Root/kernel/watchdog.c

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
30int watchdog_enabled;
31int __read_mostly softlockup_thresh = 60;
32
33static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
34static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
35static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
36static DEFINE_PER_CPU(bool, softlockup_touch_sync);
37static DEFINE_PER_CPU(bool, soft_watchdog_warn);
38#ifdef CONFIG_HARDLOCKUP_DETECTOR
39static DEFINE_PER_CPU(bool, hard_watchdog_warn);
40static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
41static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
42static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
43static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
44#endif
45
46static int __read_mostly did_panic;
47static int __initdata no_watchdog;
48
49
50/* boot commands */
51/*
52 * Should we panic when a soft-lockup or hard-lockup occurs:
53 */
54#ifdef CONFIG_HARDLOCKUP_DETECTOR
55static int hardlockup_panic;
56
57static int __init hardlockup_panic_setup(char *str)
58{
59    if (!strncmp(str, "panic", 5))
60        hardlockup_panic = 1;
61    return 1;
62}
63__setup("nmi_watchdog=", hardlockup_panic_setup);
64#endif
65
66unsigned int __read_mostly softlockup_panic =
67            CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
68
69static int __init softlockup_panic_setup(char *str)
70{
71    softlockup_panic = simple_strtoul(str, NULL, 0);
72
73    return 1;
74}
75__setup("softlockup_panic=", softlockup_panic_setup);
76
77static int __init nowatchdog_setup(char *str)
78{
79    no_watchdog = 1;
80    return 1;
81}
82__setup("nowatchdog", nowatchdog_setup);
83
84/* deprecated */
85static int __init nosoftlockup_setup(char *str)
86{
87    no_watchdog = 1;
88    return 1;
89}
90__setup("nosoftlockup", nosoftlockup_setup);
91/* */
92
93
94/*
95 * Returns seconds, approximately. We don't need nanosecond
96 * resolution, and we don't need to waste time with a big divide when
97 * 2^30ns == 1.074s.
98 */
99static unsigned long get_timestamp(int this_cpu)
100{
101    return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
102}
103
104static unsigned long get_sample_period(void)
105{
106    /*
107     * convert softlockup_thresh from seconds to ns
108     * the divide by 5 is to give hrtimer 5 chances to
109     * increment before the hardlockup detector generates
110     * a warning
111     */
112    return softlockup_thresh / 5 * NSEC_PER_SEC;
113}
114
115/* Commands for resetting the watchdog */
116static void __touch_watchdog(void)
117{
118    int this_cpu = smp_processor_id();
119
120    __get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
121}
122
123void touch_softlockup_watchdog(void)
124{
125    __raw_get_cpu_var(watchdog_touch_ts) = 0;
126}
127EXPORT_SYMBOL(touch_softlockup_watchdog);
128
129void touch_all_softlockup_watchdogs(void)
130{
131    int cpu;
132
133    /*
134     * this is done lockless
135     * do we care if a 0 races with a timestamp?
