linux_dsm_epyc7002/kernel/watchdog_hld.c
Peter Zijlstra d0b6e0a8ef watchdog/hardlockup: Provide interface to stop/restart perf events
Provide an interface to stop and restart perf NMI watchdog events on all
CPUs. This is only usable during init and especially for handling the perf
HT bug on Intel machines. It's safe to use it this way as nothing can
start/stop the NMI watchdog in parallel.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194146.167649596@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-14 11:41:03 +02:00

305 lines
8.1 KiB
C

/*
* Detect hard lockups on a system
*
* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
*
* Note: Most of this code is borrowed heavily from the original softlockup
* detector, so thanks to Ingo for the initial implementation.
* Some chunks also taken from the old x86-specific nmi watchdog code, thanks
* to those contributors as well.
*/
#define pr_fmt(fmt) "NMI watchdog: " fmt
#include <linux/nmi.h>
#include <linux/module.h>
#include <linux/sched/debug.h>
#include <asm/irq_regs.h>
#include <linux/perf_event.h>
static DEFINE_PER_CPU(bool, hard_watchdog_warn);
static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
static unsigned long hardlockup_allcpu_dumped;
void arch_touch_nmi_watchdog(void)
{
/*
* Using __raw here because some code paths have
* preemption enabled. If preemption is enabled
* then interrupts should be enabled too, in which
* case we shouldn't have to worry about the watchdog
* going off.
*/
raw_cpu_write(watchdog_nmi_touch, true);
}
EXPORT_SYMBOL(arch_touch_nmi_watchdog);
#ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMP
static DEFINE_PER_CPU(ktime_t, last_timestamp);
static DEFINE_PER_CPU(unsigned int, nmi_rearmed);
static ktime_t watchdog_hrtimer_sample_threshold __read_mostly;
void watchdog_update_hrtimer_threshold(u64 period)
{
/*
* The hrtimer runs with a period of (watchdog_threshold * 2) / 5
*
* So it runs effectively with 2.5 times the rate of the NMI
* watchdog. That means the hrtimer should fire 2-3 times before
* the NMI watchdog expires. The NMI watchdog on x86 is based on
* unhalted CPU cycles, so if Turbo-Mode is enabled the CPU cycles
* might run way faster than expected and the NMI fires in a
* smaller period than the one deduced from the nominal CPU
* frequency. Depending on the Turbo-Mode factor this might be fast
* enough to get the NMI period smaller than the hrtimer watchdog
* period and trigger false positives.
*
* The sample threshold is used to check in the NMI handler whether
* the minimum time between two NMI samples has elapsed. That
* prevents false positives.
*
* Set this to 4/5 of the actual watchdog threshold period so the
* hrtimer is guaranteed to fire at least once within the real
* watchdog threshold.
*/
watchdog_hrtimer_sample_threshold = period * 2;
}
static bool watchdog_check_timestamp(void)
{
ktime_t delta, now = ktime_get_mono_fast_ns();
delta = now - __this_cpu_read(last_timestamp);
if (delta < watchdog_hrtimer_sample_threshold) {
/*
* If ktime is jiffies based, a stalled timer would prevent
* jiffies from being incremented and the filter would look
* at a stale timestamp and never trigger.
*/
if (__this_cpu_inc_return(nmi_rearmed) < 10)
return false;
}
__this_cpu_write(nmi_rearmed, 0);
__this_cpu_write(last_timestamp, now);
return true;
}
#else
static inline bool watchdog_check_timestamp(void)
{
return true;
}
#endif
static struct perf_event_attr wd_hw_attr = {
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
.size = sizeof(struct perf_event_attr),
.pinned = 1,
.disabled = 1,
};
/* Callback function for perf event subsystem */
static void watchdog_overflow_callback(struct perf_event *event,
struct perf_sample_data *data,
struct pt_regs *regs)
{
/* Ensure the watchdog never gets throttled */
event->hw.interrupts = 0;
if (atomic_read(&watchdog_park_in_progress) != 0)
return;
if (__this_cpu_read(watchdog_nmi_touch) == true) {
__this_cpu_write(watchdog_nmi_touch, false);
return;
}
if (!watchdog_check_timestamp())
return;
/* check for a hardlockup
* This is done by making sure our timer interrupt
* is incrementing. The timer interrupt should have
* fired multiple times before we overflow'd. If it hasn't
* then this is a good indication the cpu is stuck
*/
if (is_hardlockup()) {
int this_cpu = smp_processor_id();
/* only print hardlockups once */
if (__this_cpu_read(hard_watchdog_warn) == true)
return;
pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
print_modules();
print_irqtrace_events(current);
if (regs)
show_regs(regs);
else
dump_stack();
/*
* Perform all-CPU dump only once to avoid multiple hardlockups
* generating interleaving traces
*/
if (sysctl_hardlockup_all_cpu_backtrace &&
!test_and_set_bit(0, &hardlockup_allcpu_dumped))
trigger_allbutself_cpu_backtrace();
if (hardlockup_panic)
nmi_panic(regs, "Hard LOCKUP");
__this_cpu_write(hard_watchdog_warn, true);
return;
}
__this_cpu_write(hard_watchdog_warn, false);
return;
}
/*
* People like the simple clean cpu node info on boot.
