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

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