/*
* 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 <asm/apic.h>
#include <linux/nmi.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/slab.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/smp.h>
#include <asm/i8259.h>
#include <asm/io_apic.h>
#include <asm/proto.h>
#include <asm/timer.h>
#include <asm/mce.h>
#include <asm/mach_traps.h>
int unknown_nmi_panic;
int nmi_watchdog_enabled;
/* For reliability, we're prepared to waste bits here. */
static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
/* 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 */
EXPORT_SYMBOL(nmi_active);
unsigned int nmi_watchdog = NMI_NONE;
EXPORT_SYMBOL(nmi_watchdog);
static int panic_on_timeout;
static unsigned int nmi_hz = HZ;
static DEFINE_PER_CPU(short, wd_enabled);
static int endflag __initdata;
static inline unsigned int get_nmi_count(int cpu)
{
return per_cpu(irq_stat, cpu).__nmi_count;
}
static inline int mce_in_progress(void)
{
#if defined(CONFIG_X86_MCE)
return atomic_read(&mce_entry) > 0;
#endif
return 0;
}
/*
* 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;
}
#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 void report_broken_nmi(int cpu, unsigned int *prev_nmi_count)
{
printk(KERN_CONT "\n");
printk(KERN_WARNING
"WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
printk(KERN_WARNING
"Please report this to bugzilla.kernel.org,\n");
printk(KERN_WARNING
"and attach the output of the 'dmesg' command.\n");
per_cpu(wd_enabled, cpu) = 0;
atomic_dec(&nmi_active);
}
static void __acpi_nmi_disable(void *__unused)
{
apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
}
int __init check_nmi_watchdog(void)
{
unsigned int *prev_nmi_count;
int cpu;
if (!nmi_watchdog_active() || !atomic_read(&nmi_active))
return 0;
prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);
if (!prev_nmi_count)
goto error;
printk(KERN_INFO "Testing NMI watchdog ... ");
#ifdef CONFIG_SMP
if (nmi_watchdog == NMI_LOCAL_APIC)
smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
#endif
for_each_possible_cpu(cpu)
prev_nmi_count[cpu] = get_nmi_count(cpu);
local_irq_enable();
mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
for_each_online_cpu(cpu) {
if (!per_cpu(wd_enabled, cpu))
continue;
if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
report_broken_nmi(cpu, prev_nmi_count);
}
endflag = 1;
if (!atomic_read(&nmi_active)) {
kfree(prev_nmi_count);
atomic_set(&nmi_active, -1);
goto error;
}
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;
error:
if (nmi_watchdog == NMI_IO_APIC) {
if (!timer_through_8259)
legacy_pic->chip->mask(0);
on_each_cpu(__acpi_nmi_disable, NULL, 1);
}
#ifdef CONFIG_X86_32
timer_ack = 0;
#endif
return -1;
}
static int __init setup_nmi_watchdog(char *str)
{
unsigned int nmi;
if (!strncmp(str, "panic", 5)) {
panic_on_timeout = 1;
str = strchr(str, ',');
if (!str)
return 1;
++str;
}
if (!strncmp(str, "lapic", 5))
nmi_watchdog = NMI_LOCAL_APIC;
else if (!strncmp(str, "ioapic", 6))
nmi_watchdog = NMI_IO_APIC;
else {
get_option(&str, &nmi);
if (nmi >= NMI_INVALID)
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(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, 1);
}
/*
* 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, 1);
}
/*
* This function is called as soon the LAPIC NMI watchdog driver has everything
* in place and it's ready to check if the NMIs belong to the NMI watchdog
*/
void cpu_nmi_set_wd_enabled(void)
{
__get_cpu_var(wd_enabled) = 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:
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_active())
return;
if (__get_cpu_var(wd_enabled) == 0)
return;
if (nmi_watchdog == NMI_LOCAL_APIC)
lapic_watchdog_stop();
else
__acpi_nmi_disable(NULL);
__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 DEFINE_PER_CPU(unsigned, last_irq_sum);
static DEFINE_PER_CPU(long, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);
void touch_nmi_watchdog(void)
{
if (nmi_watchdog_active()) {
unsigned cpu;
/*
* Tell other CPUs to reset their alert counters. We cannot
* do it ourselves because the alert count increase is not
* atomic.
*/
for_each_present_cpu(cpu) {
if (per_cpu(nmi_touch, cpu) != 1)
per_cpu(nmi_touch, cpu) = 1;
}
}
/*
* Tickle the softlockup detector too:
*/
touch_softlockup_watchdog();
}
EXPORT_SYMBOL(touch_nmi_watchdog);
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;
sum = get_timer_irqs(cpu);
if (__get_cpu_var(nmi_touch)) {
__get_cpu_var(nmi_touch) = 0;
touched = 1;
}
/* We can be called before check_nmi_watchdog, hence NULL check. */
if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
static DEFINE_RAW_SPINLOCK(lock); /* Serialise the printks */
raw_spin_lock(&lock);
printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
show_regs(regs);
dump_stack();
raw_spin_unlock(&lock);
cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
rc = 1;
}
/* Could check oops_in_progress here too, but it's safer not to */
if (mce_in_progress())
touched = 1;
/* if the none of the timers isn't firing, this cpu isn't doing much */
if (!touched && __get_cpu_var(last_irq_sum) == sum) {
/*
* Ayiee, looks like this CPU is stuck ...
* wait a few IRQs (5 seconds) before doing the oops ...
*/
__this_cpu_inc(alert_counter);
if (__this_cpu_read(alert_counter) == 5 * nmi_hz)
/*
* die_nmi will return ONLY if NOTIFY_STOP happens..
*/
die_nmi("BUG: NMI Watchdog detected LOCKUP",
regs, panic_on_timeout);
} else {
__get_cpu_var(last_irq_sum) = sum;
__this_cpu_write(alert_counter, 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 void enable_ioapic_nmi_watchdog_single(void *unused)
{
__get_cpu_var(wd_enabled) = 1;
atomic_inc(&nmi_active);
__acpi_nmi_enable(NULL);
}
static void enable_ioapic_nmi_watchdog(void)
{
on_each_cpu(enable_ioapic_nmi_watchdog_single, NULL, 1);
touch_nmi_watchdog();
}
static void disable_ioapic_nmi_watchdog(void)
{
on_each_cpu(stop_apic_nmi_watchdog, NULL, 1);
}
static int __init setup_unknown_nmi_panic(char *str)
{
unknown_nmi_panic = 1;
return 1;
}
__setup("unknown_nmi_panic", setup_unknown_nmi_panic);
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(buf, regs, 1); /* Always panic here */
return 0;
}
/*
* proc handler for /proc/sys/kernel/nmi
*/
int proc_nmi_enabled(struct ctl_table *table, int write,
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, buffer, length, ppos);
if (!!old_state == !!nmi_watchdog_enabled)
return 0;
if (atomic_read(&nmi_active) < 0 || !nmi_watchdog_active()) {
printk(KERN_WARNING
"NMI watchdog is permanently disabled\n");
return -EIO;
}
if (nmi_watchdog == NMI_LOCAL_APIC) {
if (nmi_watchdog_enabled)
enable_lapic_nmi_watchdog();
else
disable_lapic_nmi_watchdog();
} else if (nmi_watchdog == NMI_IO_APIC) {
if (nmi_watchdog_enabled)
enable_ioapic_nmi_watchdog();
else
disable_ioapic_nmi_watchdog();
} else {
printk(KERN_WARNING
"NMI watchdog doesn't know what hardware to touch\n");
return -EIO;
}
return 0;
}
#endif /* CONFIG_SYSCTL */
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 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);
}
}
