[Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Jan Kiszka]

Changes since last round:
 - Fix build breakage of trunk against 2.6.27
 - Make rthal_nmi_release more robust (additional patch)
 - Fix issue of last patch on 32 bit (untested last-minute changes...)

All patches are also available at
git://git.kiszka.org/xenomai.git nmi-wd-queue

Jan

[Xenomai-core] [PATCH v2 1/5] x86_32: Fix NMI watchdog build for 2.6.27

[Jan Kiszka]

Fix build breakage against 2.6.27-x86-32 due to changes of die_nmi. At
this chance, switch the internal function call wrapping to latest
unified mainline instead of using the legacy prototype.

Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
---

 ksrc/arch/x86/hal_32.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/ksrc/arch/x86/hal_32.c b/ksrc/arch/x86/hal_32.c
index e8e1258..79b7c83 100644
--- a/ksrc/arch/x86/hal_32.c
+++ b/ksrc/arch/x86/hal_32.c
@@ -107,7 +107,7 @@ extern void show_registers(struct pt_regs *regs);
 
 extern spinlock_t nmi_print_lock;
 
-void die_nmi(struct pt_regs *regs, const char *msg)
+void die_nmi(const char *msg, struct pt_regs *regs, int do_panic)
 {
 	spin_lock(&nmi_print_lock);
 	/*
@@ -124,7 +124,11 @@ void die_nmi(struct pt_regs *regs, const char *msg)
 	do_exit(SIGSEGV);
 }
 
-#endif /* Linux < 2.6 */
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,27)
+#define die_nmi(msg, regs, do_panic)	die_nmi(regs, msg)
+#else /* Linux >= 2.6.27 */
+#include <asm/nmi.h>
+#endif /* Linux >= 2.6.27 */
 
 void rthal_latency_above_max(struct pt_regs *regs)
 {
@@ -136,7 +140,7 @@ void rthal_latency_above_max(struct pt_regs *regs)
 			 sizeof(buf),
 			 "NMI watchdog detected timer latency above %u us\n",
 			 rthal_maxlat_us);
-		die_nmi(regs, buf);
+		die_nmi(buf, regs, 1);
 	}
 }
 

[Xenomai-core] [PATCH v2 2/5] Update NMI watchdog for latest Intel CPUs

[Jan Kiszka]

Add performance-counter NMI watchdog support for recent Intel CPUs. This
should also fix potential overrun (corner) cases for P6-type CPUs as the
current code incorrectly assumes that more than 31 bits are available
as watchdog delay counter.

Refactor some dispatching paths at this chance.

Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
---

 include/asm-x86/bits/timer.h |    2 +-
 ksrc/arch/x86/nmi_32.c       |  128 ++++++++++++++++++++++++++----------------
 2 files changed, 81 insertions(+), 49 deletions(-)

diff --git a/include/asm-x86/bits/timer.h b/include/asm-x86/bits/timer.h
index b742763..d957c54 100644
--- a/include/asm-x86/bits/timer.h
+++ b/include/asm-x86/bits/timer.h
@@ -37,7 +37,7 @@ static inline void xnarch_program_timer_shot(unsigned long delay)
 #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 */
diff --git a/ksrc/arch/x86/nmi_32.c b/ksrc/arch/x86/nmi_32.c
index f3b3290..78ba905 100644
--- a/ksrc/arch/x86/nmi_32.c
+++ b/ksrc/arch/x86/nmi_32.c
@@ -29,11 +29,19 @@
 #include <linux/version.h>
 #include <linux/nmi.h>
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,19)
+#include <asm/intel_arch_perfmon.h>
+#endif /* Linux < 2.6.19 */
 #include <asm/nmi.h>
 #endif /* Linux < 2.6 */
 #include <asm/msr.h>
 #include <asm/xenomai/hal.h>
 
