arch/i386/kernel/nmi.c

   1 /*
   2  *  linux/arch/i386/nmi.c
   3  *
   4  *  NMI watchdog support on APIC systems
   5  *
   6  *  Started by Ingo Molnar <mingo@redhat.com>
   7  *
   8  *  Fixes:
   9  *  Mikael Pettersson   : AMD K7 support for local APIC NMI watchdog.
  10  *  Mikael Pettersson   : Power Management for local APIC NMI watchdog.
  11  *  Mikael Pettersson   : Pentium 4 support for local APIC NMI watchdog.
  12  *  Pavel Machek and
  13  *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
  14  */
  15
  16 #include <linux/delay.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/module.h>
  19 #include <linux/nmi.h>
  20 #include <linux/sysdev.h>
  21 #include <linux/sysctl.h>
  22 #include <linux/percpu.h>
  23 #include <linux/kprobes.h>
  24 #include <linux/cpumask.h>
  25 #include <linux/kernel_stat.h>
  26 #include <linux/kdebug.h>
  27
  28 #include <asm/smp.h>
  29 #include <asm/nmi.h>
  30
  31 #include "mach_traps.h"
  32
  33 int unknown_nmi_panic;
  34 int nmi_watchdog_enabled;
  35
  36 static cpumask_t backtrace_mask = CPU_MASK_NONE;
  37
  38 /* nmi_active:
  39  * >0: the lapic NMI watchdog is active, but can be disabled
  40  * <0: the lapic NMI watchdog has not been set up, and cannot
  41  *     be enabled
  42  *  0: the lapic NMI watchdog is disabled, but can be enabled
  43  */
  44 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
  45
  46 unsigned int nmi_watchdog = NMI_DEFAULT;
  47 static unsigned int nmi_hz = HZ;
  48
  49 static DEFINE_PER_CPU(short, wd_enabled);
  50
  51 /* local prototypes */
  52 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu);
  53
  54 static int endflag __initdata = 0;
  55
  56 #ifdef CONFIG_SMP
  57 /* The performance counters used by NMI_LOCAL_APIC don't trigger when
  58  * the CPU is idle. To make sure the NMI watchdog really ticks on all
  59  * CPUs during the test make them busy.
  60  */
  61 static __init void nmi_cpu_busy(void *data)
  62 {
  63         local_irq_enable_in_hardirq();
  64         /* Intentionally don't use cpu_relax here. This is
  65            to make sure that the performance counter really ticks,
  66            even if there is a simulator or similar that catches the
  67            pause instruction. On a real HT machine this is fine because
  68            all other CPUs are busy with "useless" delay loops and don't
  69            care if they get somewhat less cycles. */
  70         while (endflag == 0)
  71                 mb();
  72 }
  73 #endif
  74
  75 static int __init check_nmi_watchdog(void)
  76 {
  77         unsigned int *prev_nmi_count;
  78         int cpu;
  79
  80         if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
  81                 return 0;
  82
  83         if (!atomic_read(&nmi_active))
  84                 return 0;
  85
  86         prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
  87         if (!prev_nmi_count)
  88                 return -1;
  89
  90         printk(KERN_INFO "Testing NMI watchdog ... ");
  91
  92         if (nmi_watchdog == NMI_LOCAL_APIC)
  93                 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
  94
  95         for_each_possible_cpu(cpu)
  96                 prev_nmi_count[cpu] = per_cpu(irq_stat, cpu).__nmi_count;
  97         local_irq_enable();
  98         mdelay((20*1000)/nmi_hz); // wait 20 ticks
  99
 100         for_each_possible_cpu(cpu) {
 101 #ifdef CONFIG_SMP
 102                 /* Check cpu_callin_map here because that is set
 103                    after the timer is started. */
 104                 if (!cpu_isset(cpu, cpu_callin_map))
 105                         continue;
 106 #endif
 107                 if (!per_cpu(wd_enabled, cpu))
 108                         continue;
 109                 if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
 110                         printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
 111                                 cpu,
 112                                 prev_nmi_count[cpu],
 113                                 nmi_count(cpu));
