v4.19.13 snapshot.
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
new file mode 100644
index 0000000..3c6ab22
--- /dev/null
+++ b/arch/powerpc/kernel/watchdog.c
@@ -0,0 +1,432 @@
+// 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 timer_list, wd_timer);
+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);
+ 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);
+ }
+ 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();
+
+ __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 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(struct timer_list *t)
+{
+ int cpu = smp_processor_id();
+
+ watchdog_timer_interrupt(cpu);
+
+ wd_timer_reset(cpu, t);
+}
+
+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 = 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_timer_on(unsigned int cpu)
+{
+ struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
+
+ per_cpu(wd_timer_tb, cpu) = get_tb();
+
+ timer_setup(t, wd_timer_fn, TIMER_PINNED);
+ 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)
+{
+ unsigned long flags;
+
+ if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
+ WARN_ON(1);
+ return 0;
+ }
+
+ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+ return 0;
+
+ if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
+ return 0;
+
+ 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);
+
+ start_watchdog_timer_on(cpu);
+
+ return 0;
+}
+
+static int stop_wd_on_cpu(unsigned int cpu)
+{
+ unsigned long flags;
+
+ if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
+ return 0; /* Can happen in CPU unplug case */
+
+ stop_watchdog_timer_on(cpu);
+
+ wd_smp_lock(&flags);
+ cpumask_clear_cpu(cpu, &wd_cpus_enabled);
+ wd_smp_unlock(&flags);
+
+ 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_stop(void)
+{
+ int cpu;
+
+ for_each_cpu(cpu, &wd_cpus_enabled)
+ stop_wd_on_cpu(cpu);
+}
+
+void watchdog_nmi_start(void)
+{
+ int cpu;
+
+ watchdog_calc_timeouts();
+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
+ start_wd_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_wd_on_cpu, stop_wd_on_cpu);
+ if (err < 0) {
+ pr_warn("could not be initialized");
+ return err;
+ }
+ return 0;
+}