1 files changed, 513 insertions, 0 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
new file mode 100644
index 000000000000..8dfe9db87a9e
--- /dev/null
+++ b/arch/x86/kernel/nmi.c
@@ -0,0 +1,513 @@
+/*
+ *  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.
+ *  Mikael Pettersson   : Pentium 4 support for local APIC NMI watchdog.
+ *  Pavel Machek and
+ *  Mikael Pettersson   : PM converted to driver model. Disable/enable API.
+ */
+#include <asm/apic.h>
+#include <linux/nmi.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/sysdev.h>
+#include <linux/sysctl.h>
+#include <linux/percpu.h>
+#include <linux/kprobes.h>
+#include <linux/cpumask.h>
+#include <linux/kernel_stat.h>
+#include <linux/kdebug.h>
+#include <linux/smp.h>
+#include <asm/i8259.h>
+#include <asm/io_apic.h>
+#include <asm/smp.h>
+#include <asm/nmi.h>
+#include <asm/proto.h>
+#include <asm/timer.h>
+#include <asm/mce.h>
+#include <mach_traps.h>
+int unknown_nmi_panic;
+int nmi_watchdog_enabled;
+static cpumask_t backtrace_mask = CPU_MASK_NONE;
+/* nmi_active:
+ * >0: the lapic NMI watchdog is active, but can be disabled
+ * <0: the lapic NMI watchdog has not been set up, and cannot
+ *     be enabled
+ *  0: the lapic NMI watchdog is disabled, but can be enabled
+ */
+atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
+EXPORT_SYMBOL(nmi_active);
+unsigned int nmi_watchdog = NMI_NONE;
+EXPORT_SYMBOL(nmi_watchdog);
+static int panic_on_timeout;
+static unsigned int nmi_hz = HZ;
+static DEFINE_PER_CPU(short, wd_enabled);
+static int endflag __initdata;
+static inline unsigned int get_nmi_count(int cpu)
+{
+#ifdef CONFIG_X86_64
+        return cpu_pda(cpu)->__nmi_count;
+#else
+        return nmi_count(cpu);
+#endif
+}
+static inline int mce_in_progress(void)
+{
+#if defined(CONFIG_X86_64) && defined(CONFIG_X86_MCE)
+        return atomic_read(&mce_entry) > 0;
+#endif
+        return 0;
+}
+/*
+ * Take the local apic timer and PIT/HPET into account. We don't
+ * know which one is active, when we have highres/dyntick on
+ */
+static inline unsigned int get_timer_irqs(int cpu)
+{
+#ifdef CONFIG_X86_64
+        return read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
+#else
+        return per_cpu(irq_stat, cpu).apic_timer_irqs +
+                per_cpu(irq_stat, cpu).irq0_irqs;
+#endif
+}
+#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)
+{
+        local_irq_enable_in_hardirq();
+        /*
+         * 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)
+                mb();
+}
+#endif
+int __init check_nmi_watchdog(void)
+{
+        unsigned int *prev_nmi_count;
+        int cpu;
+        if (!nmi_watchdog_active() || !atomic_read(&nmi_active))
+                return 0;
+        prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);
+        if (!prev_nmi_count)
+                goto error;
+        printk(KERN_INFO "Testing NMI watchdog ... ");
+#ifdef CONFIG_SMP
+        if (nmi_watchdog == NMI_LOCAL_APIC)
+                smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
+#endif
+        for_each_possible_cpu(cpu)
+                prev_nmi_count[cpu] = get_nmi_count(cpu);
+        local_irq_enable();
+        mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
+        for_each_online_cpu(cpu) {
+                if (!per_cpu(wd_enabled, cpu))
+                        continue;
+                if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
+                        printk(KERN_WARNING "WARNING: CPU#%d: NMI "
+                                "appears to be stuck (%d->%d)!\n",
+                                cpu,
+                                prev_nmi_count[cpu],
+                                get_nmi_count(cpu));
+                        per_cpu(wd_enabled, cpu) = 0;
+                        atomic_dec(&nmi_active);
