arch/powerpc/kernel/watchdog.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Watchdog support on powerpc systems.
   4  *
   5  * Copyright 2017, IBM Corporation.
   6  *
   7  * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
   8  */
   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>
  25
  26 #include <asm/paca.h>
  27
  28 /*
  29  * The watchdog has a simple timer that runs on each CPU, once per timer
  30  * period. This is the heartbeat.
  31  *
  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.
  35  *
  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.
  38  */
  39
  40 static cpumask_t wd_cpus_enabled __read_mostly;
  41
  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 */
  44
  45 static u64 wd_timer_period_ms __read_mostly;  /* interval between heartbeat */
  46
  47 static DEFINE_PER_CPU(struct timer_list, wd_timer);
  48 static DEFINE_PER_CPU(u64, wd_timer_tb);
  49
  50 /*
  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.
  54  *
  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.
  59  *
  60  * This will work best with NMI IPIs for crash code so the stuck CPUs
  61  * can be pulled out to get their backtraces.
  62  */
  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;
  67
  68 static inline void wd_smp_lock(unsigned long *flags)
  69 {
  70         /*
  71          * Avoid locking layers if possible.
  72          * This may be called from low level interrupt handlers at some
  73          * point in future.
  74          */
  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);
  81                 hard_irq_disable();
  82         }
  83 }
  84
  85 static inline void wd_smp_unlock(unsigned long *flags)
  86 {
  87         clear_bit_unlock(0, &__wd_smp_lock);
  88         raw_local_irq_restore(*flags);
  89 }
  90
  91 static void wd_lockup_ipi(struct pt_regs *regs)
  92 {
  93         pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
  94         print_modules();
  95         print_irqtrace_events(current);
  96         if (regs)
  97                 show_regs(regs);
  98         else
  99                 dump_stack();
 100
 101         /* Do not panic from here because that can recurse into NMI IPI layer */
 102 }
 103
 104 static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb)
 105 {
 106         cpumask_or(&wd_smp_cpus_stuck, &wd_smp_cpus_stuck, cpumask);
 107         cpumask_andnot(&wd_smp_cpus_pending, &wd_smp_cpus_pending, cpumask);
 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 static void set_cpu_stuck(int cpu, u64 tb)
 116 {
 117         set_cpumask_stuck(cpumask_of(cpu), tb);
 118 }
 119
 120 static void watchdog_smp_panic(int cpu, u64 tb)
 121 {
 122         unsigned long flags;
 123         int c;
 124
 125         wd_smp_lock(&flags);
 126         /* Double check some things under lock */
 127         if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
 128                 goto out;
 129         if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
 130                 goto out;
 131         if (cpumask_weight(&wd_smp_cpus_pending) == 0)
 132                 goto out;
 133
 134         pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
 135                         cpu, cpumask_pr_args(&wd_smp_cpus_pending));
 136
 137         if (!sysctl_hardlockup_all_cpu_backtrace) {
 138                 /*
 139                  * Try to trigger the stuck CPUs, unless we are going to
 140                  * get a backtrace on all of them anyway.
 141                  */
 142                 for_each_cpu(c, &wd_smp_cpus_pending) {
 143                         if (c == cpu)
 144                                 continue;
 145                         smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
 146                 }
 147                 smp_flush_nmi_ipi(1000000);
 148         }
 149
 150         /* Take the stuck CPUs out of the watch group */
 151         set_cpumask_stuck(&wd_smp_cpus_pending, tb);
 152
 153         wd_smp_unlock(&flags);
 154
 155         printk_safe_flush();
 156         /*
 157          * printk_safe_flush() seems to require another print
 158          * before anything actually goes out to console.
 159          */
 160         if (sysctl_hardlockup_all_cpu_backtrace)
 161                 trigger_allbutself_cpu_backtrace();
 162
 163         if (hardlockup_panic)
 164                 nmi_panic(NULL, "Hard LOCKUP");
 165
 166         return;
 167
 168 out:
 169         wd_smp_unlock(&flags);
 170 }
 171
 172 static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
 173 {
 174         if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
 175                 if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
 176                         unsigned long flags;
 177
 178                         pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
 179                         wd_smp_lock(&flags);
 180                         cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
 181                         wd_smp_unlock(&flags);
 182                 }
 183                 return;
 184         }
 185         cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
 186         if (cpumask_empty(&wd_smp_cpus_pending)) {
 187                 unsigned long flags;
 188
 189                 wd_smp_lock(&flags);
 190                 if (cpumask_empty(&wd_smp_cpus_pending)) {
 191                         wd_smp_last_reset_tb = tb;
 192                         cpumask_andnot(&wd_smp_cpus_pending,
 193                                         &wd_cpus_enabled,
 194                                         &wd_smp_cpus_stuck);
 195                 }
 196                 wd_smp_unlock(&flags);
 197         }
 198 }
 199
 200 static void watchdog_timer_interrupt(int cpu)
 201 {
 202         u64 tb = get_tb();
 203
 204         per_cpu(wd_timer_tb, cpu) = tb;
 205
 206         wd_smp_clear_cpu_pending(cpu, tb);
 207
 208         if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
 209                 watchdog_smp_panic(cpu, tb);
 210 }
 211
 212 void soft_nmi_interrupt(struct pt_regs *regs)
 213 {
 214         unsigned long flags;
 215         int cpu = raw_smp_processor_id();
