			/* Prevent multiple soft-lockup reports if one cpu is already
 461			 * engaged in dumping cpu back traces
 462			 */
 463			if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
 464				/* Someone else will report us. Let's give up */
 465				__this_cpu_write(soft_watchdog_warn, true);
 466				return HRTIMER_RESTART;
 467			}
 468		}
 469
 470		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 471			smp_processor_id(), duration,
 472			current->comm, task_pid_nr(current));
 473		__this_cpu_write(softlockup_task_ptr_saved, current);
 474		print_modules();
 475		print_irqtrace_events(current);
 476		if (regs)
 477			show_regs(regs);
 478		else
 479			dump_stack();
 480
 481		if (softlockup_all_cpu_backtrace) {
 482			/* Avoid generating two back traces for current
 483			 * given that one is already made above
 484			 */
 485			trigger_allbutself_cpu_backtrace();
 486
 487			clear_bit(0, &soft_lockup_nmi_warn);
 488			/* Barrier to sync with other cpus */
 489			smp_mb__after_atomic();
 490		}
 491
 492		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 493		if (softlockup_panic)
 494			panic("softlockup: hung tasks");
 495		__this_cpu_write(soft_watchdog_warn, true);
 496	} else
 497		__this_cpu_write(soft_watchdog_warn, false);
 498
 499	return HRTIMER_RESTART;
 500}
 501
 502static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 503{
 504	struct sched_param param = { .sched_priority = prio };
 505
 506	sched_setscheduler(current, policy, &param);
 507}
 508
 509static void watchdog_enable(unsigned int cpu)
 
 
 
 510{
 511	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
 
 512
 513	/* kick off the timer for the hardlockup detector */
 514	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 515	hrtimer->function = watchdog_timer_fn;
 516
 517	/* Enable the perf event */
 518	watchdog_nmi_enable(cpu);
 519
 
 520	/* done here because hrtimer_start can only pin to smp_processor_id() */
 521	hrtimer_start(hrtimer, ns_to_ktime(sample_period),
 522		      HRTIMER_MODE_REL_PINNED);
 523
 524	/* initialize timestamp */
 525	watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
 526	__touch_watchdog();
 527}
 528
 529static void watchdog_disable(unsigned int cpu)
 530{
 531	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
 
