[PATCH 0/6] lockup detector changes

[PATCH 0/6] lockup detector changes

[Don Zickus]

This patch series covers mostly the changes necessary for combining the
nmi_watchdog and softlockup code.  Also added are the cleanups associated
with the change, like removing the old files.

The changelogs in each patch are more specific to what the changes are.

Don Zickus (5):
  [watchdog] combine nmi_watchdog and softlockup
  [watchdog] convert touch_softlockup_watchdog to touch_watchdog
  [watchdog] remove old softlockup code
  [watchdog] remove nmi_watchdog.c file
  [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier
  [x86] watchdog: cleanup hw_nmi.c cruft

 Documentation/kernel-parameters.txt |    2 +
 arch/ia64/kernel/time.c             |    2 +-
 arch/ia64/kernel/uncached.c         |    2 +-
 arch/ia64/xen/time.c                |    2 +-
 arch/mn10300/kernel/gdb-stub.c      |    2 +-
 arch/powerpc/kernel/swsusp_64.c     |    2 +-
 arch/sparc/kernel/nmi.c             |    2 +-
 arch/x86/include/asm/nmi.h          |    2 +-
 arch/x86/kernel/apic/Makefile       |    4 +-
 arch/x86/kernel/apic/hw_nmi.c       |  113 +++-----
 arch/x86/kernel/apic/nmi.c          |    2 +-
 arch/x86/kernel/traps.c             |    4 +-
 arch/x86/xen/smp.c                  |    2 +-
 drivers/ide/ide-iops.c              |    2 +-
 drivers/ide/ide-taskfile.c          |    2 +-
 drivers/mtd/nand/nand_base.c        |    4 +-
 drivers/video/nvidia/nv_accel.c     |    2 +-
 include/linux/nmi.h                 |   13 +-
 include/linux/sched.h               |   20 +-
 init/Kconfig                        |    5 +-
 kernel/Makefile                     |    3 +-
 kernel/kgdb.c                       |    6 +-
 kernel/nmi_watchdog.c               |  259 ----------------
 kernel/panic.c                      |    2 +-
 kernel/power/hibernate.c            |    2 +-
 kernel/sched.c                      |    2 +-
 kernel/sched_clock.c                |    2 +-
 kernel/softlockup.c                 |  278 ------------------
 kernel/sysctl.c                     |   52 ++--
 kernel/time/tick-sched.c            |    8 +-
 kernel/time/timekeeping.c           |    2 +-
 kernel/timer.c                      |    1 -
 kernel/watchdog.c                   |  552 +++++++++++++++++++++++++++++++++++
 lib/Kconfig.debug                   |   30 ++-
 34 files changed, 692 insertions(+), 696 deletions(-)
 delete mode 100644 kernel/nmi_watchdog.c
 delete mode 100644 kernel/softlockup.c
 create mode 100644 kernel/watchdog.c

[PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Don Zickus]

The new nmi_watchdog (which uses the perf event subsystem) is very
similar in structure to the softlockup detector.  Using Ingo's suggestion,
I combined the two functionalities into one file, kernel/watchdog.c.

Now both the nmi_watchdog (or hardlockup detector) and softlockup detector
sit on top of the perf event subsystem, which is run every 60 seconds or so
to see if there are any lockups.

To detect hardlockups, cpus not responding to interrupts, I implemented an
hrtimer that runs 5 times for every perf event overflow event.  If that stops
counting on a cpu, then the cpu is most likely in trouble.

To detect softlockups, tasks not yielding to the scheduler, I used the
previous kthread idea that now gets kicked every time the hrtimer fires.
If the kthread isn't being scheduled neither is anyone else and the
warning is printed to the console.

I tested this on x86_64 and both the softlockup and hardlockup paths work.