 216         u64 tb;
 217
 218         if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
 219                 return;
 220
 221         nmi_enter();
 222
 223         __this_cpu_inc(irq_stat.soft_nmi_irqs);
 224
 225         tb = get_tb();
 226         if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
 227                 per_cpu(wd_timer_tb, cpu) = tb;
 228
 229                 wd_smp_lock(&flags);
 230                 if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
 231                         wd_smp_unlock(&flags);
 232                         goto out;
 233                 }
 234                 set_cpu_stuck(cpu, tb);
 235
 236                 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
 237                 print_modules();
 238                 print_irqtrace_events(current);
 239                 if (regs)
 240                         show_regs(regs);
 241                 else
 242                         dump_stack();
 243
 244                 wd_smp_unlock(&flags);
 245
 246                 if (sysctl_hardlockup_all_cpu_backtrace)
 247                         trigger_allbutself_cpu_backtrace();
 248
 249                 if (hardlockup_panic)
 250                         nmi_panic(regs, "Hard LOCKUP");
 251         }
 252         if (wd_panic_timeout_tb < 0x7fffffff)
 253                 mtspr(SPRN_DEC, wd_panic_timeout_tb);
 254
 255 out:
 256         nmi_exit();
 257 }
 258
 259 static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
 260 {
 261         t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
 262         if (wd_timer_period_ms > 1000)
 263                 t->expires = __round_jiffies_up(t->expires, cpu);
 264         add_timer_on(t, cpu);
 265 }
 266
 267 static void wd_timer_fn(struct timer_list *t)
 268 {
 269         int cpu = smp_processor_id();
 270
 271         watchdog_timer_interrupt(cpu);
 272
 273         wd_timer_reset(cpu, t);
 274 }
 275
 276 void arch_touch_nmi_watchdog(void)
 277 {
 278         unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
 279         int cpu = smp_processor_id();
 280         u64 tb = get_tb();
 281
 282         if (tb - per_cpu(wd_timer_tb, cpu) >= ticks) {
 283                 per_cpu(wd_timer_tb, cpu) = tb;
 284                 wd_smp_clear_cpu_pending(cpu, tb);
 285         }
 286 }
 287 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 288
 289 static void start_watchdog_timer_on(unsigned int cpu)
 290 {
 291         struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
 292
 293         per_cpu(wd_timer_tb, cpu) = get_tb();
 294
 295         timer_setup(t, wd_timer_fn, TIMER_PINNED);
 296         wd_timer_reset(cpu, t);
 297 }
 298
 299 static void stop_watchdog_timer_on(unsigned int cpu)
 300 {
 301         struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
 302
 303         del_timer_sync(t);
 304 }
 305
 306 static int start_wd_on_cpu(unsigned int cpu)
 307 {
 308         unsigned long flags;
 309
 310         if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
 311                 WARN_ON(1);
 312                 return 0;
 313         }
 314
 315         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
 316                 return 0;
 317
 318         if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
 319                 return 0;
 320
 321         wd_smp_lock(&flags);
 322         cpumask_set_cpu(cpu, &wd_cpus_enabled);
 323         if (cpumask_weight(&wd_cpus_enabled) == 1) {
 324                 cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
 325                 wd_smp_last_reset_tb = get_tb();
 326         }
 327         wd_smp_unlock(&flags);
 328
 329         start_watchdog_timer_on(cpu);
 330
 331         return 0;
 332 }
 333
 334 static int stop_wd_on_cpu(unsigned int cpu)
 335 {
 336         unsigned long flags;
 337
 338         if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
 339                 return 0; /* Can happen in CPU unplug case */
 340
 341         stop_watchdog_timer_on(cpu);
 342
 343         wd_smp_lock(&flags);
 344         cpumask_clear_cpu(cpu, &wd_cpus_enabled);
 345         wd_smp_unlock(&flags);
 346
 347         wd_smp_clear_cpu_pending(cpu, get_tb());
 348
 349         return 0;
 350 }
 351
 352 static void watchdog_calc_timeouts(void)
 353 {
 354         wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
 355
 356         /* Have the SMP detector trigger a bit later */
 357         wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
 358
 359         /* 2/5 is the factor that the perf based detector uses */
 360         wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
 361 }
 362
 363 void watchdog_nmi_stop(void)
 364 {
 365         int cpu;
 366
 367         for_each_cpu(cpu, &wd_cpus_enabled)
 368                 stop_wd_on_cpu(cpu);
 369 }
 370
 371 void watchdog_nmi_start(void)
 372 {
 373         int cpu;
 374
 375         watchdog_calc_timeouts();
 376         for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
 377                 start_wd_on_cpu(cpu);
 378 }
 379
 380 /*
 381  * Invoked from core watchdog init.
 382  */
 383 int __init watchdog_nmi_probe(void)
 384 {
 385         int err;
 386
 387         err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
 388                                         "powerpc/watchdog:online",
 389                                         start_wd_on_cpu, stop_wd_on_cpu);
 390         if (err < 0) {
 391                 pr_warn("Watchdog could not be initialized");
 392                 return err;
 393         }
 394         return 0;
 395 }
 396
 397 static void handle_backtrace_ipi(struct pt_regs *regs)
 398 {
 399         nmi_cpu_backtrace(regs);
 400 }
 401
 402 static void raise_backtrace_ipi(cpumask_t *mask)
 403 {
 404         unsigned int cpu;
 405
 406         for_each_cpu(cpu, mask) {
 407                 if (cpu == smp_processor_id())
 408                         handle_backtrace_ipi(NULL);
 409                 else
 410                         smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
 411         }
 412 }
 413
 414 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 415 {
 416         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
 417 }