[PATCH] i386: Add SMP support on i386 to reservation framework

This patch includes the changes to make the nmi watchdog on i386 SMP aware.
A bunch of code was moved around to make it simpler to read.  In addition,
it is now possible to determine if a particular NMI was the result of the
watchdog or not.  This feature allows the kernel to filter out unknown NMIs
easier.

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

5 files changed, 360 insertions, 191 deletions

diff --git a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c
index 8c844d07862f..1a34fc57800b 100644
--- a/arch/i386/kernel/apic.c
+++ b/arch/i386/kernel/apic.c
@@ -586,8 +586,7 @@ void __devinit setup_local_APIC(void)
                         printk("No ESR for 82489DX.\n");
         }
 
-        if (nmi_watchdog == NMI_LOCAL_APIC)
-                setup_apic_nmi_watchdog();
+        setup_apic_nmi_watchdog(NULL);
         apic_pm_activate();
 }
 
diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index 5d58dfeacd59..d88004343034 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -24,16 +24,10 @@
 
 #include <asm/smp.h>
 #include <asm/nmi.h>
+#include <asm/kdebug.h>
 
 #include "mach_traps.h"
 
-unsigned int nmi_watchdog = NMI_NONE;
-extern int unknown_nmi_panic;
-static unsigned int nmi_hz = HZ;
-static unsigned int nmi_perfctr_msr;    /* the MSR to reset in NMI handler */
-static unsigned int nmi_p4_cccr_val;
-extern void show_registers(struct pt_regs *regs);
-
 /* perfctr_nmi_owner tracks the ownership of the perfctr registers:
  * evtsel_nmi_owner tracks the ownership of the event selection
  * - different performance counters/ event selection may be reserved for
@@ -63,51 +57,31 @@ static unsigned int lapic_nmi_owner;
 #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
+ * >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
- * -1: the lapic NMI watchdog is disabled, but can be enabled
+ *  0: the lapic NMI watchdog is disabled, but can be enabled
  */
-int nmi_active;
+atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
 
-#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
+unsigned int nmi_watchdog = NMI_DEFAULT;
+static unsigned int nmi_hz = HZ;
 
-#define P6_EVNTSEL0_ENABLE      (1 << 22)
-#define P6_EVNTSEL_INT          (1 << 20)
-#define P6_EVNTSEL_OS           (1 << 17)
-#define P6_EVNTSEL_USR          (1 << 16)
-#define P6_EVENT_CPU_CLOCKS_NOT_HALTED  0x79
-#define P6_NMI_EVENT            P6_EVENT_CPU_CLOCKS_NOT_HALTED
+struct nmi_watchdog_ctlblk {
+        int enabled;
+        u64 check_bit;
+        unsigned int cccr_msr;
+        unsigned int perfctr_msr;  /* the MSR to reset in NMI handler */
+        unsigned int evntsel_msr;  /* the MSR to select the events to handle */
+};
+static DEFINE_PER_CPU(struct nmi_watchdog_ctlblk, nmi_watchdog_ctlblk);
 
-#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)
+/* local prototypes */
+static void stop_apic_nmi_watchdog(void *unused);
+static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu);
+
+extern void show_registers(struct pt_regs *regs);
+extern int unknown_nmi_panic;
 
 /* converts an msr to an appropriate reservation bit */
 static inline unsigned int nmi_perfctr_msr_to_bit(unsigned int msr)
@@ -208,6 +182,17 @@ void release_evntsel_nmi(unsigned int msr)
         clear_bit(counter, &__get_cpu_var(evntsel_nmi_owner)[0]);
 }
 
+static __cpuinit inline int nmi_known_cpu(void)
+{
+        switch (boot_cpu_data.x86_vendor) {
+        case X86_VENDOR_AMD:
+                return ((boot_cpu_data.x86 == 15) || (boot_cpu_data.x86 == 6));
+        case X86_VENDOR_INTEL:
+                return ((boot_cpu_data.x86 == 15) || (boot_cpu_data.x86 == 6));
+        }
+        return 0;
+}
+
 #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
@@ -234,7 +219,10 @@ static int __init check_nmi_watchdog(void)
         unsigned int *prev_nmi_count;
         int cpu;
 
