Techwizz/kernel-fxtec-pro1x
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

nmi_watchdog: Add new, generic implementation, using perf events

Browse source 
This is a new generic nmi_watchdog implementation using the perf
events infrastructure as suggested by Ingo.

The implementation is simple, just create an in-kernel perf
event and register an overflow handler to check for cpu lockups.

I created a generic implementation that lives in kernel/ and
the hardware specific part that for now lives in arch/x86.

This approach has a number of advantages:

 - It simplifies the x86 PMU implementation in the long run,
   in that it removes the hardcoded low-level PMU implementation
   that was the NMI watchdog before.

 - It allows new NMI watchdog features to be added in a central
   place.

 - It allows other architectures to enable the NMI watchdog,
   as long as they have perf events (that provide NMIs)
   implemented.

 - It also allows for more graceful co-existence of existing
   perf events apps and the NMI watchdog - before these changes
   the relationship was exclusive. (The NMI watchdog will 'spend'
   a perf event when enabled. In later iterations we might be
   able to piggyback from an existing NMI event without having
   to allocate a hardware event for the NMI watchdog - turning
   this into a no-hardware-cost feature.)

As for compatibility, we'll keep the old NMI watchdog code as
well until the new one can 100% replace it on all CPUs, old and
new alike.  That might take some time as the NMI watchdog has
been ported to many CPU models.

I have done light testing to make sure the framework works
correctly and it does.

 v2: Set the correct timeout values based on the old nmi
     watchdog

Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: gorcunov@gmail.com
Cc: aris@redhat.com
Cc: peterz@infradead.org
LKML-Reference: <1265424425-31562-3-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Don Zickus 2010-02-05 21:47:04 -05:00 committed by Ingo Molnar
parent e40b17208b
commit 1fb9d6ad27
2 changed files with 305 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

114
arch/x86/kernel/apic/hw_nmi.c Normal file
View file

@ -0,0 +1,114 @@
/*
* 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; }

191
kernel/nmi_watchdog.c Normal file
View file

@ -0,0 +1,191 @@
/*
* 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);