+#define NMI_WD_ARMED		0x0001
+#define NMI_WD_31BITS		0x1000
+#define NMI_WD_P4		0x2000
+#define NMI_WD_P6_OR_LATER	0x4000
+
 #define P4_ESCR_EVENT_SELECT(N) ((N)<<25)
 #define P4_ESCR_OS              (1<<3)
 #define P4_ESCR_USR             (1<<2)
@@ -57,7 +65,7 @@
 typedef union {
 	struct {
 		/* Xenomai watchdog data. */
-		unsigned armed;
+		unsigned int flags;
 		unsigned long perfctr_msr;
 		unsigned long long next_linux_check;
 		unsigned int p4_cccr_val;
@@ -69,11 +77,11 @@ typedef union {
 } rthal_nmi_wd_t ____cacheline_aligned;
 
 static rthal_nmi_wd_t rthal_nmi_wds[NR_CPUS];
-static unsigned long rthal_nmi_perfctr_msr;
-static unsigned int rthal_nmi_p4_cccr_val;
 static void (*rthal_nmi_emergency) (struct pt_regs *);
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
+#define MSR_ARCH_PERFMON_PERFCTR0	0xc1
+#define MSR_ARCH_PERFMON_PERFCTR1	0xc2
 static void (*rthal_linux_nmi_tick) (struct pt_regs *);
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
@@ -96,23 +104,6 @@ static int (*rthal_linux_nmi_tick) (struct pt_regs *, unsigned);
 #define rthal_nmi_active	atomic_read(&nmi_active)
 #endif /* Linux >= 2.6.19 */
 
-static void rthal_touch_nmi_watchdog(void)
-{
-	unsigned long long next_linux_check;
-	int i;
-
-	next_linux_check = rthal_rdtsc() + RTHAL_CPU_FREQ;
-
-	for (i = 0; i < NR_CPUS; i++) {
-		rthal_nmi_wd_t *wd = &rthal_nmi_wds[i];
-
-		wd->perfctr_msr = rthal_nmi_perfctr_msr;
-		wd->p4_cccr_val = rthal_nmi_p4_cccr_val;
-		wd->armed = 0;
-		wd->next_linux_check = next_linux_check;
-	}
-}
-
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19)
 #define CALL_LINUX_NMI		rthal_linux_nmi_tick(regs)
 #define NMI_RETURN		return
@@ -127,7 +118,7 @@ static int rthal_nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 	rthal_nmi_wd_t *wd = &rthal_nmi_wds[cpu];
 	unsigned long long now;
 
-	if (wd->armed) {
+	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;
@@ -148,7 +139,7 @@ static int rthal_nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 		} while ((long long)(now - wd->next_linux_check) >= 0);
 	}
 
-	if (wd->perfctr_msr == MSR_P4_IQ_COUNTER0) {
+	if (wd->flags & NMI_WD_P4) {
 		/*
 		 * P4 quirks:
 		 * - An overflown perfctr will assert its interrupt
@@ -158,14 +149,19 @@ static int rthal_nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 		 */
 		wrmsr(MSR_P4_IQ_CCCR0, wd->p4_cccr_val, 0);
 		apic_write(APIC_LVTPC, APIC_DM_NMI);
-	} else if (rthal_nmi_perfctr_msr == MSR_P6_PERFCTR0) {
-		/* Only P6 based Pentium M need to re-unmask
+	} else if (wd->flags & NMI_WD_P6_OR_LATER) {
+		/* P6 based Pentium M need to re-unmask
 		 * the apic vector but it doesn't hurt
-		 * other P6 variant */
+		 * other P6 variant.
+		 * ArchPerfom/Core Duo also needs this */
 		apic_write(APIC_LVTPC, APIC_DM_NMI);
 	}
-	
-	wrmsrl(wd->perfctr_msr, now - wd->next_linux_check);
+
+	if (wd->flags & NMI_WD_31BITS)
+		wrmsr(wd->perfctr_msr, (u32)(now - wd->next_linux_check), 0);
+	else
+		wrmsrl(wd->perfctr_msr, now - wd->next_linux_check);
+
 	NMI_RETURN;
 }
 
@@ -194,6 +190,12 @@ static int earlyshots_read_proc(char *page,
 
 int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 {
+	unsigned long long next_linux_check;
+	unsigned long perfctr_msr;
+	unsigned int wd_flags = 0;
+	unsigned int p4_cccr_val = 0;
+	int i;
+
 	if (!rthal_nmi_active || !nmi_watchdog_tick)
 		return -ENODEV;
 