 532
 533	watchdog_set_prio(SCHED_NORMAL, 0);
 534	hrtimer_cancel(hrtimer);
 535	/* disable the perf event */
 536	watchdog_nmi_disable(cpu);
 537}
 538
 539static void watchdog_cleanup(unsigned int cpu, bool online)
 540{
 541	watchdog_disable(cpu);
 542}
 543
 544static int watchdog_should_run(unsigned int cpu)
 545{
 546	return __this_cpu_read(hrtimer_interrupts) !=
 547		__this_cpu_read(soft_lockup_hrtimer_cnt);
 548}
 549
 550/*
 551 * The watchdog thread function - touches the timestamp.
 552 *
 553 * It only runs once every sample_period seconds (4 seconds by
 554 * default) to reset the softlockup timestamp. If this gets delayed
 555 * for more than 2*watchdog_thresh seconds then the debug-printout
 556 * triggers in watchdog_timer_fn().
 557 */
 558static void watchdog(unsigned int cpu)
 559{
 560	__this_cpu_write(soft_lockup_hrtimer_cnt,
 561			 __this_cpu_read(hrtimer_interrupts));
 562	__touch_watchdog();
 563
 564	/*
 565	 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
 566	 * failure path. Check for failures that can occur asynchronously -
 567	 * for example, when CPUs are on-lined - and shut down the hardware
 568	 * perf event on each CPU accordingly.
 569	 *
 570	 * The only non-obvious place this bit can be cleared is through
 571	 * watchdog_nmi_enable(), so a pr_info() is placed there.  Placing a
 572	 * pr_info here would be too noisy as it would result in a message
 573	 * every few seconds if the hardlockup was disabled but the softlockup
 574	 * enabled.
 575	 */
 576	if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
 577		watchdog_nmi_disable(cpu);
 578}
 579
 580#ifdef CONFIG_HARDLOCKUP_DETECTOR
 581/*
 582 * People like the simple clean cpu node info on boot.
 583 * Reduce the watchdog noise by only printing messages
 584 * that are different from what cpu0 displayed.
 585 */
 586static unsigned long cpu0_err;
 587
 588static int watchdog_nmi_enable(unsigned int cpu)
 589{
 590	struct perf_event_attr *wd_attr;
 591	struct perf_event *event = per_cpu(watchdog_ev, cpu);
 592
 593	/* nothing to do if the hard lockup detector is disabled */
 594	if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
 595		goto out;
 596
 597	/* is it already setup and enabled? */
 598	if (event && event->state > PERF_EVENT_STATE_OFF)
 599		goto out;
 600
 601	/* it is setup but not enabled */
 602	if (event != NULL)
 603		goto out_enable;
 604
 605	wd_attr = &wd_hw_attr;
 606	wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
 607
 608	/* Try to register using hardware perf events */
 609	event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
 610
 611	/* save cpu0 error for future comparision */
 612	if (cpu == 0 && IS_ERR(event))
 613		cpu0_err = PTR_ERR(event);
 614
 615	if (!IS_ERR(event)) {
 616		/* only print for cpu0 or different than cpu0 */
 617		if (cpu == 0 || cpu0_err)
 618			pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
 619		goto out_save;
 620	}
 621
 622	/*
 623	 * Disable the hard lockup detector if _any_ CPU fails to set up
 624	 * set up the hardware perf event. The watchdog() function checks
 625	 * the NMI_WATCHDOG_ENABLED bit periodically.
 626	 *
 627	 * The barriers are for syncing up watchdog_enabled across all the
 628	 * cpus, as clear_bit() does not use barriers.
 629	 */
 630	smp_mb__before_atomic();
 631	clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
 632	smp_mb__after_atomic();
 633
 634	/* skip displaying the same error again */
 635	if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
 636		return PTR_ERR(event);
 637
 638	/* vary the KERN level based on the returned errno */
 639	if (PTR_ERR(event) == -EOPNOTSUPP)
 640		pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
 641	else if (PTR_ERR(event) == -ENOENT)
 642		pr_warn("disabled (cpu%i): hardware events not enabled\n",
 643			 cpu);
 644	else
 645		pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
 646			cpu, PTR_ERR(event));
 647
 648	pr_info("Shutting down hard lockup detector on all cpus\n");
 649
 650	return PTR_ERR(event);
 651
 652	/* success path */
 653out_save:
 654	per_cpu(watchdog_ev, cpu) = event;
 655out_enable:
 656	perf_event_enable(per_cpu(watchdog_ev, cpu));
 657out:
 658	return 0;
 659}
 660
 661static void watchdog_nmi_disable(unsigned int cpu)
 662{
 663	struct perf_event *event = per_cpu(watchdog_ev, cpu);
 664
 665	if (event) {
 666		perf_event_disable(event);
 667		per_cpu(watchdog_ev, cpu) = NULL;
 668
 669		/* should be in cleanup, but blocks oprofile */
 670		perf_event_release_kernel(event);
 671	}
 672	if (cpu == 0) {
 673		/* watchdog_nmi_enable() expects this to be zero initially. */
 674		cpu0_err = 0;
 675	}
 676}
 677
 678#else
 679static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
 680static void watchdog_nmi_disable(unsigned int cpu) { return; }
 681#endif /* CONFIG_HARDLOCKUP_DETECTOR */
 682
 683static struct smp_hotplug_thread watchdog_threads = {
 684	.store			= &softlockup_watchdog,
 685	.thread_should_run	= watchdog_should_run,
 686	.thread_fn		= watchdog,
 687	.thread_comm		= "watchdog/%u",
 688	.setup			= watchdog_enable,
 689	.cleanup		= watchdog_cleanup,
 690	.park			= watchdog_disable,
 691	.unpark			= watchdog_enable,
 692};
 693
 694/*
 695 * park all watchdog threads that are specified in 'watchdog_cpumask'
 696 *
 697 * This function returns an error if kthread_park() of a watchdog thread
 698 * fails. In this situation, the watchdog threads of some CPUs can already
 699 * be parked and the watchdog threads of other CPUs can still be runnable.
 700 * Callers are expected to handle this special condition as appropriate in
 701 * their context.
 702 *
 703 * This function may only be called in a context that is protected against
 704 * races with CPU hotplug - for example, via get_online_cpus().
 705 */
 706static int watchdog_park_threads(void)
 707{
 708	int cpu, ret = 0;
 709
 710	for_each_watchdog_cpu(cpu) {
 711		ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
 712		if (ret)
 713			break;
 714	}
 715
 716	return ret;
 