-        if (nmi_watchdog == NMI_NONE)
+        if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
+                return 0;
+
+        if (!atomic_read(&nmi_active))
                 return 0;
 
         prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
@@ -258,18 +246,22 @@ static int __init check_nmi_watchdog(void)
                 if (!cpu_isset(cpu, cpu_callin_map))
                         continue;
 #endif
+                if (!per_cpu(nmi_watchdog_ctlblk, cpu).enabled)
+                        continue;
                 if (nmi_count(cpu) - prev_nmi_count[cpu] <= 5) {
-                        endflag = 1;
                         printk("CPU#%d: NMI appears to be stuck (%d->%d)!\n",
                                 cpu,
                                 prev_nmi_count[cpu],
                                 nmi_count(cpu));
-                        nmi_active = 0;
-                        lapic_nmi_owner &= ~LAPIC_NMI_WATCHDOG;
-                        kfree(prev_nmi_count);
-                        return -1;
+                        per_cpu(nmi_watchdog_ctlblk, cpu).enabled = 0;
+                        atomic_dec(&nmi_active);
                 }
         }
+        if (!atomic_read(&nmi_active)) {
+                kfree(prev_nmi_count);
+                atomic_set(&nmi_active, -1);
+                return -1;
+        }
         endflag = 1;
         printk("OK.\n");
 
@@ -290,31 +282,16 @@ static int __init setup_nmi_watchdog(char *str)
 
         get_option(&str, &nmi);
 
-        if (nmi >= NMI_INVALID)
+        if ((nmi >= NMI_INVALID) || (nmi < NMI_NONE))
                 return 0;
-        if (nmi == NMI_NONE)
-                nmi_watchdog = nmi;
         /*
          * If any other x86 CPU has a local APIC, then
          * please test the NMI stuff there and send me the
          * missing bits. Right now Intel P6/P4 and AMD K7 only.
          */
-        if ((nmi == NMI_LOCAL_APIC) &&
-                        (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) &&
-                        (boot_cpu_data.x86 == 6 || boot_cpu_data.x86 == 15))
-                nmi_watchdog = nmi;
-        if ((nmi == NMI_LOCAL_APIC) &&
-                        (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) &&
-                        (boot_cpu_data.x86 == 6 || boot_cpu_data.x86 == 15))
-                nmi_watchdog = nmi;
-        /*
-         * We can enable the IO-APIC watchdog
-         * unconditionally.
-         */
-        if (nmi == NMI_IO_APIC) {
-                nmi_active = 1;
-                nmi_watchdog = nmi;
-        }
+        if ((nmi == NMI_LOCAL_APIC) && (nmi_known_cpu() == 0))
+                return 0;  /* no lapic support */
+        nmi_watchdog = nmi;
         return 1;
 }
 
@@ -322,41 +299,30 @@ __setup("nmi_watchdog=", setup_nmi_watchdog);
 
 static void disable_lapic_nmi_watchdog(void)
 {
-        if (nmi_active <= 0)
+        BUG_ON(nmi_watchdog != NMI_LOCAL_APIC);
+
+        if (atomic_read(&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:
-                switch (boot_cpu_data.x86) {
-                case 6:
-                        if (boot_cpu_data.x86_model > 0xd)
-                                break;
 
-                        wrmsr(MSR_P6_EVNTSEL0, 0, 0);
-                        break;
-                case 15:
-                        if (boot_cpu_data.x86_model > 0x4)
-                                break;
+        on_each_cpu(stop_apic_nmi_watchdog, NULL, 0, 1);
 
