[PATCH] i386/x86-64: Remove un/set_nmi_callback and reserve/release_lapic_nmi functions

Removes the un/set_nmi_callback and reserve/release_lapic_nmi functions as
they are no longer needed.  The various subsystems are modified to register
with the die_notifier instead.

Also includes compile fixes by Andrew Morton.

Signed-off-by:  Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>

10 files changed, 116 insertions, 260 deletions

diff --git a/arch/i386/kernel/crash.c b/arch/i386/kernel/crash.c
index 5b96f038367f..736c76d6b31d 100644
--- a/arch/i386/kernel/crash.c
+++ b/arch/i386/kernel/crash.c
@@ -22,6 +22,8 @@
 #include <asm/nmi.h>
 #include <asm/hw_irq.h>
 #include <asm/apic.h>
+#include <asm/kdebug.h>
+
 #include <mach_ipi.h>
 
 
@@ -93,9 +95,18 @@ static void crash_save_self(struct pt_regs *regs)
 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
 static atomic_t waiting_for_crash_ipi;
 
-static int crash_nmi_callback(struct pt_regs *regs, int cpu)
+static int crash_nmi_callback(struct notifier_block *self,
+                        unsigned long val, void *data)
 {
+        struct pt_regs *regs;
         struct pt_regs fixed_regs;
+        int cpu;
+
+        if (val != DIE_NMI)
+                return NOTIFY_OK;
+
+        regs = ((struct die_args *)data)->regs;
+        cpu = raw_smp_processor_id();
 
         /* Don't do anything if this handler is invoked on crashing cpu.
          * Otherwise, system will completely hang. Crashing cpu can get
@@ -125,13 +136,18 @@ static void smp_send_nmi_allbutself(void)
         send_IPI_allbutself(NMI_VECTOR);
 }
 
+static struct notifier_block crash_nmi_nb = {
+        .notifier_call = crash_nmi_callback,
+};
+
 static void nmi_shootdown_cpus(void)
 {
         unsigned long msecs;
 
         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
         /* Would it be better to replace the trap vector here? */
-        set_nmi_callback(crash_nmi_callback);
+        if (register_die_notifier(&crash_nmi_nb))
+                return;         /* return what? */
         /* Ensure the new callback function is set before sending
          * out the NMI
          */
diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index bd96ea4f2942..acd3fdea2a21 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -42,20 +42,6 @@ static DEFINE_PER_CPU(unsigned long, evntsel_nmi_owner[3]);
  */
 #define NMI_MAX_COUNTER_BITS 66
 
-/*
- * 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:
  * >0: the lapic NMI watchdog is active, but can be disabled
  * <0: the lapic NMI watchdog has not been set up, and cannot
@@ -325,33 +311,6 @@ static void enable_lapic_nmi_watchdog(void)
         touch_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)
 {
         BUG_ON(nmi_watchdog != NMI_IO_APIC);
@@ -866,6 +825,15 @@ done:
         return rc;
 }
 
+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;
+}
+
 #ifdef CONFIG_SYSCTL
 
 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
@@ -873,37 +841,8 @@ 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(regs, buf);
-        }
-        return 0;
-}
-
-/*
- * proc handler for /proc/sys/kernel/unknown_nmi_panic
- */
-int proc_unknown_nmi_panic(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();
-        }
+        sprintf(buf, "NMI received for unknown reason %02x\n", reason);
+        die_nmi(regs, buf);
         return 0;
 }
 
@@ -917,7 +856,5 @@ EXPORT_SYMBOL(reserve_perfctr_nmi);
 EXPORT_SYMBOL(release_perfctr_nmi);
 EXPORT_SYMBOL(reserve_evntsel_nmi);
 EXPORT_SYMBOL(release_evntsel_nmi);
-EXPORT_SYMBOL(reserve_lapic_nmi);
-EXPORT_SYMBOL(release_lapic_nmi);
 EXPORT_SYMBOL(disable_timer_nmi_watchdog);
 EXPORT_SYMBOL(enable_timer_nmi_watchdog);
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 282f0bd40dfd..7db664d0b25c 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -706,13 +706,6 @@ void die_nmi (struct pt_regs *regs, const char *msg)
         do_exit(SIGSEGV);
 }
 
-static int dummy_nmi_callback(struct pt_regs * regs, int cpu)
-{
-        return 0;
-}
-
-static nmi_callback_t nmi_callback = dummy_nmi_callback;
-
 static void default_do_nmi(struct pt_regs * regs)
 {
         unsigned char reason = 0;
@@ -732,9 +725,10 @@ static void default_do_nmi(struct pt_regs * regs)
                  */
                 if (nmi_watchdog_tick(regs, reason))
                         return;
+                if (!do_nmi_callback(regs, smp_processor_id()))
 #endif
-                if (!rcu_dereference(nmi_callback)(regs, smp_processor_id()))
                         unknown_nmi_error(reason, regs);
+
                 return;
         }
         if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT) == NOTIFY_STOP)
@@ -765,19 +759,6 @@ fastcall void do_nmi(struct pt_regs * regs, long error_code)
         nmi_exit();
 }
 
