2 * NMI watchdog support on APIC systems
4 * Started by Ingo Molnar <mingo@redhat.com>
7 * Mikael Pettersson : AMD K7 support for local APIC NMI watchdog.
8 * Mikael Pettersson : Power Management for local APIC NMI watchdog.
9 * Mikael Pettersson : Pentium 4 support for local APIC NMI watchdog.
11 * Mikael Pettersson : PM converted to driver model. Disable/enable API.
16 #include <linux/nmi.h>
18 #include <linux/delay.h>
19 #include <linux/interrupt.h>
20 #include <linux/module.h>
21 #include <linux/sysdev.h>
22 #include <linux/sysctl.h>
23 #include <linux/percpu.h>
24 #include <linux/kprobes.h>
25 #include <linux/cpumask.h>
26 #include <linux/kernel_stat.h>
27 #include <linux/kdebug.h>
28 #include <linux/smp.h>
30 #include <asm/proto.h>
31 #include <asm/timer.h>
35 #include <mach_traps.h>
37 int unknown_nmi_panic;
38 int nmi_watchdog_enabled;
40 static cpumask_t backtrace_mask = CPU_MASK_NONE;
43 * >0: the lapic NMI watchdog is active, but can be disabled
44 * <0: the lapic NMI watchdog has not been set up, and cannot
46 * 0: the lapic NMI watchdog is disabled, but can be enabled
48 atomic_t nmi_active = ATOMIC_INIT(0); /* oprofile uses this */
49 EXPORT_SYMBOL(nmi_active);
51 unsigned int nmi_watchdog = NMI_DEFAULT;
52 EXPORT_SYMBOL(nmi_watchdog);
54 static int panic_on_timeout;
56 static unsigned int nmi_hz = HZ;
57 static DEFINE_PER_CPU(short, wd_enabled);
58 static int endflag __initdata;
60 static inline unsigned int get_nmi_count(int cpu)
63 return cpu_pda(cpu)->__nmi_count;
65 return nmi_count(cpu);
69 static inline int mce_in_progress(void)
71 #if defined(CONFIX_X86_64) && defined(CONFIG_X86_MCE)
72 return atomic_read(&mce_entry) > 0;
78 * Take the local apic timer and PIT/HPET into account. We don't
79 * know which one is active, when we have highres/dyntick on
81 static inline unsigned int get_timer_irqs(int cpu)
84 return read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
86 return per_cpu(irq_stat, cpu).apic_timer_irqs +
87 per_cpu(irq_stat, cpu).irq0_irqs;
91 /* Run after command line and cpu_init init, but before all other checks */
92 void nmi_watchdog_default(void)
94 if (nmi_watchdog != NMI_DEFAULT)
96 nmi_watchdog = NMI_NONE;
101 * The performance counters used by NMI_LOCAL_APIC don't trigger when
102 * the CPU is idle. To make sure the NMI watchdog really ticks on all
103 * CPUs during the test make them busy.
105 static __init void nmi_cpu_busy(void *data)
107 local_irq_enable_in_hardirq();
109 * Intentionally don't use cpu_relax here. This is
110 * to make sure that the performance counter really ticks,
111 * even if there is a simulator or similar that catches the
112 * pause instruction. On a real HT machine this is fine because
113 * all other CPUs are busy with "useless" delay loops and don't
114 * care if they get somewhat less cycles.