 
 717}
 718
 719/*
 720 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
 721 *
 722 * This function may only be called in a context that is protected against
 723 * races with CPU hotplug - for example, via get_online_cpus().
 724 */
 725static void watchdog_unpark_threads(void)
 726{
 727	int cpu;
 728
 729	for_each_watchdog_cpu(cpu)
 730		kthread_unpark(per_cpu(softlockup_watchdog, cpu));
 731}
 732
 733/*
 734 * Suspend the hard and soft lockup detector by parking the watchdog threads.
 735 */
 736int lockup_detector_suspend(void)
 737{
 738	int ret = 0;
 739
 740	get_online_cpus();
 741	mutex_lock(&watchdog_proc_mutex);
 742	/*
 743	 * Multiple suspend requests can be active in parallel (counted by
 744	 * the 'watchdog_suspended' variable). If the watchdog threads are
 745	 * running, the first caller takes care that they will be parked.
 746	 * The state of 'watchdog_running' cannot change while a suspend
 747	 * request is active (see related code in 'proc' handlers).
 748	 */
 749	if (watchdog_running && !watchdog_suspended)
 750		ret = watchdog_park_threads();
 751
 752	if (ret == 0)
 753		watchdog_suspended++;
 754	else {
 755		watchdog_disable_all_cpus();
 756		pr_err("Failed to suspend lockup detectors, disabled\n");
 757		watchdog_enabled = 0;
 
 
 
 
 
 
 
 
 
 
 
 758	}
 759
 760	mutex_unlock(&watchdog_proc_mutex);
 761
 762	return ret;
 763}
 764
 765/*
 766 * Resume the hard and soft lockup detector by unparking the watchdog threads.
 767 */
 768void lockup_detector_resume(void)
 769{
 770	mutex_lock(&watchdog_proc_mutex);
 
 771
 772	watchdog_suspended--;
 773	/*
 774	 * The watchdog threads are unparked if they were previously running
 775	 * and if there is no more active suspend request.
 776	 */
 777	if (watchdog_running && !watchdog_suspended)
 778		watchdog_unpark_threads();
 
 
 779
 780	mutex_unlock(&watchdog_proc_mutex);
 781	put_online_cpus();
 
 
 
 782}
 783
 784static int update_watchdog_all_cpus(void)
 785{
 786	int ret;
 787
 788	ret = watchdog_park_threads();
 789	if (ret)
 790		return ret;
 791
 792	watchdog_unpark_threads();
 
 
 
 
 
 
 
 793
 794	return 0;
 795}
 796
 797static int watchdog_enable_all_cpus(void)
 798{
 799	int err = 0;
 800
 801	if (!watchdog_running) {
 802		err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
 803							     &watchdog_cpumask);
 804		if (err)
 805			pr_err("Failed to create watchdog threads, disabled\n");
 806		else
 807			watchdog_running = 1;
 808	} else {
 809		/*
 810		 * Enable/disable the lockup detectors or
 811		 * change the sample period 'on the fly'.
 812		 */
 813		err = update_watchdog_all_cpus();
 814
 815		if (err) {
 816			watchdog_disable_all_cpus();
 817			pr_err("Failed to update lockup detectors, disabled\n");
 818		}
 819	}
 820
 821	if (err)
 822		watchdog_enabled = 0;
 823
 824	return err;
 