V2:
- cleaned up the Kconfig and softlockup combination
- surrounded hardlockup cases with #ifdef CONFIG_PERF_EVENTS_NMI
- seperated out the softlockup case from perf event subsystem
- re-arranged the enabling/disabling nmi watchdog from proc space
- added cpumasks for hardlockup failure cases
- removed fallback to soft events if no PMU exists for hard events

V3:
- comment cleanups
- drop support for older softlockup code
- per_cpu cleanups
- completely remove software clock base hardlockup detector
- use per_cpu masking on hard/soft lockup detection
- #ifdef cleanups
- rename config option NMI_WATCHDOG to LOCKUP_DETECTOR
- documentation additions

TODO:
- figure out how to make an arch-agnostic clock2cycles call (if possible)
  to feed into perf events as a sample period

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 Documentation/kernel-parameters.txt |    2 +
 arch/x86/include/asm/nmi.h          |    2 +-
 arch/x86/kernel/apic/Makefile       |    4 +-
 arch/x86/kernel/apic/hw_nmi.c       |    2 +-
 arch/x86/kernel/traps.c             |    4 +-
 include/linux/nmi.h                 |    8 +-
 include/linux/sched.h               |    6 +
 init/Kconfig                        |    5 +-
 kernel/Makefile                     |    3 +-
 kernel/sysctl.c                     |   21 +-
 kernel/watchdog.c                   |  580 +++++++++++++++++++++++++++++++++++
 lib/Kconfig.debug                   |   30 ++-
 12 files changed, 638 insertions(+), 29 deletions(-)
 create mode 100644 kernel/watchdog.c

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 736d456..705f16f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1764,6 +1764,8 @@ and is between 256 and 4096 characters. It is defined in the file
 
 	nousb		[USB] Disable the USB subsystem
 
+	nowatchdog	[KNL] Disable the lockup detector.
+
 	nowb		[ARM]
 
 	nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h
index 5b41b0f..932f0f8 100644
--- a/arch/x86/include/asm/nmi.h
+++ b/arch/x86/include/asm/nmi.h
@@ -17,7 +17,7 @@ int do_nmi_callback(struct pt_regs *regs, int cpu);
 
 extern void die_nmi(char *str, struct pt_regs *regs, int do_panic);
 extern int check_nmi_watchdog(void);
-#if !defined(CONFIG_NMI_WATCHDOG)
+#if !defined(CONFIG_LOCKUP_DETECTOR)
 extern int nmi_watchdog_enabled;
 #endif
 extern int avail_to_resrv_perfctr_nmi_bit(unsigned int);
diff --git a/arch/x86/kernel/apic/Makefile b/arch/x86/kernel/apic/Makefile
index 1a4512e..52f32e0 100644
--- a/arch/x86/kernel/apic/Makefile
+++ b/arch/x86/kernel/apic/Makefile
@@ -3,10 +3,10 @@
 #
 
 obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o apic_noop.o probe_$(BITS).o ipi.o
-ifneq ($(CONFIG_NMI_WATCHDOG),y)
+ifneq ($(CONFIG_LOCKUP_DETECTOR),y)
 obj-$(CONFIG_X86_LOCAL_APIC)	+= nmi.o
 endif
-obj-$(CONFIG_NMI_WATCHDOG)	+= hw_nmi.o
+obj-$(CONFIG_LOCKUP_DETECTOR)	+= hw_nmi.o
 
 obj-$(CONFIG_X86_IO_APIC)	+= io_apic.o
 obj-$(CONFIG_SMP)		+= ipi.o
diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index e8b78a0..79425f9 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -89,7 +89,7 @@ int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
 
 u64 hw_nmi_get_sample_period(void)
 {
-	return cpu_khz * 1000;
+	return (u64)(cpu_khz) * 1000 * 60;
 }
 
 #ifdef ARCH_HAS_NMI_WATCHDOG
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index bdc7fab..bd347c2 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -406,7 +406,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 							== NOTIFY_STOP)
 			return;
 