@@ -202,31 +204,50 @@ int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 
 	switch (boot_cpu_data.x86_vendor) {
         case X86_VENDOR_AMD:
-		rthal_nmi_perfctr_msr = MSR_K7_PERFCTR0;
+		perfctr_msr = MSR_K7_PERFCTR0;
 		break;
         case X86_VENDOR_INTEL:
-		switch (boot_cpu_data.x86) {
-                case 6:
-			rthal_nmi_perfctr_msr = MSR_P6_PERFCTR0;
-			break;
-                case 15:
-			rthal_nmi_perfctr_msr = MSR_P4_IQ_COUNTER0;
-			rthal_nmi_p4_cccr_val = P4_NMI_IQ_CCCR0;
+		if (cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
+			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;
+			wd_flags = NMI_WD_P6_OR_LATER | NMI_WD_31BITS;
+		} else
+			switch (boot_cpu_data.x86) {
+	                case 6:
+				perfctr_msr = MSR_P6_PERFCTR0;
+				wd_flags = NMI_WD_P6_OR_LATER | NMI_WD_31BITS;
+				break;
+	                case 15:
+				perfctr_msr = MSR_P4_IQ_COUNTER0;
+				p4_cccr_val = P4_NMI_IQ_CCCR0;
 #ifdef CONFIG_SMP
-			if (smp_num_siblings == 2)
-				rthal_nmi_p4_cccr_val |= P4_CCCR_OVF_PMI1;
+				if (smp_num_siblings == 2)
+					p4_cccr_val |= P4_CCCR_OVF_PMI1;
 #endif
-			break;
-                default:
-			return -ENODEV;
-		}
+				break;
+	                default:
+				return -ENODEV;
+			}
 		break;
         default:
 		return -ENODEV;
 	}
 
 	rthal_nmi_emergency = emergency;
-	rthal_touch_nmi_watchdog();
+
+	next_linux_check = rthal_rdtsc() + RTHAL_CPU_FREQ;
+	for (i = 0; i < NR_CPUS; i++) {
+		rthal_nmi_wd_t *wd = &rthal_nmi_wds[i];
+
+		wd->flags = wd_flags;
+		wd->perfctr_msr = perfctr_msr;
+		wd->p4_cccr_val = p4_cccr_val;
+		wd->next_linux_check = next_linux_check;
+	}
+
 	rthal_linux_nmi_tick = nmi_watchdog_tick;
 	wmb();
 	nmi_watchdog_tick = &rthal_nmi_watchdog_tick;
@@ -242,6 +263,8 @@ int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 
 void rthal_nmi_release(void)
 {
+	rthal_nmi_wd_t *wd = &rthal_nmi_wds[rthal_processor_id()];
+
 	if (!rthal_linux_nmi_tick)
 		return;
 
@@ -249,7 +272,10 @@ void rthal_nmi_release(void)
 	remove_proc_entry("nmi_early_shots", rthal_proc_root);
 #endif /* CONFIG_PROC_FS */
 
-	wrmsrl(rthal_nmi_perfctr_msr, 0 - RTHAL_CPU_FREQ);
+	if (wd->flags & NMI_WD_31BITS)
+		wrmsr(wd->perfctr_msr, (u32)(0 - RTHAL_CPU_FREQ), 0);
+	else
+		wrmsrl(wd->perfctr_msr, 0 - RTHAL_CPU_FREQ);
 	touch_nmi_watchdog();
 	wmb();
 	nmi_watchdog_tick = rthal_linux_nmi_tick;
@@ -269,23 +295,29 @@ void rthal_nmi_arm(unsigned long delay)
 
 		/* Protect from an interrupt handler calling rthal_nmi_arm. */
 		rthal_local_irq_save(flags);
-		wd->armed = 0;
+		wd->flags &= ~NMI_WD_ARMED;
 		wmb();
-		wrmsrl(wd->perfctr_msr, -1);
+		if (wd->flags & NMI_WD_31BITS)
+			wrmsr(wd->perfctr_msr, (u32)-1, 0);
+		else
+			wrmsrl(wd->perfctr_msr, -1);
 		asm("nop");
 		rthal_local_irq_restore(flags);
 	}
 
 	wd->tick_date = rthal_rdtsc() + (delay - rthal_maxlat_tsc);
 	wmb();
-	wrmsrl(wd->perfctr_msr, 0 - delay);
+	if (wd->flags & NMI_WD_31BITS)
+		wrmsr(wd->perfctr_msr, (u32)(0 - delay), 0);
+	else
+		wrmsrl(wd->perfctr_msr, 0 - delay);
 	wmb();
-	wd->armed = 1;
+	wd->flags |= NMI_WD_ARMED;
 }
 
 void rthal_nmi_disarm(void)
 {
-	rthal_nmi_wds[rthal_processor_id()].armed = 0;
+	rthal_nmi_wds[rthal_processor_id()].flags &= ~NMI_WD_ARMED;
 }
 
