x86: Fix & update NMI watchdog

Index: b/include/asm-x86/bits/timer.h
===================================================================
@@ -37,7 +37,7 @@ static inline void xnarch_program_timer_
 #ifdef CONFIG_XENO_HW_NMI_DEBUG_LATENCY
 	{
 		extern unsigned long rthal_maxlat_tsc;
-		if (delay <= (ULONG_MAX - rthal_maxlat_tsc))
+		if (delay <= (LONG_MAX - rthal_maxlat_tsc))
 			rthal_nmi_arm(delay + rthal_maxlat_tsc);
 	}
 #endif /* CONFIG_XENO_HW_NMI_DEBUG_LATENCY */

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Index: b/include/asm-x86/hal.h
===================================================================
@@ -69,6 +69,8 @@ typedef int (*compat_emutick_t)(unsigned
 
 extern enum rthal_ktimer_mode rthal_ktimer_saved_mode;
 
+void rthal_latency_above_max(struct pt_regs *regs);
+
 #ifdef __i386__
 #include "hal_32.h"
 #else

Index: b/include/asm-x86/hal_32.h
===================================================================
@@ -228,6 +228,4 @@ static inline void rthal_setup_oneshot_a
 
 long rthal_strncpy_from_user(char *dst, const char __user * src, long count);
 
-void rthal_latency_above_max(struct pt_regs *regs);
-
 #endif /* !_XENO_ASM_X86_HAL_32_H */

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Index: b/ksrc/arch/x86/nmi.c
===================================================================
@@ -65,13 +65,11 @@
 typedef union {
 	struct {
 		/* Xenomai watchdog data. */
-		unsigned int flags;
-		unsigned long perfctr_msr;
 		unsigned long long next_linux_check;
+		unsigned long perfctr_msr;
+		unsigned int perfctr_checkbit;
 		unsigned int p4_cccr_val;
-
-		unsigned early_shots;
-		unsigned long long tick_date;
+		unsigned int flags;
 	};
 	char __pad[SMP_CACHE_BYTES];
 } rthal_nmi_wd_t ____cacheline_aligned;

@@ -82,6 +80,15 @@ static void (*rthal_nmi_emergency) (stru
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
 #define MSR_ARCH_PERFMON_PERFCTR0	0xc1
 #define MSR_ARCH_PERFMON_PERFCTR1	0xc2
+union cpuid10_eax {
+	struct {
+		unsigned int version_id:8;
+		unsigned int num_counters:8;
+		unsigned int bit_width:8;
+		unsigned int mask_length:8;
+	} split;
+	unsigned int full;
+};
 static void (*rthal_linux_nmi_tick) (struct pt_regs *);
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)

@@ -105,28 +112,28 @@ static int (*rthal_linux_nmi_tick) (stru
 #endif /* Linux >= 2.6.19 */
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
-#define CALL_LINUX_NMI		rthal_linux_nmi_tick(regs)
-#define NMI_RETURN		return
+#define CALL_LINUX_NMI		({ rthal_linux_nmi_tick(regs); 1; })
+#define NMI_RETURN(code)	return
 static void rthal_nmi_watchdog_tick(struct pt_regs *regs)
 #else /* Linux >= 2.6.19 */
 #define CALL_LINUX_NMI		rthal_linux_nmi_tick(regs, reason)
-#define NMI_RETURN		return 1
+#define NMI_RETURN(code)	return (code)
 static int rthal_nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 #endif /* Linux >= 2.6.19 */
 {
 	int cpu = rthal_processor_id();
 	rthal_nmi_wd_t *wd = &rthal_nmi_wds[cpu];
 	unsigned long long now;
+	u64 perfctr;
 
-	if (wd->flags & NMI_WD_ARMED) {
-		if (rthal_rdtsc() - wd->tick_date < rthal_maxlat_tsc) {
-			++wd->early_shots;
-			wd->next_linux_check = wd->tick_date + rthal_maxlat_tsc;
-		} else {
-			printk("NMI early shots: %d\n", wd->early_shots);
-			rthal_nmi_emergency(regs);
-		}
-	}
+	rdmsrl(wd->perfctr_msr, perfctr);
+
+	if (test_bit(wd->perfctr_checkbit, &perfctr))
+		/* No watchdog tick, let Linux handle it. */
+		NMI_RETURN(CALL_LINUX_NMI);
+
+	if (wd->flags & NMI_WD_ARMED)
+		rthal_nmi_emergency(regs);
 
 	now = rthal_rdtsc();
 

@@ -162,36 +169,14 @@ static int rthal_nmi_watchdog_tick(struc
 	else
 		wrmsrl(wd->perfctr_msr, now - wd->next_linux_check);
 
