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 } 418