 EXPORT_SYMBOL(rthal_nmi_request);

[Xenomai-core] [PATCH v2 3/5] x86: Clear perfctr_msr on rthal_nmi_release

[Jan Kiszka]

Better safe than sorry: Clear all per-CPU perfctr_msr values so that
no one can rearm the NMI watchdog after we released it.

Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
---

 ksrc/arch/x86/nmi_32.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/ksrc/arch/x86/nmi_32.c b/ksrc/arch/x86/nmi_32.c
index 78ba905..69a392a 100644
--- a/ksrc/arch/x86/nmi_32.c
+++ b/ksrc/arch/x86/nmi_32.c
@@ -264,6 +264,7 @@ int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 void rthal_nmi_release(void)
 {
 	rthal_nmi_wd_t *wd = &rthal_nmi_wds[rthal_processor_id()];
+	int i;
 
 	if (!rthal_linux_nmi_tick)
 		return;
@@ -276,6 +277,8 @@ void rthal_nmi_release(void)
 		wrmsr(wd->perfctr_msr, (u32)(0 - RTHAL_CPU_FREQ), 0);
 	else
 		wrmsrl(wd->perfctr_msr, 0 - RTHAL_CPU_FREQ);
+	for (i = 0; i < NR_CPUS; i++)
+		rthal_nmi_wds[i].perfctr_msr = 0;
 	touch_nmi_watchdog();
 	wmb();
 	nmi_watchdog_tick = rthal_linux_nmi_tick;

[Xenomai-core] [PATCH v2 4/5] NMI watchdog support for x86-64

[Jan Kiszka]

No need to lock the NMI away from x86-64 boxes, it just takes a bit
refactoring.

NOTE: Whoever applies this to SVN, make sure to MOVE nmi_32.c to nmi.c!

Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
---

 include/asm-x86/hal.h             |    2 +
 include/asm-x86/hal_32.h          |    2 -
 ksrc/arch/x86/Kconfig             |    4 ---
 ksrc/arch/x86/Makefile            |    4 +-
 ksrc/arch/x86/hal-common.c        |   48 ++++++++++++++++++++++++++++++++++++
 ksrc/arch/x86/hal_32.c            |   49 -------------------------------------
 ksrc/arch/x86/{nmi_32.c => nmi.c} |    0 
 7 files changed, 52 insertions(+), 57 deletions(-)
 rename ksrc/arch/x86/{nmi_32.c => nmi.c} (100%)

diff --git a/include/asm-x86/hal.h b/include/asm-x86/hal.h
index 4df6bf6..158e3e6 100644
--- a/include/asm-x86/hal.h
+++ b/include/asm-x86/hal.h
@@ -69,6 +69,8 @@ typedef int (*compat_emutick_t)(unsigned long evt,
 
 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
diff --git a/include/asm-x86/hal_32.h b/include/asm-x86/hal_32.h
index ddcec08..9a707d0 100644
--- a/include/asm-x86/hal_32.h
+++ b/include/asm-x86/hal_32.h
@@ -234,6 +234,4 @@ static inline void rthal_setup_oneshot_apic(int vector)
 
 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 */
diff --git a/ksrc/arch/x86/Kconfig b/ksrc/arch/x86/Kconfig
index 865ade7..ad8a5de 100644
--- a/ksrc/arch/x86/Kconfig
+++ b/ksrc/arch/x86/Kconfig
@@ -27,8 +27,6 @@ config XENO_HW_FPU
 	Float-Point Unit on the x86 platform at the following URL:
 	http://www.intel.com/design/intarch/techinfo/Pentium/fpu.htm
 