-                        wrmsr(MSR_P4_IQ_CCCR0, 0, 0);
-                        wrmsr(MSR_P4_CRU_ESCR0, 0, 0);
-                        break;
-                }
-                break;
-        }
-        nmi_active = -1;
-        /* tell do_nmi() and others that we're not active any more */
-        nmi_watchdog = 0;
+        BUG_ON(atomic_read(&nmi_active) != 0);
 }
 
 static void enable_lapic_nmi_watchdog(void)
 {
-        if (nmi_active < 0) {
-                nmi_watchdog = NMI_LOCAL_APIC;
-                setup_apic_nmi_watchdog();
-        }
+        BUG_ON(nmi_watchdog != NMI_LOCAL_APIC);
+
+        /* are we already enabled */
+        if (atomic_read(&nmi_active) != 0)
+                return;
+
+        /* are we lapic aware */
+        if (nmi_known_cpu() <= 0)
+                return;
+
+        on_each_cpu(setup_apic_nmi_watchdog, NULL, 0, 1);
+        touch_nmi_watchdog();
 }
 
 int reserve_lapic_nmi(void)
@@ -388,20 +354,25 @@ void release_lapic_nmi(void)
 
 void disable_timer_nmi_watchdog(void)
 {
-        if ((nmi_watchdog != NMI_IO_APIC) || (nmi_active <= 0))
+        BUG_ON(nmi_watchdog != NMI_IO_APIC);
+
+        if (atomic_read(&nmi_active) <= 0)
                 return;
 
-        unset_nmi_callback();
-        nmi_active = -1;
-        nmi_watchdog = NMI_NONE;
+        disable_irq(0);
+        on_each_cpu(stop_apic_nmi_watchdog, NULL, 0, 1);
+
+        BUG_ON(atomic_read(&nmi_active) != 0);
 }
 
 void enable_timer_nmi_watchdog(void)
 {
-        if (nmi_active < 0) {
-                nmi_watchdog = NMI_IO_APIC;
+        BUG_ON(nmi_watchdog != NMI_IO_APIC);
+
+        if (atomic_read(&nmi_active) == 0) {
                 touch_nmi_watchdog();
-                nmi_active = 1;
+                on_each_cpu(setup_apic_nmi_watchdog, NULL, 0, 1);
+                enable_irq(0);
         }
 }
 
@@ -411,7 +382,7 @@ static int nmi_pm_active; /* nmi_active before suspend */
 
 static int lapic_nmi_suspend(struct sys_device *dev, pm_message_t state)
 {
-        nmi_pm_active = nmi_active;
+        nmi_pm_active = atomic_read(&nmi_active);
         disable_lapic_nmi_watchdog();
         return 0;
 }
@@ -439,7 +410,13 @@ static int __init init_lapic_nmi_sysfs(void)
 {
         int error;
 
-        if (nmi_active == 0 || nmi_watchdog != NMI_LOCAL_APIC)
+        /* 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);
@@ -457,143 +434,312 @@ late_initcall(init_lapic_nmi_sysfs);
  * Original code written by Keith Owens.
  */
 
-static void write_watchdog_counter(const char *descr)
+static void write_watchdog_counter(unsigned int perfctr_msr, const char *descr)
 {
         u64 count = (u64)cpu_khz * 1000;
 
         do_div(count, nmi_hz);
         if(descr)
                 Dprintk("setting %s to -0x%08Lx\n", descr, count);
-        wrmsrl(nmi_perfctr_msr, 0 - count);
+        wrmsrl(perfctr_msr, 0 - count);
 }
 
+/* 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
+
 static int setup_k7_watchdog(void)
 {
+        unsigned int perfctr_msr, evntsel_msr;
         unsigned int evntsel;
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-        nmi_perfctr_msr = MSR_K7_PERFCTR0;
-
-        if (!reserve_perfctr_nmi(nmi_perfctr_msr))
+        perfctr_msr = MSR_K7_PERFCTR0;
+        evntsel_msr = MSR_K7_EVNTSEL0;
+        if (!reserve_perfctr_nmi(perfctr_msr))
                 goto fail;
 
-        if (!reserve_evntsel_nmi(MSR_K7_EVNTSEL0))
+        if (!reserve_evntsel_nmi(evntsel_msr))
                 goto fail1;
 
-        wrmsrl(MSR_K7_PERFCTR0, 0UL);
+        wrmsrl(perfctr_msr, 0UL);
 
         evntsel = K7_EVNTSEL_INT
                 | K7_EVNTSEL_OS
                 | K7_EVNTSEL_USR
                 | K7_NMI_EVENT;
 
