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_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 /* 138 * Try to trigger the stuck CPUs. 139 */ 140 for_each_cpu(c, &wd_smp_cpus_pending) { 141 if (c == cpu) 142 continue; 143 smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000); 144 } 145 smp_flush_nmi_ipi(1000000); 146 147 /* Take the stuck CPUs out of the watch group */ 148 set_cpumask_stuck(&wd_smp_cpus_pending, tb); 149 150 wd_smp_unlock(&flags); 151 152 printk_safe_flush(); 153 /* 154 * printk_safe_flush() seems to require another print 155 * before anything actually goes out to console. 156 */ 157 if (sysctl_hardlockup_all_cpu_backtrace) 158 trigger_allbutself_cpu_backtrace(); 159 160 if (hardlockup_panic) 161 nmi_panic(NULL, "Hard LOCKUP"); 162 163 return; 164 165 out: 166 wd_smp_unlock(&flags); 167 } 168 169 static void wd_smp_clear_cpu_pending(int cpu, u64 tb) 170 { 171 if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) { 172 if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) { 173 unsigned long flags; 174 175 pr_emerg("Watchdog CPU:%d became unstuck\n", cpu); 176 wd_smp_lock(&flags); 177 cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck); 178 wd_smp_unlock(&flags); 179 } 180 return; 181 } 182 cpumask_clear_cpu(cpu, &wd_smp_cpus_pending); 183 if (cpumask_empty(&wd_smp_cpus_pending)) { 184 unsigned long flags; 185 186 wd_smp_lock(&flags); 187 if (cpumask_empty(&wd_smp_cpus_pending)) { 188 wd_smp_last_reset_tb = tb; 189 cpumask_andnot(&wd_smp_cpus_pending, 190 &wd_cpus_enabled, 191 &wd_smp_cpus_stuck); 192 } 193 wd_smp_unlock(&flags); 194 } 195 } 196 197 static void watchdog_timer_interrupt(int cpu) 198 { 199 u64 tb = get_tb(); 200 201 per_cpu(wd_timer_tb, cpu) = tb; 202 203 wd_smp_clear_cpu_pending(cpu, tb); 204 205 if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb) 206 watchdog_smp_panic(cpu, tb); 207 } 208 209 void soft_nmi_interrupt(struct pt_regs *regs) 210 { 211 unsigned long flags; 212 int cpu = raw_smp_processor_id(); 213 u64 tb; 214 215 if (!cpumask_test_cpu(cpu, &wd_cpus_enabled)) 216 return; 217 218 nmi_enter(); 219 tb = get_tb(); 220 if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) { 221 per_cpu(wd_timer_tb, cpu) = tb; 222 223 wd_smp_lock(&flags); 224 if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) { 225 wd_smp_unlock(&flags); 226 goto out; 227 } 228 set_cpu_stuck(cpu, tb); 229 230 pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu); 231 print_modules(); 232 print_irqtrace_events(current); 233 if (regs) 234 show_regs(regs); 235 else 236 dump_stack(); 237 238 wd_smp_unlock(&flags); 239 240 if (sysctl_hardlockup_all_cpu_backtrace) 241 trigger_allbutself_cpu_backtrace(); 242 243 if (hardlockup_panic) 244 nmi_panic(regs, "Hard LOCKUP"); 245 } 246 if (wd_panic_timeout_tb < 0x7fffffff) 247 mtspr(SPRN_DEC, wd_panic_timeout_tb); 248 249 out: 250 nmi_exit(); 251 } 252 253 static void wd_timer_reset(unsigned int cpu, struct timer_list *t) 254 { 255 t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms); 256 if (wd_timer_period_ms > 1000) 257 t->expires = __round_jiffies_up(t->expires, cpu); 258 add_timer_on(t, cpu); 259 } 260 261 static void wd_timer_fn(unsigned long data) 262 { 263 struct timer_list *t = this_cpu_ptr(&wd_timer); 264 int cpu = smp_processor_id(); 265 266 watchdog_timer_interrupt(cpu); 267 268 wd_timer_reset(cpu, t); 269 } 270 271 void arch_touch_nmi_watchdog(void) 272 { 273 unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000; 274 int cpu = smp_processor_id(); 275 276 if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks) 277 watchdog_timer_interrupt(cpu); 278 } 279 EXPORT_SYMBOL(arch_touch_nmi_watchdog); 280 281 static void start_watchdog_timer_on(unsigned int cpu) 282 { 283 struct timer_list *t = per_cpu_ptr(&wd_timer, cpu); 284 285 per_cpu(wd_timer_tb, cpu) = get_tb(); 286 287 setup_pinned_timer(t, wd_timer_fn, 0); 288 wd_timer_reset(cpu, t); 289 } 290 291 static void stop_watchdog_timer_on(unsigned int cpu) 292 { 293 struct timer_list *t = per_cpu_ptr(&wd_timer, cpu); 294 295 del_timer_sync(t); 296 } 297 298 static int start_wd_on_cpu(unsigned int cpu) 299 { 300 unsigned long flags; 301 302 if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) { 303 WARN_ON(1); 304 return 0; 305 } 306 307 if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) 308 return 0; 309 310 if (watchdog_suspended) 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_reconfigure(void) 359 { 360 int cpu; 361 362 watchdog_calc_timeouts(); 363 364 for_each_cpu(cpu, &wd_cpus_enabled) 365 stop_wd_on_cpu(cpu); 366 367 for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) 368 start_wd_on_cpu(cpu); 369 } 370 371 /* 372 * This runs after lockup_detector_init() which sets up watchdog_cpumask. 373 */ 374 static int __init powerpc_watchdog_init(void) 375 { 376 int err; 377 378 watchdog_calc_timeouts(); 379 380 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online", 381 start_wd_on_cpu, stop_wd_on_cpu); 382 if (err < 0) 383 pr_warn("Watchdog could not be initialized"); 384 385 return 0; 386 } 387 arch_initcall(powerpc_watchdog_init); 388 389 static void handle_backtrace_ipi(struct pt_regs *regs) 390 { 391 nmi_cpu_backtrace(regs); 392 } 393 394 static void raise_backtrace_ipi(cpumask_t *mask) 395 { 396 unsigned int cpu; 397 398 for_each_cpu(cpu, mask) { 399 if (cpu == smp_processor_id()) 400 handle_backtrace_ipi(NULL); 401 else 402 smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000); 403 } 404 } 405 406 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) 407 { 408 nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); 409 } 410