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Separate print_modules() and hard lockup error message. Before the patch: NMI watchdog: Watchdog detected hard LOCKUP on cpu 1Modules linked in: nls_cp437 Link: http://lkml.kernel.org/r/20190412062557.2700-1-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
297 lines
7.7 KiB
C
297 lines
7.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Detect hard lockups on a system
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*
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* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
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*
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* Note: Most of this code is borrowed heavily from the original softlockup
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* detector, so thanks to Ingo for the initial implementation.
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* Some chunks also taken from the old x86-specific nmi watchdog code, thanks
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* to those contributors as well.
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*/
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#define pr_fmt(fmt) "NMI watchdog: " fmt
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#include <linux/nmi.h>
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#include <linux/atomic.h>
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#include <linux/module.h>
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#include <linux/sched/debug.h>
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#include <asm/irq_regs.h>
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#include <linux/perf_event.h>
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static DEFINE_PER_CPU(bool, hard_watchdog_warn);
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static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
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static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
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static DEFINE_PER_CPU(struct perf_event *, dead_event);
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static struct cpumask dead_events_mask;
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static unsigned long hardlockup_allcpu_dumped;
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static atomic_t watchdog_cpus = ATOMIC_INIT(0);
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notrace void arch_touch_nmi_watchdog(void)
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{
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/*
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* Using __raw here because some code paths have
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* preemption enabled. If preemption is enabled
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* then interrupts should be enabled too, in which
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* case we shouldn't have to worry about the watchdog
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* going off.
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*/
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raw_cpu_write(watchdog_nmi_touch, true);
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}
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EXPORT_SYMBOL(arch_touch_nmi_watchdog);
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#ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMP
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static DEFINE_PER_CPU(ktime_t, last_timestamp);
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static DEFINE_PER_CPU(unsigned int, nmi_rearmed);
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static ktime_t watchdog_hrtimer_sample_threshold __read_mostly;
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void watchdog_update_hrtimer_threshold(u64 period)
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{
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/*
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* The hrtimer runs with a period of (watchdog_threshold * 2) / 5
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*
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* So it runs effectively with 2.5 times the rate of the NMI
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* watchdog. That means the hrtimer should fire 2-3 times before
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* the NMI watchdog expires. The NMI watchdog on x86 is based on
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* unhalted CPU cycles, so if Turbo-Mode is enabled the CPU cycles
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* might run way faster than expected and the NMI fires in a
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* smaller period than the one deduced from the nominal CPU
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* frequency. Depending on the Turbo-Mode factor this might be fast
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* enough to get the NMI period smaller than the hrtimer watchdog
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* period and trigger false positives.
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*
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* The sample threshold is used to check in the NMI handler whether
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* the minimum time between two NMI samples has elapsed. That
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* prevents false positives.
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*
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* Set this to 4/5 of the actual watchdog threshold period so the
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* hrtimer is guaranteed to fire at least once within the real
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* watchdog threshold.
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*/
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watchdog_hrtimer_sample_threshold = period * 2;
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}
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static bool watchdog_check_timestamp(void)
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{
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ktime_t delta, now = ktime_get_mono_fast_ns();
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delta = now - __this_cpu_read(last_timestamp);
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if (delta < watchdog_hrtimer_sample_threshold) {
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/*
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* If ktime is jiffies based, a stalled timer would prevent
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* jiffies from being incremented and the filter would look
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* at a stale timestamp and never trigger.
