7d16dafa1bb6b041d93f9b88015055bfa83feef8
[karo-tx-linux.git] / arch / powerpc / kernel / watchdog.c
1 /*
2  * Watchdog support on powerpc systems.
3  *
4  * Copyright 2017, IBM Corporation.
5  *
6  * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
7  */
8 #include <linux/kernel.h>
9 #include <linux/param.h>
10 #include <linux/init.h>
11 #include <linux/percpu.h>
12 #include <linux/cpu.h>
13 #include <linux/nmi.h>
14 #include <linux/module.h>
15 #include <linux/export.h>
16 #include <linux/kprobes.h>
17 #include <linux/hardirq.h>
18 #include <linux/reboot.h>
19 #include <linux/slab.h>
20 #include <linux/kdebug.h>
21 #include <linux/sched/debug.h>
22 #include <linux/delay.h>
23 #include <linux/smp.h>
24
25 #include <asm/paca.h>
26
27 /*
28  * The watchdog has a simple timer that runs on each CPU, once per timer
29  * period. This is the heartbeat.
30  *
31  * Then there are checks to see if the heartbeat has not triggered on a CPU
32  * for the panic timeout period. Currently the watchdog only supports an
33  * SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
34  *
35  * This is not an NMI watchdog, but Linux uses that name for a generic
36  * watchdog in some cases, so NMI gets used in some places.
37  */
38
39 static cpumask_t wd_cpus_enabled __read_mostly;
40
41 static u64 wd_panic_timeout_tb __read_mostly; /* timebase ticks until panic */
42 static u64 wd_smp_panic_timeout_tb __read_mostly; /* panic other CPUs */
43
44 static u64 wd_timer_period_ms __read_mostly;  /* interval between heartbeat */
45
46 static DEFINE_PER_CPU(struct timer_list, wd_timer);
47 static DEFINE_PER_CPU(u64, wd_timer_tb);
48
49 /*
50  * These are for the SMP checker. CPUs clear their pending bit in their
51  * heartbeat. If the bitmask becomes empty, the time is noted and the
52  * bitmask is refilled.
53  *
54  * All CPUs clear their bit in the pending mask every timer period.
55  * Once all have cleared, the time is noted and the bits are reset.
56  * If the time since all clear was greater than the panic timeout,
57  * we can panic with the list of stuck CPUs.
58  *
59  * This will work best with NMI IPIs for crash code so the stuck CPUs
60  * can be pulled out to get their backtraces.
61  */
62 static unsigned long __wd_smp_lock;
63 static cpumask_t wd_smp_cpus_pending;
64 static cpumask_t wd_smp_cpus_stuck;
65 static u64 wd_smp_last_reset_tb;
66
67 static inline void wd_smp_lock(unsigned long *flags)
68 {
69         /*
70          * Avoid locking layers if possible.
71          * This may be called from low level interrupt handlers at some
72          * point in future.
73          */
74         raw_local_irq_save(*flags);
75         hard_irq_disable(); /* Make it soft-NMI safe */
76         while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock))) {
77                 raw_local_irq_restore(*flags);
78                 spin_until_cond(!test_bit(0, &__wd_smp_lock));
79                 raw_local_irq_save(*flags);
80                 hard_irq_disable();
81         }
82 }
83
84 static inline void wd_smp_unlock(unsigned long *flags)
85 {
86         clear_bit_unlock(0, &__wd_smp_lock);
87         raw_local_irq_restore(*flags);
88 }
89
90 static void wd_lockup_ipi(struct pt_regs *regs)
91 {
92         pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
93         print_modules();
94         print_irqtrace_events(current);
95         if (regs)
96                 show_regs(regs);
97         else
98                 dump_stack();
99
100         if (hardlockup_panic)
101                 nmi_panic(regs, "Hard LOCKUP");
102 }
103
104 static void set_cpu_stuck(int cpu, u64 tb)
105 {
106         cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
107         cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
108         if (cpumask_empty(&wd_smp_cpus_pending)) {
109                 wd_smp_last_reset_tb = tb;
110                 cpumask_andnot(&wd_smp_cpus_pending,
111                                 &wd_cpus_enabled,
112                                 &wd_smp_cpus_stuck);
113         }
114 }
115
116 static void watchdog_smp_panic(int cpu, u64 tb)
117 {
118         unsigned long flags;
119         int c;
120
121         wd_smp_lock(&flags);
122         /* Double check some things under lock */
123         if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
124                 goto out;
125         if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
126                 goto out;
127         if (cpumask_weight(&wd_smp_cpus_pending) == 0)
128                 goto out;
129
130         pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
131                         cpu, cpumask_pr_args(&wd_smp_cpus_pending));
132
133         /*
134          * Try to trigger the stuck CPUs.