-#ifndef CONFIG_NMI_WATCHDOG
+#ifndef CONFIG_LOCKUP_DETECTOR
 		/*
 		 * Ok, so this is none of the documented NMI sources,
 		 * so it must be the NMI watchdog.
@@ -414,7 +414,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 		if (nmi_watchdog_tick(regs, reason))
 			return;
 		if (!do_nmi_callback(regs, cpu))
-#endif /* !CONFIG_NMI_WATCHDOG */
+#endif /* !CONFIG_LOCKUP_DETECTOR */
 			unknown_nmi_error(reason, regs);
 #else
 		unknown_nmi_error(reason, regs);
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 22cc796..abd48aa 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -20,7 +20,7 @@ extern void touch_nmi_watchdog(void);
 extern void acpi_nmi_disable(void);
 extern void acpi_nmi_enable(void);
 #else
-#ifndef CONFIG_NMI_WATCHDOG
+#ifndef CONFIG_LOCKUP_DETECTOR
 static inline void touch_nmi_watchdog(void)
 {
 	touch_softlockup_watchdog();
@@ -51,12 +51,12 @@ static inline bool trigger_all_cpu_backtrace(void)
 }
 #endif
 
-#ifdef CONFIG_NMI_WATCHDOG
+#ifdef CONFIG_LOCKUP_DETECTOR
 int hw_nmi_is_cpu_stuck(struct pt_regs *);
 u64 hw_nmi_get_sample_period(void);
-extern int nmi_watchdog_enabled;
+extern int watchdog_enabled;
 struct ctl_table;
-extern int proc_nmi_enabled(struct ctl_table *, int ,
+extern int proc_dowatchdog_enabled(struct ctl_table *, int ,
 			void __user *, size_t *, loff_t *);
 #endif
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6f7bba9..2455ff5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -338,6 +338,12 @@ extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
 					 size_t *lenp, loff_t *ppos);
 #endif
 
+#ifdef CONFIG_LOCKUP_DETECTOR
+extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
+				  void __user *buffer,
+				  size_t *lenp, loff_t *ppos);
+#endif
+
 /* Attach to any functions which should be ignored in wchan output. */
 #define __sched		__attribute__((__section__(".sched.text")))
 
diff --git a/init/Kconfig b/init/Kconfig
index 7331a16..98e3f5f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -948,8 +948,11 @@ config PERF_USE_VMALLOC
 
 config PERF_EVENTS_NMI
 	bool
+	depends on PERF_EVENTS
 	help
-	  Arch has support for nmi_watchdog
+	  Arch can generate an NMI using the perf event subsystem
+	  Also has support for calculating cpu cycle events to
+	  determine how many clock cycles in a given period
 
 menu "Kernel Performance Events And Counters"
 
diff --git a/kernel/Makefile b/kernel/Makefile
index 8a5abe5..cc3acb3 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -75,9 +75,8 @@ obj-$(CONFIG_GCOV_KERNEL) += gcov/
 obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
 obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_KGDB) += kgdb.o
-obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
-obj-$(CONFIG_NMI_WATCHDOG) += nmi_watchdog.o
 obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
+obj-$(CONFIG_LOCKUP_DETECTOR) += watchdog.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ac72c9e..1083897 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -60,7 +60,7 @@
 #include <asm/io.h>
 #endif
 
-#ifdef CONFIG_NMI_WATCHDOG
+#ifdef CONFIG_LOCKUP_DETECTOR
 #include <linux/nmi.h>
 #endif
 