121 int __init check_nmi_watchdog(void)
123 unsigned int *prev_nmi_count;
126 if (nmi_watchdog == NMI_NONE || nmi_watchdog == NMI_DISABLED)
129 if (!atomic_read(&nmi_active))
132 prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
136 printk(KERN_INFO "Testing NMI watchdog ... ");
139 if (nmi_watchdog == NMI_LOCAL_APIC)
140 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
143 for_each_possible_cpu(cpu)
144 prev_nmi_count[cpu] = get_nmi_count(cpu);
146 mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
148 for_each_online_cpu(cpu) {
149 if (!per_cpu(wd_enabled, cpu))
151 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
152 printk(KERN_WARNING "WARNING: CPU#%d: NMI "
153 "appears to be stuck (%d->%d)!\n",
157 per_cpu(wd_enabled, cpu) = 0;
158 atomic_dec(&nmi_active);
162 if (!atomic_read(&nmi_active)) {
163 kfree(prev_nmi_count);
164 atomic_set(&nmi_active, -1);
170 * now that we know it works we can reduce NMI frequency to
171 * something more reasonable; makes a difference in some configs
173 if (nmi_watchdog == NMI_LOCAL_APIC)
174 nmi_hz = lapic_adjust_nmi_hz(1);
176 kfree(prev_nmi_count);
181 timer_ack = !cpu_has_tsc;
186 static int __init setup_nmi_watchdog(char *str)
190 if (!strncmp(str, "panic", 5)) {
191 panic_on_timeout = 1;
192 str = strchr(str, ',');
198 get_option(&str, &nmi);
200 if (nmi >= NMI_INVALID || nmi < NMI_NONE)
206 __setup("nmi_watchdog=", setup_nmi_watchdog);
209 * Suspend/resume support
213 static int nmi_pm_active; /* nmi_active before suspend */
215 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
217 /* only CPU0 goes here, other CPUs should be offline */
218 nmi_pm_active = atomic_read(&nmi_active);
219 stop_apic_nmi_watchdog(NULL);
220 BUG_ON(atomic_read(&nmi_active) != 0);
224 static int lapic_nmi_resume(struct sys_device *dev)
226 /* only CPU0 goes here, other CPUs should be offline */
227 if (nmi_pm_active > 0) {
228 setup_apic_nmi_watchdog(NULL);
229 touch_nmi_watchdog();
234 static struct sysdev_class nmi_sysclass = {
236 .resume = lapic_nmi_resume,
237 .suspend = lapic_nmi_suspend,
240 static struct sys_device device_lapic_nmi = {
242 .cls = &nmi_sysclass,
245 static int __init init_lapic_nmi_sysfs(void)
250 * should really be a BUG_ON but b/c this is an
251 * init call, it just doesn't work. -dcz
253 if (nmi_watchdog != NMI_LOCAL_APIC)
256 if (atomic_read(&nmi_active) < 0)
259 error = sysdev_class_register(&nmi_sysclass);
261 error = sysdev_register(&device_lapic_nmi);
265 /* must come after the local APIC's device_initcall() */
266 late_initcall(init_lapic_nmi_sysfs);
268 #endif /* CONFIG_PM */
270 static void __acpi_nmi_enable(void *__unused)
272 apic_write_around(APIC_LVT0, APIC_DM_NMI);
276 * Enable timer based NMIs on all CPUs:
278 void acpi_nmi_enable(void)
280 if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
281 on_each_cpu(__acpi_nmi_enable, NULL, 0, 1);
284 static void __acpi_nmi_disable(void *__unused)
286 apic_write_around(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
290 * Disable timer based NMIs on all CPUs:
292 void acpi_nmi_disable(void)
294 if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
295 on_each_cpu(__acpi_nmi_disable, NULL, 0, 1);
298 void setup_apic_nmi_watchdog(void *unused)
300 if (__get_cpu_var(wd_enabled))
303 /* cheap hack to support suspend/resume */
304 /* if cpu0 is not active neither should the other cpus */
305 if (smp_processor_id() != 0 && atomic_read(&nmi_active) <= 0)
308 switch (nmi_watchdog) {
310 /* enable it before to avoid race with handler */
311 __get_cpu_var(wd_enabled) = 1;
312 if (lapic_watchdog_init(nmi_hz) < 0) {
313 __get_cpu_var(wd_enabled) = 0;
318 __get_cpu_var(wd_enabled) = 1;
319 atomic_inc(&nmi_active);
323 void stop_apic_nmi_watchdog(void *unused)
325 /* only support LOCAL and IO APICs for now */
326 if (nmi_watchdog != NMI_LOCAL_APIC &&
327 nmi_watchdog != NMI_IO_APIC)
329 if (__get_cpu_var(wd_enabled) == 0)
331 if (nmi_watchdog == NMI_LOCAL_APIC)
332 lapic_watchdog_stop();
333 __get_cpu_var(wd_enabled) = 0;
334 atomic_dec(&nmi_active);
338 * the best way to detect whether a CPU has a 'hard lockup' problem
339 * is to check it's local APIC timer IRQ counts. If they are not
340 * changing then that CPU has some problem.
342 * as these watchdog NMI IRQs are generated on every CPU, we only
343 * have to check the current processor.
345 * since NMIs don't listen to _any_ locks, we have to be extremely
346 * careful not to rely on unsafe variables. The printk might lock
347 * up though, so we have to break up any console locks first ...