135          */
136         for_each_cpu(c, &wd_smp_cpus_pending) {
137                 if (c == cpu)
138                         continue;
139                 smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
140         }
141         smp_flush_nmi_ipi(1000000);
142
143         /* Take the stuck CPU out of the watch group */
144         for_each_cpu(c, &wd_smp_cpus_pending)
145                 set_cpu_stuck(c, tb);
146
147         wd_smp_unlock(&flags);
148
149         printk_safe_flush();
150         /*
151          * printk_safe_flush() seems to require another print
152          * before anything actually goes out to console.
153          */
154         if (sysctl_hardlockup_all_cpu_backtrace)
155                 trigger_allbutself_cpu_backtrace();
156
157         if (hardlockup_panic)
158                 nmi_panic(NULL, "Hard LOCKUP");
159
160         return;
161
162 out:
163         wd_smp_unlock(&flags);
164 }
165
166 static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
167 {
168         if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
169                 if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
170                         unsigned long flags;
171
172                         pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
173                         wd_smp_lock(&flags);
174                         cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
175                         wd_smp_unlock(&flags);
176                 }
177                 return;
178         }
179         cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
180         if (cpumask_empty(&wd_smp_cpus_pending)) {
181                 unsigned long flags;
182
183                 wd_smp_lock(&flags);
184                 if (cpumask_empty(&wd_smp_cpus_pending)) {
185                         wd_smp_last_reset_tb = tb;
186                         cpumask_andnot(&wd_smp_cpus_pending,
187                                         &wd_cpus_enabled,
188                                         &wd_smp_cpus_stuck);
189                 }
190                 wd_smp_unlock(&flags);
191         }
192 }
193
194 static void watchdog_timer_interrupt(int cpu)
195 {
196         u64 tb = get_tb();
197
198         per_cpu(wd_timer_tb, cpu) = tb;
199
200         wd_smp_clear_cpu_pending(cpu, tb);
201
202         if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
203                 watchdog_smp_panic(cpu, tb);
204 }
205
206 void soft_nmi_interrupt(struct pt_regs *regs)
207 {
208         unsigned long flags;
209         int cpu = raw_smp_processor_id();
210         u64 tb;
211
212         if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
213                 return;
214
215         nmi_enter();
216         tb = get_tb();
217         if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
218                 per_cpu(wd_timer_tb, cpu) = tb;
219
220                 wd_smp_lock(&flags);
221                 if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
222                         wd_smp_unlock(&flags);
223                         goto out;
224                 }
225                 set_cpu_stuck(cpu, tb);
226
227                 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
228                 print_modules();
229                 print_irqtrace_events(current);
230                 if (regs)
231                         show_regs(regs);
232                 else
233                         dump_stack();
234
235                 wd_smp_unlock(&flags);
236
237                 if (sysctl_hardlockup_all_cpu_backtrace)
238                         trigger_allbutself_cpu_backtrace();
239
240                 if (hardlockup_panic)
241                         nmi_panic(regs, "Hard LOCKUP");
242         }
243         if (wd_panic_timeout_tb < 0x7fffffff)
244                 mtspr(SPRN_DEC, wd_panic_timeout_tb);
245
246 out:
247         nmi_exit();
248 }
249
250 static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
251 {
252         t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
253         if (wd_timer_period_ms > 1000)
254                 t->expires = __round_jiffies_up(t->expires, cpu);