 825}
 826
 827static void watchdog_disable_all_cpus(void)
 828{
 829	if (watchdog_running) {
 830		watchdog_running = 0;
 831		smpboot_unregister_percpu_thread(&watchdog_threads);
 832	}
 833}
 834
 
 835#ifdef CONFIG_SYSCTL
 836
 837/*
 838 * Update the run state of the lockup detectors.
 839 */
 840static int proc_watchdog_update(void)
 841{
 842	int err = 0;
 843
 844	/*
 845	 * Watchdog threads won't be started if they are already active.
 846	 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
 847	 * care of this. If those threads are already active, the sample
 848	 * period will be updated and the lockup detectors will be enabled
 849	 * or disabled 'on the fly'.
 850	 */
 851	if (watchdog_enabled && watchdog_thresh)
 852		err = watchdog_enable_all_cpus();
 853	else
 854		watchdog_disable_all_cpus();
 855
 856	return err;
 857
 858}
 859
 860/*
 861 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
 862 *
 863 * caller             | table->data points to | 'which' contains the flag(s)
 864 * -------------------|-----------------------|-----------------------------
 865 * proc_watchdog      | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
 866 *                    |                       | with SOFT_WATCHDOG_ENABLED
 867 * -------------------|-----------------------|-----------------------------
 868 * proc_nmi_watchdog  | nmi_watchdog_enabled  | NMI_WATCHDOG_ENABLED
 869 * -------------------|-----------------------|-----------------------------
 870 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
 871 */
 872static int proc_watchdog_common(int which, struct ctl_table *table, int write,
 873				void __user *buffer, size_t *lenp, loff_t *ppos)
 874{
 875	int err, old, new;
 876	int *watchdog_param = (int *)table->data;
 877
 878	get_online_cpus();
 879	mutex_lock(&watchdog_proc_mutex);
 880
 881	if (watchdog_suspended) {
 882		/* no parameter changes allowed while watchdog is suspended */
 883		err = -EAGAIN;
 884		goto out;
 885	}
 886
 887	/*
 888	 * If the parameter is being read return the state of the corresponding
 889	 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
 890	 * run state of the lockup detectors.
 891	 */
 892	if (!write) {
 893		*watchdog_param = (watchdog_enabled & which) != 0;
 894		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 895	} else {
 896		err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 897		if (err)
 898			goto out;
 899
 900		/*
 901		 * There is a race window between fetching the current value
 902		 * from 'watchdog_enabled' and storing the new value. During
 903		 * this race window, watchdog_nmi_enable() can sneak in and
 904		 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
 905		 * The 'cmpxchg' detects this race and the loop retries.
 906		 */
 907		do {
 908			old = watchdog_enabled;
 909			/*
 910			 * If the parameter value is not zero set the
 911			 * corresponding bit(s), else clear it(them).
 912			 */
 913			if (*watchdog_param)
 914				new = old | which;
 915			else
 916				new = old & ~which;
 917		} while (cmpxchg(&watchdog_enabled, old, new) != old);
 918
 919		/*
 920		 * Update the run state of the lockup detectors. There is _no_
 921		 * need to check the value returned by proc_watchdog_update()
 922		 * and to restore the previous value of 'watchdog_enabled' as
 923		 * both lockup detectors are disabled if proc_watchdog_update()
 924		 * returns an error.
 925		 */
 926		if (old == new)
 927			goto out;
 928
 929		err = proc_watchdog_update();
 930	}
 931out:
 932	mutex_unlock(&watchdog_proc_mutex);
 933	put_online_cpus();
 934	return err;
 935}
 936
 937/*
 938 * /proc/sys/kernel/watchdog
 939 */
 940int proc_watchdog(struct ctl_table *table, int write,
 941		  void __user *buffer, size_t *lenp, loff_t *ppos)
 942{
 943	return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
 944				    table, write, buffer, lenp, ppos);
 945}
 946
 947/*
 948 * /proc/sys/kernel/nmi_watchdog
 949 */
 950int proc_nmi_watchdog(struct ctl_table *table, int write,
 951		      void __user *buffer, size_t *lenp, loff_t *ppos)
 952{
 953	return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
 954				    table, write, buffer, lenp, ppos);
 955}
 
