nmi_watchdog: Add new, generic implementation, using perf events

/*

 *  HW NMI watchdog support

 *

 *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.

 *

 *  Arch specific calls to support NMI watchdog

 *

 *  Bits copied from original nmi.c file

 *

 */

#include <asm/apic.h>

#include <linux/smp.h>

#include <linux/cpumask.h>

#include <linux/sched.h>

#include <linux/percpu.h>

#include <linux/cpumask.h>

#include <linux/kernel_stat.h>

#include <asm/mce.h>

#include <linux/nmi.h>

#include <linux/module.h>

/* For reliability, we're prepared to waste bits here. */

static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;

static DEFINE_PER_CPU(unsigned, last_irq_sum);

/*

 * Take the local apic timer and PIT/HPET into account. We don't

 * know which one is active, when we have highres/dyntick on

 */

static inline unsigned int get_timer_irqs(int cpu)

{

        return per_cpu(irq_stat, cpu).apic_timer_irqs +

                per_cpu(irq_stat, cpu).irq0_irqs;

}

static inline int mce_in_progress(void)

{

#if defined(CONFIG_X86_MCE)

        return atomic_read(&mce_entry) > 0;

#endif

        return 0;

}

int hw_nmi_is_cpu_stuck(struct pt_regs *regs)

{

	unsigned int sum;

	int cpu = smp_processor_id();

	/* FIXME: cheap hack for this check, probably should get its own

	 * die_notifier handler

	 */

	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {

		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */

		spin_lock(&lock);

		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);

		show_regs(regs);

		dump_stack();

		spin_unlock(&lock);

		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));

	}

	/* if we are doing an mce, just assume the cpu is not stuck */

        /* Could check oops_in_progress here too, but it's safer not to */

        if (mce_in_progress())

                return 0;

	/* We determine if the cpu is stuck by checking whether any

	 * interrupts have happened since we last checked.  Of course

	 * an nmi storm could create false positives, but the higher

	 * level logic should account for that

	 */

	sum = get_timer_irqs(cpu);

	if (__get_cpu_var(last_irq_sum) == sum) {

		return 1;

	} else {

		__get_cpu_var(last_irq_sum) = sum;

		return 0;

	}

}

void arch_trigger_all_cpu_backtrace(void)

{

	int i;

	cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);

	printk(KERN_INFO "sending NMI to all CPUs:\n");

	apic->send_IPI_all(NMI_VECTOR);

	/* Wait for up to 10 seconds for all CPUs to do the backtrace */

	for (i = 0; i < 10 * 1000; i++) {

		if (cpumask_empty(to_cpumask(backtrace_mask)))

			break;

		mdelay(1);

	}

}

/* STUB calls to mimic old nmi_watchdog behaviour */

unsigned int nmi_watchdog = NMI_NONE;

EXPORT_SYMBOL(nmi_watchdog);

atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */

EXPORT_SYMBOL(nmi_active);

int nmi_watchdog_enabled;

int unknown_nmi_panic;

void cpu_nmi_set_wd_enabled(void) { return; }

void acpi_nmi_enable(void) { return; }

void acpi_nmi_disable(void) { return; }

void stop_apic_nmi_watchdog(void *unused) { return; }

void setup_apic_nmi_watchdog(void *unused) { return; }

int __init check_nmi_watchdog(void) { return 0; }

/*

 * Detect Hard Lockups using the NMI

 *

 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.

 *

 * this code detects hard lockups: incidents in where on a CPU

 * the kernel does not respond to anything except NMI.

 *

 * Note: Most of this code is borrowed heavily from softlockup.c,

 * so thanks to Ingo for the initial implementation.

 * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks

 * to those contributors as well.

 */

#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/lockdep.h>

#include <linux/notifier.h>

#include <linux/module.h>

#include <linux/sysctl.h>

#include <asm/irq_regs.h>

#include <linux/perf_event.h>

static DEFINE_PER_CPU(struct perf_event *, nmi_watchdog_ev);

static DEFINE_PER_CPU(int, nmi_watchdog_touch);

static DEFINE_PER_CPU(long, alert_counter);

void touch_nmi_watchdog(void)

{

	__raw_get_cpu_var(nmi_watchdog_touch) = 1;

	touch_softlockup_watchdog();

}

EXPORT_SYMBOL(touch_nmi_watchdog);

void touch_all_nmi_watchdog(void)

{

	int cpu;

	for_each_online_cpu(cpu)

		per_cpu(nmi_watchdog_touch, cpu) = 1;

	touch_softlockup_watchdog();

