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/*
* Detect hard and soft lockups on a system
*
* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
*
* Note: Most of this code is borrowed heavily from the original softlockup
* detector, so thanks to Ingo for the initial implementation.
* Some chunks also taken from the old x86-specific nmi watchdog code, thanks
* to those contributors as well.
*/

#define pr_fmt(fmt) "NMI watchdog: " fmt

#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/lockdep.h>
#include <linux/notifier.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/smpboot.h>

#include <asm/irq_regs.h>
#include <linux/kvm_para.h>
#include <linux/perf_event.h>

int watchdog_enabled = 1;
int __read_mostly watchdog_thresh = 10;
static int __read_mostly watchdog_disabled;

static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
static DEFINE_PER_CPU(bool, softlockup_touch_sync);
static DEFINE_PER_CPU(bool, soft_watchdog_warn);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
#ifdef CONFIG_HARDLOCKUP_DETECTOR
static DEFINE_PER_CPU(bool, hard_watchdog_warn);
static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
#endif

/* boot commands */
/*
* Should we panic when a soft-lockup or hard-lockup occurs:
*/
#ifdef CONFIG_HARDLOCKUP_DETECTOR
static int hardlockup_panic =
CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;

static int __init hardlockup_panic_setup(char *str)
{
if (!strncmp(str, "panic", 5))
hardlockup_panic = 1;
else if (!strncmp(str, "nopanic", 7))
hardlockup_panic = 0;
else if (!strncmp(str, "0", 1))
watchdog_enabled = 0;
return 1;
}
__setup("nmi_watchdog=", hardlockup_panic_setup);
#endif

unsigned int __read_mostly softlockup_panic =
CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;

static int __init softlockup_panic_setup(char *str)
{
softlockup_panic = simple_strtoul(str, NULL, 0);

return 1;
}
__setup("softlockup_panic=", softlockup_panic_setup);

static int __init nowatchdog_setup(char *str)
{
watchdog_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);

/* deprecated */
static int __init nosoftlockup_setup(char *str)
{
watchdog_enabled = 0;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
/* */

/*
* Hard-lockup warnings should be triggered after just a few seconds. Soft-
* lockups can have false positives under extreme conditions. So we generally
* want a higher threshold for soft lockups than for hard lockups. So we couple
* the thresholds with a factor: we make the soft threshold twice the amount of
* time the hard threshold is.
*/
static int get_softlockup_thresh(void)
{
return watchdog_thresh * 2;
}

/*
* Returns seconds, approximately. We don't need nanosecond
* resolution, and we don't need to waste time with a big divide when
* 2^30ns == 1.074s.
*/
static unsigned long get_timestamp(int this_cpu)
{
return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
}

static unsigned long get_sample_period(void)
{
/*
* convert watchdog_thresh from seconds to ns
* the divide by 5 is to give hrtimer several chances (two
* or three with the current relation between the soft
* and hard thresholds) to increment before the
* hardlockup detector generates a warning
*/
return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
}

/* Commands for resetting the watchdog */
static void __touch_watchdog(void)
{
int this_cpu = smp_processor_id();

__this_cpu_write(watchdog_touch_ts, get_timestamp(this_cpu));
}

void touch_softlockup_watchdog(void)
{
__this_cpu_write(watchdog_touch_ts, 0);
}
EXPORT_SYMBOL(touch_softlockup_watchdog);

void touch_all_softlockup_watchdogs(void)
{
int cpu;

/*
* this is done lockless
* do we care if a 0 races with a timestamp?
* all it means is the softlock check starts one cycle later
*/
for_each_online_cpu(cpu)
per_cpu(watchdog_touch_ts, cpu) = 0;
}

#ifdef CONFIG_HARDLOCKUP_DETECTOR
void touch_nmi_watchdog(void)
{
if (watchdog_enabled) {
unsigned cpu;

for_each_present_cpu(cpu) {
if (per_cpu(watchdog_nmi_touch, cpu) != true)
per_cpu(watchdog_nmi_touch, cpu) = true;
}
}
touch_softlockup_watchdog();
}
EXPORT_SYMBOL(touch_nmi_watchdog);

#endif

void touch_softlockup_watchdog_sync(void)
{
__raw_get_cpu_var(softlockup_touch_sync) = true;
__raw_get_cpu_var(watchdog_touch_ts) = 0;
}

#ifdef CONFIG_HARDLOCKUP_DETECTOR
/* watchdog detector functions */
static int is_hardlockup(void)
{
unsigned long hrint = __this_cpu_read(hrtimer_interrupts);

if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
return 1;