 956
 957/*
 958 * /proc/sys/kernel/soft_watchdog
 959 */
 960int proc_soft_watchdog(struct ctl_table *table, int write,
 961			void __user *buffer, size_t *lenp, loff_t *ppos)
 962{
 963	return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
 964				    table, write, buffer, lenp, ppos);
 965}
 966
 967/*
 968 * /proc/sys/kernel/watchdog_thresh
 969 */
 970int proc_watchdog_thresh(struct ctl_table *table, int write,
 971			 void __user *buffer, size_t *lenp, loff_t *ppos)
 972{
 973	int err, old, new;
 974
 975	get_online_cpus();
 976	mutex_lock(&watchdog_proc_mutex);
 977
 978	if (watchdog_suspended) {
 979		/* no parameter changes allowed while watchdog is suspended */
 980		err = -EAGAIN;
 981		goto out;
 
 
 
 
 
 
 
 
 
 
 
 
 
 982	}
 983
 984	old = ACCESS_ONCE(watchdog_thresh);
 985	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 986
 987	if (err || !write)
 988		goto out;
 989
 990	/*
 991	 * Update the sample period. Restore on failure.
 
 
 992	 */
 993	new = ACCESS_ONCE(watchdog_thresh);
 994	if (old == new)
 995		goto out;
 996
 997	set_sample_period();
 998	err = proc_watchdog_update();
 999	if (err) {
1000		watchdog_thresh = old;
1001		set_sample_period();
1002	}
1003out:
1004	mutex_unlock(&watchdog_proc_mutex);
1005	put_online_cpus();
1006	return err;
1007}
1008
1009/*
1010 * The cpumask is the mask of possible cpus that the watchdog can run
1011 * on, not the mask of cpus it is actually running on.  This allows the
1012 * user to specify a mask that will include cpus that have not yet
1013 * been brought online, if desired.
1014 */
1015int proc_watchdog_cpumask(struct ctl_table *table, int write,
1016			  void __user *buffer, size_t *lenp, loff_t *ppos)
1017{
1018	int err;
1019
1020	get_online_cpus();
1021	mutex_lock(&watchdog_proc_mutex);
1022
1023	if (watchdog_suspended) {
1024		/* no parameter changes allowed while watchdog is suspended */
1025		err = -EAGAIN;
1026		goto out;
1027	}
1028
1029	err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
1030	if (!err && write) {
1031		/* Remove impossible cpus to keep sysctl output cleaner. */
1032		cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
1033			    cpu_possible_mask);
1034
1035		if (watchdog_running) {
1036			/*
1037			 * Failure would be due to being unable to allocate
1038			 * a temporary cpumask, so we are likely not in a
1039			 * position to do much else to make things better.
1040			 */
1041			if (smpboot_update_cpumask_percpu_thread(
1042				    &watchdog_threads, &watchdog_cpumask) != 0)
1043				pr_err("cpumask update failed\n");
1044		}
1045	}
1046out:
1047	mutex_unlock(&watchdog_proc_mutex);
1048	put_online_cpus();
1049	return err;
1050}
1051
1052#endif /* CONFIG_SYSCTL */
1053
1054void __init lockup_detector_init(void)
1055{
1056	set_sample_period();
 
1057
1058#ifdef CONFIG_NO_HZ_FULL
1059	if (tick_nohz_full_enabled()) {
1060		pr_info("Disabling watchdog on nohz_full cores by default\n");
1061		cpumask_copy(&watchdog_cpumask, housekeeping_mask);
1062	} else
1063		cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1064#else
1065	cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
1066#endif
1067
1068	if (watchdog_enabled)
1069		watchdog_enable_all_cpus();
 
 
1070}