255         add_timer_on(t, cpu);
256 }
257
258 static void wd_timer_fn(unsigned long data)
259 {
260         struct timer_list *t = this_cpu_ptr(&wd_timer);
261         int cpu = smp_processor_id();
262
263         watchdog_timer_interrupt(cpu);
264
265         wd_timer_reset(cpu, t);
266 }
267
268 void arch_touch_nmi_watchdog(void)
269 {
270         unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
271         int cpu = smp_processor_id();
272
273         if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
274                 watchdog_timer_interrupt(cpu);
275 }
276 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
277
278 static void start_watchdog_timer_on(unsigned int cpu)
279 {
280         struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
281
282         per_cpu(wd_timer_tb, cpu) = get_tb();
283
284         setup_pinned_timer(t, wd_timer_fn, 0);
285         wd_timer_reset(cpu, t);
286 }
287
288 static void stop_watchdog_timer_on(unsigned int cpu)
289 {
290         struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
291
292         del_timer_sync(t);
293 }
294
295 static int start_wd_on_cpu(unsigned int cpu)
296 {
297         if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
298                 WARN_ON(1);
299                 return 0;
300         }
301
302         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
303                 return 0;
304
305         if (watchdog_suspended)
306                 return 0;
307
308         if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
309                 return 0;
310
311         cpumask_set_cpu(cpu, &wd_cpus_enabled);
312         if (cpumask_weight(&wd_cpus_enabled) == 1) {
313                 cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
314                 wd_smp_last_reset_tb = get_tb();
315         }
316         smp_wmb();
317         start_watchdog_timer_on(cpu);
318
319         return 0;
320 }
321
322 static int stop_wd_on_cpu(unsigned int cpu)
323 {
324         if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
325                 return 0; /* Can happen in CPU unplug case */
326
327         stop_watchdog_timer_on(cpu);
328
329         cpumask_clear_cpu(cpu, &wd_cpus_enabled);
330         wd_smp_clear_cpu_pending(cpu, get_tb());
331
332         return 0;
333 }
334
335 static void watchdog_calc_timeouts(void)
336 {
337         wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
338
339         /* Have the SMP detector trigger a bit later */
340         wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
341
342         /* 2/5 is the factor that the perf based detector uses */
343         wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
344 }
345
346 void watchdog_nmi_reconfigure(void)
347 {
348         int cpu;
349
350         watchdog_calc_timeouts();
351
352         for_each_cpu(cpu, &wd_cpus_enabled)
353                 stop_wd_on_cpu(cpu);
354
355         for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
356                 start_wd_on_cpu(cpu);
357 }
358
359 /*
360  * This runs after lockup_detector_init() which sets up watchdog_cpumask.
361  */
362 static int __init powerpc_watchdog_init(void)
363 {
364         int err;
365
366         watchdog_calc_timeouts();
367
368         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
369                                 start_wd_on_cpu, stop_wd_on_cpu);
370         if (err < 0)
371                 pr_warn("Watchdog could not be initialized");
372
373         return 0;
374 }
375 arch_initcall(powerpc_watchdog_init);
376
377 static void handle_backtrace_ipi(struct pt_regs *regs)
378 {
379         nmi_cpu_backtrace(regs);
380 }
381
382 static void raise_backtrace_ipi(cpumask_t *mask)
383 {
384         unsigned int cpu;
385
386         for_each_cpu(cpu, mask) {
387                 if (cpu == smp_processor_id())
388                         handle_backtrace_ipi(NULL);
389                 else
390                         smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
391         }
392 }
393
394 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
395 {
396         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
397 }