-        wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
-        write_watchdog_counter("K7_PERFCTR0");
+        /* setup the timer */
+        wrmsr(evntsel_msr, evntsel, 0);
+        write_watchdog_counter(perfctr_msr, "K7_PERFCTR0");
         apic_write(APIC_LVTPC, APIC_DM_NMI);
         evntsel |= K7_EVNTSEL_ENABLE;
-        wrmsr(MSR_K7_EVNTSEL0, evntsel, 0);
+        wrmsr(evntsel_msr, evntsel, 0);
+
+        wd->perfctr_msr = perfctr_msr;
+        wd->evntsel_msr = evntsel_msr;
+        wd->cccr_msr = 0;  //unused
+        wd->check_bit = 1ULL<<63;
         return 1;
 fail1:
-        release_perfctr_nmi(nmi_perfctr_msr);
+        release_perfctr_nmi(perfctr_msr);
 fail:
         return 0;
 }
 
+static void stop_k7_watchdog(void)
+{
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+
+        wrmsr(wd->evntsel_msr, 0, 0);
+
+        release_evntsel_nmi(wd->evntsel_msr);
+        release_perfctr_nmi(wd->perfctr_msr);
+}
+
+#define P6_EVNTSEL0_ENABLE      (1 << 22)
+#define P6_EVNTSEL_INT          (1 << 20)
+#define P6_EVNTSEL_OS           (1 << 17)
+#define P6_EVNTSEL_USR          (1 << 16)
+#define P6_EVENT_CPU_CLOCKS_NOT_HALTED  0x79
+#define P6_NMI_EVENT            P6_EVENT_CPU_CLOCKS_NOT_HALTED
+
 static int setup_p6_watchdog(void)
 {
+        unsigned int perfctr_msr, evntsel_msr;
         unsigned int evntsel;
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-        nmi_perfctr_msr = MSR_P6_PERFCTR0;
-
-        if (!reserve_perfctr_nmi(nmi_perfctr_msr))
+        perfctr_msr = MSR_P6_PERFCTR0;
+        evntsel_msr = MSR_P6_EVNTSEL0;
+        if (!reserve_perfctr_nmi(perfctr_msr))
                 goto fail;
 
-        if (!reserve_evntsel_nmi(MSR_P6_EVNTSEL0))
+        if (!reserve_evntsel_nmi(evntsel_msr))
                 goto fail1;
 
+        wrmsrl(perfctr_msr, 0UL);
+
         evntsel = P6_EVNTSEL_INT
                 | P6_EVNTSEL_OS
                 | P6_EVNTSEL_USR
                 | P6_NMI_EVENT;
 
-        wrmsr(MSR_P6_EVNTSEL0, evntsel, 0);
-        write_watchdog_counter("P6_PERFCTR0");
+        /* setup the timer */
+        wrmsr(evntsel_msr, evntsel, 0);
+        write_watchdog_counter(perfctr_msr, "P6_PERFCTR0");
         apic_write(APIC_LVTPC, APIC_DM_NMI);
         evntsel |= P6_EVNTSEL0_ENABLE;
-        wrmsr(MSR_P6_EVNTSEL0, evntsel, 0);
+        wrmsr(evntsel_msr, evntsel, 0);
+
+        wd->perfctr_msr = perfctr_msr;
+        wd->evntsel_msr = evntsel_msr;
+        wd->cccr_msr = 0;  //unused
+        wd->check_bit = 1ULL<<39;
         return 1;
 fail1:
-        release_perfctr_nmi(nmi_perfctr_msr);
+        release_perfctr_nmi(perfctr_msr);
 fail:
         return 0;
 }
 
+static void stop_p6_watchdog(void)
+{
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+
+        wrmsr(wd->evntsel_msr, 0, 0);
+
+        release_evntsel_nmi(wd->evntsel_msr);
+        release_perfctr_nmi(wd->perfctr_msr);
+}
+
+/* Note that these events don't tick when the CPU idles. This means
+   the frequency varies with CPU load. */
+
+#define MSR_P4_MISC_ENABLE_PERF_AVAIL   (1<<7)
+#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)
+#define P4_CCCR_OVF             (1<<31)
+/* 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] */
+
 static int setup_p4_watchdog(void)
 {
+        unsigned int perfctr_msr, evntsel_msr, cccr_msr;
+        unsigned int evntsel, cccr_val;
         unsigned int misc_enable, dummy;
+        unsigned int ht_num;
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
 