-void set_nmi_callback(nmi_callback_t callback)
-{
-        vmalloc_sync_all();
-        rcu_assign_pointer(nmi_callback, callback);
-}
-EXPORT_SYMBOL_GPL(set_nmi_callback);
-
-void unset_nmi_callback(void)
-{
-        nmi_callback = dummy_nmi_callback;
-}
-EXPORT_SYMBOL_GPL(unset_nmi_callback);
-
 #ifdef CONFIG_KPROBES
 fastcall void __kprobes do_int3(struct pt_regs *regs, long error_code)
 {
diff --git a/arch/i386/oprofile/nmi_int.c b/arch/i386/oprofile/nmi_int.c
index 8710ca081b1e..b3610188bcf0 100644
--- a/arch/i386/oprofile/nmi_int.c
+++ b/arch/i386/oprofile/nmi_int.c
@@ -17,14 +17,15 @@
 #include <asm/nmi.h>
 #include <asm/msr.h>
 #include <asm/apic.h>
+#include <asm/kdebug.h>
  
 #include "op_counter.h"
 #include "op_x86_model.h"
- 
+
 static struct op_x86_model_spec const * model;
 static struct op_msrs cpu_msrs[NR_CPUS];
 static unsigned long saved_lvtpc[NR_CPUS];
- 
+
 static int nmi_start(void);
 static void nmi_stop(void);
 
@@ -82,13 +83,24 @@ static void exit_driverfs(void)
 #define exit_driverfs() do { } while (0)
 #endif /* CONFIG_PM */
 
-
-static int nmi_callback(struct pt_regs * regs, int cpu)
+int profile_exceptions_notify(struct notifier_block *self,
+                                unsigned long val, void *data)
 {
-        return model->check_ctrs(regs, &cpu_msrs[cpu]);
+        struct die_args *args = (struct die_args *)data;
+        int ret = NOTIFY_DONE;
+        int cpu = smp_processor_id();
+
+        switch(val) {
+        case DIE_NMI:
+                if (model->check_ctrs(args->regs, &cpu_msrs[cpu]))
+                        ret = NOTIFY_STOP;
+                break;
+        default:
+                break;
+        }
+        return ret;
 }
- 
- 
+
 static void nmi_cpu_save_registers(struct op_msrs * msrs)
 {
         unsigned int const nr_ctrs = model->num_counters;
@@ -174,27 +186,29 @@ static void nmi_cpu_setup(void * dummy)
         apic_write(APIC_LVTPC, APIC_DM_NMI);
 }
 
+static struct notifier_block profile_exceptions_nb = {
+        .notifier_call = profile_exceptions_notify,
+        .next = NULL,
+        .priority = 0
+};
 
 static int nmi_setup(void)
 {
+        int err=0;
+
         if (!allocate_msrs())
                 return -ENOMEM;
 
-        /* We walk a thin line between law and rape here.
-         * We need to be careful to install our NMI handler
-         * without actually triggering any NMIs as this will
-         * break the core code horrifically.
-         */
-        if (reserve_lapic_nmi() < 0) {
+        if ((err = register_die_notifier(&profile_exceptions_nb))){
                 free_msrs();
-                return -EBUSY;
+                return err;
         }
+
         /* We need to serialize save and setup for HT because the subset
          * of msrs are distinct for save and setup operations
          */
         on_each_cpu(nmi_save_registers, NULL, 0, 1);
         on_each_cpu(nmi_cpu_setup, NULL, 0, 1);
-        set_nmi_callback(nmi_callback);
         nmi_enabled = 1;
         return 0;
 }
@@ -250,8 +264,7 @@ static void nmi_shutdown(void)
 {
         nmi_enabled = 0;
         on_each_cpu(nmi_cpu_shutdown, NULL, 0, 1);
-        unset_nmi_callback();
-        release_lapic_nmi();
+        unregister_die_notifier(&profile_exceptions_nb);
         free_msrs();
 }
 
diff --git a/arch/i386/oprofile/nmi_timer_int.c b/arch/i386/oprofile/nmi_timer_int.c
index a33a73bb502d..93ca48f804ac 100644
--- a/arch/i386/oprofile/nmi_timer_int.c
+++ b/arch/i386/oprofile/nmi_timer_int.c
@@ -17,32 +17,49 @@
 #include <asm/nmi.h>
 #include <asm/apic.h>
 #include <asm/ptrace.h>
+#include <asm/kdebug.h>
  
