/*
* 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 <linux/slab.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);
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
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 ... ");
#ifdef CONFIG_SMP
if (nmi_watchdog == NMI_LOCAL_APIC)
smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
#endif
for_each_possible_cpu(cpu)
prev_nmi_count[cpu] = nmi_count(cpu);
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(KERN_WARNING "WARNING: 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);
}
}
endflag = 1;
if (!atomic_read(&nmi_active)) {
kfree(prev_nmi_count);
atomic_set(&nmi_active, -1);
return -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;
}
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 = {
.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);
notrace __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 +
per_cpu(irq_stat, cpu).irq0_irqs;
/* 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;
}
#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
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;
}
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);
