1 // SPDX-License-Identifier: GPL-2.0
3 * Watchdog support on powerpc systems.
5 * Copyright 2017, IBM Corporation.
7 * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
9 #include <linux/kernel.h>
10 #include <linux/param.h>
11 #include <linux/init.h>
12 #include <linux/percpu.h>
13 #include <linux/cpu.h>
14 #include <linux/nmi.h>
15 #include <linux/module.h>
16 #include <linux/export.h>
17 #include <linux/kprobes.h>
18 #include <linux/hardirq.h>
19 #include <linux/reboot.h>
20 #include <linux/slab.h>
21 #include <linux/kdebug.h>
22 #include <linux/sched/debug.h>
23 #include <linux/delay.h>
24 #include <linux/smp.h>
29 * The watchdog has a simple timer that runs on each CPU, once per timer
30 * period. This is the heartbeat.
32 * Then there are checks to see if the heartbeat has not triggered on a CPU
33 * for the panic timeout period. Currently the watchdog only supports an
34 * SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
36 * This is not an NMI watchdog, but Linux uses that name for a generic
37 * watchdog in some cases, so NMI gets used in some places.
40 static cpumask_t wd_cpus_enabled __read_mostly
;
42 static u64 wd_panic_timeout_tb __read_mostly
; /* timebase ticks until panic */
43 static u64 wd_smp_panic_timeout_tb __read_mostly
; /* panic other CPUs */
45 static u64 wd_timer_period_ms __read_mostly
; /* interval between heartbeat */
47 static DEFINE_PER_CPU(struct timer_list
, wd_timer
);
48 static DEFINE_PER_CPU(u64
, wd_timer_tb
);
51 * These are for the SMP checker. CPUs clear their pending bit in their
52 * heartbeat. If the bitmask becomes empty, the time is noted and the
53 * bitmask is refilled.
55 * All CPUs clear their bit in the pending mask every timer period.
56 * Once all have cleared, the time is noted and the bits are reset.
57 * If the time since all clear was greater than the panic timeout,
58 * we can panic with the list of stuck CPUs.
60 * This will work best with NMI IPIs for crash code so the stuck CPUs
61 * can be pulled out to get their backtraces.
63 static unsigned long __wd_smp_lock
;
64 static cpumask_t wd_smp_cpus_pending
;
65 static cpumask_t wd_smp_cpus_stuck
;
66 static u64 wd_smp_last_reset_tb
;
68 static inline void wd_smp_lock(unsigned long *flags
)
71 * Avoid locking layers if possible.
72 * This may be called from low level interrupt handlers at some
75 raw_local_irq_save(*flags
);
76 hard_irq_disable(); /* Make it soft-NMI safe */
77 while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock
))) {
78 raw_local_irq_restore(*flags
);
79 spin_until_cond(!test_bit(0, &__wd_smp_lock
));
80 raw_local_irq_save(*flags
);
85 static inline void wd_smp_unlock(unsigned long *flags
)
87 clear_bit_unlock(0, &__wd_smp_lock
);
88 raw_local_irq_restore(*flags
);
91 static void wd_lockup_ipi(struct pt_regs
*regs
)
93 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
95 print_irqtrace_events(current
);
101 if (hardlockup_panic
)
102 nmi_panic(regs
, "Hard LOCKUP");
105 static void set_cpumask_stuck(const struct cpumask
*cpumask
, u64 tb
)
107 cpumask_or(&wd_smp_cpus_stuck
, &wd_smp_cpus_stuck
, cpumask
);
108 cpumask_andnot(&wd_smp_cpus_pending
, &wd_smp_cpus_pending
, cpumask
);
109 if (cpumask_empty(&wd_smp_cpus_pending
)) {
110 wd_smp_last_reset_tb
= tb
;
111 cpumask_andnot(&wd_smp_cpus_pending
,
116 static void set_cpu_stuck(int cpu
, u64 tb
)
118 set_cpumask_stuck(cpumask_of(cpu
), tb
);
121 static void watchdog_smp_panic(int cpu
, u64 tb
)
127 /* Double check some things under lock */
128 if ((s64
)(tb
- wd_smp_last_reset_tb
) < (s64
)wd_smp_panic_timeout_tb
)
130 if (cpumask_test_cpu(cpu
, &wd_smp_cpus_pending
))
132 if (cpumask_weight(&wd_smp_cpus_pending
) == 0)
135 pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
136 cpu
, cpumask_pr_args(&wd_smp_cpus_pending
));
139 * Try to trigger the stuck CPUs.