@@ -696,16 +696,25 @@ static struct ctl_table kern_table[] = {
 		.mode		= 0444,
 		.proc_handler	= proc_dointvec,
 	},
-#if defined(CONFIG_NMI_WATCHDOG)
+#if defined(CONFIG_LOCKUP_DETECTOR)
 	{
-		.procname       = "nmi_watchdog",
-		.data           = &nmi_watchdog_enabled,
+		.procname       = "watchdog",
+		.data           = &watchdog_enabled,
 		.maxlen         = sizeof (int),
 		.mode           = 0644,
-		.proc_handler   = proc_nmi_enabled,
+		.proc_handler   = proc_dowatchdog_enabled,
+	},
+	{
+		.procname	= "watchdog_thresh",
+		.data		= &softlockup_thresh,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dowatchdog_thresh,
+		.extra1		= &neg_one,
+		.extra2		= &sixty,
 	},
 #endif
-#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86) && !defined(CONFIG_NMI_WATCHDOG)
+#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86) && !defined(CONFIG_LOCKUP_DETECTOR)
 	{
 		.procname       = "unknown_nmi_panic",
 		.data           = &unknown_nmi_panic,
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
new file mode 100644
index 0000000..6c87d7d
--- /dev/null
+++ b/kernel/watchdog.c
@@ -0,0 +1,580 @@
+/*
+ * Detect hard and soft lockups on a system
+ *
+ * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
+ *
+ * this code detects hard lockups: incidents in where on a CPU
+ * the kernel does not respond to anything except NMI.
+ *
+ * Note: Most of this code is borrowed heavily from softlockup.c,
+ * so thanks to Ingo for the initial implementation.
+ * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks
+ * to those contributors as well.
+ */
+
+#include <linux/mm.h>
+#include <linux/cpu.h>
+#include <linux/nmi.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include <linux/lockdep.h>
+#include <linux/notifier.h>
+#include <linux/module.h>
+#include <linux/sysctl.h>
+
+#include <asm/irq_regs.h>
+#include <linux/perf_event.h>
+
+int watchdog_enabled;
+int __read_mostly softlockup_thresh = 60;
+
+static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
+static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
+static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
+#define HARDLOCKUP	1
+#define SOFTLOCKUP	2
+static DEFINE_PER_CPU(char, watchdog_warn);
+#ifdef CONFIG_PERF_EVENTS_NMI
+static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
+static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
+static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
+#endif
+
+static int __read_mostly did_panic;
+static int __initdata no_watchdog;
+
+
+/* boot commands */
+/*
+ * Should we panic when a soft-lockup or hard-lockup occurs:
+ */
+#ifdef CONFIG_PERF_EVENTS_NMI
+static int hardlockup_panic;
+
+static int __init hardlockup_panic_setup(char *str)
+{
+	if (!strncmp(str, "panic", 5))
+		hardlockup_panic = 1;
+	return 1;
+}
+__setup("nmi_watchdog=", hardlockup_panic_setup);
+#endif
+
+unsigned int __read_mostly softlockup_panic =
+			CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
+
+static int __init softlockup_panic_setup(char *str)
+{
+	softlockup_panic = simple_strtoul(str, NULL, 0);
+
+	return 1;
+}
+__setup("softlockup_panic=", softlockup_panic_setup);
+
+static int __init nowatchdog_setup(char *str)
+{
+	no_watchdog = 1;
+	return 1;
+}
+__setup("nowatchdog", nowatchdog_setup);
+
+/* deprecated */
+static int __init nosoftlockup_setup(char *str)
+{
+	no_watchdog = 1;
+	return 1;
+}
+__setup("nosoftlockup", nosoftlockup_setup);
+/*  */