 114                         per_cpu(wd_enabled, cpu) = 0;
 115                         atomic_dec(&nmi_active);
 116                 }
 117         }
 118         if (!atomic_read(&nmi_active)) {
 119                 kfree(prev_nmi_count);
 120                 atomic_set(&nmi_active, -1);
 121                 return -1;
 122         }
 123         endflag = 1;
 124         printk("OK.\n");
 125
 126         /* now that we know it works we can reduce NMI frequency to
 127            something more reasonable; makes a difference in some configs */
 128         if (nmi_watchdog == NMI_LOCAL_APIC)
 129                 nmi_hz = lapic_adjust_nmi_hz(1);
 130
 131         kfree(prev_nmi_count);
 132         return 0;
 133 }
 134 /* This needs to happen later in boot so counters are working */
 135 late_initcall(check_nmi_watchdog);
 136
 137 static int __init setup_nmi_watchdog(char *str)
 138 {
 139         int nmi;
 140
 141         get_option(&str, &nmi);
 142
 143         if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
 144                 return 0;
 145
 146         nmi_watchdog = nmi;
 147         return 1;
 148 }
 149
 150 __setup("nmi_watchdog=", setup_nmi_watchdog);
 151
 152
 153 /* Suspend/resume support */
 154
 155 #ifdef CONFIG_PM
 156
 157 static int nmi_pm_active; /* nmi_active before suspend */
 158
 159 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 160 {
 161         /* only CPU0 goes here, other CPUs should be offline */
 162         nmi_pm_active = atomic_read(&nmi_active);
 163         stop_apic_nmi_watchdog(NULL);
 164         BUG_ON(atomic_read(&nmi_active) != 0);
 165         return 0;
 166 }
 167
 168 static int lapic_nmi_resume(struct sys_device *dev)
 169 {
 170         /* only CPU0 goes here, other CPUs should be offline */
 171         if (nmi_pm_active > 0) {
 172                 setup_apic_nmi_watchdog(NULL);
 173                 touch_nmi_watchdog();
 174         }
 175         return 0;
 176 }
 177
 178
 179 static struct sysdev_class nmi_sysclass = {
 180         set_kset_name("lapic_nmi"),
 181         .resume         = lapic_nmi_resume,
 182         .suspend        = lapic_nmi_suspend,
 183 };
 184
 185 static struct sys_device device_lapic_nmi = {
 186         .id     = 0,
 187         .cls    = &nmi_sysclass,
 188 };
 189
 190 static int __init init_lapic_nmi_sysfs(void)
 191 {
 192         int error;
 193
 194         /* should really be a BUG_ON but b/c this is an
 195          * init call, it just doesn't work.  -dcz
 196          */
 197         if (nmi_watchdog != NMI_LOCAL_APIC)
 198                 return 0;
 199
 200         if (atomic_read(&nmi_active) < 0)
 201                 return 0;
 202
 203         error = sysdev_class_register(&nmi_sysclass);
 204         if (!error)
 205                 error = sysdev_register(&device_lapic_nmi);
 206         return error;
 207 }
 208 /* must come after the local APIC's device_initcall() */
 209 late_initcall(init_lapic_nmi_sysfs);
 210
 211 #endif  /* CONFIG_PM */
 212
 213 static void __acpi_nmi_enable(void *__unused)
 214 {
 215         apic_write_around(APIC_LVT0, APIC_DM_NMI);
 216 }
 217
 218 /*
 219  * Enable timer based NMIs on all CPUs:
 220  */
 221 void acpi_nmi_enable(void)
 222 {
 223         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 224                 on_each_cpu(__acpi_nmi_enable, NULL, 0, 1);
 225 }
 226
 227 static void __acpi_nmi_disable(void *__unused)
 228 {
 229         apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
 230 }
 231
 232 /*
 233  * Disable timer based NMIs on all CPUs:
 234  */
 235 void acpi_nmi_disable(void)
 236 {
 237         if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
 238                 on_each_cpu(__acpi_nmi_disable, NULL, 0, 1);
 239 }
 240
 241 void setup_apic_nmi_watchdog (void *unused)
 242 {
 243         if (__get_cpu_var(wd_enabled))
 244                 return;
 245
 246         /* cheap hack to support suspend/resume */
 247         /* if cpu0 is not active neither should the other cpus */
 248         if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