141 for_each_cpu(c
, &wd_smp_cpus_pending
) {
144 smp_send_nmi_ipi(c
, wd_lockup_ipi
, 1000000);
146 smp_flush_nmi_ipi(1000000);
148 /* Take the stuck CPUs out of the watch group */
149 set_cpumask_stuck(&wd_smp_cpus_pending
, tb
);
151 wd_smp_unlock(&flags
);
155 * printk_safe_flush() seems to require another print
156 * before anything actually goes out to console.
158 if (sysctl_hardlockup_all_cpu_backtrace
)
159 trigger_allbutself_cpu_backtrace();
161 if (hardlockup_panic
)
162 nmi_panic(NULL
, "Hard LOCKUP");
167 wd_smp_unlock(&flags
);
170 static void wd_smp_clear_cpu_pending(int cpu
, u64 tb
)
172 if (!cpumask_test_cpu(cpu
, &wd_smp_cpus_pending
)) {
173 if (unlikely(cpumask_test_cpu(cpu
, &wd_smp_cpus_stuck
))) {
176 pr_emerg("Watchdog CPU:%d became unstuck\n", cpu
);
178 cpumask_clear_cpu(cpu
, &wd_smp_cpus_stuck
);
179 wd_smp_unlock(&flags
);
183 cpumask_clear_cpu(cpu
, &wd_smp_cpus_pending
);
184 if (cpumask_empty(&wd_smp_cpus_pending
)) {
188 if (cpumask_empty(&wd_smp_cpus_pending
)) {
189 wd_smp_last_reset_tb
= tb
;
190 cpumask_andnot(&wd_smp_cpus_pending
,
194 wd_smp_unlock(&flags
);
198 static void watchdog_timer_interrupt(int cpu
)
202 per_cpu(wd_timer_tb
, cpu
) = tb
;
204 wd_smp_clear_cpu_pending(cpu
, tb
);
206 if ((s64
)(tb
- wd_smp_last_reset_tb
) >= (s64
)wd_smp_panic_timeout_tb
)
207 watchdog_smp_panic(cpu
, tb
);
210 void soft_nmi_interrupt(struct pt_regs
*regs
)
213 int cpu
= raw_smp_processor_id();
216 if (!cpumask_test_cpu(cpu
, &wd_cpus_enabled
))
221 __this_cpu_inc(irq_stat
.soft_nmi_irqs
);
224 if (tb
- per_cpu(wd_timer_tb
, cpu
) >= wd_panic_timeout_tb
) {
225 per_cpu(wd_timer_tb
, cpu
) = tb
;
228 if (cpumask_test_cpu(cpu
, &wd_smp_cpus_stuck
)) {
229 wd_smp_unlock(&flags
);
232 set_cpu_stuck(cpu
, tb
);
234 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu
);
236 print_irqtrace_events(current
);
242 wd_smp_unlock(&flags
);
244 if (sysctl_hardlockup_all_cpu_backtrace
)
245 trigger_allbutself_cpu_backtrace();
247 if (hardlockup_panic
)
248 nmi_panic(regs
, "Hard LOCKUP");
250 if (wd_panic_timeout_tb
< 0x7fffffff)
251 mtspr(SPRN_DEC
, wd_panic_timeout_tb
);
257 static void wd_timer_reset(unsigned int cpu
, struct timer_list
*t
)
259 t
->expires
= jiffies
+ msecs_to_jiffies(wd_timer_period_ms
);
260 if (wd_timer_period_ms
> 1000)
261 t
->expires
= __round_jiffies_up(t
->expires
, cpu
);
262 add_timer_on(t
, cpu
);
265 static void wd_timer_fn(unsigned long data
)
267 struct timer_list
*t
= this_cpu_ptr(&wd_timer
);
268 int cpu
= smp_processor_id();
270 watchdog_timer_interrupt(cpu
);
272 wd_timer_reset(cpu
, t
);
275 void arch_touch_nmi_watchdog(void)
277 unsigned long ticks