-static int nmi_timer_callback(struct pt_regs * regs, int cpu)
+int profile_timer_exceptions_notify(struct notifier_block *self,
+                                unsigned long val, void *data)
 {
-        oprofile_add_sample(regs, 0);
-        return 1;
+        struct die_args *args = (struct die_args *)data;
+        int ret = NOTIFY_DONE;
+
+        switch(val) {
+        case DIE_NMI:
+                oprofile_add_sample(args->regs, 0);
+                ret = NOTIFY_STOP;
+                break;
+        default:
+                break;
+        }
+        return ret;
 }
 
+static struct notifier_block profile_timer_exceptions_nb = {
+        .notifier_call = profile_timer_exceptions_notify,
+        .next = NULL,
+        .priority = 0
+};
+
 static int timer_start(void)
 {
-        disable_timer_nmi_watchdog();
-        set_nmi_callback(nmi_timer_callback);
+        if (register_die_notifier(&profile_timer_exceptions_nb))
+                return 1;
         return 0;
 }
 
 
 static void timer_stop(void)
 {
-        enable_timer_nmi_watchdog();
-        unset_nmi_callback();
+        unregister_die_notifier(&profile_timer_exceptions_nb);
         synchronize_sched();  /* Allow already-started NMIs to complete. */
 }
 
 
 int __init op_nmi_timer_init(struct oprofile_operations * ops)
 {
-        if (atomic_read(&nmi_active) <= 0)
+        if ((nmi_watchdog != NMI_IO_APIC) || (atomic_read(&nmi_active) <= 0))
                 return -ENODEV;
 
         ops->start = timer_start;
diff --git a/arch/x86_64/kernel/crash.c b/arch/x86_64/kernel/crash.c
index d8d5750d6106..44c8af65325e 100644
--- a/arch/x86_64/kernel/crash.c
+++ b/arch/x86_64/kernel/crash.c
@@ -23,6 +23,7 @@
 #include <asm/nmi.h>
 #include <asm/hw_irq.h>
 #include <asm/mach_apic.h>
+#include <asm/kdebug.h>
 
 /* This keeps a track of which one is crashing cpu. */
 static int crashing_cpu;
@@ -95,8 +96,18 @@ static void crash_save_self(struct pt_regs *regs)
 #ifdef CONFIG_SMP
 static atomic_t waiting_for_crash_ipi;
 
-static int crash_nmi_callback(struct pt_regs *regs, int cpu)
+static int crash_nmi_callback(struct notifier_block *self,
+                                unsigned long val, void *data)
 {
+        struct pt_regs *regs;
+        int cpu;
+
+        if (val != DIE_NMI)
+                return NOTIFY_OK;
+
+        regs = ((struct die_args *)data)->regs;
+        cpu = raw_smp_processor_id();
+
         /*
          * Don't do anything if this handler is invoked on crashing cpu.
          * Otherwise, system will completely hang. Crashing cpu can get
@@ -127,12 +138,17 @@ static void smp_send_nmi_allbutself(void)
  * cpu hotplug shouldn't matter.
  */
 
+static struct notifier_block crash_nmi_nb = {
+        .notifier_call = crash_nmi_callback,
+};
+
 static void nmi_shootdown_cpus(void)
 {
         unsigned long msecs;
 
         atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
-        set_nmi_callback(crash_nmi_callback);
+        if (register_die_notifier(&crash_nmi_nb))
+                return;         /* return what? */
 
         /*
          * Ensure the new callback function is set before sending
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index f6b881b23a70..9d175dcf3a2d 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -41,20 +41,6 @@ static DEFINE_PER_CPU(unsigned, evntsel_nmi_owner[2]);
  */
 #define NMI_MAX_COUNTER_BITS 66
 
-/*
- * 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:
  * >0: the lapic NMI watchdog is active, but can be disabled
  * <0: the lapic NMI watchdog has not been set up, and cannot
@@ -321,33 +307,6 @@ static void enable_lapic_nmi_watchdog(void)
         touch_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)
 {
         BUG_ON(nmi_watchdog != NMI_IO_APIC);
@@ -762,13 +721,6 @@ done:
         return rc;
 }
 
