nmi.c 14.1 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
/*
 *  linux/arch/x86_64/nmi.c
 *
 *  NMI watchdog support on APIC systems
 *
 *  Started by Ingo Molnar <mingo@redhat.com>
 *
 *  Fixes:
 *  Mikael Pettersson	: AMD K7 support for local APIC NMI watchdog.
 *  Mikael Pettersson	: Power Management for local APIC NMI watchdog.
 *  Pavel Machek and
 *  Mikael Pettersson	: PM converted to driver model. Disable/enable API.
 */

#include <linux/config.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/bootmem.h>
#include <linux/smp_lock.h>
#include <linux/interrupt.h>
#include <linux/mc146818rtc.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/sysdev.h>
#include <linux/nmi.h>
#include <linux/sysctl.h>

#include <asm/smp.h>
#include <asm/mtrr.h>
#include <asm/mpspec.h>
#include <asm/nmi.h>
#include <asm/msr.h>
#include <asm/proto.h>
#include <asm/kdebug.h>
35
#include <asm/local.h>
Linus Torvalds's avatar
Linus Torvalds committed
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61

/*
 * lapic_nmi_owner tracks the ownership of the lapic NMI hardware:
 * - it may be reserved by some other driver, or not
 * - when not reserved by some other driver, it may be used for
 *   the NMI watchdog, or not
 *
 * This is maintained separately from nmi_active because the NMI
 * watchdog may also be driven from the I/O APIC timer.
 */
static DEFINE_SPINLOCK(lapic_nmi_owner_lock);
static unsigned int lapic_nmi_owner;
#define LAPIC_NMI_WATCHDOG	(1<<0)
#define LAPIC_NMI_RESERVED	(1<<1)

/* nmi_active:
 * +1: the lapic NMI watchdog is active, but can be disabled
 *  0: the lapic NMI watchdog has not been set up, and cannot
 *     be enabled
 * -1: the lapic NMI watchdog is disabled, but can be enabled
 */
int nmi_active;		/* oprofile uses this */
int panic_on_timeout;

unsigned int nmi_watchdog = NMI_DEFAULT;
static unsigned int nmi_hz = HZ;
62
63
static unsigned int nmi_perfctr_msr;	/* the MSR to reset in NMI handler */
static unsigned int nmi_p4_cccr_val;
Linus Torvalds's avatar
Linus Torvalds committed
64
65
66
67
68
69
70
71
72
73
74

/* Note that these events don't tick when the CPU idles. This means
   the frequency varies with CPU load. */

#define K7_EVNTSEL_ENABLE	(1 << 22)
#define K7_EVNTSEL_INT		(1 << 20)
#define K7_EVNTSEL_OS		(1 << 17)
#define K7_EVNTSEL_USR		(1 << 16)
#define K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING	0x76
#define K7_NMI_EVENT		K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING

75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
#define MSR_P4_MISC_ENABLE	0x1A0
#define MSR_P4_MISC_ENABLE_PERF_AVAIL	(1<<7)
#define MSR_P4_MISC_ENABLE_PEBS_UNAVAIL	(1<<12)
#define MSR_P4_PERFCTR0		0x300
#define MSR_P4_CCCR0		0x360
#define P4_ESCR_EVENT_SELECT(N)	((N)<<25)
#define P4_ESCR_OS		(1<<3)
#define P4_ESCR_USR		(1<<2)
#define P4_CCCR_OVF_PMI0	(1<<26)
#define P4_CCCR_OVF_PMI1	(1<<27)
#define P4_CCCR_THRESHOLD(N)	((N)<<20)
#define P4_CCCR_COMPLEMENT	(1<<19)
#define P4_CCCR_COMPARE		(1<<18)
#define P4_CCCR_REQUIRED	(3<<16)
#define P4_CCCR_ESCR_SELECT(N)	((N)<<13)
#define P4_CCCR_ENABLE		(1<<12)
/* Set up IQ_COUNTER0 to behave like a clock, by having IQ_CCCR0 filter
   CRU_ESCR0 (with any non-null event selector) through a complemented
   max threshold. [IA32-Vol3, Section 14.9.9] */
#define MSR_P4_IQ_COUNTER0	0x30C
#define P4_NMI_CRU_ESCR0	(P4_ESCR_EVENT_SELECT(0x3F)|P4_ESCR_OS|P4_ESCR_USR)
#define P4_NMI_IQ_CCCR0	\
	(P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT|	\
	 P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE)