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*/
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if (__this_cpu_inc_return(nmi_rearmed) < 10)
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return false;
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}
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__this_cpu_write(nmi_rearmed, 0);
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__this_cpu_write(last_timestamp, now);
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return true;
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}
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#else
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static inline bool watchdog_check_timestamp(void)
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{
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return true;
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}
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#endif
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static struct perf_event_attr wd_hw_attr = {
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.type = PERF_TYPE_HARDWARE,
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.config = PERF_COUNT_HW_CPU_CYCLES,
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.size = sizeof(struct perf_event_attr),
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.pinned = 1,
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.disabled = 1,
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};
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/* Callback function for perf event subsystem */
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static void watchdog_overflow_callback(struct perf_event *event,
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struct perf_sample_data *data,
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struct pt_regs *regs)
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{
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/* Ensure the watchdog never gets throttled */
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event->hw.interrupts = 0;
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if (__this_cpu_read(watchdog_nmi_touch) == true) {
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__this_cpu_write(watchdog_nmi_touch, false);
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return;
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}
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if (!watchdog_check_timestamp())
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return;
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/* check for a hardlockup
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* This is done by making sure our timer interrupt
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* is incrementing. The timer interrupt should have
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* fired multiple times before we overflow'd. If it hasn't
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* then this is a good indication the cpu is stuck
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*/
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if (is_hardlockup()) {
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int this_cpu = smp_processor_id();
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/* only print hardlockups once */
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if (__this_cpu_read(hard_watchdog_warn) == true)
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return;
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pr_emerg("Watchdog detected hard LOCKUP on cpu %d\n",
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this_cpu);
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print_modules();
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print_irqtrace_events(current);
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if (regs)
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show_regs(regs);
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else
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dump_stack();
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/*
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* Perform all-CPU dump only once to avoid multiple hardlockups
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* generating interleaving traces
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*/
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if (sysctl_hardlockup_all_cpu_backtrace &&
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!test_and_set_bit(0, &hardlockup_allcpu_dumped))
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trigger_allbutself_cpu_backtrace();
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if (hardlockup_panic)
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nmi_panic(regs, "Hard LOCKUP");
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__this_cpu_write(hard_watchdog_warn, true);
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return;
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}
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__this_cpu_write(hard_watchdog_warn, false);
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return;
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}
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static int hardlockup_detector_event_create(void)
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{
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unsigned int cpu = smp_processor_id();
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struct perf_event_attr *wd_attr;
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struct perf_event *evt;
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wd_attr = &wd_hw_attr;
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wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
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/* Try to register using hardware perf events */
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evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
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watchdog_overflow_callback, NULL);
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if (IS_ERR(evt)) {
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pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
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PTR_ERR(evt));
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return PTR_ERR(evt);
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}
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this_cpu_write(watchdog_ev, evt);
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return 0;
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}
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/**
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* hardlockup_detector_perf_enable - Enable the local event
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*/
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void hardlockup_detector_perf_enable(void)
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{
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if (hardlockup_detector_event_create())
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return;
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/* use original value for check */
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if (!atomic_fetch_inc(&watchdog_cpus))
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pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
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perf_event_enable(this_cpu_read(watchdog_ev));
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}
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/**
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* hardlockup_detector_perf_disable - Disable the local event
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*/
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void hardlockup_detector_perf_disable(void)
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{
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struct perf_event *event = this_cpu_read(watchdog_ev);
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if (event) {
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perf_event_disable(event);
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this_cpu_write(watchdog_ev, NULL);
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this_cpu_write(dead_event, event);
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cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
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atomic_dec(&watchdog_cpus);
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}
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}
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/**
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* hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them
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*
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* Called from lockup_detector_cleanup(). Serialized by the caller.
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*/
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void hardlockup_detector_perf_cleanup(void)
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{
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int cpu;
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for_each_cpu(cpu, &dead_events_mask) {
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struct perf_event *event = per_cpu(dead_event, cpu);
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/*
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* Required because for_each_cpu() reports unconditionally
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* CPU0 as set on UP kernels. Sigh.
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*/
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if (event)
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perf_event_release_kernel(event);
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per_cpu(dead_event, cpu) = NULL;
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}
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cpumask_clear(&dead_events_mask);
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}
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/**
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* hardlockup_detector_perf_stop - Globally stop watchdog events
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*
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* Special interface for x86 to handle the perf HT bug.
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*/
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void __init hardlockup_detector_perf_stop(void)
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{
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int cpu;
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lockdep_assert_cpus_held();
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for_each_online_cpu(cpu) {
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struct perf_event *event = per_cpu(watchdog_ev, cpu);
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if (event)
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perf_event_disable(event);
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}
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}
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/**
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* hardlockup_detector_perf_restart - Globally restart watchdog events
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*
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* Special interface for x86 to handle the perf HT bug.
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*/
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void __init hardlockup_detector_perf_restart(void)
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{
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int cpu;
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lockdep_assert_cpus_held();
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if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
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return;
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for_each_online_cpu(cpu) {
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struct perf_event *event = per_cpu(watchdog_ev, cpu);
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if (event)
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perf_event_enable(event);
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}
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}
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/**
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* hardlockup_detector_perf_init - Probe whether NMI event is available at all
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*/
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int __init hardlockup_detector_perf_init(void)
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{
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int ret = hardlockup_detector_event_create();
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if (ret) {
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pr_info("Perf NMI watchdog permanently disabled\n");
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} else {
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perf_event_release_kernel(this_cpu_read(watchdog_ev));
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this_cpu_write(watchdog_ev, NULL);
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}
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return ret;
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}
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