nmi.c

/*
 *  linux/arch/i386/nmi.c
 *
 *  NMI watchdog support on APIC systems
 *
 *  Started by Ingo Molnar <mingo@redhat.com>
 *
 *  Fixes:
 *  Mikael Pettersson	: AMD K7 support for local APIC NMI watchdog.
 *  Mikael Pettersson	: Power Management for local APIC NMI watchdog.
 *  Mikael Pettersson	: Pentium 4 support for local APIC NMI watchdog.
 *  Pavel Machek and
 *  Mikael Pettersson	: PM converted to driver model. Disable/enable API.
 */

#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/sysdev.h>
#include <linux/sysctl.h>
#include <linux/percpu.h>
#include <linux/kprobes.h>
#include <linux/cpumask.h>
#include <linux/kernel_stat.h>
#include <linux/kdebug.h>

#include <asm/smp.h>
#include <asm/nmi.h>

#include "mach_traps.h"

int unknown_nmi_panic;
int nmi_watchdog_enabled;

static cpumask_t backtrace_mask = CPU_MASK_NONE;

/* nmi_active:
 * >0: the lapic NMI watchdog is active, but can be disabled
 * <0: the lapic NMI watchdog has not been set up, and cannot
 *     be enabled
 *  0: the lapic NMI watchdog is disabled, but can be enabled
 */
atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */

unsigned int nmi_watchdog = NMI_DEFAULT;
static unsigned int nmi_hz = HZ;

static DEFINE_PER_CPU(short, wd_enabled);

/* local prototypes */
static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu);

static int endflag __initdata = 0;

#ifdef CONFIG_SMP
/* The performance counters used by NMI_LOCAL_APIC don't trigger when
 * the CPU is idle. To make sure the NMI watchdog really ticks on all
 * CPUs during the test make them busy.
 */
static __init void nmi_cpu_busy(void *data)
{
	local_irq_enable_in_hardirq();
	/* Intentionally don't use cpu_relax here. This is
	   to make sure that the performance counter really ticks,
	   even if there is a simulator or similar that catches the
	   pause instruction. On a real HT machine this is fine because
	   all other CPUs are busy with "useless" delay loops and don't
	   care if they get somewhat less cycles. */
	while (endflag == 0)
		mb();
}
#endif

static int __init check_nmi_watchdog(void)
{
	unsigned int *prev_nmi_count;
	int cpu;

	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DISABLED))
		return 0;

	if (!atomic_read(&nmi_active))
		return 0;

	prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
	if (!prev_nmi_count)
		return -1;

	printk(KERN_INFO "Testing NMI watchdog ... ");

	if (nmi_watchdog == NMI_LOCAL_APIC)
		smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);

	for_each_possible_cpu(cpu)
		prev_nmi_count[cpu] = per_cpu(irq_stat, cpu).__nmi_count;
	local_irq_enable();
	mdelay((20*1000)/nmi_hz); // wait 20 ticks

	for_each_possible_cpu(cpu) {
#ifdef CONFIG_SMP
		/* Check cpu_callin_map here because that is set
		   after the timer is started. */
		if (!cpu_isset(cpu, cpu_callin_map))
			continue;
#endif
		if (!per_cpu(wd_enabled, cpu))
			continue;
		if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
			printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
				cpu,
				prev_nmi_count[cpu],
				nmi_count(cpu));
			per_cpu(wd_enabled, cpu) = 0;
			atomic_dec(&nmi_active);
		}
	}
	if (!atomic_read(&nmi_active)) {
		kfree(prev_nmi_count);
		atomic_set(&nmi_active, -1);
		return -1;
	}
	endflag = 1;
	printk("OK.\n");

	/* now that we know it works we can reduce NMI frequency to
	   something more reasonable; makes a difference in some configs */
	if (nmi_watchdog == NMI_LOCAL_APIC)
		nmi_hz = lapic_adjust_nmi_hz(1);

	kfree(prev_nmi_count);
	return 0;
}
/* This needs to happen later in boot so counters are working */
late_initcall(check_nmi_watchdog);

static int __init setup_nmi_watchdog(char *str)
{
	int nmi;

	get_option(&str, &nmi);

	if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
		return 0;