100
static __cpuinit inline int nmi_known_cpu(void)
101
102
103
104
105
106
107
108
109
{
	switch (boot_cpu_data.x86_vendor) {
	case X86_VENDOR_AMD:
		return boot_cpu_data.x86 == 15;
	case X86_VENDOR_INTEL:
		return boot_cpu_data.x86 == 15;
	}
	return 0;
}
Linus Torvalds's avatar
Linus Torvalds committed
110
111

/* Run after command line and cpu_init init, but before all other checks */
112
void __cpuinit nmi_watchdog_default(void)
Linus Torvalds's avatar
Linus Torvalds committed
113
114
115
{
	if (nmi_watchdog != NMI_DEFAULT)
		return;
116
117
118
	if (nmi_known_cpu())
		nmi_watchdog = NMI_LOCAL_APIC;
	else
Linus Torvalds's avatar
Linus Torvalds committed
119
120
121
		nmi_watchdog = NMI_IO_APIC;
}

122
123
124
125
126
127
#ifdef CONFIG_SMP
/* The performance counters used by NMI_LOCAL_APIC don't trigger when
 * the CPU is idle. To make sure the NMI watchdog really ticks on all
 * CPUs during the test make them busy.
 */
static __init void nmi_cpu_busy(void *data)
Linus Torvalds's avatar
Linus Torvalds committed
128
{
129
130
131
132
133
134
135
136
137
138
	volatile int *endflag = data;
	local_irq_enable();
	/* Intentionally don't use cpu_relax here. This is
	   to make sure that the performance counter really ticks,
	   even if there is a simulator or similar that catches the
	   pause instruction. On a real HT machine this is fine because
	   all other CPUs are busy with "useless" delay loops and don't
	   care if they get somewhat less cycles. */
	while (*endflag == 0)
		barrier();
Linus Torvalds's avatar
Linus Torvalds committed
139
}
140
#endif
Linus Torvalds's avatar
Linus Torvalds committed
141

142
int __init check_nmi_watchdog (void)
Linus Torvalds's avatar
Linus Torvalds committed
143
{
144
	volatile int endflag = 0;
145
	int *counts;
Linus Torvalds's avatar
Linus Torvalds committed
146
147
	int cpu;

148
149
150
	counts = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
	if (!counts)
		return -1;
Linus Torvalds's avatar
Linus Torvalds committed
151

152
	printk(KERN_INFO "testing NMI watchdog ... ");
153

154
155
	if (nmi_watchdog == NMI_LOCAL_APIC)
		smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
Linus Torvalds's avatar
Linus Torvalds committed
156
157
158
159
160
161
162

	for (cpu = 0; cpu < NR_CPUS; cpu++)
		counts[cpu] = cpu_pda[cpu].__nmi_count; 
	local_irq_enable();
	mdelay((10*1000)/nmi_hz); // wait 10 ticks

	for (cpu = 0; cpu < NR_CPUS; cpu++) {
163
164
		if (!cpu_online(cpu))
			continue;
Linus Torvalds's avatar
Linus Torvalds committed
165
		if (cpu_pda[cpu].__nmi_count - counts[cpu] <= 5) {
166
167
			endflag = 1;
			printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
Linus Torvalds's avatar
Linus Torvalds committed
168
			       cpu,
169
			       counts[cpu],
Linus Torvalds's avatar
Linus Torvalds committed
170
171
172
			       cpu_pda[cpu].__nmi_count);
			nmi_active = 0;
			lapic_nmi_owner &= ~LAPIC_NMI_WATCHDOG;
173
			nmi_perfctr_msr = 0;
174
			kfree(counts);
Linus Torvalds's avatar
Linus Torvalds committed
175
176
177
			return -1;
		}
	}
178
	endflag = 1;
Linus Torvalds's avatar
Linus Torvalds committed
179
180
181
182
183
184
185
	printk("OK.\n");