+
+
+/*
+ * Returns seconds, approximately.  We don't need nanosecond
+ * resolution, and we don't need to waste time with a big divide when
+ * 2^30ns == 1.074s.
+ */
+static unsigned long get_timestamp(int this_cpu)
+{
+	return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
+}
+
+static unsigned long get_sample_period(void)
+{
+	/*
+	 * convert softlockup_thresh from seconds to ns
+	 * the divide by 5 is to give hrtimer 5 chances to
+	 * increment before the hardlockup detector generates
+	 * a warning
+	 */
+	return softlockup_thresh / 5 * NSEC_PER_SEC;
+}
+
+/* Commands for resetting the watchdog */
+static void __touch_watchdog(void)
+{
+	int this_cpu = raw_smp_processor_id();
+
+	__get_cpu_var(watchdog_touch_ts) = get_timestamp(this_cpu);
+}
+
+void touch_watchdog(void)
+{
+	__get_cpu_var(watchdog_touch_ts) = 0;
+}
+EXPORT_SYMBOL(touch_watchdog);
+
+void touch_all_watchdog(void)
+{
+	int cpu;
+
+	/*
+	 * this is done lockless
+	 * do we care if a 0 races with a timestamp?
+	 * all it means is the softlock check starts one cycle later
+	 */
+	for_each_online_cpu(cpu)
+		per_cpu(watchdog_touch_ts, cpu) = 0;
+}
+
+void touch_nmi_watchdog(void)
+{
+	touch_watchdog();
+}
+EXPORT_SYMBOL(touch_nmi_watchdog);
+
+void touch_all_nmi_watchdog(void)
+{
+	touch_all_watchdog();
+}
+
+void touch_softlockup_watchdog(void)
+{
+	touch_watchdog();
+}
+
+void touch_all_softlockup_watchdogs(void)
+{
+	touch_all_watchdog();
+}
+
+void softlockup_tick(void)
+{
+}
+
+#ifdef CONFIG_PERF_EVENTS_NMI
+/* watchdog detector functions */
+static int is_hardlockup(int cpu)
+{
+	unsigned long hrint = per_cpu(hrtimer_interrupts, cpu);
+
+	if (per_cpu(hrtimer_interrupts_saved, cpu) == hrint)
+		return 1;
+
+	per_cpu(hrtimer_interrupts_saved, cpu) = hrint;
+	return 0;
+}
+#endif
+
+static int is_softlockup(unsigned long touch_ts, int cpu)
+{
+	unsigned long now = get_timestamp(cpu);
+
+	/* Warn about unreasonable delays: */
+	if (now > (touch_ts + softlockup_thresh))
+		return now - touch_ts;
+
+	return 0;
+}
+
+static int
+watchdog_panic(struct notifier_block *this, unsigned long event, void *ptr)
+{
+	did_panic = 1;
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block panic_block = {
+	.notifier_call = watchdog_panic,
+};
+
+#ifdef CONFIG_PERF_EVENTS_NMI
+struct perf_event_attr wd_hw_attr = {
+	.type		= PERF_TYPE_HARDWARE,
+	.config		= PERF_COUNT_HW_CPU_CYCLES,
+	.size		= sizeof(struct perf_event_attr),
+	.pinned		= 1,
+	.disabled	= 1,
+};
+
+/* Callback function for perf event subsystem */
+void watchdog_overflow_callback(struct perf_event *event, int nmi,
+		 struct perf_sample_data *data,
+		 struct pt_regs *regs)
+{
+	int this_cpu = smp_processor_id();
+	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
+	char warn = per_cpu(watchdog_warn, this_cpu);
+
+	if (touch_ts == 0) {
+		__touch_watchdog();
+		return;
+	}
+
+	/* check for a hardlockup
+	 * This is done by making sure our timer interrupt
+	 * is incrementing.  The timer interrupt should have
+	 * fired multiple times before we overflow'd.  If it hasn't
+	 * then this is a good indication the cpu is stuck
+	 */
+	if (is_hardlockup(this_cpu)) {
+		/* only print hardlockups once */
+		if (warn & HARDLOCKUP)
+			return;
+
+		if (hardlockup_panic)
+			panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
+		else
+			WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
+
+		per_cpu(watchdog_warn, this_cpu) = warn | HARDLOCKUP;
