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@@ -0,0 +1,386 @@
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+/*
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+ * Watchdog support on powerpc systems.
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+ *
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+ * Copyright 2017, IBM Corporation.
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+ *
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+ * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
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+ */
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+#include <linux/kernel.h>
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+#include <linux/param.h>
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+#include <linux/init.h>
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+#include <linux/percpu.h>
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+#include <linux/cpu.h>
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+#include <linux/nmi.h>
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+#include <linux/module.h>
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+#include <linux/export.h>
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+#include <linux/kprobes.h>
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+#include <linux/hardirq.h>
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+#include <linux/reboot.h>
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+#include <linux/slab.h>
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+#include <linux/kdebug.h>
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+#include <linux/sched/debug.h>
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+#include <linux/delay.h>
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+#include <linux/smp.h>
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+
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+#include <asm/paca.h>
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+
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+/*
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+ * The watchdog has a simple timer that runs on each CPU, once per timer
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+ * period. This is the heartbeat.
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+ *
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+ * Then there are checks to see if the heartbeat has not triggered on a CPU
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+ * for the panic timeout period. Currently the watchdog only supports an
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+ * SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
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+ *
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+ * This is not an NMI watchdog, but Linux uses that name for a generic
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+ * watchdog in some cases, so NMI gets used in some places.
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+ */
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+
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+static cpumask_t wd_cpus_enabled __read_mostly;
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+
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+static u64 wd_panic_timeout_tb __read_mostly; /* timebase ticks until panic */
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+static u64 wd_smp_panic_timeout_tb __read_mostly; /* panic other CPUs */
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+
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+static u64 wd_timer_period_ms __read_mostly; /* interval between heartbeat */
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+
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+static DEFINE_PER_CPU(struct timer_list, wd_timer);
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+static DEFINE_PER_CPU(u64, wd_timer_tb);
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+
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+/*
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+ * These are for the SMP checker. CPUs clear their pending bit in their
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+ * heartbeat. If the bitmask becomes empty, the time is noted and the
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+ * bitmask is refilled.
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+ *
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+ * All CPUs clear their bit in the pending mask every timer period.
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+ * Once all have cleared, the time is noted and the bits are reset.
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+ * If the time since all clear was greater than the panic timeout,
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+ * we can panic with the list of stuck CPUs.
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+ *
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+ * This will work best with NMI IPIs for crash code so the stuck CPUs
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+ * can be pulled out to get their backtraces.
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+ */
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+static unsigned long __wd_smp_lock;
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+static cpumask_t wd_smp_cpus_pending;
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+static cpumask_t wd_smp_cpus_stuck;
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+static u64 wd_smp_last_reset_tb;
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+
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+static inline void wd_smp_lock(unsigned long *flags)
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+{
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+ /*
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+ * Avoid locking layers if possible.
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+ * This may be called from low level interrupt handlers at some
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+ * point in future.
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+ */
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+ local_irq_save(*flags);
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+ while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock)))
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+ cpu_relax();
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+}
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+
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+static inline void wd_smp_unlock(unsigned long *flags)
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+{
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+ clear_bit_unlock(0, &__wd_smp_lock);
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+ local_irq_restore(*flags);
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+}
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+
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+static void wd_lockup_ipi(struct pt_regs *regs)
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+{
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+ pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
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+ print_modules();
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+ print_irqtrace_events(current);
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+ if (regs)
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+ show_regs(regs);
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+ else
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+ dump_stack();
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+
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+ if (hardlockup_panic)
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+ nmi_panic(regs, "Hard LOCKUP");
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+}
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+
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+static void set_cpu_stuck(int cpu, u64 tb)
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+{
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+ cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
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+ cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
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+ if (cpumask_empty(&wd_smp_cpus_pending)) {
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+ wd_smp_last_reset_tb = tb;
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+ cpumask_andnot(&wd_smp_cpus_pending,
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+ &wd_cpus_enabled,
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+ &wd_smp_cpus_stuck);
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+ }
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+}
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+
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+static void watchdog_smp_panic(int cpu, u64 tb)
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+{
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+ unsigned long flags;
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+ int c;
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+
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+ wd_smp_lock(&flags);
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+ /* Double check some things under lock */
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+ if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
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+ goto out;
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+ if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
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+ goto out;
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+ if (cpumask_weight(&wd_smp_cpus_pending) == 0)
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+ goto out;
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+
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+ pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
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+ cpu, cpumask_pr_args(&wd_smp_cpus_pending));
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+
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+ /*
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+ * Try to trigger the stuck CPUs.
