b67f8b03a32d0f12ce29eeb4ac3be0a97384fe72
[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         local_irq_save(*flags);
75         while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock)))
76                 cpu_relax();
77 }
78
79 static inline void wd_smp_unlock(unsigned long *flags)
80 {
81         clear_bit_unlock(0, &__wd_smp_lock);
82         local_irq_restore(*flags);
83 }
84
85 static void wd_lockup_ipi(struct pt_regs *regs)
86 {
87         pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
88         print_modules();
89         print_irqtrace_events(current);
90         if (regs)
91                 show_regs(regs);
92         else
93                 dump_stack();
94
95         if (hardlockup_panic)
96                 nmi_panic(regs, "Hard LOCKUP");
97 }
98
99 static void set_cpu_stuck(int cpu, u64 tb)
100 {
101         cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
102         cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
103         if (cpumask_empty(&wd_smp_cpus_pending)) {
104                 wd_smp_last_reset_tb = tb;
105                 cpumask_andnot(&wd_smp_cpus_pending,
106                                 &wd_cpus_enabled,
107                                 &wd_smp_cpus_stuck);
108         }
109 }
110
111 static void watchdog_smp_panic(int cpu, u64 tb)
112 {
113         unsigned long flags;
114         int c;
115
116         wd_smp_lock(&flags);
117         /* Double check some things under lock */
118         if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
119                 goto out;
120         if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
121                 goto out;
122         if (cpumask_weight(&wd_smp_cpus_pending) == 0)
123                 goto out;
124
125         pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
126                         cpu, cpumask_pr_args(&wd_smp_cpus_pending));
127
128         /*
129          * Try to trigger the stuck CPUs.
130          */
131         for_each_cpu(c, &wd_smp_cpus_pending) {
132                 if (c == cpu)
133                         continue;
134                 smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
135         }
136         smp_flush_nmi_ipi(1000000);
137
138         /* Take the stuck CPU out of the watch group */
139         for_each_cpu(c, &wd_smp_cpus_pending)
140                 set_cpu_stuck(c, tb);
141
142 out:
143         wd_smp_unlock(&flags);
144
145         printk_safe_flush();
146         /*
147          * printk_safe_flush() seems to require another print
148          * before anything actually goes out to console.
149          */
150         if (sysctl_hardlockup_all_cpu_backtrace)
151                 trigger_allbutself_cpu_backtrace();
152
153         if (hardlockup_panic)
154                 nmi_panic(NULL, "Hard LOCKUP");
155 }
156
157 static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
158 {
159         if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
160                 if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
161                         unsigned long flags;
162
163                         pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
164                         wd_smp_lock(&flags);
165                         cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
166                         wd_smp_unlock(&flags);
167                 }
168                 return;
169         }
170         cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
171         if (cpumask_empty(&wd_smp_cpus_pending)) {
172                 unsigned long flags;
173
174                 wd_smp_lock(&flags);
175                 if (cpumask_empty(&wd_smp_cpus_pending)) {
176                         wd_smp_last_reset_tb = tb;
177                         cpumask_andnot(&wd_smp_cpus_pending,
178                                         &wd_cpus_enabled,
179                                         &wd_smp_cpus_stuck);
180                 }
181                 wd_smp_unlock(&flags);
182         }
183 }
184
185 static void watchdog_timer_interrupt(int cpu)
186 {
187         u64 tb = get_tb();
188
189         per_cpu(wd_timer_tb, cpu) = tb;
190
191         wd_smp_clear_cpu_pending(cpu, tb);
192
193         if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
194                 watchdog_smp_panic(cpu, tb);
195 }
196
197 void soft_nmi_interrupt(struct pt_regs *regs)
198 {
199         unsigned long flags;
200         int cpu = raw_smp_processor_id();
201         u64 tb;
202
203         if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
204                 return;
205
206         nmi_enter();
207         tb = get_tb();
208         if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
209                 per_cpu(wd_timer_tb, cpu) = tb;
210
211                 wd_smp_lock(&flags);
212                 if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
213                         wd_smp_unlock(&flags);
214                         goto out;
215                 }
216                 set_cpu_stuck(cpu, tb);
