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 if (hardlockup_panic) 102 nmi_panic(regs, "Hard LOCKUP"); 103 } 104 105 static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb) 106 { 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, 112 &wd_cpus_enabled, 113 &wd_smp_cpus_stuck); 114 } 115 } 116 static void set_cpu_stuck(int cpu, u64 tb) 117 { 118 set_cpumask_stuck(cpumask_of(cpu), tb); 119 } 120 121 static void watchdog_smp_panic(int cpu, u64 tb) 122 { 123 unsigned long flags; 124 int c; 125 126 wd_smp_lock(&flags); 127 /* Double check some things under lock */ 128 if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb) 129 goto out; 130 if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) 131 goto out; 132 if (cpumask_weight(&wd_smp_cpus_pending) == 0) 133 goto out; 134 135 pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n", 136 cpu, cpumask_pr_args(&wd_smp_cpus_pending)); 137 138 /* 139 * Try to trigger the stuck CPUs. 140 */ 141 for_each_cpu(c, &wd_smp_cpus_pending) { 142 if (c == cpu) 143 continue; 144 smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000); 145 } 146 smp_flush_nmi_ipi(1000000); 147 148 /* Take the stuck CPUs out of the watch group */ 149 set_cpumask_stuck(&wd_smp_cpus_pending, tb); 150 151 wd_smp_unlock(&flags); 152 153 printk_safe_flush(); 154 /* 155 * printk_safe_flush() seems to require another print 156 * before anything actually goes out to console. 157 */ 158 if (sysctl_hardlockup_all_cpu_backtrace) 159 trigger_allbutself_cpu_backtrace(); 160 161 if (hardlockup_panic) 162 nmi_panic(NULL, "Hard LOCKUP"); 163 164 return; 165 166 out: 167 wd_smp_unlock(&flags); 168 } 169 170 static void wd_smp_clear_cpu_pending(int cpu, u64 tb) 171 { 172 if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) { 173 if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) { 174 unsigned long flags; 175 176 pr_emerg("Watchdog CPU:%d became unstuck\n", cpu); 177 wd_smp_lock(&flags); 178 cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck); 179 wd_smp_unlock(&flags); 180 } 181 return; 182 } 183 cpumask_clear_cpu(cpu, &wd_smp_cpus_pending); 184 if (cpumask_empty(&wd_smp_cpus_pending)) { 185 unsigned long flags; 186 187 wd_smp_lock(&flags); 188 if (cpumask_empty(&wd_smp_cpus_pending)) { 189 wd_smp_last_reset_tb = tb; 190 cpumask_andnot(&wd_smp_cpus_pending, 191 &wd_cpus_enabled, 192 &wd_smp_cpus_stuck); 193 } 194 wd_smp_unlock(&flags); 195 } 196 } 197 198 static void watchdog_timer_interrupt(int cpu) 199 { 200 u64 tb = get_tb(); 201 202 per_cpu(wd_timer_tb, cpu) = tb; 203 204 wd_smp_clear_cpu_pending(cpu, tb); 205 206 if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb) 207 watchdog_smp_panic(cpu, tb); 208 } 209 210 void soft_nmi_interrupt(struct pt_regs *regs) 211 { 212 unsigned long flags; 213 int cpu = raw_smp_processor_id(); 214 u64 tb; 215 216 if (!cpumask_test_cpu(cpu, &wd_cpus_enabled)) 217 return; 218 219 nmi_enter(); 220 221 __this_cpu_inc(irq_stat.soft_nmi_irqs); 222 223 tb = get_tb(); 224 if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) { 225 per_cpu(wd_timer_tb, cpu) = tb; 226 227 wd_smp_lock(&flags); 228 if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) { 229 wd_smp_unlock(&flags); 230 goto out; 231 } 232 set_cpu_stuck(cpu, tb); 233 234 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu); 235 print_modules(); 236 print_irqtrace_events(current); 237 if (regs) 238 show_regs(regs); 239 else 240 dump_stack(); 241 242 wd_smp_unlock(&flags); 243 244 if (sysctl_hardlockup_all_cpu_backtrace) 245 trigger_allbutself_cpu_backtrace(); 246 247 if (hardlockup_panic) 248 nmi_panic(regs, "Hard LOCKUP"); 249 } 250 if (wd_panic_timeout_tb < 0x7fffffff) 251 