	/* now that we know it works we can reduce NMI frequency to
	   something more reasonable; makes a difference in some configs */
	if (nmi_watchdog == NMI_LOCAL_APIC)
		nmi_hz = 1;

186
	kfree(counts);
Linus Torvalds's avatar
Linus Torvalds committed
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
	return 0;
}

int __init setup_nmi_watchdog(char *str)
{
	int nmi;

	if (!strncmp(str,"panic",5)) {
		panic_on_timeout = 1;
		str = strchr(str, ',');
		if (!str)
			return 1;
		++str;
	}

	get_option(&str, &nmi);

	if (nmi >= NMI_INVALID)
		return 0;
206
	nmi_watchdog = nmi;
Linus Torvalds's avatar
Linus Torvalds committed
207
208
209
210
211
212
213
214
215
216
217
218
219
220
	return 1;
}

__setup("nmi_watchdog=", setup_nmi_watchdog);

static void disable_lapic_nmi_watchdog(void)
{
	if (nmi_active <= 0)
		return;
	switch (boot_cpu_data.x86_vendor) {
	case X86_VENDOR_AMD:
		wrmsr(MSR_K7_EVNTSEL0, 0, 0);
		break;
	case X86_VENDOR_INTEL:
221
222
223
224
		if (boot_cpu_data.x86 == 15) {
			wrmsr(MSR_P4_IQ_CCCR0, 0, 0);
			wrmsr(MSR_P4_CRU_ESCR0, 0, 0);
		}
Linus Torvalds's avatar
Linus Torvalds committed
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
		break;
	}
	nmi_active = -1;
	/* tell do_nmi() and others that we're not active any more */
	nmi_watchdog = 0;
}

static void enable_lapic_nmi_watchdog(void)
{
	if (nmi_active < 0) {
		nmi_watchdog = NMI_LOCAL_APIC;
		setup_apic_nmi_watchdog();
	}
}

int reserve_lapic_nmi(void)
{
	unsigned int old_owner;

	spin_lock(&lapic_nmi_owner_lock);
	old_owner = lapic_nmi_owner;
	lapic_nmi_owner |= LAPIC_NMI_RESERVED;
	spin_unlock(&lapic_nmi_owner_lock);
	if (old_owner & LAPIC_NMI_RESERVED)
		return -EBUSY;
	if (old_owner & LAPIC_NMI_WATCHDOG)
		disable_lapic_nmi_watchdog();
	return 0;
}

void release_lapic_nmi(void)
{
	unsigned int new_owner;

	spin_lock(&lapic_nmi_owner_lock);
	new_owner = lapic_nmi_owner & ~LAPIC_NMI_RESERVED;
	lapic_nmi_owner = new_owner;
	spin_unlock(&lapic_nmi_owner_lock);
	if (new_owner & LAPIC_NMI_WATCHDOG)
		enable_lapic_nmi_watchdog();
}

void disable_timer_nmi_watchdog(void)
{
	if ((nmi_watchdog != NMI_IO_APIC) || (nmi_active <= 0))
		return;

	disable_irq(0);
	unset_nmi_callback();
	nmi_active = -1;
	nmi_watchdog = NMI_NONE;
}

void enable_timer_nmi_watchdog(void)
{
	if (nmi_active < 0) {
		nmi_watchdog = NMI_IO_APIC;
		touch_nmi_watchdog();
		nmi_active = 1;
		enable_irq(0);
	}
}