-	NMI_RETURN;
-}
-
-#ifdef CONFIG_PROC_FS
-static int earlyshots_read_proc(char *page,
-				char **start,
-				off_t off, int count, int *eof, void *data)
-{
-	int i, len = 0;
-
-	for_each_online_cpu(i)
-		len += sprintf(page + len, "CPU#%d: %u\n",
-			       i, rthal_nmi_wds[i].early_shots);
-	len -= off;
-	if (len <= off + count)
-		*eof = 1;
-	*start = page + off;
-	if (len > count)
-		len = count;
-	if (len < 0)
-		len = 0;
-
-	return len;
+	NMI_RETURN(1);
 }
-#endif /* CONFIG_PROC_FS */
 
 int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 {
 	unsigned long long next_linux_check;
 	unsigned long perfctr_msr;
+ 	unsigned int perfctr_checkbit;
 	unsigned int wd_flags = 0;
 	unsigned int p4_cccr_val = 0;
 	int i;

@@ -205,23 +190,30 @@ int rthal_nmi_request(void (*emergency)
 	switch (boot_cpu_data.x86_vendor) {
         case X86_VENDOR_AMD:
 		perfctr_msr = MSR_K7_PERFCTR0;
+		perfctr_checkbit = 47;
 		break;
         case X86_VENDOR_INTEL:
 		if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
+			union cpuid10_eax eax;
+
 			if (boot_cpu_data.x86 == 6 &&
 			    boot_cpu_data.x86_model == 14)
 				perfctr_msr = MSR_ARCH_PERFMON_PERFCTR0;
 			else
 				perfctr_msr = MSR_ARCH_PERFMON_PERFCTR1;
+			cpuid(10, &eax.full, &i, &i, &i);
+			perfctr_checkbit = eax.split.bit_width - 1;
 			wd_flags = NMI_WD_P6_OR_LATER | NMI_WD_31BITS;
 		} else
 			switch (boot_cpu_data.x86) {
 	                case 6:
 				perfctr_msr = MSR_P6_PERFCTR0;
+				perfctr_checkbit = 39;
 				wd_flags = NMI_WD_P6_OR_LATER | NMI_WD_31BITS;
 				break;
 	                case 15:
 				perfctr_msr = MSR_P4_IQ_COUNTER0;
+				perfctr_checkbit = 39;
 				p4_cccr_val = P4_NMI_IQ_CCCR0;
 #ifdef CONFIG_SMP
 				if (smp_num_siblings == 2)

@@ -244,6 +236,7 @@ int rthal_nmi_request(void (*emergency)
 
 		wd->flags = wd_flags;
 		wd->perfctr_msr = perfctr_msr;
+ 		wd->perfctr_checkbit = perfctr_checkbit;
 		wd->p4_cccr_val = p4_cccr_val;
 		wd->next_linux_check = next_linux_check;
 	}

@@ -252,12 +245,6 @@ int rthal_nmi_request(void (*emergency)
 	wmb();
 	nmi_watchdog_tick = &rthal_nmi_watchdog_tick;
 
-#ifdef CONFIG_PROC_FS
-	rthal_add_proc_leaf("nmi_early_shots",
-			    &earlyshots_read_proc,
-			    NULL, NULL, rthal_proc_root);
-#endif /* CONFIG_PROC_FS */
-
 	return 0;
 }
 

@@ -268,10 +255,6 @@ void rthal_nmi_release(void)
 	if (!rthal_linux_nmi_tick)
 		return;
 
-#ifdef CONFIG_PROC_FS
-	remove_proc_entry("nmi_early_shots", rthal_proc_root);
-#endif /* CONFIG_PROC_FS */
-
 	if (wd->flags & NMI_WD_31BITS)
 		wrmsr(wd->perfctr_msr, (u32)(0 - RTHAL_CPU_FREQ), 0);
 	else

@@ -296,6 +279,10 @@ void rthal_nmi_arm(unsigned long delay)
 		/* Protect from an interrupt handler calling rthal_nmi_arm. */
 		rthal_local_irq_save(flags);
 		wd->flags &= ~NMI_WD_ARMED;
+		/*
+		 * Our watchdog must be declared unarmed before we triger the
+		 * Linux watchdog NMI, entering rthal_nmi_watchdog_tick.
+		 */
 		wmb();
 		if (wd->flags & NMI_WD_31BITS)
 			wrmsr(wd->perfctr_msr, (u32)-1, 0);

@@ -305,12 +292,14 @@ void rthal_nmi_arm(unsigned long delay)
 		rthal_local_irq_restore(flags);
 	}
 
-	wd->tick_date = rthal_rdtsc() + (delay - rthal_maxlat_tsc);
-	wmb();
 	if (wd->flags & NMI_WD_31BITS)
 		wrmsr(wd->perfctr_msr, (u32)(0 - delay), 0);
 	else
 		wrmsrl(wd->perfctr_msr, 0 - delay);
+	/*
+	 * New perfctr must have been written before we can declare the
+	 * watchdog armed (avoid race with previously programmed value).
+	 */
 	wmb();
 	wd->flags |= NMI_WD_ARMED;
 }