	nmi_watchdog = nmi;
	return 1;
}

__setup("nmi_watchdog=", setup_nmi_watchdog);


/* Suspend/resume support */

#ifdef CONFIG_PM

static int nmi_pm_active; /* nmi_active before suspend */

static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
{
	/* only CPU0 goes here, other CPUs should be offline */
	nmi_pm_active = atomic_read(&nmi_active);
	stop_apic_nmi_watchdog(NULL);
	BUG_ON(atomic_read(&nmi_active) != 0);
	return 0;
}

static int lapic_nmi_resume(struct sys_device *dev)
{
	/* only CPU0 goes here, other CPUs should be offline */
	if (nmi_pm_active > 0) {
		setup_apic_nmi_watchdog(NULL);
		touch_nmi_watchdog();
	}
	return 0;
}


static struct sysdev_class nmi_sysclass = {
	set_kset_name("lapic_nmi"),
	.resume		= lapic_nmi_resume,
	.suspend	= lapic_nmi_suspend,
};

static struct sys_device device_lapic_nmi = {
	.id	= 0,
	.cls	= &nmi_sysclass,
};

static int __init init_lapic_nmi_sysfs(void)
{
	int error;

	/* should really be a BUG_ON but b/c this is an
	 * init call, it just doesn't work.  -dcz
	 */
	if (nmi_watchdog != NMI_LOCAL_APIC)
		return 0;

	if (atomic_read(&nmi_active) < 0)
		return 0;

	error = sysdev_class_register(&nmi_sysclass);
	if (!error)
		error = sysdev_register(&device_lapic_nmi);
	return error;
}
/* must come after the local APIC's device_initcall() */
late_initcall(init_lapic_nmi_sysfs);

#endif	/* CONFIG_PM */

static void __acpi_nmi_enable(void *__unused)
{
	apic_write_around(APIC_LVT0, APIC_DM_NMI);
}

/*
 * Enable timer based NMIs on all CPUs:
 */
void acpi_nmi_enable(void)
{
	if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
		on_each_cpu(__acpi_nmi_enable, NULL, 0, 1);
}

static void __acpi_nmi_disable(void *__unused)
{
	apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
}

/*
 * Disable timer based NMIs on all CPUs:
 */
void acpi_nmi_disable(void)
{
	if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
		on_each_cpu(__acpi_nmi_disable, NULL, 0, 1);
}

void setup_apic_nmi_watchdog (void *unused)
{
	if (__get_cpu_var(wd_enabled))
 		return;

	/* cheap hack to support suspend/resume */
	/* if cpu0 is not active neither should the other cpus */
	if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
		return;

	switch (nmi_watchdog) {
	case NMI_LOCAL_APIC:
		__get_cpu_var(wd_enabled) = 1; /* enable it before to avoid race with handler */
		if (lapic_watchdog_init(nmi_hz) < 0) {
			__get_cpu_var(wd_enabled) = 0;
			return;
		}
		/* FALL THROUGH */
	case NMI_IO_APIC:
		__get_cpu_var(wd_enabled) = 1;
		atomic_inc(&nmi_active);
	}
}

void stop_apic_nmi_watchdog(void *unused)
{
	/* only support LOCAL and IO APICs for now */
	if ((nmi_watchdog != NMI_LOCAL_APIC) &&
	    (nmi_watchdog != NMI_IO_APIC))
	    	return;
	if (__get_cpu_var(wd_enabled) == 0)
		return;
	if (nmi_watchdog == NMI_LOCAL_APIC)
		lapic_watchdog_stop();
	__get_cpu_var(wd_enabled) = 0;
	atomic_dec(&nmi_active);
}

/*
 * the best way to detect whether a CPU has a 'hard lockup' problem
 * is to check it's local APIC timer IRQ counts. If they are not
 * changing then that CPU has some problem.
 *
 * as these watchdog NMI IRQs are generated on every CPU, we only
 * have to check the current processor.
 *
 * since NMIs don't listen to _any_ locks, we have to be extremely
 * careful not to rely on unsafe variables. The printk might lock
 * up though, so we have to break up any console locks first ...
 * [when there will be more tty-related locks, break them up
 *  here too!]
 */

static unsigned int
	last_irq_sums [NR_CPUS],
	alert_counter [NR_CPUS];

void touch_nmi_watchdog(void)
{
	if (nmi_watchdog > 0) {
		unsigned cpu;

		/*
		 * Just reset the alert counters, (other CPUs might be
		 * spinning on locks we hold):
		 */
		for_each_present_cpu(cpu) {
			if (alert_counter[cpu])
				alert_counter[cpu] = 0;
		}
	}