136     * all it means is the softlock check starts one cycle later
137     */
138    for_each_online_cpu(cpu)
139        per_cpu(watchdog_touch_ts, cpu) = 0;
140}
141
142#ifdef CONFIG_HARDLOCKUP_DETECTOR
143void touch_nmi_watchdog(void)
144{
145    if (watchdog_enabled) {
146        unsigned cpu;
147
148        for_each_present_cpu(cpu) {
149            if (per_cpu(watchdog_nmi_touch, cpu) != true)
150                per_cpu(watchdog_nmi_touch, cpu) = true;
151        }
152    }
153    touch_softlockup_watchdog();
154}
155EXPORT_SYMBOL(touch_nmi_watchdog);
156
157#endif
158
159void touch_softlockup_watchdog_sync(void)
160{
161    __raw_get_cpu_var(softlockup_touch_sync) = true;
162    __raw_get_cpu_var(watchdog_touch_ts) = 0;
163}
164
165#ifdef CONFIG_HARDLOCKUP_DETECTOR
166/* watchdog detector functions */
167static int is_hardlockup(void)
168{
169    unsigned long hrint = __get_cpu_var(hrtimer_interrupts);
170
171    if (__get_cpu_var(hrtimer_interrupts_saved) == hrint)
172        return 1;
173
174    __get_cpu_var(hrtimer_interrupts_saved) = hrint;
175    return 0;
176}
177#endif
178
179static int is_softlockup(unsigned long touch_ts)
180{
181    unsigned long now = get_timestamp(smp_processor_id());
182
183    /* Warn about unreasonable delays: */
184    if (time_after(now, touch_ts + softlockup_thresh))
185        return now - touch_ts;
186
187    return 0;
188}
189
190static int
191watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
192{
193    did_panic = 1;
194
195    return NOTIFY_DONE;
196}
197
198static struct notifier_block panic_block = {
199    .notifier_call = watchdog_panic,
200};
201
202#ifdef CONFIG_HARDLOCKUP_DETECTOR
203static struct perf_event_attr wd_hw_attr = {
204    .type = PERF_TYPE_HARDWARE,
205    .config = PERF_COUNT_HW_CPU_CYCLES,
206    .size = sizeof(struct perf_event_attr),
207    .pinned = 1,
208    .disabled = 1,
209};
210
211/* Callback function for perf event subsystem */
212void watchdog_overflow_callback(struct perf_event *event, int nmi,
213         struct perf_sample_data *data,
214         struct pt_regs *regs)
215{
216    /* Ensure the watchdog never gets throttled */
217    event->hw.interrupts = 0;
218
219    if (__get_cpu_var(watchdog_nmi_touch) == true) {
220        __get_cpu_var(watchdog_nmi_touch) = false;
221        return;
222    }
223
224    /* check for a hardlockup
225     * This is done by making sure our timer interrupt
226     * is incrementing. The timer interrupt should have
227     * fired multiple times before we overflow'd. If it hasn't
228     * then this is a good indication the cpu is stuck
229     */
230    if (is_hardlockup()) {
231        int this_cpu = smp_processor_id();
232
233        /* only print hardlockups once */
234        if (__get_cpu_var(hard_watchdog_warn) == true)
235            return;
236
237        if (hardlockup_panic)
238            panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
239        else
240            WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
241
242        __get_cpu_var(hard_watchdog_warn) = true;
243        return;
244    }
245
246    __get_cpu_var(hard_watchdog_warn) = false;
247    return;
248}
249static void watchdog_interrupt_count(void)
250{
251    __get_cpu_var(hrtimer_interrupts)++;
252}
253#else
254static inline void watchdog_interrupt_count(void) { return; }
255#endif /* CONFIG_HARDLOCKUP_DETECTOR */
256
257/* watchdog kicker functions */
258static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
259{
260    unsigned long touch_ts = __get_cpu_var(watchdog_touch_ts);
261    struct pt_regs *regs = get_irq_regs();
262    int duration;
263
264    /* kick the hardlockup detector */
265    watchdog_interrupt_count();
266
267    /* kick the softlockup detector */
268    wake_up_process(__get_cpu_var(softlockup_watchdog));
269
270    /* .. and repeat */
271    hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
272
273    if (touch_ts == 0) {
274        if (unlikely(__get_cpu_var(softlockup_touch_sync))) {
275            /*
276             * If the time stamp was touched atomically
277             * make sure the scheduler tick is up to date.