348 * [when there will be more tty-related locks, break them up here too!]
351 static DEFINE_PER_CPU(unsigned, last_irq_sum);
352 static DEFINE_PER_CPU(local_t, alert_counter);
353 static DEFINE_PER_CPU(int, nmi_touch);
355 void touch_nmi_watchdog(void)
357 if (nmi_watchdog > 0) {
361 * Tell other CPUs to reset their alert counters. We cannot
362 * do it ourselves because the alert count increase is not
365 for_each_present_cpu(cpu) {
366 if (per_cpu(nmi_touch, cpu) != 1)
367 per_cpu(nmi_touch, cpu) = 1;
372 * Tickle the softlockup detector too:
374 touch_softlockup_watchdog();
376 EXPORT_SYMBOL(touch_nmi_watchdog);
378 notrace __kprobes int
379 nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
382 * Since current_thread_info()-> is always on the stack, and we
383 * always switch the stack NMI-atomically, it's safe to use
384 * smp_processor_id().
388 int cpu = smp_processor_id();
391 /* check for other users first */
392 if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
398 sum = get_timer_irqs(cpu);
400 if (__get_cpu_var(nmi_touch)) {
401 __get_cpu_var(nmi_touch) = 0;
405 if (cpu_isset(cpu, backtrace_mask)) {
406 static DEFINE_SPINLOCK(lock); /* Serialise the printks */
409 printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
412 cpu_clear(cpu, backtrace_mask);
415 /* Could check oops_in_progress here too, but it's safer not to */
416 if (mce_in_progress())
419 /* if the none of the timers isn't firing, this cpu isn't doing much */
420 if (!touched && __get_cpu_var(last_irq_sum) == sum) {
422 * Ayiee, looks like this CPU is stuck ...
423 * wait a few IRQs (5 seconds) before doing the oops ...
425 local_inc(&__get_cpu_var(alert_counter));
426 if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
428 * die_nmi will return ONLY if NOTIFY_STOP happens..
430 die_nmi("BUG: NMI Watchdog detected LOCKUP",
431 regs, panic_on_timeout);
433 __get_cpu_var(last_irq_sum) = sum;
434 local_set(&__get_cpu_var(alert_counter), 0);
437 /* see if the nmi watchdog went off */
438 if (!__get_cpu_var(wd_enabled))
440 switch (nmi_watchdog) {
442 rc |= lapic_wd_event(nmi_hz);
446 * don't know how to accurately check for this.
447 * just assume it was a watchdog timer interrupt
448 * This matches the old behaviour.
458 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
460 unsigned char reason = get_nmi_reason();
463 sprintf(buf, "NMI received for unknown reason %02x\n", reason);
464 die_nmi(buf, regs, 1); /* Always panic here */
469 * proc handler for /proc/sys/kernel/nmi
471 int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
472 void __user *buffer, size_t *length, loff_t *ppos)
476 nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
477 old_state = nmi_watchdog_enabled;
478 proc_dointvec(table, write, file, buffer, length, ppos);
479 if (!!old_state == !!nmi_watchdog_enabled)
482 if (atomic_read(&nmi_active) < 0 || nmi_watchdog == NMI_DISABLED) {
484 "NMI watchdog is permanently disabled\n");
488 /* if nmi_watchdog is not set yet, then set it */
489 nmi_watchdog_default();
492 if (nmi_watchdog == NMI_NONE) {
493 if (lapic_watchdog_ok())
494 nmi_watchdog = NMI_LOCAL_APIC;
496 nmi_watchdog = NMI_IO_APIC;
500 if (nmi_watchdog == NMI_LOCAL_APIC) {
501 if (nmi_watchdog_enabled)
502 enable_lapic_nmi_watchdog();
504 disable_lapic_nmi_watchdog();
507 "NMI watchdog doesn't know what hardware to touch\n");
513 #endif /* CONFIG_SYSCTL */
515 int do_nmi_callback(struct pt_regs *regs, int cpu)
518 if (unknown_nmi_panic)
519 return unknown_nmi_panic_callback(regs, cpu);
524 void __trigger_all_cpu_backtrace(void)
528 backtrace_mask = cpu_online_map;
529 /* Wait for up to 10 seconds for all CPUs to do the backtrace */
530 for (i = 0; i < 10 * 1000; i++) {
531 if (cpus_empty(backtrace_mask))