+                }
+        }
+        endflag = 1;
+        if (!atomic_read(&nmi_active)) {
+                kfree(prev_nmi_count);
+                atomic_set(&nmi_active, -1);
+                goto error;
+        }
+        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 = lapic_adjust_nmi_hz(1);
+        kfree(prev_nmi_count);
+        return 0;
+error:
+        if (nmi_watchdog == NMI_IO_APIC && !timer_through_8259)
+                disable_8259A_irq(0);
+        return -1;
+}
+static int __init setup_nmi_watchdog(char *str)
+{
+        unsigned 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;
+        nmi_watchdog = nmi;
+        return 1;
+}
+__setup("nmi_watchdog=", setup_nmi_watchdog);
+/*
+ * Suspend/resume support
+ */
+#ifdef CONFIG_PM
+static int nmi_pm_active; /* nmi_active before suspend */
+static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
+{
+        /* only CPU0 goes here, other CPUs should be offline */
+        nmi_pm_active = atomic_read(&nmi_active);
+        stop_apic_nmi_watchdog(NULL);
+        BUG_ON(atomic_read(&nmi_active) != 0);
+        return 0;
+}
+static int lapic_nmi_resume(struct sys_device *dev)
+{
+        /* only CPU0 goes here, other CPUs should be offline */
+        if (nmi_pm_active > 0) {
+                setup_apic_nmi_watchdog(NULL);
+                touch_nmi_watchdog();
+        }
+        return 0;
+}
+static struct sysdev_class nmi_sysclass = {
+        .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;
+        /*
+         * should really be a BUG_ON but b/c this is an
+         * init call, it just doesn't work.  -dcz
+         */
+        if (nmi_watchdog != NMI_LOCAL_APIC)
+                return 0;
+        if (atomic_read(&nmi_active) < 0)
+                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 */
+static void __acpi_nmi_enable(void *__unused)
+{
+        apic_write_around(APIC_LVT0, APIC_DM_NMI);
+}
+/*
+ * Enable timer based NMIs on all CPUs:
+ */
+void acpi_nmi_enable(void)
+{
+        if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
+                on_each_cpu(__acpi_nmi_enable, NULL, 0, 1);
+}
+static void __acpi_nmi_disable(void *__unused)
+{
+        apic_write_around(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
+}
+/*
+ * Disable timer based NMIs on all CPUs:
+ */
+void acpi_nmi_disable(void)
+{
+        if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
+                on_each_cpu(__acpi_nmi_disable, NULL, 0, 1);
+}
+void setup_apic_nmi_watchdog(void *unused)
+{
+        if (__get_cpu_var(wd_enabled))
+                return;
+        /* cheap hack to support suspend/resume */
+        /* if cpu0 is not active neither should the other cpus */
+        if (smp_processor_id() != 0 && atomic_read(&nmi_active) <= 0)
+                return;
+        switch (nmi_watchdog) {
+        case NMI_LOCAL_APIC:
+                 /* enable it before to avoid race with handler */
+                __get_cpu_var(wd_enabled) = 1;
+                if (lapic_watchdog_init(nmi_hz) < 0) {
+                        __get_cpu_var(wd_enabled) = 0;
+                        return;
+                }
+                /* FALL THROUGH */
+        case NMI_IO_APIC:
+                __get_cpu_var(wd_enabled) = 1;
+                atomic_inc(&nmi_active);
+        }
+}
+void stop_apic_nmi_watchdog(void *unused)
+{
+        /* only support LOCAL and IO APICs for now */
+        if (!nmi_watchdog_active())
+                return;
+        if (__get_cpu_var(wd_enabled) == 0)
+                return;
+        if (nmi_watchdog == NMI_LOCAL_APIC)
+                lapic_watchdog_stop();
+        __get_cpu_var(wd_enabled) = 0;
+        atomic_dec(&nmi_active);
+}
+/*
+ * 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.