__this_cpu_write(hrtimer_interrupts_saved, hrint);
return 0;
}
#endif

static int is_softlockup(unsigned long touch_ts)
{
unsigned long now = get_timestamp(smp_processor_id());

/* Warn about unreasonable delays: */
if (time_after(now, touch_ts + get_softlockup_thresh()))
return now - touch_ts;

return 0;
}

#ifdef CONFIG_HARDLOCKUP_DETECTOR

static struct perf_event_attr wd_hw_attr = {
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
.size = sizeof(struct perf_event_attr),
.pinned = 1,
.disabled = 1,
};

/* Callback function for perf event subsystem */
static void watchdog_overflow_callback(struct perf_event *event,
struct perf_sample_data *data,
struct pt_regs *regs)
{
/* Ensure the watchdog never gets throttled */
event->hw.interrupts = 0;

if (__this_cpu_read(watchdog_nmi_touch) == true) {
__this_cpu_write(watchdog_nmi_touch, false);
return;
}

/* check for a hardlockup
* This is done by making sure our timer interrupt
* is incrementing. The timer interrupt should have
* fired multiple times before we overflow'd. If it hasn't
* then this is a good indication the cpu is stuck
*/
if (is_hardlockup()) {
int this_cpu = smp_processor_id();

/* only print hardlockups once */
if (__this_cpu_read(hard_watchdog_warn) == true)
return;

if (hardlockup_panic)
panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
else
WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);

__this_cpu_write(hard_watchdog_warn, true);
return;
}

__this_cpu_write(hard_watchdog_warn, false);
return;
}
#endif /* CONFIG_HARDLOCKUP_DETECTOR */

static void watchdog_interrupt_count(void)
{
__this_cpu_inc(hrtimer_interrupts);
}

static int watchdog_nmi_enable(unsigned int cpu);
static void watchdog_nmi_disable(unsigned int cpu);

/* watchdog kicker functions */
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
{
unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
struct pt_regs *regs = get_irq_regs();
int duration;

/* kick the hardlockup detector */
watchdog_interrupt_count();

/* kick the softlockup detector */
wake_up_process(__this_cpu_read(softlockup_watchdog));

/* .. and repeat */
hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));

if (touch_ts == 0) {
if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
/*
* If the time stamp was touched atomically
* make sure the scheduler tick is up to date.
*/
__this_cpu_write(softlockup_touch_sync, false);
sched_clock_tick();
}

/* Clear the guest paused flag on watchdog reset */
kvm_check_and_clear_guest_paused();
__touch_watchdog();
return HRTIMER_RESTART;
}

/* check for a softlockup
* This is done by making sure a high priority task is
* being scheduled. The task touches the watchdog to
* indicate it is getting cpu time. If it hasn't then
* this is a good indication some task is hogging the cpu
*/
duration = is_softlockup(touch_ts);
if (unlikely(duration)) {
/*
* If a virtual machine is stopped by the host it can look to
* the watchdog like a soft lockup, check to see if the host
* stopped the vm before we issue the warning
*/
if (kvm_check_and_clear_guest_paused())
return HRTIMER_RESTART;

/* only warn once */
if (__this_cpu_read(soft_watchdog_warn) == true)
return HRTIMER_RESTART;

printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
print_modules();
print_irqtrace_events(current);
if (regs)
show_regs(regs);
else
dump_stack();

if (softlockup_panic)
panic("softlockup: hung tasks");
__this_cpu_write(soft_watchdog_warn, true);
} else
__this_cpu_write(soft_watchdog_warn, false);

return HRTIMER_RESTART;
}

static void watchdog_set_prio(unsigned int policy, unsigned int prio)
{
struct sched_param param = { .sched_priority = prio };

sched_setscheduler(current, policy, &param);
}

static void watchdog_enable(unsigned int cpu)
{
struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);

if (!watchdog_enabled) {
kthread_park(current);
return;
}

/* Enable the perf event */
watchdog_nmi_enable(cpu);

/* kick off the timer for the hardlockup detector */
hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hrtimer->function = watchdog_timer_fn;

/* done here because hrtimer_start can only pin to smp_processor_id() */
hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
HRTIMER_MODE_REL_PINNED);