-static __kprobes int dummy_nmi_callback(struct pt_regs * regs, int cpu)
-{
-        return 0;
-}
- 
-static nmi_callback_t nmi_callback = dummy_nmi_callback;
- 
 asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
 {
         nmi_enter();
@@ -779,21 +731,12 @@ asmlinkage __kprobes void do_nmi(struct pt_regs * regs, long error_code)
 
 int do_nmi_callback(struct pt_regs * regs, int cpu)
 {
-        return rcu_dereference(nmi_callback)(regs, cpu);
-}
-
-void set_nmi_callback(nmi_callback_t callback)
-{
-        vmalloc_sync_all();
-        rcu_assign_pointer(nmi_callback, callback);
-}
-EXPORT_SYMBOL_GPL(set_nmi_callback);
-
-void unset_nmi_callback(void)
-{
-        nmi_callback = dummy_nmi_callback;
+#ifdef CONFIG_SYSCTL
+        if (unknown_nmi_panic)
+                return unknown_nmi_panic_callback(regs, cpu);
+#endif
+        return 0;
 }
-EXPORT_SYMBOL_GPL(unset_nmi_callback);
 
 #ifdef CONFIG_SYSCTL
 
@@ -802,37 +745,8 @@ 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();
-        }
+        sprintf(buf, "NMI received for unknown reason %02x\n", reason);
+        die_nmi(buf,regs);
         return 0;
 }
 
@@ -846,8 +760,6 @@ EXPORT_SYMBOL(reserve_perfctr_nmi);
 EXPORT_SYMBOL(release_perfctr_nmi);
 EXPORT_SYMBOL(reserve_evntsel_nmi);
 EXPORT_SYMBOL(release_evntsel_nmi);
-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);
diff --git a/include/asm-i386/nmi.h b/include/asm-i386/nmi.h
index da0e0b4e9139..34d6bf063b6e 100644
--- a/include/asm-i386/nmi.h
+++ b/include/asm-i386/nmi.h
@@ -6,24 +6,13 @@
 
 #include <linux/pm.h>
 
-struct pt_regs;
-
-typedef int (*nmi_callback_t)(struct pt_regs * regs, int cpu);
-
-/**
- * set_nmi_callback
- *
- * Set a handler for an NMI. Only one handler may be
- * set. Return 1 if the NMI was handled.
- */
-void set_nmi_callback(nmi_callback_t callback);
-
 /**
- * unset_nmi_callback
+ * do_nmi_callback
  *
- * Remove the handler previously set.
+ * Check to see if a callback exists and execute it.  Return 1
+ * if the handler exists and was handled successfully.
  */
-void unset_nmi_callback(void);
+int do_nmi_callback(struct pt_regs *regs, int cpu);
 
 extern int avail_to_resrv_perfctr_nmi_bit(unsigned int);
 extern int avail_to_resrv_perfctr_nmi(unsigned int);
@@ -33,8 +22,6 @@ extern int reserve_evntsel_nmi(unsigned int);
 extern void release_evntsel_nmi(unsigned int);
 
 extern void setup_apic_nmi_watchdog (void *);
-extern int reserve_lapic_nmi(void);
-extern void release_lapic_nmi(void);
 extern void disable_timer_nmi_watchdog(void);
 extern void enable_timer_nmi_watchdog(void);
 extern int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);
diff --git a/include/asm-x86_64/nmi.h b/include/asm-x86_64/nmi.h
index 8f02a2a416e6..8818c39d34e0 100644
--- a/include/asm-x86_64/nmi.h
+++ b/include/asm-x86_64/nmi.h
@@ -7,25 +7,6 @@
 #include <linux/pm.h>
 #include <asm/io.h>
  
-struct pt_regs;
-
-typedef int (*nmi_callback_t)(struct pt_regs * regs, int cpu);
-
-/**
- * set_nmi_callback
- *
- * Set a handler for an NMI. Only one handler may be
- * set. Return 1 if the NMI was handled.
- */
-void set_nmi_callback(nmi_callback_t callback);
-
-/**
- * unset_nmi_callback
- *
- * Remove the handler previously set.
- */
-void unset_nmi_callback(void);
-
 /**
  * do_nmi_callback
  *
@@ -72,8 +53,6 @@ extern int reserve_evntsel_nmi(unsigned int);
 extern void release_evntsel_nmi(unsigned int);
 
 extern void setup_apic_nmi_watchdog (void *);
-extern int reserve_lapic_nmi(void);
-extern void release_lapic_nmi(void);
 extern void disable_timer_nmi_watchdog(void);
 extern void enable_timer_nmi_watchdog(void);
 extern int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 362a0cc37138..83f168361624 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -76,8 +76,6 @@ extern int compat_log;
 
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 int unknown_nmi_panic;
-extern int proc_unknown_nmi_panic(ctl_table *, int, struct file *,
-                                  void __user *, size_t *, loff_t *);
 #endif
 
 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
@@ -628,7 +626,7 @@ static ctl_table kern_table[] = {
                 .data           = &unknown_nmi_panic,
                 .maxlen         = sizeof (int),
                 .mode           = 0644,
-                .proc_handler   = &proc_unknown_nmi_panic,
+                .proc_handler   = &proc_dointvec,
         },
 #endif
 #if defined(CONFIG_X86)