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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315// SPDX-License-Identifier: GPL-2.0/* * Detect hard lockups on a system using perf * * 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/panic.h>#include <linux/nmi.h>#include <linux/atomic.h>#include <linux/module.h>#include <linux/sched/debug.h>
#include <asm/irq_regs.h>#include <linux/perf_event.h>
static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
static atomic_t watchdog_cpus = ATOMIC_INIT(0);
#ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMPstatic 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;}
static void watchdog_init_timestamp(void){ __this_cpu_write(nmi_rearmed, 0); __this_cpu_write(last_timestamp, ktime_get_mono_fast_ns());}#elsestatic inline bool watchdog_check_timestamp(void) { return true; }static inline void watchdog_init_timestamp(void) { }#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,};
static struct perf_event_attr fallback_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 (panic_in_progress()) return;
if (!watchdog_check_timestamp()) return;
watchdog_hardlockup_check(smp_processor_id(), regs);}
static struct perf_event *hardlockup_detector_event_create(unsigned int cpu){ struct perf_event_attr *wd_attr; struct perf_event *evt;
wd_attr = &wd_hw_attr; wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
/* Try to register using hardware perf events */ evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); if (IS_ERR(evt)) { wd_attr = &fallback_wd_hw_attr; wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); }
return evt;}
/** * watchdog_hardlockup_enable - Enable the local event * @cpu: The CPU to enable hard lockup on. */void watchdog_hardlockup_enable(unsigned int cpu){ struct perf_event *evt;
WARN_ON_ONCE(cpu != smp_processor_id());
evt = hardlockup_detector_event_create(cpu); if (IS_ERR(evt)) { pr_debug("Perf event create on CPU %d failed with %ld\n", cpu, PTR_ERR(evt)); return; }
/* use original value for check */ if (!atomic_fetch_inc(&watchdog_cpus)) pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
WARN_ONCE(this_cpu_read(watchdog_ev), "unexpected watchdog_ev leak"); this_cpu_write(watchdog_ev, evt);
watchdog_init_timestamp(); perf_event_enable(evt);}
/** * watchdog_hardlockup_disable - Disable the local event * @cpu: The CPU to enable hard lockup on. */void watchdog_hardlockup_disable(unsigned int cpu){ struct perf_event *event = this_cpu_read(watchdog_ev);
WARN_ON_ONCE(cpu != smp_processor_id());
if (event) { perf_event_disable(event); perf_event_release_kernel(event); this_cpu_write(watchdog_ev, NULL); atomic_dec(&watchdog_cpus); }}
/** * hardlockup_detector_perf_adjust_period - Adjust the event period due * to current cpu frequency change * @period: The target period to be set */void hardlockup_detector_perf_adjust_period(u64 period){ struct perf_event *event = this_cpu_read(watchdog_ev);
if (!(watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED)) return;
if (!event) return;
if (event->attr.sample_period == period) return;
if (perf_event_period(event, period)) pr_err("failed to change period to %llu\n", period);}
/** * 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 & WATCHDOG_HARDLOCKUP_ENABLED)) return;
for_each_online_cpu(cpu) { struct perf_event *event = per_cpu(watchdog_ev, cpu);
if (event) perf_event_enable(event); }}
bool __weak __init arch_perf_nmi_is_available(void){ return true;}
/** * watchdog_hardlockup_probe - Probe whether NMI event is available at all */int __init watchdog_hardlockup_probe(void){ struct perf_event *evt; unsigned int cpu; int ret;
if (!arch_perf_nmi_is_available()) return -ENODEV;
if (!hw_nmi_get_sample_period(watchdog_thresh)) return -EINVAL;
/* * Test hardware PMU availability by creating a temporary perf event. * The event is released immediately. */ cpu = raw_smp_processor_id(); evt = hardlockup_detector_event_create(cpu); if (IS_ERR(evt)) { pr_info("Perf NMI watchdog permanently disabled\n"); ret = PTR_ERR(evt); } else { perf_event_release_kernel(evt); ret = 0; }
return ret;}
/** * hardlockup_config_perf_event - Overwrite config of wd_hw_attr. * @str: number which identifies the raw perf event to use */void __init hardlockup_config_perf_event(const char *str){ u64 config; char buf[24]; char *comma = strchr(str, ',');
if (!comma) { if (kstrtoull(str, 16, &config)) return; } else { unsigned int len = comma - str;
if (len > sizeof(buf)) return;
strscpy(buf, str, len); if (kstrtoull(buf, 16, &config)) return; }
wd_hw_attr.type = PERF_TYPE_RAW; wd_hw_attr.config = config;}