#ifdef CONFIG_PM

static int nmi_pm_active; /* nmi_active before suspend */

292
static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
Linus Torvalds's avatar
Linus Torvalds committed
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
{
	nmi_pm_active = nmi_active;
	disable_lapic_nmi_watchdog();
	return 0;
}

static int lapic_nmi_resume(struct sys_device *dev)
{
	if (nmi_pm_active > 0)
	enable_lapic_nmi_watchdog();
	return 0;
}

static struct sysdev_class nmi_sysclass = {
	set_kset_name("lapic_nmi"),
	.resume		= lapic_nmi_resume,
	.suspend	= lapic_nmi_suspend,
};

static struct sys_device device_lapic_nmi = {
	.id		= 0,
	.cls	= &nmi_sysclass,
};

static int __init init_lapic_nmi_sysfs(void)
{
	int error;

	if (nmi_active == 0 || nmi_watchdog != NMI_LOCAL_APIC)
		return 0;

	error = sysdev_class_register(&nmi_sysclass);
	if (!error)
		error = sysdev_register(&device_lapic_nmi);
	return error;
}
/* must come after the local APIC's device_initcall() */
late_initcall(init_lapic_nmi_sysfs);

#endif	/* CONFIG_PM */

/*
 * Activate the NMI watchdog via the local APIC.
 * Original code written by Keith Owens.
 */

339
340
341
342
343
344
345
346
static void clear_msr_range(unsigned int base, unsigned int n)
{
	unsigned int i;

	for(i = 0; i < n; ++i)
		wrmsr(base+i, 0, 0);
}

Linus Torvalds's avatar
Linus Torvalds committed
347
348
349
350
351
352
353
354
355
static void setup_k7_watchdog(void)
{
	int i;
	unsigned int evntsel;

	nmi_perfctr_msr = MSR_K7_PERFCTR0;

	for(i = 0; i < 4; ++i) {
		/* Simulator may not support it */
356
357
		if (checking_wrmsrl(MSR_K7_EVNTSEL0+i, 0UL)) {
			nmi_perfctr_msr = 0;
Linus Torvalds's avatar
Linus Torvalds committed
358
			return;
359
		}
Linus Torvalds's avatar
Linus Torvalds committed
360
361
362
363
364
365
366
367
368
		wrmsrl(MSR_K7_PERFCTR0+i, 0UL);
	}

	evntsel = K7_EVNTSEL_INT
		| K7_EVNTSEL_OS
		| K7_EVNTSEL_USR
		| K7_NMI_EVENT;

	wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
369
	wrmsr(MSR_K7_PERFCTR0, -(cpu_khz/nmi_hz*1000), -1);
Linus Torvalds's avatar
Linus Torvalds committed
370
371
372
373
374
	apic_write(APIC_LVTPC, APIC_DM_NMI);
	evntsel |= K7_EVNTSEL_ENABLE;
	wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
}

375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416

static int setup_p4_watchdog(void)
{
	unsigned int misc_enable, dummy;

	rdmsr(MSR_P4_MISC_ENABLE, misc_enable, dummy);
	if (!(misc_enable & MSR_P4_MISC_ENABLE_PERF_AVAIL))
		return 0;

	nmi_perfctr_msr = MSR_P4_IQ_COUNTER0;
	nmi_p4_cccr_val = P4_NMI_IQ_CCCR0;
#ifdef CONFIG_SMP
	if (smp_num_siblings == 2)
		nmi_p4_cccr_val |= P4_CCCR_OVF_PMI1;
#endif

	if (!(misc_enable & MSR_P4_MISC_ENABLE_PEBS_UNAVAIL))
		clear_msr_range(0x3F1, 2);
	/* MSR 0x3F0 seems to have a default value of 0xFC00, but current
	   docs doesn't fully define it, so leave it alone for now. */
	if (boot_cpu_data.x86_model >= 0x3) {
		/* MSR_P4_IQ_ESCR0/1 (0x3ba/0x3bb) removed */
		clear_msr_range(0x3A0, 26);
		clear_msr_range(0x3BC, 3);
	} else {
		clear_msr_range(0x3A0, 31);
	}
	clear_msr_range(0x3C0, 6);
	clear_msr_range(0x3C8, 6);
	clear_msr_range(0x3E0, 2);
	clear_msr_range(MSR_P4_CCCR0, 18);
	clear_msr_range(MSR_P4_PERFCTR0, 18);