	/*
	 * Tickle the softlockup detector too:
	 */
	touch_softlockup_watchdog();
}
EXPORT_SYMBOL(touch_nmi_watchdog);

extern void die_nmi(struct pt_regs *, const char *msg);

__kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
{

	/*
	 * Since current_thread_info()-> is always on the stack, and we
	 * always switch the stack NMI-atomically, it's safe to use
	 * smp_processor_id().
	 */
	unsigned int sum;
	int touched = 0;
	int cpu = smp_processor_id();
	int rc=0;

	/* check for other users first */
	if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
			== NOTIFY_STOP) {
		rc = 1;
		touched = 1;
	}

	if (cpu_isset(cpu, backtrace_mask)) {
		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */

		spin_lock(&lock);
		printk("NMI backtrace for cpu %d\n", cpu);
		dump_stack();
		spin_unlock(&lock);
		cpu_clear(cpu, backtrace_mask);
	}

	/*
	 * Take the local apic timer and PIT/HPET into account. We don't
	 * know which one is active, when we have highres/dyntick on
	 */
	sum = per_cpu(irq_stat, cpu).apic_timer_irqs + kstat_cpu(cpu).irqs[0];

	/* if the none of the timers isn't firing, this cpu isn't doing much */
	if (!touched && last_irq_sums[cpu] == sum) {
		/*
		 * Ayiee, looks like this CPU is stuck ...
		 * wait a few IRQs (5 seconds) before doing the oops ...
		 */
		alert_counter[cpu]++;
		if (alert_counter[cpu] == 5*nmi_hz)
			/*
			 * die_nmi will return ONLY if NOTIFY_STOP happens..
			 */
			die_nmi(regs, "BUG: NMI Watchdog detected LOCKUP");
	} else {
		last_irq_sums[cpu] = sum;
		alert_counter[cpu] = 0;
	}
	/* see if the nmi watchdog went off */
	if (!__get_cpu_var(wd_enabled))
		return rc;
	switch (nmi_watchdog) {
	case NMI_LOCAL_APIC:
		rc |= lapic_wd_event(nmi_hz);
		break;
	case NMI_IO_APIC:
		/* don't know how to accurately check for this.
		 * just assume it was a watchdog timer interrupt
		 * This matches the old behaviour.
		 */
		rc = 1;
		break;
	}
	return rc;
}

int do_nmi_callback(struct pt_regs * regs, int cpu)
{
#ifdef CONFIG_SYSCTL
	if (unknown_nmi_panic)
		return unknown_nmi_panic_callback(regs, cpu);
#endif
	return 0;
}

#ifdef CONFIG_SYSCTL

static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
{
	unsigned char reason = get_nmi_reason();
	char buf[64];

	sprintf(buf, "NMI received for unknown reason %02x\n", reason);
	die_nmi(regs, buf);
	return 0;
}

/*
 * proc handler for /proc/sys/kernel/nmi
 */
int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
			void __user *buffer, size_t *length, loff_t *ppos)
{
	int old_state;

	nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
	old_state = nmi_watchdog_enabled;
	proc_dointvec(table, write, file, buffer, length, ppos);
	if (!!old_state == !!nmi_watchdog_enabled)
		return 0;

	if (atomic_read(&nmi_active) < 0 || nmi_watchdog == NMI_DISABLED) {
		printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
		return -EIO;
	}

	if (nmi_watchdog == NMI_DEFAULT) {
		if (lapic_watchdog_ok())
			nmi_watchdog = NMI_LOCAL_APIC;
		else
			nmi_watchdog = NMI_IO_APIC;
	}

	if (nmi_watchdog == NMI_LOCAL_APIC) {
		if (nmi_watchdog_enabled)
			enable_lapic_nmi_watchdog();
		else
			disable_lapic_nmi_watchdog();
	} else {
		printk( KERN_WARNING
			"NMI watchdog doesn't know what hardware to touch\n");
		return -EIO;
	}
	return 0;
}

#endif

void __trigger_all_cpu_backtrace(void)
{
	int i;

	backtrace_mask = cpu_online_map;
	/* Wait for up to 10 seconds for all CPUs to do the backtrace */
	for (i = 0; i < 10 * 1000; i++) {
		if (cpus_empty(backtrace_mask))
			break;
		mdelay(1);
	}
}

EXPORT_SYMBOL(nmi_active);
EXPORT_SYMBOL(nmi_watchdog);