278             */
279            __get_cpu_var(softlockup_touch_sync) = false;
280            sched_clock_tick();
281        }
282        __touch_watchdog();
283        return HRTIMER_RESTART;
284    }
285
286    /* check for a softlockup
287     * This is done by making sure a high priority task is
288     * being scheduled. The task touches the watchdog to
289     * indicate it is getting cpu time. If it hasn't then
290     * this is a good indication some task is hogging the cpu
291     */
292    duration = is_softlockup(touch_ts);
293    if (unlikely(duration)) {
294        /* only warn once */
295        if (__get_cpu_var(soft_watchdog_warn) == true)
296            return HRTIMER_RESTART;
297
298        printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
299            smp_processor_id(), duration,
300            current->comm, task_pid_nr(current));
301        print_modules();
302        print_irqtrace_events(current);
303        if (regs)
304            show_regs(regs);
305        else
306            dump_stack();
307
308        if (softlockup_panic)
309            panic("softlockup: hung tasks");
310        __get_cpu_var(soft_watchdog_warn) = true;
311    } else
312        __get_cpu_var(soft_watchdog_warn) = false;
313
314    return HRTIMER_RESTART;
315}
316
317
318/*
319 * The watchdog thread - touches the timestamp.
320 */
321static int watchdog(void *unused)
322{
323    struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
324    struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
325
326    sched_setscheduler(current, SCHED_FIFO, &param);
327
328    /* initialize timestamp */
329    __touch_watchdog();
330
331    /* kick off the timer for the hardlockup detector */
332    /* done here because hrtimer_start can only pin to smp_processor_id() */
333    hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
334              HRTIMER_MODE_REL_PINNED);
335
336    set_current_state(TASK_INTERRUPTIBLE);
337    /*
338     * Run briefly once per second to reset the softlockup timestamp.
339     * If this gets delayed for more than 60 seconds then the
340     * debug-printout triggers in watchdog_timer_fn().
341     */
342    while (!kthread_should_stop()) {
343        __touch_watchdog();
344        schedule();
345
346        if (kthread_should_stop())
347            break;
348
349        set_current_state(TASK_INTERRUPTIBLE);
350    }
351    __set_current_state(TASK_RUNNING);
352
353    return 0;
354}
355
356
357#ifdef CONFIG_HARDLOCKUP_DETECTOR
358static int watchdog_nmi_enable(int cpu)
359{
360    struct perf_event_attr *wd_attr;
361    struct perf_event *event = per_cpu(watchdog_ev, cpu);
362
363    /* is it already setup and enabled? */
364    if (event && event->state > PERF_EVENT_STATE_OFF)
365        goto out;
366
367    /* it is setup but not enabled */
368    if (event != NULL)
369        goto out_enable;
370
371    /* Try to register using hardware perf events */
372    wd_attr = &wd_hw_attr;
373    wd_attr->sample_period = hw_nmi_get_sample_period();
374    event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
375    if (!IS_ERR(event)) {
376        printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
377        goto out_save;
378    }
379
380    printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
381    return -1;
382
383    /* success path */
384out_save:
385    per_cpu(watchdog_ev, cpu) = event;
386out_enable:
387    perf_event_enable(per_cpu(watchdog_ev, cpu));
388out:
389    return 0;
390}
391
392static void watchdog_nmi_disable(int cpu)
393{
394    struct perf_event *event = per_cpu(watchdog_ev, cpu);
395
396    if (event) {
397        perf_event_disable(event);
398        per_cpu(watchdog_ev, cpu) = NULL;
399
400        /* should be in cleanup, but blocks oprofile */
401        perf_event_release_kernel(event);
402    }
403    return;
404}
405#else
406static int watchdog_nmi_enable(int cpu) { return 0; }
407static void watchdog_nmi_disable(int cpu) { return; }
408#endif /* CONFIG_HARDLOCKUP_DETECTOR */
409
410/* prepare/enable/disable routines */
411static int watchdog_prepare_cpu(int cpu)
412{
413    struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
414
415    WARN_ON(per_cpu(softlockup_watchdog, cpu));
416    hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