mtspr(SPRN_DEC, wd_panic_timeout_tb); 252 253 out: 254 nmi_exit(); 255 } 256 257 static void wd_timer_reset(unsigned int cpu, struct timer_list *t) 258 { 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); 263 } 264 265 static void wd_timer_fn(struct timer_list *t) 266 { 267 int cpu = smp_processor_id(); 268 269 watchdog_timer_interrupt(cpu); 270 271 wd_timer_reset(cpu, t); 272 } 273 274 void arch_touch_nmi_watchdog(void) 275 { 276 unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000; 277 int cpu = smp_processor_id(); 278 279 if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks) 280 watchdog_timer_interrupt(cpu); 281 } 282 EXPORT_SYMBOL(arch_touch_nmi_watchdog); 283 284 static void start_watchdog_timer_on(unsigned int cpu) 285 { 286 struct timer_list *t = per_cpu_ptr(&wd_timer, cpu); 287 288 per_cpu(wd_timer_tb, cpu) = get_tb(); 289 290 timer_setup(t, wd_timer_fn, TIMER_PINNED); 291 wd_timer_reset(cpu, t); 292 } 293 294 static void stop_watchdog_timer_on(unsigned int cpu) 295 { 296 struct timer_list *t = per_cpu_ptr(&wd_timer, cpu); 297 298 del_timer_sync(t); 299 } 300 301 static int start_wd_on_cpu(unsigned int cpu) 302 { 303 unsigned long flags; 304 305 if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) { 306 WARN_ON(1); 307 return 0; 308 } 309 310 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) 311 return 0; 312 313 if (!cpumask_test_cpu(cpu, &watchdog_cpumask)) 314 return 0; 315 316 wd_smp_lock(&flags); 317 cpumask_set_cpu(cpu, &wd_cpus_enabled); 318 if (cpumask_weight(&wd_cpus_enabled) == 1) { 319 cpumask_set_cpu(cpu, &wd_smp_cpus_pending); 320 wd_smp_last_reset_tb = get_tb(); 321 } 322 wd_smp_unlock(&flags); 323 324 start_watchdog_timer_on(cpu); 325 326 return 0; 327 } 328 329 static int stop_wd_on_cpu(unsigned int cpu) 330 { 331 unsigned long flags; 332 333 if (!cpumask_test_cpu(cpu, &wd_cpus_enabled)) 334 return 0; /* Can happen in CPU unplug case */ 335 336 stop_watchdog_timer_on(cpu); 337 338 wd_smp_lock(&flags); 339 cpumask_clear_cpu(cpu, &wd_cpus_enabled); 340 wd_smp_unlock(&flags); 341 342 wd_smp_clear_cpu_pending(cpu, get_tb()); 343 344 return 0; 345 } 346 347 static void watchdog_calc_timeouts(void) 348 { 349 wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq; 350 351 /* Have the SMP detector trigger a bit later */ 352 wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2; 353 354 /* 2/5 is the factor that the perf based detector uses */ 355 wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5; 356 } 357 358 void watchdog_nmi_stop(void) 359 { 360 int cpu; 361 362 for_each_cpu(cpu, &wd_cpus_enabled) 363 stop_wd_on_cpu(cpu); 364 } 365 366 void watchdog_nmi_start(void) 367 { 368 int cpu; 369 370 watchdog_calc_timeouts(); 371 for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) 372 start_wd_on_cpu(cpu); 373 } 374 375 /* 376 * Invoked from core watchdog init. 377 */ 378 int __init watchdog_nmi_probe(void) 379 { 380 int err; 381 382 err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, 383 "powerpc/watchdog:online", 384 start_wd_on_cpu, stop_wd_on_cpu); 385 if (err < 0) { 386 pr_warn("Watchdog could not be initialized"); 387 return err; 388 } 389 return 0; 390 } 391 392 static void handle_backtrace_ipi(struct pt_regs *regs) 393 { 394 nmi_cpu_backtrace(regs); 395 } 396 397 static void raise_backtrace_ipi(cpumask_t *mask) 398 { 399 unsigned int cpu; 400 401 for_each_cpu(cpu, mask) { 402 if (cpu == smp_processor_id()) 403 handle_backtrace_ipi(NULL); 404 else 405 smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000); 406 } 407 } 408 409 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) 410 { 411 nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); 412 } 413