-        rdmsr(MSR_P4_MISC_ENABLE, misc_enable, dummy);
+        rdmsr(MSR_IA32_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;
+        /* detect which hyperthread we are on */
+        if (smp_num_siblings == 2) {
+                unsigned int ebx, apicid;
+
+                ebx = cpuid_ebx(1);
+                apicid = (ebx >> 24) & 0xff;
+                ht_num = apicid & 1;
+        } else
 #endif
+                ht_num = 0;
+
+        /* performance counters are shared resources
+         * assign each hyperthread its own set
+         * (re-use the ESCR0 register, seems safe
+         * and keeps the cccr_val the same)
+         */
+        if (!ht_num) {
+                /* logical cpu 0 */
+                perfctr_msr = MSR_P4_IQ_PERFCTR0;
+                evntsel_msr = MSR_P4_CRU_ESCR0;
+                cccr_msr = MSR_P4_IQ_CCCR0;
+                cccr_val = P4_CCCR_OVF_PMI0 | P4_CCCR_ESCR_SELECT(4);
+        } else {
+                /* logical cpu 1 */
+                perfctr_msr = MSR_P4_IQ_PERFCTR1;
+                evntsel_msr = MSR_P4_CRU_ESCR0;
+                cccr_msr = MSR_P4_IQ_CCCR1;
+                cccr_val = P4_CCCR_OVF_PMI1 | P4_CCCR_ESCR_SELECT(4);
+        }
 
-        if (!reserve_perfctr_nmi(nmi_perfctr_msr))
+        if (!reserve_perfctr_nmi(perfctr_msr))
                 goto fail;
 
-        if (!reserve_evntsel_nmi(MSR_P4_CRU_ESCR0))
+        if (!reserve_evntsel_nmi(evntsel_msr))
                 goto fail1;
 
-        wrmsr(MSR_P4_CRU_ESCR0, P4_NMI_CRU_ESCR0, 0);
-        wrmsr(MSR_P4_IQ_CCCR0, P4_NMI_IQ_CCCR0 & ~P4_CCCR_ENABLE, 0);
-        write_watchdog_counter("P4_IQ_COUNTER0");
+        evntsel = P4_ESCR_EVENT_SELECT(0x3F)
+                | P4_ESCR_OS
+                | P4_ESCR_USR;
+
+        cccr_val |= P4_CCCR_THRESHOLD(15)
+                 | P4_CCCR_COMPLEMENT
+                 | P4_CCCR_COMPARE
+                 | P4_CCCR_REQUIRED;
+
+        wrmsr(evntsel_msr, evntsel, 0);
+        wrmsr(cccr_msr, cccr_val, 0);
+        write_watchdog_counter(perfctr_msr, "P4_IQ_COUNTER0");
         apic_write(APIC_LVTPC, APIC_DM_NMI);
-        wrmsr(MSR_P4_IQ_CCCR0, nmi_p4_cccr_val, 0);
+        cccr_val |= P4_CCCR_ENABLE;
+        wrmsr(cccr_msr, cccr_val, 0);
+        wd->perfctr_msr = perfctr_msr;
+        wd->evntsel_msr = evntsel_msr;
+        wd->cccr_msr = cccr_msr;
+        wd->check_bit = 1ULL<<39;
         return 1;
 fail1:
-        release_perfctr_nmi(nmi_perfctr_msr);
+        release_perfctr_nmi(perfctr_msr);
 fail:
         return 0;
 }
 