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+ */
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+ for_each_cpu(c, &wd_smp_cpus_pending) {
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+ if (c == cpu)
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+ continue;
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+ smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
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+ }
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+ smp_flush_nmi_ipi(1000000);
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+
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+ /* Take the stuck CPU out of the watch group */
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+ for_each_cpu(c, &wd_smp_cpus_pending)
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+ set_cpu_stuck(c, tb);
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+
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+out:
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+ wd_smp_unlock(&flags);
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+
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+ printk_safe_flush();
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+ /*
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+ * printk_safe_flush() seems to require another print
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+ * before anything actually goes out to console.
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+ */
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+ if (sysctl_hardlockup_all_cpu_backtrace)
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+ trigger_allbutself_cpu_backtrace();
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+
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+ if (hardlockup_panic)
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+ nmi_panic(NULL, "Hard LOCKUP");
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+}
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+
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+static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
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+{
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+ if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
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+ if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
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+ unsigned long flags;
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+
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+ pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
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+ wd_smp_lock(&flags);
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+ cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
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+ wd_smp_unlock(&flags);
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+ }
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+ return;
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+ }
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+ cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
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+ if (cpumask_empty(&wd_smp_cpus_pending)) {
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+ unsigned long flags;
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+
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+ wd_smp_lock(&flags);
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+ if (cpumask_empty(&wd_smp_cpus_pending)) {
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+ wd_smp_last_reset_tb = tb;
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+ cpumask_andnot(&wd_smp_cpus_pending,
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+ &wd_cpus_enabled,
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+ &wd_smp_cpus_stuck);
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+ }
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+ wd_smp_unlock(&flags);
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+ }
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+}
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+
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+static void watchdog_timer_interrupt(int cpu)
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+{
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+ u64 tb = get_tb();
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+
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+ per_cpu(wd_timer_tb, cpu) = tb;
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+
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+ wd_smp_clear_cpu_pending(cpu, tb);
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+
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+ if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
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+ watchdog_smp_panic(cpu, tb);
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+}
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+
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+void soft_nmi_interrupt(struct pt_regs *regs)
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+{
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+ unsigned long flags;
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+ int cpu = raw_smp_processor_id();
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+ u64 tb;
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+
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+ if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
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+ return;
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+
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+ nmi_enter();
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+ tb = get_tb();
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+ if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
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+ per_cpu(wd_timer_tb, cpu) = tb;
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+
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+ wd_smp_lock(&flags);
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+ if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
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+ wd_smp_unlock(&flags);
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+ goto out;
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+ }
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+ set_cpu_stuck(cpu, tb);
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+
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+ pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
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+ print_modules();
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+ print_irqtrace_events(current);
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+ if (regs)
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+ show_regs(regs);
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+ else
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+ dump_stack();
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+
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+ wd_smp_unlock(&flags);
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+
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+ if (sysctl_hardlockup_all_cpu_backtrace)
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+ trigger_allbutself_cpu_backtrace();
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+
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+ if (hardlockup_panic)
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+ nmi_panic(regs, "Hard LOCKUP");
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+ }
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+ if (wd_panic_timeout_tb < 0x7fffffff)
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+ mtspr(SPRN_DEC, wd_panic_timeout_tb);
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+
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+out:
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+ nmi_exit();
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+}
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+
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+static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
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+{
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+ t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
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+ if (wd_timer_period_ms > 1000)
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+ t->expires = __round_jiffies_up(t->expires, cpu);
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+ add_timer_on(t, cpu);
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+}
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+
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+static void wd_timer_fn(unsigned long data)
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+{
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+ struct timer_list *t = this_cpu_ptr(&wd_timer);
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+ int cpu = smp_processor_id();
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+
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+ watchdog_timer_interrupt(cpu);
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+
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+ wd_timer_reset(cpu, t);
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+}