217
218                 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
219                 print_modules();
220                 print_irqtrace_events(current);
221                 if (regs)
222                         show_regs(regs);
223                 else
224                         dump_stack();
225
226                 wd_smp_unlock(&flags);
227
228                 if (sysctl_hardlockup_all_cpu_backtrace)
229                         trigger_allbutself_cpu_backtrace();
230
231                 if (hardlockup_panic)
232                         nmi_panic(regs, "Hard LOCKUP");
233         }
234         if (wd_panic_timeout_tb < 0x7fffffff)
235                 mtspr(SPRN_DEC, wd_panic_timeout_tb);
236
237 out:
238         nmi_exit();
239 }
240
241 static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
242 {
243         t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
244         if (wd_timer_period_ms > 1000)
245                 t->expires = __round_jiffies_up(t->expires, cpu);
246         add_timer_on(t, cpu);
247 }
248
249 static void wd_timer_fn(unsigned long data)
250 {
251         struct timer_list *t = this_cpu_ptr(&wd_timer);
252         int cpu = smp_processor_id();
253
254         watchdog_timer_interrupt(cpu);
255
256         wd_timer_reset(cpu, t);
257 }
258
259 void arch_touch_nmi_watchdog(void)
260 {
261         int cpu = smp_processor_id();
262
263         watchdog_timer_interrupt(cpu);
264 }
265 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
266
267 static void start_watchdog_timer_on(unsigned int cpu)
268 {
269         struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
270
271         per_cpu(wd_timer_tb, cpu) = get_tb();
272
273         setup_pinned_timer(t, wd_timer_fn, 0);
274         wd_timer_reset(cpu, t);
275 }
276
277 static void stop_watchdog_timer_on(unsigned int cpu)
278 {
279         struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
280
281         del_timer_sync(t);
282 }
283
284 static int start_wd_on_cpu(unsigned int cpu)
285 {
286         if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
287                 WARN_ON(1);
288                 return 0;
289         }
290
291         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
292                 return 0;
293
294         if (watchdog_suspended)
295                 return 0;
296
297         if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
298                 return 0;
299
300         cpumask_set_cpu(cpu, &wd_cpus_enabled);
301         if (cpumask_weight(&wd_cpus_enabled) == 1) {
302                 cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
303                 wd_smp_last_reset_tb = get_tb();
304         }
305         smp_wmb();
306         start_watchdog_timer_on(cpu);
307
308         return 0;
309 }
310
311 static int stop_wd_on_cpu(unsigned int cpu)
312 {
313         if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
314                 return 0; /* Can happen in CPU unplug case */
315
316         stop_watchdog_timer_on(cpu);
317
318         cpumask_clear_cpu(cpu, &wd_cpus_enabled);
319         wd_smp_clear_cpu_pending(cpu, get_tb());
320
321         return 0;
322 }
323
324 static void watchdog_calc_timeouts(void)
325 {
326         wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
327
328         /* Have the SMP detector trigger a bit later */
329         wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
330
331         /* 2/5 is the factor that the perf based detector uses */
332         wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
333 }
334
335 void watchdog_nmi_reconfigure(void)
336 {
337         int cpu;
338
339         watchdog_calc_timeouts();
340
341         for_each_cpu(cpu, &wd_cpus_enabled)
342                 stop_wd_on_cpu(cpu);
343
344         for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
345                 start_wd_on_cpu(cpu);
346 }
347
348 /*
349  * This runs after lockup_detector_init() which sets up watchdog_cpumask.
350  */
351 static int __init powerpc_watchdog_init(void)
352 {
353         int err;
354
355         watchdog_calc_timeouts();
356
357         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
358                                 start_wd_on_cpu, stop_wd_on_cpu);
359         if (err < 0)
360                 pr_warn("Watchdog could not be initialized");
361
362         return 0;
363 }
364 arch_initcall(powerpc_watchdog_init);
365
366 static void handle_backtrace_ipi(struct pt_regs *regs)
367 {
368         nmi_cpu_backtrace(regs);
369 }
370
371 static void raise_backtrace_ipi(cpumask_t *mask)
372 {
373         unsigned int cpu;
374
375         for_each_cpu(cpu, mask) {
376                 if (cpu == smp_processor_id())
377                         handle_backtrace_ipi(NULL);
378                 else
379                         smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
380         }
381 }
382
383 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
384 {
385         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
386 }