-if !X86_64
-
 menu "NMI watchdog"
 
 config XENO_HW_NMI_DEBUG_LATENCY
@@ -59,8 +57,6 @@ config XENO_HW_NMI_DEBUG_LATENCY_MAX
 
 endmenu
 
-endif
-
 menu "SMI workaround"
 
 config XENO_HW_SMI_DETECT_DISABLE
diff --git a/ksrc/arch/x86/Makefile b/ksrc/arch/x86/Makefile
index 71cc8ec..3296206 100644
--- a/ksrc/arch/x86/Makefile
+++ b/ksrc/arch/x86/Makefile
@@ -12,7 +12,7 @@ obj-$(CONFIG_XENOMAI) += xeno_hal.o
 
 xeno_hal-y := hal_$(X86_MODE).o hal-common.o usercopy_$(X86_MODE).o
 
-xeno_hal-$(CONFIG_XENO_HW_NMI_DEBUG_LATENCY) += nmi_$(X86_MODE).o
+xeno_hal-$(CONFIG_XENO_HW_NMI_DEBUG_LATENCY) += nmi.o
 
 xeno_hal-$(CONFIG_XENO_HW_SMI_DETECT) += smi.o
 
@@ -28,7 +28,7 @@ O_TARGET := built-in.o
 
 obj-y := hal_32.o hal-common.o
 
-obj-$(CONFIG_XENO_HW_NMI_DEBUG_LATENCY) += nmi_32.o
+obj-$(CONFIG_XENO_HW_NMI_DEBUG_LATENCY) += nmi.o
 
 obj-$(CONFIG_XENO_HW_SMI_DETECT) += smi.o
 
diff --git a/ksrc/arch/x86/hal-common.c b/ksrc/arch/x86/hal-common.c
index 2b04dcf..315ce2a 100644
--- a/ksrc/arch/x86/hal-common.c
+++ b/ksrc/arch/x86/hal-common.c
@@ -278,6 +278,54 @@ void rthal_timer_release(int cpu)
 		rthal_timer_set_oneshot(0);
 }
 
+#ifdef CONFIG_XENO_HW_NMI_DEBUG_LATENCY
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+
+#include <linux/vt_kern.h>
+
+extern void show_registers(struct pt_regs *regs);
+
+extern spinlock_t nmi_print_lock;
+
+void die_nmi(const char *msg, struct pt_regs *regs, int do_panic)
+{
+	spin_lock(&nmi_print_lock);
+	/*
+	 * We are in trouble anyway, lets at least try
+	 * to get a message out.
+	 */
+	bust_spinlocks(1);
+	printk(msg);
+	show_registers(regs);
+	printk("console shuts up ...\n");
+	console_silent();
+	spin_unlock(&nmi_print_lock);
+	bust_spinlocks(0);
+	do_exit(SIGSEGV);
+}
+
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,27) && defined(CONFIG_X86_32)
+#define die_nmi(msg, regs, do_panic)	die_nmi(regs, msg)
+#else /* Linux >= 2.6.27 || CONFIG_X86_64 */
+#include <asm/nmi.h>
+#endif /* Linux >= 2.6.27 || CONFIG_X86_64*/
+
+void rthal_latency_above_max(struct pt_regs *regs)
+{
+	/* Try to report via latency tracer first, then fall back to panic. */
+	if (rthal_trace_user_freeze(rthal_maxlat_us, 1) < 0) {
+		char buf[128];
+
+		snprintf(buf,
+			 sizeof(buf),
+			 "NMI watchdog detected timer latency above %u us\n",
+			 rthal_maxlat_us);
+		die_nmi(buf, regs, 1);
+	}
+}
+
+#endif /* CONFIG_XENO_HW_NMI_DEBUG_LATENCY */
 
 #endif /* CONFIG_X86_LOCAL_APIC */
 
diff --git a/ksrc/arch/x86/hal_32.c b/ksrc/arch/x86/hal_32.c
index 79b7c83..026b03f 100644
--- a/ksrc/arch/x86/hal_32.c
+++ b/ksrc/arch/x86/hal_32.c
@@ -97,55 +97,6 @@ unsigned long rthal_timer_calibrate(void)
 	return rthal_imuldiv(dt, 20, RTHAL_CPU_FREQ);
 }
 