	wrmsr(MSR_P4_CRU_ESCR0, P4_NMI_CRU_ESCR0, 0);
	wrmsr(MSR_P4_IQ_CCCR0, P4_NMI_IQ_CCCR0 & ~P4_CCCR_ENABLE, 0);
	Dprintk("setting P4_IQ_COUNTER0 to 0x%08lx\n", -(cpu_khz/nmi_hz*1000));
	wrmsr(MSR_P4_IQ_COUNTER0, -(cpu_khz/nmi_hz*1000), -1);
	apic_write(APIC_LVTPC, APIC_DM_NMI);
	wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
	return 1;
}

Linus Torvalds's avatar
Linus Torvalds committed
417
418
419
420
void setup_apic_nmi_watchdog(void)
{
	switch (boot_cpu_data.x86_vendor) {
	case X86_VENDOR_AMD:
421
		if (boot_cpu_data.x86 != 15)
Linus Torvalds's avatar
Linus Torvalds committed
422
423
424
425
426
			return;
		if (strstr(boot_cpu_data.x86_model_id, "Screwdriver"))
			return;
		setup_k7_watchdog();
		break;
427
428
429
430
431
432
433
	case X86_VENDOR_INTEL:
		if (boot_cpu_data.x86 != 15)
			return;
		if (!setup_p4_watchdog())
			return;
		break;

Linus Torvalds's avatar
Linus Torvalds committed
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
	default:
		return;
	}
	lapic_nmi_owner = LAPIC_NMI_WATCHDOG;
	nmi_active = 1;
}

/*
 * the best way to detect whether a CPU has a 'hard lockup' problem
 * is to check it's local APIC timer IRQ counts. If they are not
 * changing then that CPU has some problem.
 *
 * as these watchdog NMI IRQs are generated on every CPU, we only
 * have to check the current processor.
 */

450
451
452
static DEFINE_PER_CPU(unsigned, last_irq_sum);
static DEFINE_PER_CPU(local_t, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);
Linus Torvalds's avatar
Linus Torvalds committed
453
454
455
456
457
458

void touch_nmi_watchdog (void)
{
	int i;

	/*
459
460
461
 	 * Tell other CPUs to reset their alert counters. We cannot
	 * do it ourselves because the alert count increase is not
	 * atomic.
Linus Torvalds's avatar
Linus Torvalds committed
462
463
	 */
	for (i = 0; i < NR_CPUS; i++)
464
		per_cpu(nmi_touch, i) = 1;
Ingo Molnar's avatar
Ingo Molnar committed
465
466

 	touch_softlockup_watchdog();
Linus Torvalds's avatar
Linus Torvalds committed
467
468
469
470
}

void nmi_watchdog_tick (struct pt_regs * regs, unsigned reason)
{
471
472
	int sum;
	int touched = 0;
Linus Torvalds's avatar
Linus Torvalds committed
473
474