-void setup_apic_nmi_watchdog (void)
+static void stop_p4_watchdog(void)
 {
-        switch (boot_cpu_data.x86_vendor) {
-        case X86_VENDOR_AMD:
-                if (boot_cpu_data.x86 != 6 && boot_cpu_data.x86 != 15)
-                        return;
-                if (!setup_k7_watchdog())
-                        return;
-                break;
-        case X86_VENDOR_INTEL:
-                switch (boot_cpu_data.x86) {
-                case 6:
-                        if (boot_cpu_data.x86_model > 0xd)
-                                return;
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+
+        wrmsr(wd->cccr_msr, 0, 0);
+        wrmsr(wd->evntsel_msr, 0, 0);
 
-                        if(!setup_p6_watchdog())
+        release_evntsel_nmi(wd->evntsel_msr);
+        release_perfctr_nmi(wd->perfctr_msr);
+}
+
+void setup_apic_nmi_watchdog (void *unused)
+{
+        /* only support LOCAL and IO APICs for now */
+        if ((nmi_watchdog != NMI_LOCAL_APIC) &&
+            (nmi_watchdog != NMI_IO_APIC))
+                return;
+
+        if (nmi_watchdog == NMI_LOCAL_APIC) {
+                switch (boot_cpu_data.x86_vendor) {
+                case X86_VENDOR_AMD:
+                        if (boot_cpu_data.x86 != 6 && boot_cpu_data.x86 != 15)
                                 return;
-                        break;
-                case 15:
-                        if (boot_cpu_data.x86_model > 0x4)
+                        if (!setup_k7_watchdog())
                                 return;
+                        break;
+                case X86_VENDOR_INTEL:
+                        switch (boot_cpu_data.x86) {
+                        case 6:
+                                if (boot_cpu_data.x86_model > 0xd)
+                                        return;
+
+                                if (!setup_p6_watchdog())
+                                        return;
+                                break;
+                        case 15:
+                                if (boot_cpu_data.x86_model > 0x4)
+                                        return;
 
-                        if (!setup_p4_watchdog())
+                                if (!setup_p4_watchdog())
+                                        return;
+                                break;
+                        default:
                                 return;
+                        }
+                        break;
+                default:
+                        return;
+                }
+        }
+        __get_cpu_var(nmi_watchdog_ctlblk.enabled) = 1;
+        atomic_inc(&nmi_active);
+}
+
+static void stop_apic_nmi_watchdog(void *unused)
+{
+        /* only support LOCAL and IO APICs for now */
+        if ((nmi_watchdog != NMI_LOCAL_APIC) &&
+            (nmi_watchdog != NMI_IO_APIC))
+                return;
+
+        if (nmi_watchdog == NMI_LOCAL_APIC) {
+                switch (boot_cpu_data.x86_vendor) {
+                case X86_VENDOR_AMD:
+                        stop_k7_watchdog();
+                        break;
+                case X86_VENDOR_INTEL:
+                        switch (boot_cpu_data.x86) {
+                        case 6:
+                                if (boot_cpu_data.x86_model > 0xd)
+                                        break;
+                                stop_p6_watchdog();
+                                break;
+                        case 15:
+                                if (boot_cpu_data.x86_model > 0x4)
+                                        break;
+                                stop_p4_watchdog();
+                                break;
+                        }
                         break;
                 default:
                         return;
                 }
-                break;
-        default:
-                return;
         }
-        lapic_nmi_owner = LAPIC_NMI_WATCHDOG;
-        nmi_active = 1;
+        __get_cpu_var(nmi_watchdog_ctlblk.enabled) = 0;
+        atomic_dec(&nmi_active);
 }
 
 /*
@@ -635,7 +781,7 @@ EXPORT_SYMBOL(touch_nmi_watchdog);
 
 extern void die_nmi(struct pt_regs *, const char *msg);
 
-void nmi_watchdog_tick (struct pt_regs * regs)
+void nmi_watchdog_tick (struct pt_regs * regs, unsigned reason)
 {
 
         /*
@@ -644,11 +790,21 @@ void nmi_watchdog_tick (struct pt_regs * regs)
          * smp_processor_id().
          */
         unsigned int sum;
+        int touched = 0;
         int cpu = smp_processor_id();
+        struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);
+        u64 dummy;
+
+        /* check for other users first */
+        if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT)
+                        == NOTIFY_STOP) {
+                touched = 1;
+        }
 
         sum = per_cpu(irq_stat, cpu).apic_timer_irqs;
 