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+
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+void arch_touch_nmi_watchdog(void)
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+{
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+ int cpu = smp_processor_id();
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+
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+ watchdog_timer_interrupt(cpu);
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+}
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+EXPORT_SYMBOL(arch_touch_nmi_watchdog);
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+
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+static void start_watchdog_timer_on(unsigned int cpu)
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+{
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+ struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
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+
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+ per_cpu(wd_timer_tb, cpu) = get_tb();
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+
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+ setup_pinned_timer(t, wd_timer_fn, 0);
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+ wd_timer_reset(cpu, t);
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+}
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+
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+static void stop_watchdog_timer_on(unsigned int cpu)
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+{
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+ struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
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+
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+ del_timer_sync(t);
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+}
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+
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+static int start_wd_on_cpu(unsigned int cpu)
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+{
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+ if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
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+ WARN_ON(1);
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+ return 0;
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+ }
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+
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+ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
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+ return 0;
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+
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+ if (watchdog_suspended)
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+ return 0;
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+
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+ if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
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+ return 0;
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+
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+ cpumask_set_cpu(cpu, &wd_cpus_enabled);
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+ if (cpumask_weight(&wd_cpus_enabled) == 1) {
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+ cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
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+ wd_smp_last_reset_tb = get_tb();
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+ }
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+ smp_wmb();
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+ start_watchdog_timer_on(cpu);
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+
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+ return 0;
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+}
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+
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+static int stop_wd_on_cpu(unsigned int cpu)
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+{
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+ if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
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+ return 0; /* Can happen in CPU unplug case */
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+
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+ stop_watchdog_timer_on(cpu);
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+
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+ cpumask_clear_cpu(cpu, &wd_cpus_enabled);
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+ wd_smp_clear_cpu_pending(cpu, get_tb());
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+
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+ return 0;
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+}
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+
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+static void watchdog_calc_timeouts(void)
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+{
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+ wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
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+
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+ /* Have the SMP detector trigger a bit later */
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+ wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
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+
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+ /* 2/5 is the factor that the perf based detector uses */
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+ wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
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+}
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+
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+void watchdog_nmi_reconfigure(void)
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+{
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+ int cpu;
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+
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+ watchdog_calc_timeouts();
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+
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+ for_each_cpu(cpu, &wd_cpus_enabled)
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+ stop_wd_on_cpu(cpu);
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+
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+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
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+ start_wd_on_cpu(cpu);
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+}
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+
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+/*
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+ * This runs after lockup_detector_init() which sets up watchdog_cpumask.
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+ */
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+static int __init powerpc_watchdog_init(void)
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+{
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+ int err;
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+
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+ watchdog_calc_timeouts();
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+
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+ err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
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+ start_wd_on_cpu, stop_wd_on_cpu);
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+ if (err < 0)
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+ pr_warn("Watchdog could not be initialized");
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+
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+ return 0;
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+}
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+arch_initcall(powerpc_watchdog_init);
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+
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+static void handle_backtrace_ipi(struct pt_regs *regs)
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+{
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+ nmi_cpu_backtrace(regs);
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+}
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+
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+static void raise_backtrace_ipi(cpumask_t *mask)
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+{
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+ unsigned int cpu;
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+
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+ for_each_cpu(cpu, mask) {
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+ if (cpu == smp_processor_id())
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+ handle_backtrace_ipi(NULL);
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+ else
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+ smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
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+ }
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+}
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+
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+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
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+{
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+ nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
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+}
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Nicholas Piggin