+ *
+ * since NMIs don't listen to _any_ locks, we have to be extremely
+ * careful not to rely on unsafe variables. The printk might lock
+ * up though, so we have to break up any console locks first ...
+ * [when there will be more tty-related locks, break them up here too!]
+ */
+static DEFINE_PER_CPU(unsigned, last_irq_sum);
+static DEFINE_PER_CPU(local_t, alert_counter);
+static DEFINE_PER_CPU(int, nmi_touch);
+void touch_nmi_watchdog(void)
+{
+        if (nmi_watchdog_active()) {
+                unsigned cpu;
+                /*
+                 * Tell other CPUs to reset their alert counters. We cannot
+                 * do it ourselves because the alert count increase is not
+                 * atomic.
+                 */
+                for_each_present_cpu(cpu) {
+                        if (per_cpu(nmi_touch, cpu) != 1)
+                                per_cpu(nmi_touch, cpu) = 1;
+                }
+        }
+        /*
+         * Tickle the softlockup detector too:
+         */
+        touch_softlockup_watchdog();
+}
+EXPORT_SYMBOL(touch_nmi_watchdog);
+notrace __kprobes int
+nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
+{
+        /*
+         * Since current_thread_info()-> is always on the stack, and we
+         * always switch the stack NMI-atomically, it's safe to use
+         * smp_processor_id().
+         */
+        unsigned int sum;
+        int touched = 0;
+        int cpu = smp_processor_id();
+        int rc = 0;
+        /* check for other users first */
+        if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
+                        == NOTIFY_STOP) {
+                rc = 1;
+                touched = 1;
+        }
+        sum = get_timer_irqs(cpu);
+        if (__get_cpu_var(nmi_touch)) {
+                __get_cpu_var(nmi_touch) = 0;
+                touched = 1;
+        }
+        if (cpu_isset(cpu, backtrace_mask)) {
+                static DEFINE_SPINLOCK(lock);   /* Serialise the printks */
+                spin_lock(&lock);
+                printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
+                dump_stack();
+                spin_unlock(&lock);
+                cpu_clear(cpu, backtrace_mask);
+        }
+        /* Could check oops_in_progress here too, but it's safer not to */
+        if (mce_in_progress())
+                touched = 1;
+        /* if the none of the timers isn't firing, this cpu isn't doing much */
+        if (!touched && __get_cpu_var(last_irq_sum) == sum) {
+                /*
+                 * Ayiee, looks like this CPU is stuck ...
+                 * wait a few IRQs (5 seconds) before doing the oops ...
+                 */
+                local_inc(&__get_cpu_var(alert_counter));
+                if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
+                        /*
+                         * die_nmi will return ONLY if NOTIFY_STOP happens..
+                         */
+                        die_nmi("BUG: NMI Watchdog detected LOCKUP",
+                                regs, panic_on_timeout);
+        } else {
+                __get_cpu_var(last_irq_sum) = sum;
+                local_set(&__get_cpu_var(alert_counter), 0);
+        }
+        /* see if the nmi watchdog went off */
+        if (!__get_cpu_var(wd_enabled))
+                return rc;
+        switch (nmi_watchdog) {
+        case NMI_LOCAL_APIC:
+                rc |= lapic_wd_event(nmi_hz);
+                break;
+        case NMI_IO_APIC:
+                /*
+                 * don't know how to accurately check for this.
+                 * just assume it was a watchdog timer interrupt
+                 * This matches the old behaviour.