+		return;
+	}
+
+	per_cpu(watchdog_warn, this_cpu) = warn & ~HARDLOCKUP;
+	return;
+}
+static void watchdog_interrupt_count(void)
+{
+	__get_cpu_var(hrtimer_interrupts)++;
+}
+#else
+static void watchdog_interrupt_count(void) { return; }
+#endif /* CONFIG_PERF_EVENTS_NMI */
+
+/* watchdog kicker functions */
+static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
+{
+	int this_cpu = smp_processor_id();
+	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
+	char warn = per_cpu(watchdog_warn, this_cpu);
+	struct pt_regs *regs = get_irq_regs();
+	int duration;
+
+	/* kick the hardlockup detector */
+	watchdog_interrupt_count();
+
+	/* kick the softlockup detector */
+	wake_up_process(__get_cpu_var(softlockup_watchdog));
+
+	/* .. and repeat */
+	hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
+
+	if (touch_ts == 0) {
+		__touch_watchdog();
+		return HRTIMER_RESTART;
+	}
+
+	/* check for a softlockup
+	 * This is done by making sure a high priority task is
+	 * being scheduled.  The task touches the watchdog to
+	 * indicate it is getting cpu time.  If it hasn't then
+	 * this is a good indication some task is hogging the cpu
+	 */
+	duration = is_softlockup(touch_ts, this_cpu);
+	if (unlikely(duration)) {
+		/* only warn once */
+		if (warn & SOFTLOCKUP)
+			return HRTIMER_RESTART;
+
+		printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
+			this_cpu, duration,
+			current->comm, task_pid_nr(current));
+		print_modules();
+		print_irqtrace_events(current);
+		if (regs)
+			show_regs(regs);
+		else
+			dump_stack();
+
+		if (softlockup_panic)
+			panic("softlockup: hung tasks");
+		per_cpu(watchdog_warn, this_cpu) = warn | SOFTLOCKUP;
+	} else
+		per_cpu(watchdog_warn, this_cpu) = warn & ~SOFTLOCKUP;
+
+	return HRTIMER_RESTART;
+}
+
+
+/*
+ * The watchdog thread - touches the timestamp.
+ */
+static int watchdog(void *__bind_cpu)
+{
+	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+	struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, (unsigned long)__bind_cpu);
+
+	sched_setscheduler(current, SCHED_FIFO, &param);
+
+	/* initialize timestamp */
+	__touch_watchdog();
+
+	/* kick off the timer for the hardlockup detector */
+	/* done here because hrtimer_start can only pin to smp_processor_id() */
+	hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
+		      HRTIMER_MODE_REL_PINNED);
+
+	set_current_state(TASK_INTERRUPTIBLE);
+	/*
+	 * Run briefly once per second to reset the softlockup timestamp.
+	 * If this gets delayed for more than 60 seconds then the
+	 * debug-printout triggers in softlockup_tick().
+	 */
+	while (!kthread_should_stop()) {
+		__touch_watchdog();
+		schedule();
+
+		if (kthread_should_stop())
+			break;
+
+		set_current_state(TASK_INTERRUPTIBLE);
+	}
+	__set_current_state(TASK_RUNNING);
+
+	return 0;
+}
+
+
+#ifdef CONFIG_PERF_EVENTS_NMI
+static int watchdog_nmi_enable(int cpu)
+{
+	struct perf_event_attr *wd_attr;
+	struct perf_event *event = per_cpu(watchdog_ev, cpu);
+
+	/* is it already setup and enabled? */
+	if (event && event->state > PERF_EVENT_STATE_OFF)
+		goto out;
+
+	/* it is setup but not enabled */
+	if (event != NULL)
+		goto out_enable;
+
+	/* Try to register using hardware perf events */
+	wd_attr = &wd_hw_attr;
+	wd_attr->sample_period = hw_nmi_get_sample_period();
+	event = perf_event_create_kernel_counter(wd_attr, cpu, -1, watchdog_overflow_callback);
+	if (!IS_ERR(event)) {