 249                 return;
 250
 251         switch (nmi_watchdog) {
 252         case NMI_LOCAL_APIC:
 253                 __get_cpu_var(wd_enabled) = 1; /* enable it before to avoid race with handler */
 254                 if (lapic_watchdog_init(nmi_hz) < 0) {
 255                         __get_cpu_var(wd_enabled) = 0;
 256                         return;
 257                 }
 258                 /* FALL THROUGH */
 259         case NMI_IO_APIC:
 260                 __get_cpu_var(wd_enabled) = 1;
 261                 atomic_inc(&nmi_active);
 262         }
 263 }
 264
 265 void stop_apic_nmi_watchdog(void *unused)
 266 {
 267         /* only support LOCAL and IO APICs for now */
 268         if ((nmi_watchdog != NMI_LOCAL_APIC) &&
 269             (nmi_watchdog != NMI_IO_APIC))
 270                 return;
 271         if (__get_cpu_var(wd_enabled) == 0)
 272                 return;
 273         if (nmi_watchdog == NMI_LOCAL_APIC)
 274                 lapic_watchdog_stop();
 275         __get_cpu_var(wd_enabled) = 0;
 276         atomic_dec(&nmi_active);
 277 }
 278
 279 /*
 280  * the best way to detect whether a CPU has a 'hard lockup' problem
 281  * is to check it's local APIC timer IRQ counts. If they are not
 282  * changing then that CPU has some problem.
 283  *
 284  * as these watchdog NMI IRQs are generated on every CPU, we only
 285  * have to check the current processor.
 286  *
 287  * since NMIs don't listen to _any_ locks, we have to be extremely
 288  * careful not to rely on unsafe variables. The printk might lock
 289  * up though, so we have to break up any console locks first ...
 290  * [when there will be more tty-related locks, break them up
 291  *  here too!]
 292  */
 293
 294 static unsigned int
 295         last_irq_sums [NR_CPUS],
 296         alert_counter [NR_CPUS];
 297
 298 void touch_nmi_watchdog (void)
 299 {
 300         if (nmi_watchdog > 0) {
 301                 unsigned cpu;
 302
 303                 /*
 304                  * Just reset the alert counters, (other CPUs might be
 305                  * spinning on locks we hold):
 306                  */
 307                 for_each_present_cpu (cpu)
 308                         alert_counter[cpu] = 0;
 309         }
 310
 311         /*
 312          * Tickle the softlockup detector too:
 313          */
 314         touch_softlockup_watchdog();
 315 }
 316 EXPORT_SYMBOL(touch_nmi_watchdog);
 317
 318 extern void die_nmi(struct pt_regs *, const char *msg);
 319
 320 __kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
 321 {
 322
 323         /*
 324          * Since current_thread_info()-> is always on the stack, and we
 325          * always switch the stack NMI-atomically, it's safe to use
 326          * smp_processor_id().
 327          */
 328         unsigned int sum;
 329         int touched = 0;
 330         int cpu = smp_processor_id();
 331         int rc=0;
 332
 333         /* check for other users first */
 334         if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
 335                         == NOTIFY_STOP) {
 336                 rc = 1;
 337                 touched = 1;
 338         }
 339
 340         if (cpu_isset(cpu, backtrace_mask)) {
 341                 static DEFINE_SPINLOCK(lock);   /* Serialise the printks */
 342
 343                 spin_lock(&lock);
 344                 printk("NMI backtrace for cpu %d\n", cpu);
 345                 dump_stack();
 346                 spin_unlock(&lock);
 347                 cpu_clear(cpu, backtrace_mask);
 348         }
 349
 350         /*
 351          * Take the local apic timer and PIT/HPET into account. We don't
 352          * know which one is active, when we have highres/dyntick on
 353          */
 354         sum = per_cpu(irq_stat, cpu).apic_timer_irqs + kstat_irqs(0);
 355
 356         /* if the none of the timers isn't firing, this cpu isn't doing much */
 357         if (!touched && last_irq_sums[cpu] == sum) {
 358                 /*
 359                  * Ayiee, looks like this CPU is stuck ...