+                 */
+                rc = 1;
+                break;
+        }
+        return rc;
+}
+#ifdef CONFIG_SYSCTL
+static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
+{
+        unsigned char reason = get_nmi_reason();
+        char buf[64];
+        sprintf(buf, "NMI received for unknown reason %02x\n", reason);
+        die_nmi(buf, regs, 1); /* Always panic here */
+        return 0;
+}
+/*
+ * proc handler for /proc/sys/kernel/nmi
+ */
+int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
+                        void __user *buffer, size_t *length, loff_t *ppos)
+{
+        int old_state;
+        nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
+        old_state = nmi_watchdog_enabled;
+        proc_dointvec(table, write, file, buffer, length, ppos);
+        if (!!old_state == !!nmi_watchdog_enabled)
+                return 0;
+        if (atomic_read(&nmi_active) < 0 || !nmi_watchdog_active()) {
+                printk(KERN_WARNING
+                        "NMI watchdog is permanently disabled\n");
+                return -EIO;
+        }
+        if (nmi_watchdog == NMI_LOCAL_APIC) {
+                if (nmi_watchdog_enabled)
+                        enable_lapic_nmi_watchdog();
+                else
+                        disable_lapic_nmi_watchdog();
+        } else {
+                printk(KERN_WARNING
+                        "NMI watchdog doesn't know what hardware to touch\n");
+                return -EIO;
+        }
+        return 0;
+}
+#endif /* CONFIG_SYSCTL */
+int do_nmi_callback(struct pt_regs *regs, int cpu)
+{
+#ifdef CONFIG_SYSCTL
+        if (unknown_nmi_panic)
+                return unknown_nmi_panic_callback(regs, cpu);
+#endif
+        return 0;
+}
+void __trigger_all_cpu_backtrace(void)
+{
+        int i;
+        backtrace_mask = cpu_online_map;
+        /* Wait for up to 10 seconds for all CPUs to do the backtrace */
+        for (i = 0; i < 10 * 1000; i++) {
+                if (cpus_empty(backtrace_mask))
+                        break;
+                mdelay(1);
+        }
+}

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c new file mode 100644 index 000000000000..8dfe9db87a9e --- /dev/null +++ b/arch/x86/kernel/nmi.c
@@ -0,0 +1,513 @@
	1	/*
	2	* NMI watchdog support on APIC systems
	3	*
	4	* Started by Ingo Molnar <mingo@redhat.com>
	5	*
	6	* Fixes:
	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.
	10	* Pavel Machek and
	11	* Mikael Pettersson : PM converted to driver model. Disable/enable API.
	12	*/
	13
	14	#include <asm/apic.h>
	15
	16	#include <linux/nmi.h>
	17	#include <linux/mm.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>
	29
	30	#include <asm/i8259.h>
	31	#include <asm/io_apic.h>
	32	#include <asm/smp.h>
	33	#include <asm/nmi.h>
	34	#include <asm/proto.h>
	35	#include <asm/timer.h>
	36
	37	#include <asm/mce.h>
	38
	39	#include <mach_traps.h>
	40
	41	int unknown_nmi_panic;
	42	int nmi_watchdog_enabled;
	43
	44	static cpumask_t backtrace_mask = CPU_MASK_NONE;
	45
	46	/* nmi_active:
	47	* >0: the lapic NMI watchdog is active, but can be disabled
	48	* <0: the lapic NMI watchdog has not been set up, and cannot
	49	* be enabled
	50	* 0: the lapic NMI watchdog is disabled, but can be enabled
	51	*/
