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// 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
*/
#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.
*/
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)
{
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_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("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 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))) {
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();
__this_cpu_inc(irq_stat.soft_nmi_irqs);
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(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();
if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
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();
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
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