-#ifdef CONFIG_XENO_HW_NMI_DEBUG_LATENCY
-
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
-
-#include <linux/vt_kern.h>
-
-extern void show_registers(struct pt_regs *regs);
-
-extern spinlock_t nmi_print_lock;
-
-void die_nmi(const char *msg, struct pt_regs *regs, int do_panic)
-{
-	spin_lock(&nmi_print_lock);
-	/*
-	 * We are in trouble anyway, lets at least try
-	 * to get a message out.
-	 */
-	bust_spinlocks(1);
-	printk(msg);
-	show_registers(regs);
-	printk("console shuts up ...\n");
-	console_silent();
-	spin_unlock(&nmi_print_lock);
-	bust_spinlocks(0);
-	do_exit(SIGSEGV);
-}
-
-#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,27)
-#define die_nmi(msg, regs, do_panic)	die_nmi(regs, msg)
-#else /* Linux >= 2.6.27 */
-#include <asm/nmi.h>
-#endif /* Linux >= 2.6.27 */
-
-void rthal_latency_above_max(struct pt_regs *regs)
-{
-	/* Try to report via latency tracer first, then fall back to panic. */
-	if (rthal_trace_user_freeze(rthal_maxlat_us, 1) < 0) {
-		char buf[128];
-
-		snprintf(buf,
-			 sizeof(buf),
-			 "NMI watchdog detected timer latency above %u us\n",
-			 rthal_maxlat_us);
-		die_nmi(buf, regs, 1);
-	}
-}
-
-#endif /* CONFIG_XENO_HW_NMI_DEBUG_LATENCY */
-
 #else /* !CONFIG_X86_LOCAL_APIC */
 
 unsigned long rthal_timer_calibrate(void)
diff --git a/ksrc/arch/x86/nmi_32.c b/ksrc/arch/x86/nmi.c
similarity index 100%
rename from ksrc/arch/x86/nmi_32.c
rename to ksrc/arch/x86/nmi.c

[Xenomai-core] [PATCH v2 5/5] Rework x86 NMI watchdog pass-through

[Jan Kiszka]

Currently, Xenomai's NMI watchdog handler assumes to be called only on
watchdog events. Other reasons are considered spurious, and a TSC-based
method is used to detect such conditions. This has several issues
 - the return code of the Linux handler is ignored
 - KGDB's NMI events (CPU roundups) are not passed through
 - early_shot mechanism suffers from a signedness bug and misses too
   early shots
 - printk from NMI can cause lock-ups, but we also support non-fatal
   reports (ipipe tracer active)

This patch therefore switches to the watchdog detection pattern that
Linux uses: Check for the highest perfctr bit being zero for true
timeouts. In case the watchdog did not time out, the Linux handler is
invoked and its return code is properly forwarded. Finally, the
early_shot reporting is dropped as it becomes pointless when KGDB is in
use (and I suspect that patch 1 of this series fixes most of the
original reasons).

Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
---

 ksrc/arch/x86/nmi.c |   95 ++++++++++++++++++++++----------------------------
 1 files changed, 42 insertions(+), 53 deletions(-)

diff --git a/ksrc/arch/x86/nmi.c b/ksrc/arch/x86/nmi.c
index 69a392a..a9d9380 100644
--- a/ksrc/arch/x86/nmi.c
+++ 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;
+		u64 perfctr_checkmask;
 		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) (struct pt_regs *);
 #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) (struct pt_regs *, unsigned);
 #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 (perfctr & wd->perfctr_checkmask)
+		/* 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(struct pt_regs *regs, unsigned reason)
 	else
 		wrmsrl(wd->perfctr_msr, now - wd->next_linux_check);
 
-	NMI_RETURN;
+	NMI_RETURN(1);
 }
 
-#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;
-}
-#endif /* CONFIG_PROC_FS */
-
 int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 {
 	unsigned long long next_linux_check;
 	unsigned long perfctr_msr;
+	u64 perfctr_checkmask;
 	unsigned int wd_flags = 0;
 	unsigned int p4_cccr_val = 0;
 	int i;
@@ -205,23 +190,30 @@ int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 	switch (boot_cpu_data.x86_vendor) {
         case X86_VENDOR_AMD:
 		perfctr_msr = MSR_K7_PERFCTR0;
+		perfctr_checkmask = 1ULL << 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_checkmask = 1ULL << (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_checkmask = 1ULL << 39;
 				wd_flags = NMI_WD_P6_OR_LATER | NMI_WD_31BITS;
 				break;
 	                case 15:
 				perfctr_msr = MSR_P4_IQ_COUNTER0;
+				perfctr_checkmask = 1ULL << 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) (struct pt_regs *))
 