}

#ifdef CONFIG_SYSCTL

/*

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

 */

int proc_nmi_enabled(struct ctl_table *table, int write,

		     void __user *buffer, size_t *length, loff_t *ppos)

{

	int cpu;

	if (per_cpu(nmi_watchdog_ev, smp_processor_id()) == NULL)

		nmi_watchdog_enabled = 0;

	else

		nmi_watchdog_enabled = 1;

	touch_all_nmi_watchdog();

	proc_dointvec(table, write, buffer, length, ppos);

	if (nmi_watchdog_enabled)

		for_each_online_cpu(cpu)

			perf_event_enable(per_cpu(nmi_watchdog_ev, cpu));

	else

		for_each_online_cpu(cpu)

			perf_event_disable(per_cpu(nmi_watchdog_ev, cpu));

	return 0;

}

#endif /* CONFIG_SYSCTL */

struct perf_event_attr wd_attr = {

	.type = PERF_TYPE_HARDWARE,

	.config = PERF_COUNT_HW_CPU_CYCLES,

	.size = sizeof(struct perf_event_attr),

	.pinned = 1,

	.disabled = 1,

};

static int panic_on_timeout;

void wd_overflow(struct perf_event *event, int nmi,

		 struct perf_sample_data *data,

		 struct pt_regs *regs)

{

	int cpu = smp_processor_id();

	int touched = 0;

	if (__get_cpu_var(nmi_watchdog_touch)) {

		per_cpu(nmi_watchdog_touch, cpu) = 0;

		touched = 1;

	}

	/* check to see if the cpu is doing anything */

	if (!touched && hw_nmi_is_cpu_stuck(regs)) {

		/*

		 * Ayiee, looks like this CPU is stuck ...

		 * wait a few IRQs (5 seconds) before doing the oops ...

		 */

		per_cpu(alert_counter,cpu) += 1;

		if (per_cpu(alert_counter,cpu) == 5) {

			/*

			 * die_nmi will return ONLY if NOTIFY_STOP happens..

			 */

			die_nmi("BUG: NMI Watchdog detected LOCKUP",

				regs, panic_on_timeout);

		}

	} else {

		per_cpu(alert_counter,cpu) = 0;

	}

	return;

}

/*

 * Create/destroy watchdog threads as CPUs come and go:

 */

static int __cpuinit

cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)

{

	int hotcpu = (unsigned long)hcpu;

	struct perf_event *event;

	switch (action) {

	case CPU_UP_PREPARE:

	case CPU_UP_PREPARE_FROZEN:

		per_cpu(nmi_watchdog_touch, hotcpu) = 0;

		break;

	case CPU_ONLINE:

	case CPU_ONLINE_FROZEN:

		/* originally wanted the below chunk to be in CPU_UP_PREPARE, but caps is unpriv for non-CPU0 */

		wd_attr.sample_period = cpu_khz * 1000;

		event = perf_event_create_kernel_counter(&wd_attr, hotcpu, -1, wd_overflow);

		if (IS_ERR(event)) {

			printk(KERN_ERR "nmi watchdog failed to create perf event on %i: %p\n", hotcpu, event);

			return NOTIFY_BAD;

		}

		per_cpu(nmi_watchdog_ev, hotcpu) = event;

		perf_event_enable(per_cpu(nmi_watchdog_ev, hotcpu));

		break;

#ifdef CONFIG_HOTPLUG_CPU

	case CPU_UP_CANCELED:

	case CPU_UP_CANCELED_FROZEN:

		perf_event_disable(per_cpu(nmi_watchdog_ev, hotcpu));

	case CPU_DEAD:

	case CPU_DEAD_FROZEN:

		event = per_cpu(nmi_watchdog_ev, hotcpu);

		per_cpu(nmi_watchdog_ev, hotcpu) = NULL;

		perf_event_release_kernel(event);

		break;

#endif /* CONFIG_HOTPLUG_CPU */

	}

	return NOTIFY_OK;

}

static struct notifier_block __cpuinitdata cpu_nfb = {

	.notifier_call = cpu_callback

};

static int __initdata nonmi_watchdog;

static int __init nonmi_watchdog_setup(char *str)

{

	nonmi_watchdog = 1;

	return 1;

}

__setup("nonmi_watchdog", nonmi_watchdog_setup);

static int __init spawn_nmi_watchdog_task(void)

{

	void *cpu = (void *)(long)smp_processor_id();

	int err;

	if (nonmi_watchdog)

		return 0;

	err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);

	if (err == NOTIFY_BAD) {

		BUG();

		return 1;

	}

	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);

	register_cpu_notifier(&cpu_nfb);

	return 0;

}

early_initcall(spawn_nmi_watchdog_task);