= tb_ticks_per_usec
* wd_timer_period_ms
* 1000;
278 int cpu
= smp_processor_id();
280 if (get_tb() - per_cpu(wd_timer_tb
, cpu
) >= ticks
)
281 watchdog_timer_interrupt(cpu
);
283 EXPORT_SYMBOL(arch_touch_nmi_watchdog
);
285 static void start_watchdog_timer_on(unsigned int cpu
)
287 struct timer_list
*t
= per_cpu_ptr(&wd_timer
, cpu
);
289 per_cpu(wd_timer_tb
, cpu
) = get_tb();
291 setup_pinned_timer(t
, wd_timer_fn
, 0);
292 wd_timer_reset(cpu
, t
);
295 static void stop_watchdog_timer_on(unsigned int cpu
)
297 struct timer_list
*t
= per_cpu_ptr(&wd_timer
, cpu
);
302 static int start_wd_on_cpu(unsigned int cpu
)
306 if (cpumask_test_cpu(cpu
, &wd_cpus_enabled
)) {
311 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
314 if (!cpumask_test_cpu(cpu
, &watchdog_cpumask
))
318 cpumask_set_cpu(cpu
, &wd_cpus_enabled
);
319 if (cpumask_weight(&wd_cpus_enabled
) == 1) {
320 cpumask_set_cpu(cpu
, &wd_smp_cpus_pending
);
321 wd_smp_last_reset_tb
= get_tb();
323 wd_smp_unlock(&flags
);
325 start_watchdog_timer_on(cpu
);
330 static int stop_wd_on_cpu(unsigned int cpu
)
334 if (!cpumask_test_cpu(cpu
, &wd_cpus_enabled
))
335 return 0; /* Can happen in CPU unplug case */
337 stop_watchdog_timer_on(cpu
);
340 cpumask_clear_cpu(cpu
, &wd_cpus_enabled
);
341 wd_smp_unlock(&flags
);
343 wd_smp_clear_cpu_pending(cpu
, get_tb());
348 static void watchdog_calc_timeouts(void)
350 wd_panic_timeout_tb
= watchdog_thresh
* ppc_tb_freq
;
352 /* Have the SMP detector trigger a bit later */
353 wd_smp_panic_timeout_tb
= wd_panic_timeout_tb
* 3 / 2;
355 /* 2/5 is the factor that the perf based detector uses */
356 wd_timer_period_ms
= watchdog_thresh
* 1000 * 2 / 5;
359 void watchdog_nmi_stop(void)
363 for_each_cpu(cpu
, &wd_cpus_enabled
)
367 void watchdog_nmi_start(void)
371 watchdog_calc_timeouts();
372 for_each_cpu_and(cpu
, cpu_online_mask
, &watchdog_cpumask
)
373 start_wd_on_cpu(cpu
);
377 * Invoked from core watchdog init.
379 int __init
watchdog_nmi_probe(void)
383 err
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
,
384 "powerpc/watchdog:online",
385 start_wd_on_cpu
, stop_wd_on_cpu
);
387 pr_warn("Watchdog could not be initialized");
393 static void handle_backtrace_ipi(struct pt_regs
*regs
)
395 nmi_cpu_backtrace(regs
);
398 static void raise_backtrace_ipi(cpumask_t
*mask
)
402 for_each_cpu(cpu
, mask
) {
403 if (cpu
== smp_processor_id())
404 handle_backtrace_ipi(NULL
);
406 smp_send_nmi_ipi(cpu
, handle_backtrace_ipi
, 1000000);
410 void arch_trigger_cpumask_backtrace(const cpumask_t
*mask
, bool exclude_self
)
412 nmi_trigger_cpumask_backtrace(mask
, exclude_self
, raise_backtrace_ipi
);