* Reduce the watchdog noise by only printing messages
* that are different from what cpu0 displayed.
*/
static unsigned long firstcpu_err;
static atomic_t watchdog_cpus;
int watchdog_nmi_enable(unsigned int cpu)
{
struct perf_event_attr *wd_attr;
struct perf_event *event = per_cpu(watchdog_ev, cpu);
int firstcpu = 0;
/* nothing to do if the hard lockup detector is disabled */
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
goto out;
/* is it already setup and enabled? */
if (event && event->state > PERF_EVENT_STATE_OFF)
goto out;
/* it is setup but not enabled */
if (event != NULL)
goto out_enable;
if (atomic_inc_return(&watchdog_cpus) == 1)
firstcpu = 1;
wd_attr = &wd_hw_attr;
wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
/* Try to register using hardware perf events */
event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
/* save the first cpu's error for future comparision */
if (firstcpu && IS_ERR(event))
firstcpu_err = PTR_ERR(event);
if (!IS_ERR(event)) {
/* only print for the first cpu initialized */
if (firstcpu || firstcpu_err)
pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
goto out_save;
}
/*
* Disable the hard lockup detector if _any_ CPU fails to set up
* set up the hardware perf event. The watchdog() function checks
* the NMI_WATCHDOG_ENABLED bit periodically.
*
* The barriers are for syncing up watchdog_enabled across all the
* cpus, as clear_bit() does not use barriers.
*/
smp_mb__before_atomic();
clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
smp_mb__after_atomic();
/* skip displaying the same error again */
if (!firstcpu && (PTR_ERR(event) == firstcpu_err))
return PTR_ERR(event);
/* vary the KERN level based on the returned errno */
if (PTR_ERR(event) == -EOPNOTSUPP)
pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
else if (PTR_ERR(event) == -ENOENT)
pr_warn("disabled (cpu%i): hardware events not enabled\n",
cpu);
else
pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
cpu, PTR_ERR(event));
pr_info("Shutting down hard lockup detector on all cpus\n");
return PTR_ERR(event);
/* success path */
out_save:
per_cpu(watchdog_ev, cpu) = event;
out_enable:
perf_event_enable(per_cpu(watchdog_ev, cpu));
out:
return 0;
}
void watchdog_nmi_disable(unsigned int cpu)
{
struct perf_event *event = per_cpu(watchdog_ev, cpu);
if (event) {
perf_event_disable(event);
per_cpu(watchdog_ev, cpu) = NULL;
/* should be in cleanup, but blocks oprofile */
perf_event_release_kernel(event);
/* watchdog_nmi_enable() expects this to be zero initially. */
if (atomic_dec_and_test(&watchdog_cpus))
firstcpu_err = 0;
}
}
/**
* hardlockup_detector_perf_stop - Globally stop watchdog events
*
* Special interface for x86 to handle the perf HT bug.
*/
void __init hardlockup_detector_perf_stop(void)
{
int cpu;
lockdep_assert_cpus_held();
for_each_online_cpu(cpu) {
struct perf_event *event = per_cpu(watchdog_ev, cpu);
if (event)
perf_event_disable(event);
}
}
/**
* hardlockup_detector_perf_restart - Globally restart watchdog events
*
* Special interface for x86 to handle the perf HT bug.
*/
void __init hardlockup_detector_perf_restart(void)
{
int cpu;
lockdep_assert_cpus_held();
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
return;
for_each_online_cpu(cpu) {
struct perf_event *event = per_cpu(watchdog_ev, cpu);
if (event)
perf_event_enable(event);
}
}