From 1fb9d6ad2766a1dd70d167552988375049a97f21 Mon Sep 17 00:00:00 2001 From: Don Zickus Date: Fri, 5 Feb 2010 21:47:04 -0500 Subject: 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 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) create mode 100644 arch/x86/kernel/apic/hw_nmi.c (limited to 'arch') diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c new file mode 100644 index 000000000000..8c0e6a410d05 --- /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; } -- cgit v1.2.1