From 1fb9d6ad2766a1dd70d167552988375049a97f21 Mon Sep 17 00:00:00 2001 From: Don Zickus Date: Fri, 5 Feb 2010 21:47:04 -0500 Subject: [PATCH] nmi_watchdog: Add new, generic implementation, using perf events 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 Cc: Linus Torvalds Cc: Andrew Morton 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 --- arch/x86/kernel/apic/hw_nmi.c | 114 +++++++++++++++++++++++++ kernel/nmi_watchdog.c | 191 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 305 insertions(+) create mode 100644 arch/x86/kernel/apic/hw_nmi.c create mode 100644 kernel/nmi_watchdog.c diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c new file mode 100644 index 0000000..8c0e6a4 --- /dev/null +++ b/arch/x86/kernel/apic/hw_nmi.c @@ -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 +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +/* 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; } diff --git a/kernel/nmi_watchdog.c b/kernel/nmi_watchdog.c new file mode 100644 index 0000000..36817b2 --- /dev/null +++ b/kernel/nmi_watchdog.c @@ -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 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +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); -- 2.7.4