	52	atomic_t nmi_active = ATOMIC_INIT(0); /* oprofile uses this */
	53	EXPORT_SYMBOL(nmi_active);
	54
	55	unsigned int nmi_watchdog = NMI_NONE;
	56	EXPORT_SYMBOL(nmi_watchdog);
	57
	58	static int panic_on_timeout;
	59
	60	static unsigned int nmi_hz = HZ;
	61	static DEFINE_PER_CPU(short, wd_enabled);
	62	static int endflag __initdata;
	63
	64	static inline unsigned int get_nmi_count(int cpu)
	65	{
	66	#ifdef CONFIG_X86_64
	67	return cpu_pda(cpu)->__nmi_count;
	68	#else
	69	return nmi_count(cpu);
	70	#endif
	71	}
	72
	73	static inline int mce_in_progress(void)
	74	{
	75	#if defined(CONFIG_X86_64) && defined(CONFIG_X86_MCE)
	76	return atomic_read(&mce_entry) > 0;
	77	#endif
	78	return 0;
	79	}
	80
	81	/*
	82	* Take the local apic timer and PIT/HPET into account. We don't
	83	* know which one is active, when we have highres/dyntick on
	84	*/
	85	static inline unsigned int get_timer_irqs(int cpu)
	86	{
	87	#ifdef CONFIG_X86_64
	88	return read_pda(apic_timer_irqs) + read_pda(irq0_irqs);
	89	#else
	90	return per_cpu(irq_stat, cpu).apic_timer_irqs +
	91	per_cpu(irq_stat, cpu).irq0_irqs;
	92	#endif
	93	}
	94
	95	#ifdef CONFIG_SMP
	96	/*
	97	* The performance counters used by NMI_LOCAL_APIC don't trigger when
	98	* the CPU is idle. To make sure the NMI watchdog really ticks on all
	99	* CPUs during the test make them busy.
	100	*/
	101	static __init void nmi_cpu_busy(void *data)
	102	{
	103	local_irq_enable_in_hardirq();
	104	/*
	105	* Intentionally don't use cpu_relax here. This is
	106	* to make sure that the performance counter really ticks,
	107	* even if there is a simulator or similar that catches the
	108	* pause instruction. On a real HT machine this is fine because
	109	* all other CPUs are busy with "useless" delay loops and don't
	110	* care if they get somewhat less cycles.
	111	*/
	112	while (endflag == 0)
	113	mb();
	114	}
	115	#endif
	116
	117	int __init check_nmi_watchdog(void)
	118	{
	119	unsigned int *prev_nmi_count;
	120	int cpu;
	121
	122	if (!nmi_watchdog_active() \|\| !atomic_read(&nmi_active))
	123	return 0;
	124
	125	prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);
	126	if (!prev_nmi_count)
	127	goto error;
	128
	129	printk(KERN_INFO "Testing NMI watchdog ... ");
	130
	131	#ifdef CONFIG_SMP
	132	if (nmi_watchdog == NMI_LOCAL_APIC)
	133	smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
	134	#endif
	135
	136	for_each_possible_cpu(cpu)
	137	prev_nmi_count[cpu] = get_nmi_count(cpu);
	138	local_irq_enable();
	139	mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
	140
	141	for_each_online_cpu(cpu) {
	142	if (!per_cpu(wd_enabled, cpu))
	143	continue;
	144	if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
	145	printk(KERN_WARNING "WARNING: CPU#%d: NMI "
	146	"appears to be stuck (%d->%d)!\n",
	147	cpu,
	148	prev_nmi_count[cpu],
	149	get_nmi_count(cpu));
	150	per_cpu(wd_enabled, cpu) = 0;
	151	atomic_dec(&nmi_active);
	152	}
	153	}
	154	endflag = 1;
	155	if (!atomic_read(&nmi_active)) {
	156	kfree(prev_nmi_count);
	157	atomic_set(&nmi_active, -1);
	158	goto error;
	159	}
	160	printk("OK.\n");
	161
	162	/*
	163	* now that we know it works we can reduce NMI frequency to
	164	* something more reasonable; makes a difference in some configs
	165	*/
	166	if (nmi_watchdog == NMI_LOCAL_APIC)