-        if (last_irq_sums[cpu] == sum) {
+        /* if the apic timer isn't firing, this cpu isn't doing much */
+        if (!touched && last_irq_sums[cpu] == sum) {
                 /*
                  * Ayiee, looks like this CPU is stuck ...
                  * wait a few IRQs (5 seconds) before doing the oops ...
@@ -663,26 +819,41 @@ void nmi_watchdog_tick (struct pt_regs * regs)
                 last_irq_sums[cpu] = sum;
                 alert_counter[cpu] = 0;
         }
-        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);
-                }
-                else if (nmi_perfctr_msr == MSR_P6_PERFCTR0) {
-                        /* Only P6 based Pentium M need to re-unmask
-                         * the apic vector but it doesn't hurt
-                         * other P6 variant */
-                        apic_write(APIC_LVTPC, APIC_DM_NMI);
+        /* see if the nmi watchdog went off */
+        if (wd->enabled) {
+                if (nmi_watchdog == NMI_LOCAL_APIC) {
+                        rdmsrl(wd->perfctr_msr, dummy);
+                        if (dummy & wd->check_bit){
+                                /* this wasn't a watchdog timer interrupt */
+                                goto done;
+                        }
+
+                        /* only Intel P4 uses the cccr msr */
+                        if (wd->cccr_msr != 0) {
+                                /*
+                                 * 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.
+                                 */
+                                rdmsrl(wd->cccr_msr, dummy);
+                                dummy &= ~P4_CCCR_OVF;
+                                wrmsrl(wd->cccr_msr, dummy);
+                                apic_write(APIC_LVTPC, APIC_DM_NMI);
+                        }
+                        else if (wd->perfctr_msr == MSR_P6_PERFCTR0) {
+                                /* Only P6 based Pentium M need to re-unmask
+                                 * the apic vector but it doesn't hurt
+                                 * other P6 variant */
+                                apic_write(APIC_LVTPC, APIC_DM_NMI);
+                        }
+                        /* start the cycle over again */
+                        write_watchdog_counter(wd->perfctr_msr, NULL);
                 }
-                write_watchdog_counter(NULL);
         }
+done:
+        return;
 }
 
 #ifdef CONFIG_SYSCTL
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index 7e9edafffd8a..3a07b2677e2a 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -724,7 +724,7 @@ static void default_do_nmi(struct pt_regs * regs)
                  * so it must be the NMI watchdog.
                  */
                 if (nmi_watchdog) {
-                        nmi_watchdog_tick(regs);
+                        nmi_watchdog_tick(regs, reason);
                         return;
                 }
 #endif
diff --git a/arch/i386/oprofile/nmi_timer_int.c b/arch/i386/oprofile/nmi_timer_int.c
index 930a1127bb30..a33a73bb502d 100644
--- a/arch/i386/oprofile/nmi_timer_int.c
+++ b/arch/i386/oprofile/nmi_timer_int.c
@@ -42,9 +42,7 @@ static void timer_stop(void)
 
 int __init op_nmi_timer_init(struct oprofile_operations * ops)
 {
-        extern int nmi_active;
-
-        if (nmi_active <= 0)
+        if (atomic_read(&nmi_active) <= 0)
                 return -ENODEV;
 
         ops->start = timer_start;
diff --git a/include/asm-i386/nmi.h b/include/asm-i386/nmi.h
index 27fc9e6f630e..4cda6801ecb8 100644
--- a/include/asm-i386/nmi.h
+++ b/include/asm-i386/nmi.h
@@ -32,13 +32,14 @@ extern void release_perfctr_nmi(unsigned int);
 extern int reserve_evntsel_nmi(unsigned int);
 extern void release_evntsel_nmi(unsigned int);
 
-extern void setup_apic_nmi_watchdog (void);
+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 void nmi_watchdog_tick (struct pt_regs * regs);
+extern void nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);
 
+extern atomic_t nmi_active;
 extern unsigned int nmi_watchdog;
 #define NMI_DEFAULT     -1
 #define NMI_NONE        0