 360                  * wait a few IRQs (5 seconds) before doing the oops ...
 361                  */
 362                 alert_counter[cpu]++;
 363                 if (alert_counter[cpu] == 5*nmi_hz)
 364                         /*
 365                          * die_nmi will return ONLY if NOTIFY_STOP happens..
 366                          */
 367                         die_nmi(regs, "BUG: NMI Watchdog detected LOCKUP");
 368         } else {
 369                 last_irq_sums[cpu] = sum;
 370                 alert_counter[cpu] = 0;
 371         }
 372         /* see if the nmi watchdog went off */
 373         if (!__get_cpu_var(wd_enabled))
 374                 return rc;
 375         switch (nmi_watchdog) {
 376         case NMI_LOCAL_APIC:
 377                 rc |= lapic_wd_event(nmi_hz);
 378                 break;
 379         case NMI_IO_APIC:
 380                 /* don't know how to accurately check for this.
 381                  * just assume it was a watchdog timer interrupt
 382                  * This matches the old behaviour.
 383                  */
 384                 rc = 1;
 385                 break;
 386         }
 387         return rc;
 388 }
 389
 390 int do_nmi_callback(struct pt_regs * regs, int cpu)
 391 {
 392 #ifdef CONFIG_SYSCTL
 393         if (unknown_nmi_panic)
 394                 return unknown_nmi_panic_callback(regs, cpu);
 395 #endif
 396         return 0;
 397 }
 398
 399 #ifdef CONFIG_SYSCTL
 400
 401 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 402 {
 403         unsigned char reason = get_nmi_reason();
 404         char buf[64];
 405
 406         sprintf(buf, "NMI received for unknown reason %02x\n", reason);
 407         die_nmi(regs, buf);
 408         return 0;
 409 }
 410
 411 /*
 412  * proc handler for /proc/sys/kernel/nmi
 413  */
 414 int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
 415                         void __user *buffer, size_t *length, loff_t *ppos)
 416 {
 417         int old_state;
 418
 419         nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
 420         old_state = nmi_watchdog_enabled;
 421         proc_dointvec(table, write, file, buffer, length, ppos);
 422         if (!!old_state == !!nmi_watchdog_enabled)
 423                 return 0;
 424
 425         if (atomic_read(&nmi_active) < 0) {
 426                 printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
 427                 return -EIO;
 428         }
 429
 430         if (nmi_watchdog == NMI_DEFAULT) {
 431                 if (lapic_watchdog_ok())
 432                         nmi_watchdog = NMI_LOCAL_APIC;
 433                 else
 434                         nmi_watchdog = NMI_IO_APIC;
 435         }
 436
 437         if (nmi_watchdog == NMI_LOCAL_APIC) {
 438                 if (nmi_watchdog_enabled)
 439                         enable_lapic_nmi_watchdog();
 440                 else
 441                         disable_lapic_nmi_watchdog();
 442         } else {
 443                 printk( KERN_WARNING
 444                         "NMI watchdog doesn't know what hardware to touch\n");
 445                 return -EIO;
 446         }
 447         return 0;
 448 }
 449
 450 #endif
 451
 452 void __trigger_all_cpu_backtrace(void)
 453 {
 454         int i;
 455
 456         backtrace_mask = cpu_online_map;
 457         /* Wait for up to 10 seconds for all CPUs to do the backtrace */
 458         for (i = 0; i < 10 * 1000; i++) {
 459                 if (cpus_empty(backtrace_mask))
 460                         break;
 461                 mdelay(1);
 462         }
 463 }
 464
 465 EXPORT_SYMBOL(nmi_active);
 466 EXPORT_SYMBOL(nmi_watchdog);