	167	nmi_hz = lapic_adjust_nmi_hz(1);
	168
	169	kfree(prev_nmi_count);
	170	return 0;
	171	error:
	172	if (nmi_watchdog == NMI_IO_APIC && !timer_through_8259)
	173	disable_8259A_irq(0);
	174	return -1;
	175	}
	176
	177	static int __init setup_nmi_watchdog(char *str)
	178	{
	179	unsigned int nmi;
	180
	181	if (!strncmp(str, "panic", 5)) {
	182	panic_on_timeout = 1;
	183	str = strchr(str, ',');
	184	if (!str)
	185	return 1;
	186	++str;
	187	}
	188
	189	get_option(&str, &nmi);
	190
	191	if (nmi >= NMI_INVALID)
	192	return 0;
	193
	194	nmi_watchdog = nmi;
	195	return 1;
	196	}
	197	__setup("nmi_watchdog=", setup_nmi_watchdog);
	198
	199	/*
	200	* Suspend/resume support
	201	*/
	202	#ifdef CONFIG_PM
	203
	204	static int nmi_pm_active; /* nmi_active before suspend */
	205
	206	static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
	207	{
	208	/* only CPU0 goes here, other CPUs should be offline */
	209	nmi_pm_active = atomic_read(&nmi_active);
	210	stop_apic_nmi_watchdog(NULL);
	211	BUG_ON(atomic_read(&nmi_active) != 0);
	212	return 0;
	213	}
	214
	215	static int lapic_nmi_resume(struct sys_device *dev)
	216	{
	217	/* only CPU0 goes here, other CPUs should be offline */
	218	if (nmi_pm_active > 0) {
	219	setup_apic_nmi_watchdog(NULL);
	220	touch_nmi_watchdog();
	221	}
	222	return 0;
	223	}
	224
	225	static struct sysdev_class nmi_sysclass = {
	226	.name = "lapic_nmi",
	227	.resume = lapic_nmi_resume,
	228	.suspend = lapic_nmi_suspend,
	229	};
	230
	231	static struct sys_device device_lapic_nmi = {
	232	.id = 0,
	233	.cls = &nmi_sysclass,
	234	};
	235
	236	static int __init init_lapic_nmi_sysfs(void)
	237	{
	238	int error;
	239
	240	/*
	241	* should really be a BUG_ON but b/c this is an
	242	* init call, it just doesn't work. -dcz
	243	*/
	244	if (nmi_watchdog != NMI_LOCAL_APIC)
	245	return 0;
	246
	247	if (atomic_read(&nmi_active) < 0)
	248	return 0;
	249
	250	error = sysdev_class_register(&nmi_sysclass);
	251	if (!error)
	252	error = sysdev_register(&device_lapic_nmi);
	253	return error;
	254	}
	255
	256	/* must come after the local APIC's device_initcall() */
	257	late_initcall(init_lapic_nmi_sysfs);
	258
	259	#endif /* CONFIG_PM */
	260
	261	static void __acpi_nmi_enable(void *__unused)
	262	{
	263	apic_write_around(APIC_LVT0, APIC_DM_NMI);
	264	}
	265
	266	/*
	267	* Enable timer based NMIs on all CPUs:
	268	*/
	269	void acpi_nmi_enable(void)
	270	{
	271	if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
	272	on_each_cpu(__acpi_nmi_enable, NULL, 0, 1);
	273	}
	274
	275	static void __acpi_nmi_disable(void *__unused)
	276	{
	277	apic_write_around(APIC_LVT0, APIC_DM_NMI \| APIC_LVT_MASKED);
	278	}
	279
	280	/*
	281	* Disable timer based NMIs on all CPUs:
	282	*/
	283	void acpi_nmi_disable(void)
	284	{
	285	if (atomic_read(&nmi_active) && nmi_watchdog == NMI_IO_APIC)
	286	on_each_cpu(__acpi_nmi_disable, NULL, 0, 1);
	287	}
	288
	289	void setup_apic_nmi_watchdog(void *unused)
	290	{
	291	if (__get_cpu_var(wd_enabled))
	292	return;
	293
	294	/* cheap hack to support suspend/resume */
	295	/* if cpu0 is not active neither should the other cpus */
	296	if (smp_processor_id() != 0 && atomic_read(&nmi_active) <= 0)
	297	return;
	298
	299	switch (nmi_watchdog) {
	300	case NMI_LOCAL_APIC:
	301	/* enable it before to avoid race with handler */
	302	__get_cpu_var(wd_enabled) = 1;
	303	if (lapic_watchdog_init(nmi_hz) < 0) {
	304	__get_cpu_var(wd_enabled) = 0;
	305	return;
	306	}
	307	/* FALL THROUGH */
	308	case NMI_IO_APIC:
	309	__get_cpu_var(wd_enabled) = 1;
	310	atomic_inc(&nmi_active);
	311	}
	312	}
	313
	314	void stop_apic_nmi_watchdog(void *unused)
	315	{
	316	/* only support LOCAL and IO APICs for now */
	317	if (!nmi_watchdog_active())
	318	return;
	319	if (__get_cpu_var(wd_enabled) == 0)
	320	return;
	321	if (nmi_watchdog == NMI_LOCAL_APIC)
	322	lapic_watchdog_stop();
	323	__get_cpu_var(wd_enabled) = 0;
	324	atomic_dec(&nmi_active);
	325	}
	326
	327	/*
	328	* the best way to detect whether a CPU has a 'hard lockup' problem
	329	* is to check it's local APIC timer IRQ counts. If they are not
	330	* changing then that CPU has some problem.
	331	*
	332	* as these watchdog NMI IRQs are generated on every CPU, we only
	333	* have to check the current processor.
	334	*
	335	* since NMIs don't listen to _any_ locks, we have to be extremely
	336	* careful not to rely on unsafe variables. The printk might lock
	337	* up though, so we have to break up any console locks first ...
	338	* [when there will be more tty-related locks, break them up here too!]
	339	*/
	340
	341	static DEFINE_PER_CPU(unsigned, last_irq_sum);
	342	static DEFINE_PER_CPU(local_t, alert_counter);
	343	static DEFINE_PER_CPU(int, nmi_touch);
	344
	345	void touch_nmi_watchdog(void)
	346	{
	347	if (nmi_watchdog_active()) {
	348	unsigned cpu;
	349
	350	/*
	351	* Tell other CPUs to reset their alert counters. We cannot
	352	* do it ourselves because the alert count increase is not
	353	* atomic.
	354	*/
	355	for_each_present_cpu(cpu) {
	356	if (per_cpu(nmi_touch, cpu) != 1)
	357	per_cpu(nmi_touch, cpu) = 1;
	358	}
	359	}
	360
	361	/*
	362	* Tickle the softlockup detector too:
	363	*/
	364	touch_softlockup_watchdog();
	365	}
	366	EXPORT_SYMBOL(touch_nmi_watchdog);
	367
	368	notrace __kprobes int
	369	nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
	370	{
	371	/*
	372	* Since current_thread_info()-> is always on the stack, and we
	373	* always switch the stack NMI-atomically, it's safe to use
	374	* smp_processor_id().
	375	*/
	376	unsigned int sum;
	377	int touched = 0;
	378	int cpu = smp_processor_id();
	379	int rc = 0;
	380
	381	/* check for other users first */
	382	if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
	383	== NOTIFY_STOP) {
	384	rc = 1;
	385	touched = 1;
	386	}
	387
	388	sum = get_timer_irqs(cpu);
	389
	390	if (__get_cpu_var(nmi_touch)) {
	391	__get_cpu_var(nmi_touch) = 0;
	392	touched = 1;
	393	}
	394
	395	if (cpu_isset(cpu, backtrace_mask)) {
	396	static DEFINE_SPINLOCK(lock); /* Serialise the printks */
	397
	398	spin_lock(&lock);
	399	printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
	400	dump_stack();
	401	spin_unlock(&lock);
	402	cpu_clear(cpu, backtrace_mask);
	403	}
	404
	405	/* Could check oops_in_progress here too, but it's safer not to */
	406	if (mce_in_progress())
	407	touched = 1;
	408
	409	/* if the none of the timers isn't firing, this cpu isn't doing much */
	410	if (!touched && __get_cpu_var(last_irq_sum) == sum) {
	411	/*
	412	* Ayiee, looks like this CPU is stuck ...
