--- /dev/null
+/*
+ * Watchdog support on powerpc systems.
+ *
+ * Copyright 2017, IBM Corporation.
+ *
+ * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
+ */
+#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 watchdog has a simple timer that runs on each CPU, once per timer
+ * period. This is the heartbeat.
+ *
+ * Then there are checks to see if the heartbeat has not triggered on a CPU
+ * for the panic timeout period. Currently the watchdog only supports an
+ * SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
+ *
+ * This is not an NMI watchdog, but Linux uses that name for a generic
+ * watchdog in some cases, so NMI gets used in some places.
+ */
+
+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 timer_list, wd_timer);
+static DEFINE_PER_CPU(u64, wd_timer_tb);
+
+/*
+ * These are for the SMP checker. CPUs clear their pending bit in their
+ * heartbeat. If the bitmask becomes empty, the time is noted and the
+ * bitmask is refilled.
+ *
+ * All CPUs clear their bit in the pending mask every timer period.
+ * Once all have cleared, the time is noted and the bits are reset.
+ * If the time since all clear was greater than the panic timeout,
+ * we can panic with the list of stuck CPUs.
+ *
+ * This will work best with NMI IPIs for crash code so the stuck CPUs
+ * can be pulled out to get their backtraces.
+ */
+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.
+ */
+ local_irq_save(*flags);
+ while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock)))
+ cpu_relax();
+}
+
+static inline void wd_smp_unlock(unsigned long *flags)
+{
+ clear_bit_unlock(0, &__wd_smp_lock);
+ local_irq_restore(*flags);
+}
+
+static void wd_lockup_ipi(struct pt_regs *regs)
+{
+ pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
+ print_modules();
+ print_irqtrace_events(current);
+ if (regs)
+ show_regs(regs);
+ else
+ dump_stack();
+
+ if (hardlockup_panic)
+ nmi_panic(regs, "Hard LOCKUP");
+}
+
+static void set_cpu_stuck(int cpu, u64 tb)
+{
+ cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
+ cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
+ 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 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("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
+ cpu, cpumask_pr_args(&wd_smp_cpus_pending));
+
+ /*
+ * Try to trigger the stuck CPUs.
+ */
+ for_each_cpu(c, &wd_smp_cpus_pending) {
+ if (c == cpu)
+ continue;
+ smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
+ }
+ smp_flush_nmi_ipi(1000000);
+
+ /* Take the stuck CPU out of the watch group */
+ for_each_cpu(c, &wd_smp_cpus_pending)
+ set_cpu_stuck(c, tb);
+
+out:
+ 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");
+}
+
+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))) {
+ unsigned long flags;
+
+ pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
+ wd_smp_lock(&flags);
+ cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
+ wd_smp_unlock(&flags);
+ }
+ return;
+ }
+ cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
+ if (cpumask_empty(&wd_smp_cpus_pending)) {
+ unsigned long flags;
+
+ 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();
+ tb = get_tb();
+ if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
+ per_cpu(wd_timer_tb, cpu) = 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("Watchdog CPU:%d Hard LOCKUP\n", cpu);
+ print_modules();
+ print_irqtrace_events(current);
+ if (regs)
+ show_regs(regs);
+ else
+ dump_stack();
+
+ 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 void wd_timer_reset(unsigned int cpu, struct timer_list *t)
+{
+ t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
+ if (wd_timer_period_ms > 1000)
+ t->expires = __round_jiffies_up(t->expires, cpu);
+ add_timer_on(t, cpu);
+}
+
+static void wd_timer_fn(unsigned long data)
+{
+ struct timer_list *t = this_cpu_ptr(&wd_timer);
+ int cpu = smp_processor_id();
+
+ watchdog_timer_interrupt(cpu);
+
+ wd_timer_reset(cpu, t);
+}
+
+void arch_touch_nmi_watchdog(void)
+{
+ int cpu = smp_processor_id();
+
+ watchdog_timer_interrupt(cpu);
+}
+EXPORT_SYMBOL(arch_touch_nmi_watchdog);
+
+static void start_watchdog_timer_on(unsigned int cpu)
+{
+ struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
+
+ per_cpu(wd_timer_tb, cpu) = get_tb();
+
+ setup_pinned_timer(t, wd_timer_fn, 0);
+ wd_timer_reset(cpu, t);
+}
+
+static void stop_watchdog_timer_on(unsigned int cpu)
+{
+ struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
+
+ del_timer_sync(t);
+}
+
+static int start_wd_on_cpu(unsigned int cpu)
+{
+ if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
+ WARN_ON(1);
+ return 0;
+ }
+
+ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+ return 0;
+
+ if (watchdog_suspended)
+ return 0;
+
+ if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
+ return 0;
+
+ 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();
+ }
+ smp_wmb();
+ start_watchdog_timer_on(cpu);
+
+ return 0;
+}
+
+static int stop_wd_on_cpu(unsigned int cpu)
+{
+ if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
+ return 0; /* Can happen in CPU unplug case */
+
+ stop_watchdog_timer_on(cpu);
+
+ cpumask_clear_cpu(cpu, &wd_cpus_enabled);
+ wd_smp_clear_cpu_pending(cpu, get_tb());
+
+ return 0;
+}
+
+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_reconfigure(void)
+{
+ int cpu;
+
+ watchdog_calc_timeouts();
+
+ for_each_cpu(cpu, &wd_cpus_enabled)
+ stop_wd_on_cpu(cpu);
+
+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
+ start_wd_on_cpu(cpu);
+}
+
+/*
+ * This runs after lockup_detector_init() which sets up watchdog_cpumask.
+ */
+static int __init powerpc_watchdog_init(void)
+{
+ int err;
+
+ watchdog_calc_timeouts();
+
+ err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
+ start_wd_on_cpu, stop_wd_on_cpu);
+ if (err < 0)
+ pr_warn("Watchdog could not be initialized");
+
+ return 0;
+}
+arch_initcall(powerpc_watchdog_init);
+
+static void handle_backtrace_ipi(struct pt_regs *regs)
+{
+ nmi_cpu_backtrace(regs);
+}
+
+static void raise_backtrace_ipi(cpumask_t *mask)
+{
+ unsigned int cpu;
+
+ for_each_cpu(cpu, mask) {
+ if (cpu == smp_processor_id())
+ handle_backtrace_ipi(NULL);
+ else
+ smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
+ }
+}
+
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+{
+ nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
+}
projects / karo-tx-linux.git / commitdiff