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Diffstat (limited to '')
| -rw-r--r-- | arch/powerpc/kernel/watchdog.c | 470 |
1 files changed, 470 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c new file mode 100644 index 000000000..75b2a6c4d --- /dev/null +++ b/arch/powerpc/kernel/watchdog.c @@ -0,0 +1,470 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Watchdog support on powerpc systems. + * + * Copyright 2017, IBM Corporation. + * + * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c + */ + +#define pr_fmt(fmt) "watchdog: " fmt + +#include <linux/kernel.h> +#include <linux/param.h> +#include <linux/init.h> +#include <linux/percpu.h> +#include <linux/cpu.h> +#include <linux/nmi.h> +#include <linux/module.h> +#include <linux/export.h> +#include <linux/kprobes.h> +#include <linux/hardirq.h> +#include <linux/reboot.h> +#include <linux/slab.h> +#include <linux/kdebug.h> +#include <linux/sched/debug.h> +#include <linux/delay.h> +#include <linux/smp.h> + +#include <asm/paca.h> + +/* + * The powerpc watchdog ensures that each CPU is able to service timers. + * The watchdog sets up a simple timer on each CPU to run once per timer + * period, and updates a per-cpu timestamp and a "pending" cpumask. This is + * the heartbeat. + * + * Then there are two systems to check that the heartbeat is still running. + * The local soft-NMI, and the SMP checker. + * + * The soft-NMI checker can detect lockups on the local CPU. When interrupts + * are disabled with local_irq_disable(), platforms that use soft-masking + * can leave hardware interrupts enabled and handle them with a masked + * interrupt handler. The masked handler can send the timer interrupt to the + * watchdog's soft_nmi_interrupt(), which appears to Linux as an NMI + * interrupt, and can be used to detect CPUs stuck with IRQs disabled. + * + * The soft-NMI checker will compare the heartbeat timestamp for this CPU + * with the current time, and take action if the difference exceeds the + * watchdog threshold. + * + * The limitation of the soft-NMI watchdog is that it does not work when + * interrupts are hard disabled or otherwise not being serviced. This is + * solved by also having a SMP watchdog where all CPUs check all other + * CPUs heartbeat. + * + * The SMP checker can detect lockups on other CPUs. A gobal "pending" + * cpumask is kept, containing all CPUs which enable the watchdog. Each + * CPU clears their pending bit in their heartbeat timer. When the bitmask + * becomes empty, the last CPU to clear its pending bit updates a global + * timestamp and refills the pending bitmask. + * + * In the heartbeat timer, if any CPU notices that the global timestamp has + * not been updated for a period exceeding the watchdog threshold, then it + * means the CPU(s) with their bit still set in the pending mask have had + * their heartbeat stop, and action is taken. + * + * Some platforms implement true NMI IPIs, which can be used by the SMP + * watchdog to detect an unresponsive CPU and pull it out of its stuck + * state with the NMI IPI, to get crash/debug data from it. This way the + * SMP watchdog can detect hardware interrupts off lockups. + */ + +static cpumask_t wd_cpus_enabled __read_mostly; + +static u64 wd_panic_timeout_tb __read_mostly; /* timebase ticks until panic */ +static u64 wd_smp_panic_timeout_tb __read_mostly; /* panic other CPUs */ + +static u64 wd_timer_period_ms __read_mostly; /* interval between heartbeat */ + +static DEFINE_PER_CPU(struct hrtimer, wd_hrtimer); +static DEFINE_PER_CPU(u64, wd_timer_tb); + +/* SMP checker bits */ +static unsigned long __wd_smp_lock; +static cpumask_t wd_smp_cpus_pending; +static cpumask_t wd_smp_cpus_stuck; +static u64 wd_smp_last_reset_tb; + +static inline void wd_smp_lock(unsigned long *flags) +{ + /* + * Avoid locking layers if possible. + * This may be called from low level interrupt handlers at some + * point in future. + */ + raw_local_irq_save(*flags); + hard_irq_disable(); /* Make it soft-NMI safe */ + while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock))) { + raw_local_irq_restore(*flags); + spin_until_cond(!test_bit(0, &__wd_smp_lock)); + raw_local_irq_save(*flags); + hard_irq_disable(); + } +} + +static inline void wd_smp_unlock(unsigned long *flags) +{ + clear_bit_unlock(0, &__wd_smp_lock); + raw_local_irq_restore(*flags); +} + +static void wd_lockup_ipi(struct pt_regs *regs) +{ + int cpu = raw_smp_processor_id(); + u64 tb = get_tb(); + + pr_emerg("CPU %d Hard LOCKUP\n", cpu); + pr_emerg("CPU %d TB:%lld, last heartbeat TB:%lld (%lldms ago)\n", + cpu, tb, per_cpu(wd_timer_tb, cpu), + tb_to_ns(tb - per_cpu(wd_timer_tb, cpu)) / 1000000); + print_modules(); + print_irqtrace_events(current); + if (regs) + show_regs(regs); + else + dump_stack(); + + /* Do not panic from here because that can recurse into NMI IPI layer */ +} + +static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb) +{ + cpumask_or(&wd_smp_cpus_stuck, &wd_smp_cpus_stuck, cpumask); + cpumask_andnot(&wd_smp_cpus_pending, &wd_smp_cpus_pending, cpumask); + /* + * See wd_smp_clear_cpu_pending() + */ + smp_mb(); + if (cpumask_empty(&wd_smp_cpus_pending)) { + wd_smp_last_reset_tb = tb; + cpumask_andnot(&wd_smp_cpus_pending, + &wd_cpus_enabled, + &wd_smp_cpus_stuck); + } +} +static void set_cpu_stuck(int cpu, u64 tb) +{ + set_cpumask_stuck(cpumask_of(cpu), tb); +} + +static void watchdog_smp_panic(int cpu, u64 tb) +{ + unsigned long flags; + int c; + + wd_smp_lock(&flags); + /* Double check some things under lock */ + if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb) + goto out; + if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) + goto out; + if (cpumask_weight(&wd_smp_cpus_pending) == 0) + goto out; + + pr_emerg("CPU %d detected hard LOCKUP on other CPUs %*pbl\n", + cpu, cpumask_pr_args(&wd_smp_cpus_pending)); + pr_emerg("CPU %d TB:%lld, last SMP heartbeat TB:%lld (%lldms ago)\n", + cpu, tb, wd_smp_last_reset_tb, + tb_to_ns(tb - wd_smp_last_reset_tb) / 1000000); + + if (!sysctl_hardlockup_all_cpu_backtrace) { + /* + * Try to trigger the stuck CPUs, unless we are going to + * get a backtrace on all of them anyway. + */ + for_each_cpu(c, &wd_smp_cpus_pending) { + if (c == cpu) + continue; + smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000); + } + } + + /* Take the stuck CPUs out of the watch group */ + set_cpumask_stuck(&wd_smp_cpus_pending, tb); + + wd_smp_unlock(&flags); + + printk_safe_flush(); + /* + * printk_safe_flush() seems to require another print + * before anything actually goes out to console. + */ + if (sysctl_hardlockup_all_cpu_backtrace) + trigger_allbutself_cpu_backtrace(); + + if (hardlockup_panic) + nmi_panic(NULL, "Hard LOCKUP"); + + return; + +out: + wd_smp_unlock(&flags); +} + +static void wd_smp_clear_cpu_pending(int cpu, u64 tb) +{ + if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) { + if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) { + struct pt_regs *regs = get_irq_regs(); + unsigned long flags; + + wd_smp_lock(&flags); + + pr_emerg("CPU %d became unstuck TB:%lld\n", + cpu, tb); + print_irqtrace_events(current); + if (regs) + show_regs(regs); + else + dump_stack(); + + cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck); + wd_smp_unlock(&flags); + } else { + /* + * The last CPU to clear pending should have reset the + * watchdog so we generally should not find it empty + * here if our CPU was clear. However it could happen + * due to a rare race with another CPU taking the + * last CPU out of the mask concurrently. + * + * We can't add a warning for it. But just in case + * there is a problem with the watchdog that is causing + * the mask to not be reset, try to kick it along here. + */ + if (unlikely(cpumask_empty(&wd_smp_cpus_pending))) + goto none_pending; + } + return; + } + + cpumask_clear_cpu(cpu, &wd_smp_cpus_pending); + + /* + * Order the store to clear pending with the load(s) to check all + * words in the pending mask to check they are all empty. This orders + * with the same barrier on another CPU. This prevents two CPUs + * clearing the last 2 pending bits, but neither seeing the other's + * store when checking if the mask is empty, and missing an empty + * mask, which ends with a false positive. + */ + smp_mb(); + if (cpumask_empty(&wd_smp_cpus_pending)) { + unsigned long flags; + +none_pending: + /* + * Double check under lock because more than one CPU could see + * a clear mask with the lockless check after clearing their + * pending bits. + */ + wd_smp_lock(&flags); + if (cpumask_empty(&wd_smp_cpus_pending)) { + wd_smp_last_reset_tb = tb; + cpumask_andnot(&wd_smp_cpus_pending, + &wd_cpus_enabled, + &wd_smp_cpus_stuck); + } + wd_smp_unlock(&flags); + } +} + +static void watchdog_timer_interrupt(int cpu) +{ + u64 tb = get_tb(); + + per_cpu(wd_timer_tb, cpu) = tb; + + wd_smp_clear_cpu_pending(cpu, tb); + + if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb) + watchdog_smp_panic(cpu, tb); +} + +void soft_nmi_interrupt(struct pt_regs *regs) +{ + unsigned long flags; + int cpu = raw_smp_processor_id(); + u64 tb; + + if (!cpumask_test_cpu(cpu, &wd_cpus_enabled)) + return; + + nmi_enter(); + + __this_cpu_inc(irq_stat.soft_nmi_irqs); + + tb = get_tb(); + if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) { + wd_smp_lock(&flags); + if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) { + wd_smp_unlock(&flags); + goto out; + } + set_cpu_stuck(cpu, tb); + + pr_emerg("CPU %d self-detected hard LOCKUP @ %pS\n", + cpu, (void *)regs->nip); + pr_emerg("CPU %d TB:%lld, last heartbeat TB:%lld (%lldms ago)\n", + cpu, tb, per_cpu(wd_timer_tb, cpu), + tb_to_ns(tb - per_cpu(wd_timer_tb, cpu)) / 1000000); + print_modules(); + print_irqtrace_events(current); + show_regs(regs); + + wd_smp_unlock(&flags); + + if (sysctl_hardlockup_all_cpu_backtrace) + trigger_allbutself_cpu_backtrace(); + + if (hardlockup_panic) + nmi_panic(regs, "Hard LOCKUP"); + } + if (wd_panic_timeout_tb < 0x7fffffff) + mtspr(SPRN_DEC, wd_panic_timeout_tb); + +out: + nmi_exit(); +} + +static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) +{ + int cpu = smp_processor_id(); + + if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) + return HRTIMER_NORESTART; + + if (!cpumask_test_cpu(cpu, &watchdog_cpumask)) + return HRTIMER_NORESTART; + + watchdog_timer_interrupt(cpu); + + hrtimer_forward_now(hrtimer, ms_to_ktime(wd_timer_period_ms)); + + return HRTIMER_RESTART; +} + +void arch_touch_nmi_watchdog(void) +{ + unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000; + int cpu = smp_processor_id(); + u64 tb; + + if (!cpumask_test_cpu(cpu, &watchdog_cpumask)) + return; + + tb = get_tb(); + if (tb - per_cpu(wd_timer_tb, cpu) >= ticks) { + per_cpu(wd_timer_tb, cpu) = tb; + wd_smp_clear_cpu_pending(cpu, tb); + } +} +EXPORT_SYMBOL(arch_touch_nmi_watchdog); + +static void start_watchdog(void *arg) +{ + struct hrtimer *hrtimer = this_cpu_ptr(&wd_hrtimer); + int cpu = smp_processor_id(); + unsigned long flags; + + if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) { + WARN_ON(1); + return; + } + + if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) + return; + + if (!cpumask_test_cpu(cpu, &watchdog_cpumask)) + return; + + wd_smp_lock(&flags); + cpumask_set_cpu(cpu, &wd_cpus_enabled); + if (cpumask_weight(&wd_cpus_enabled) == 1) { + cpumask_set_cpu(cpu, &wd_smp_cpus_pending); + wd_smp_last_reset_tb = get_tb(); + } + wd_smp_unlock(&flags); + + *this_cpu_ptr(&wd_timer_tb) = get_tb(); + + hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer->function = watchdog_timer_fn; + hrtimer_start(hrtimer, ms_to_ktime(wd_timer_period_ms), + HRTIMER_MODE_REL_PINNED); +} + +static int start_watchdog_on_cpu(unsigned int cpu) +{ + return smp_call_function_single(cpu, start_watchdog, NULL, true); +} + +static void stop_watchdog(void *arg) +{ + struct hrtimer *hrtimer = this_cpu_ptr(&wd_hrtimer); + int cpu = smp_processor_id(); + unsigned long flags; + + if (!cpumask_test_cpu(cpu, &wd_cpus_enabled)) + return; /* Can happen in CPU unplug case */ + + hrtimer_cancel(hrtimer); + + wd_smp_lock(&flags); + cpumask_clear_cpu(cpu, &wd_cpus_enabled); + wd_smp_unlock(&flags); + + wd_smp_clear_cpu_pending(cpu, get_tb()); +} + +static int stop_watchdog_on_cpu(unsigned int cpu) +{ + return smp_call_function_single(cpu, stop_watchdog, NULL, true); +} + +static void watchdog_calc_timeouts(void) +{ + wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq; + + /* Have the SMP detector trigger a bit later */ + wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2; + + /* 2/5 is the factor that the perf based detector uses */ + wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5; +} + +void watchdog_nmi_stop(void) +{ + int cpu; + + for_each_cpu(cpu, &wd_cpus_enabled) + stop_watchdog_on_cpu(cpu); +} + +void watchdog_nmi_start(void) +{ + int cpu; + + watchdog_calc_timeouts(); + for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) + start_watchdog_on_cpu(cpu); +} + +/* + * Invoked from core watchdog init. + */ +int __init watchdog_nmi_probe(void) +{ + int err; + + err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "powerpc/watchdog:online", + start_watchdog_on_cpu, + stop_watchdog_on_cpu); + if (err < 0) { + pr_warn("could not be initialized"); + return err; + } + return 0; +} |