/* initialize timestamp */
watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
__touch_watchdog();
}

static void watchdog_disable(unsigned int cpu)
{
struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);

watchdog_set_prio(SCHED_NORMAL, 0);
hrtimer_cancel(hrtimer);
/* disable the perf event */
watchdog_nmi_disable(cpu);
}

static int watchdog_should_run(unsigned int cpu)
{
return __this_cpu_read(hrtimer_interrupts) !=
__this_cpu_read(soft_lockup_hrtimer_cnt);
}

/*
* The watchdog thread function - touches the timestamp.
*
* It only runs once every get_sample_period() seconds (4 seconds by
* default) to reset the softlockup timestamp. If this gets delayed
* for more than 2*watchdog_thresh seconds then the debug-printout
* triggers in watchdog_timer_fn().
*/
static void watchdog(unsigned int cpu)
{
__this_cpu_write(soft_lockup_hrtimer_cnt,
__this_cpu_read(hrtimer_interrupts));
__touch_watchdog();
}

#ifdef CONFIG_HARDLOCKUP_DETECTOR
/*
* People like the simple clean cpu node info on boot.
* Reduce the watchdog noise by only printing messages
* that are different from what cpu0 displayed.
*/
static unsigned long cpu0_err;

static int watchdog_nmi_enable(unsigned int cpu)
{
struct perf_event_attr *wd_attr;
struct perf_event *event = per_cpu(watchdog_ev, cpu);

/* is it already setup and enabled? */
if (event && event->state > PERF_EVENT_STATE_OFF)
goto out;

/* it is setup but not enabled */
if (event != NULL)
goto out_enable;

wd_attr = &wd_hw_attr;
wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);

/* Try to register using hardware perf events */
event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);

/* save cpu0 error for future comparision */
if (cpu == 0 && IS_ERR(event))
cpu0_err = PTR_ERR(event);

if (!IS_ERR(event)) {
/* only print for cpu0 or different than cpu0 */
if (cpu == 0 || cpu0_err)
pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
goto out_save;
}

/* skip displaying the same error again */
if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
return PTR_ERR(event);

/* vary the KERN level based on the returned errno */
if (PTR_ERR(event) == -EOPNOTSUPP)
pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
else if (PTR_ERR(event) == -ENOENT)
pr_warning("disabled (cpu%i): hardware events not enabled\n",
cpu);
else
pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
cpu, PTR_ERR(event));
return PTR_ERR(event);

/* success path */
out_save:
per_cpu(watchdog_ev, cpu) = event;
out_enable:
perf_event_enable(per_cpu(watchdog_ev, cpu));
out:
return 0;
}

static void watchdog_nmi_disable(unsigned int cpu)
{
struct perf_event *event = per_cpu(watchdog_ev, cpu);

if (event) {
perf_event_disable(event);
per_cpu(watchdog_ev, cpu) = NULL;

/* should be in cleanup, but blocks oprofile */
perf_event_release_kernel(event);
}
return;
}
#else
static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
static void watchdog_nmi_disable(unsigned int cpu) { return; }
#endif /* CONFIG_HARDLOCKUP_DETECTOR */

/* prepare/enable/disable routines */
/* sysctl functions */
#ifdef CONFIG_SYSCTL
static void watchdog_enable_all_cpus(void)
{
unsigned int cpu;

if (watchdog_disabled) {
watchdog_disabled = 0;
for_each_online_cpu(cpu)
kthread_unpark(per_cpu(softlockup_watchdog, cpu));
}
}

static void watchdog_disable_all_cpus(void)
{
unsigned int cpu;

if (!watchdog_disabled) {
watchdog_disabled = 1;
for_each_online_cpu(cpu)
kthread_park(per_cpu(softlockup_watchdog, cpu));
}
}

/*
* proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
*/

int proc_dowatchdog(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int ret;

if (watchdog_disabled < 0)
return -ENODEV;

ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (ret || !write)
return ret;

if (watchdog_enabled && watchdog_thresh)
watchdog_enable_all_cpus();
else
watchdog_disable_all_cpus();

return ret;
}
#endif /* CONFIG_SYSCTL */

static struct smp_hotplug_thread watchdog_threads = {
.store = &softlockup_watchdog,
.thread_should_run = watchdog_should_run,
.thread_fn = watchdog,
.thread_comm = "watchdog/%u",
.setup = watchdog_enable,
.park = watchdog_disable,
.unpark = watchdog_enable,
};

void __init lockup_detector_init(void)
{
if (smpboot_register_percpu_thread(&watchdog_threads)) {
pr_err("Failed to create watchdog threads, disabled\n");
watchdog_disabled = -ENODEV;
}
}
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