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/*
* 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);
static int panic_on_timeout;
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();
}
static int __init setup_nmi_watchdog(char *str)
{
if (!strncmp(str, "panic", 5)) {
panic_on_timeout = 1;
str = strchr(str, ',');
if (!str)
return 1;
++str;
}
return 1;
}
__setup("nmi_watchdog=", setup_nmi_watchdog);
#ifdef CONFIG_SYSCTL
/*
* proc handler for /proc/sys/kernel/nmi_watchdog
*/
int nmi_watchdog_enabled;
int proc_nmi_enabled(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos)
{
int cpu;
if (!write) {
struct perf_event *event;
for_each_online_cpu(cpu) {
event = per_cpu(nmi_watchdog_ev, cpu);
if (event->state > PERF_EVENT_STATE_OFF) {
nmi_watchdog_enabled = 1;
break;
}
}
proc_dointvec(table, write, buffer, length, ppos);
return 0;
}
if (per_cpu(nmi_watchdog_ev, smp_processor_id()) == NULL) {
nmi_watchdog_enabled = 0;
proc_dointvec(table, write, buffer, length, ppos);
printk("NMI watchdog failed configuration, can not be enabled\n");
return 0;
}
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,
};
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) {
if (panic_on_timeout) {
panic("NMI Watchdog detected LOCKUP on cpu %d", cpu);
} else {
WARN(1, "NMI Watchdog detected LOCKUP on cpu %d", cpu);
}
}
} 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 = hw_nmi_get_sample_period();
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);
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