	sum = read_pda(apic_timer_irqs);
475
476
477
478
479
	if (__get_cpu_var(nmi_touch)) {
		__get_cpu_var(nmi_touch) = 0;
		touched = 1;
	}
	if (!touched && __get_cpu_var(last_irq_sum) == sum) {
Linus Torvalds's avatar
Linus Torvalds committed
480
481
482
483
		/*
		 * Ayiee, looks like this CPU is stuck ...
		 * wait a few IRQs (5 seconds) before doing the oops ...
		 */
484
485
		local_inc(&__get_cpu_var(alert_counter));
		if (local_read(&__get_cpu_var(alert_counter)) == 5*nmi_hz) {
Linus Torvalds's avatar
Linus Torvalds committed
486
487
			if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
							== NOTIFY_STOP) {
488
				local_set(&__get_cpu_var(alert_counter), 0);
Linus Torvalds's avatar
Linus Torvalds committed
489
				return;
490
491
			}
			die_nmi("NMI Watchdog detected LOCKUP on CPU %d\n", regs);
Linus Torvalds's avatar
Linus Torvalds committed
492
493
		}
	} else {
494
495
		__get_cpu_var(last_irq_sum) = sum;
		local_set(&__get_cpu_var(alert_counter), 0);
Linus Torvalds's avatar
Linus Torvalds committed
496
	}
497
498
499
500
501
502
503
504
505
506
507
508
	if (nmi_perfctr_msr) {
 		if (nmi_perfctr_msr == MSR_P4_IQ_COUNTER0) {
 			/*
 			 * P4 quirks:
 			 * - An overflown perfctr will assert its interrupt
 			 *   until the OVF flag in its CCCR is cleared.
 			 * - LVTPC is masked on interrupt and must be
 			 *   unmasked by the LVTPC handler.
 			 */
 			wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
 			apic_write(APIC_LVTPC, APIC_DM_NMI);
 		}
Linus Torvalds's avatar
Linus Torvalds committed
509
		wrmsr(nmi_perfctr_msr, -(cpu_khz/nmi_hz*1000), -1);
510
	}
Linus Torvalds's avatar
Linus Torvalds committed
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
}

static int dummy_nmi_callback(struct pt_regs * regs, int cpu)
{
	return 0;
}
 
static nmi_callback_t nmi_callback = dummy_nmi_callback;
 
asmlinkage void do_nmi(struct pt_regs * regs, long error_code)
{
	int cpu = safe_smp_processor_id();

	nmi_enter();
	add_pda(__nmi_count,1);
526
	if (!rcu_dereference(nmi_callback)(regs, cpu))
Linus Torvalds's avatar
Linus Torvalds committed
527
528
529
530
531
532
		default_do_nmi(regs);
	nmi_exit();
}

void set_nmi_callback(nmi_callback_t callback)
{
533
	rcu_assign_pointer(nmi_callback, callback);
Linus Torvalds's avatar
Linus Torvalds committed
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
}

void unset_nmi_callback(void)
{
	nmi_callback = dummy_nmi_callback;
}

#ifdef CONFIG_SYSCTL

static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
{
	unsigned char reason = get_nmi_reason();
	char buf[64];

	if (!(reason & 0xc0)) {
		sprintf(buf, "NMI received for unknown reason %02x\n", reason);
		die_nmi(buf,regs);
	}
	return 0;
}

/*
 * proc handler for /proc/sys/kernel/unknown_nmi_panic
 */
int proc_unknown_nmi_panic(struct ctl_table *table, int write, struct file *file,
			void __user *buffer, size_t *length, loff_t *ppos)
{
	int old_state;

	old_state = unknown_nmi_panic;
	proc_dointvec(table, write, file, buffer, length, ppos);
	if (!!old_state == !!unknown_nmi_panic)
		return 0;

	if (unknown_nmi_panic) {
		if (reserve_lapic_nmi() < 0) {
			unknown_nmi_panic = 0;
			return -EBUSY;
		} else {
			set_nmi_callback(unknown_nmi_panic_callback);
		}
	} else {
		release_lapic_nmi();
		unset_nmi_callback();
	}
	return 0;
}

#endif

EXPORT_SYMBOL(nmi_active);
EXPORT_SYMBOL(nmi_watchdog);
EXPORT_SYMBOL(reserve_lapic_nmi);
EXPORT_SYMBOL(release_lapic_nmi);
EXPORT_SYMBOL(disable_timer_nmi_watchdog);
EXPORT_SYMBOL(enable_timer_nmi_watchdog);
EXPORT_SYMBOL(touch_nmi_watchdog);