	413	* wait a few IRQs (5 seconds) before doing the oops ...
	414	*/
	415	local_inc(&__get_cpu_var(alert_counter));
	416	if (local_read(&__get_cpu_var(alert_counter)) == 5 * nmi_hz)
	417	/*
	418	* die_nmi will return ONLY if NOTIFY_STOP happens..
	419	*/
	420	die_nmi("BUG: NMI Watchdog detected LOCKUP",
	421	regs, panic_on_timeout);
	422	} else {
	423	__get_cpu_var(last_irq_sum) = sum;
	424	local_set(&__get_cpu_var(alert_counter), 0);
	425	}
	426
	427	/* see if the nmi watchdog went off */
	428	if (!__get_cpu_var(wd_enabled))
	429	return rc;
	430	switch (nmi_watchdog) {
	431	case NMI_LOCAL_APIC:
	432	rc \|= lapic_wd_event(nmi_hz);
	433	break;
	434	case NMI_IO_APIC:
	435	/*
	436	* don't know how to accurately check for this.
	437	* just assume it was a watchdog timer interrupt
	438	* This matches the old behaviour.
	439	*/
	440	rc = 1;
	441	break;
	442	}
	443	return rc;
	444	}
	445
	446	#ifdef CONFIG_SYSCTL
	447
	448	static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
	449	{
	450	unsigned char reason = get_nmi_reason();
	451	char buf[64];
	452
	453	sprintf(buf, "NMI received for unknown reason %02x\n", reason);
	454	die_nmi(buf, regs, 1); /* Always panic here */
	455	return 0;
	456	}
	457
	458	/*
	459	* proc handler for /proc/sys/kernel/nmi
	460	*/
	461	int proc_nmi_enabled(struct ctl_table table, int write, struct file file,
	462	void __user buffer, size_t length, loff_t *ppos)
	463	{
	464	int old_state;
	465
	466	nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
	467	old_state = nmi_watchdog_enabled;
	468	proc_dointvec(table, write, file, buffer, length, ppos);
	469	if (!!old_state == !!nmi_watchdog_enabled)
	470	return 0;
	471
	472	if (atomic_read(&nmi_active) < 0 \|\| !nmi_watchdog_active()) {
	473	printk(KERN_WARNING
	474	"NMI watchdog is permanently disabled\n");
	475	return -EIO;
	476	}
	477
	478	if (nmi_watchdog == NMI_LOCAL_APIC) {
	479	if (nmi_watchdog_enabled)
	480	enable_lapic_nmi_watchdog();
	481	else
	482	disable_lapic_nmi_watchdog();
	483	} else {
	484	printk(KERN_WARNING
	485	"NMI watchdog doesn't know what hardware to touch\n");
	486	return -EIO;
	487	}
	488	return 0;
	489	}
	490
	491	#endif /* CONFIG_SYSCTL */
	492
	493	int do_nmi_callback(struct pt_regs *regs, int cpu)
	494	{
	495	#ifdef CONFIG_SYSCTL
	496	if (unknown_nmi_panic)
	497	return unknown_nmi_panic_callback(regs, cpu);
	498	#endif
	499	return 0;
	500	}
	501
	502	void __trigger_all_cpu_backtrace(void)
	503	{
	504	int i;
	505
	506	backtrace_mask = cpu_online_map;
	507	/* Wait for up to 10 seconds for all CPUs to do the backtrace */
	508	for (i = 0; i < 10 * 1000; i++) {
	509	if (cpus_empty(backtrace_mask))
	510	break;
	511	mdelay(1);
	512	}
	513	}