 		wd->flags = wd_flags;
 		wd->perfctr_msr = perfctr_msr;
+		wd->perfctr_checkmask = perfctr_checkmask;
 		wd->p4_cccr_val = p4_cccr_val;
 		wd->next_linux_check = next_linux_check;
 	}
@@ -252,12 +245,6 @@ int rthal_nmi_request(void (*emergency) (struct pt_regs *))
 	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;
 }
 
@@ -269,10 +256,6 @@ 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
@@ -299,6 +282,10 @@ 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);
@@ -308,12 +295,14 @@ 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;
 }

Re: [Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Changes since last round:
>  - Fix build breakage of trunk against 2.6.27
>  - Make rthal_nmi_release more robust (additional patch)
>  - Fix issue of last patch on 32 bit (untested last-minute changes...)
> 
> All patches are also available at
> git://git.kiszka.org/xenomai.git nmi-wd-queue

I remind you that trunk is currently broken for the posix skin on arm, a
regression introduced by your FASTSYNCH patches. From my point of view,
fixing this regression is more important than fixing an option that
almost nobody uses with untested patches...

-- 
					    Gilles.

Re: [Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Jan Kiszka]

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Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Changes since last round:
>>  - Fix build breakage of trunk against 2.6.27
>>  - Make rthal_nmi_release more robust (additional patch)
>>  - Fix issue of last patch on 32 bit (untested last-minute changes...)
>>
>> All patches are also available at
>> git://git.kiszka.org/xenomai.git nmi-wd-queue
> 
> I remind you that trunk is currently broken for the posix skin on arm, a
> regression introduced by your FASTSYNCH patches. From my point of view,
> fixing this regression is more important than fixing an option that
> almost nobody uses with untested patches...

Many things are broken and awaiting a fix. I also have 6 posted bug
fixes in my assorted patch queue for Xenomai ATM. But this doesn't mean
everything else has to wait just because review or merging is delayed
due to current overload.

And FYI, I've discussed the posix skin setup race with Wolfgang last
week, suggesting a few things to try next on his target - what he will
likely do as soon as time permits. I can't help at this point as A) the
race is not yet obvious for me and B) I've no chance to reproduce it.
But any further information on this is always welcome - if you happen to
see the problem as well.

Regarding this thread, I would appreciate if we could just stay on
topic. If you don't have the time for the patches, then it's absolutely
OK, just leave them alone.

Jan


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Re: [Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Regarding this thread, I would appreciate if we could just stay on
> topic. If you don't have the time for the patches, then it's absolutely
> OK, just leave them alone.

I am reluctant to test patches which are explicitely labeled as
"untested", and prefer to wait the tested ones. Trunk is already broken
enough, that is my point.

-- 
					    Gilles.

Re: [Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Jan Kiszka]

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Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Regarding this thread, I would appreciate if we could just stay on
>> topic. If you don't have the time for the patches, then it's absolutely
>> OK, just leave them alone.
> 
> I am reluctant to test patches which are explicitely labeled as
> "untested", and prefer to wait the tested ones. Trunk is already broken
> enough, that is my point.
> 

Oh, that was a misunderstanding due to my unfortunate changelog.
Untested referred to a specific config set and a last-minute change of
the previous version.

Jan



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Re: [Xenomai-core] [PATCH v2 0/5] NMI watchdog fixes / enhancements

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Regarding this thread, I would appreciate if we could just stay on
>>> topic. If you don't have the time for the patches, then it's absolutely
>>> OK, just leave them alone.
>> I am reluctant to test patches which are explicitely labeled as
>> "untested", and prefer to wait the tested ones. Trunk is already broken
>> enough, that is my point.
>>
> 
> Oh, that was a misunderstanding due to my unfortunate changelog.
> Untested referred to a specific config set and a last-minute change of
> the previous version.

Ok. Forget about solving the issue on ARM, I have to solve it now.

-- 
                                                 Gilles.