417    hrtimer->function = watchdog_timer_fn;
418
419    return 0;
420}
421
422static int watchdog_enable(int cpu)
423{
424    struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
425
426    /* enable the perf event */
427    if (watchdog_nmi_enable(cpu) != 0)
428        return -1;
429
430    /* create the watchdog thread */
431    if (!p) {
432        p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
433        if (IS_ERR(p)) {
434            printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
435            return -1;
436        }
437        kthread_bind(p, cpu);
438        per_cpu(watchdog_touch_ts, cpu) = 0;
439        per_cpu(softlockup_watchdog, cpu) = p;
440        wake_up_process(p);
441    }
442
443    /* if any cpu succeeds, watchdog is considered enabled for the system */
444    watchdog_enabled = 1;
445
446    return 0;
447}
448
449static void watchdog_disable(int cpu)
450{
451    struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
452    struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
453
454    /*
455     * cancel the timer first to stop incrementing the stats
456     * and waking up the kthread
457     */
458    hrtimer_cancel(hrtimer);
459
460    /* disable the perf event */
461    watchdog_nmi_disable(cpu);
462
463    /* stop the watchdog thread */
464    if (p) {
465        per_cpu(softlockup_watchdog, cpu) = NULL;
466        kthread_stop(p);
467    }
468}
469
470static void watchdog_enable_all_cpus(void)
471{
472    int cpu;
473    int result = 0;
474
475    for_each_online_cpu(cpu)
476        result += watchdog_enable(cpu);
477
478    if (result)
479        printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
480
481}
482
483static void watchdog_disable_all_cpus(void)
484{
485    int cpu;
486
487    for_each_online_cpu(cpu)
488        watchdog_disable(cpu);
489
490    /* if all watchdogs are disabled, then they are disabled for the system */
491    watchdog_enabled = 0;
492}
493
494
495/* sysctl functions */
496#ifdef CONFIG_SYSCTL
497/*
498 * proc handler for /proc/sys/kernel/nmi_watchdog
499 */
500
501int proc_dowatchdog_enabled(struct ctl_table *table, int write,
502             void __user *buffer, size_t *length, loff_t *ppos)
503{
504    proc_dointvec(table, write, buffer, length, ppos);
505
506    if (watchdog_enabled)
507        watchdog_enable_all_cpus();
508    else
509        watchdog_disable_all_cpus();
510    return 0;
511}
512
513int proc_dowatchdog_thresh(struct ctl_table *table, int write,
514                 void __user *buffer,
515                 size_t *lenp, loff_t *ppos)
516{
517    return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
518}
519#endif /* CONFIG_SYSCTL */
520
521
522/*
523 * Create/destroy watchdog threads as CPUs come and go:
524 */
525static int __cpuinit
526cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
527{
528    int hotcpu = (unsigned long)hcpu;
529
530    switch (action) {
531    case CPU_UP_PREPARE:
532    case CPU_UP_PREPARE_FROZEN:
533        if (watchdog_prepare_cpu(hotcpu))
534            return NOTIFY_BAD;
535        break;
536    case CPU_ONLINE:
537    case CPU_ONLINE_FROZEN:
538        if (watchdog_enable(hotcpu))
539            return NOTIFY_BAD;
540        break;
541#ifdef CONFIG_HOTPLUG_CPU
542    case CPU_UP_CANCELED:
543    case CPU_UP_CANCELED_FROZEN:
544        watchdog_disable(hotcpu);
545        break;
546    case CPU_DEAD:
547    case CPU_DEAD_FROZEN:
548        watchdog_disable(hotcpu);
549        break;
550#endif /* CONFIG_HOTPLUG_CPU */
551    }
552    return NOTIFY_OK;
553}
554
555static struct notifier_block __cpuinitdata cpu_nfb = {
556    .notifier_call = cpu_callback
557};
558
559static int __init spawn_watchdog_task(void)
560{
561    void *cpu = (void *)(long)smp_processor_id();
562    int err;
563
564    if (no_watchdog)
565        return 0;
566
567    err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
568    WARN_ON(err == NOTIFY_BAD);
569
570    cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
571    register_cpu_notifier(&cpu_nfb);
572
573    atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
574
575    return 0;
576}
577early_initcall(spawn_watchdog_task);
578

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