+		printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
+		goto out_save;
+	}
+
+	printk(KERN_ERR "NMI watchdog failed to create perf event on cpu%i: %p\n", cpu, event);
+	return -1;
+
+	/* success path */
+out_save:
+	per_cpu(watchdog_ev, cpu) = event;
+out_enable:
+	perf_event_enable(per_cpu(watchdog_ev, cpu));
+out:
+	return 0;
+}
+
+static void watchdog_nmi_disable(int cpu)
+{
+	struct perf_event *event = per_cpu(watchdog_ev, cpu);
+
+	if (event) {
+		perf_event_disable(event);
+		per_cpu(watchdog_ev, cpu) = NULL;
+
+		/* should be in cleanup, but blocks oprofile */
+		perf_event_release_kernel(event);
+	}
+	return;
+}
+#else
+static int watchdog_nmi_enable(int cpu) { return 0; }
+static void watchdog_nmi_disable(int cpu) { return; }
+#endif /* CONFIG_PERF_EVENTS_NMI */
+
+/* prepare/enable/disable routines */
+static int watchdog_prepare_cpu(int cpu)
+{
+	struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
+
+	WARN_ON(per_cpu(softlockup_watchdog, cpu));
+	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer->function = watchdog_timer_fn;
+
+	return 0;
+}
+
+static int watchdog_enable(int cpu)
+{
+	struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
+
+	/* enable the perf event */
+	if (watchdog_nmi_enable(cpu) != 0)
+		return -1;
+
+	/* create the watchdog thread */
+	if (!p) {
+		p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
+		if (IS_ERR(p)) {
+			printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
+			return -1;
+		}
+		kthread_bind(p, cpu);
+		per_cpu(watchdog_touch_ts, cpu) = 0;
+		per_cpu(softlockup_watchdog, cpu) = p;
+		wake_up_process(p);
+	}
+
+	return 0;
+}
+
+static void watchdog_disable(int cpu)
+{
+	struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
+	struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
+
+	/*
+	 * cancel the timer first to stop incrementing the stats
+	 * and waking up the kthread
+	 */
+	hrtimer_cancel(hrtimer);
+
+	/* disable the perf event */
+	watchdog_nmi_disable(cpu);
+
+	/* stop the watchdog thread */
+	if (p) {
+		per_cpu(softlockup_watchdog, cpu) = NULL;
+		kthread_stop(p);
+	}
+
+	/* if any cpu succeeds, watchdog is considered enabled for the system */
+	watchdog_enabled = 1;
+}
+
+static void watchdog_enable_all_cpus(void)
+{
+	int cpu;
+	int result;
+
+	for_each_online_cpu(cpu)
+		result += watchdog_enable(cpu);
+
+	if (result)
+		printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
+
+}
+
+static void watchdog_disable_all_cpus(void)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu)
+		watchdog_disable(cpu);
+
+	/* if all watchdogs are disabled, then they are disabled for the system */
+	watchdog_enabled = 0;
+}
+
+
+/* sysctl functions */
+#ifdef CONFIG_SYSCTL
+/*
+ * proc handler for /proc/sys/kernel/nmi_watchdog
+ */
+
+int proc_dowatchdog_enabled(struct ctl_table *table, int write,
+		     void __user *buffer, size_t *length, loff_t *ppos)
+{
+	proc_dointvec(table, write, buffer, length, ppos);
+
+	if (watchdog_enabled)
+		watchdog_enable_all_cpus();
+	else
+		watchdog_disable_all_cpus();
+	return 0;
+}
+
+int proc_dowatchdog_thresh(struct ctl_table *table, int write,
+			     void __user *buffer,
+			     size_t *lenp, loff_t *ppos)
+{
+	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+}
+
+/* stub functions */
+int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
+			     void __user *buffer,
+			     size_t *lenp, loff_t *ppos)
+{
+	return proc_dowatchdog_thresh(table, write, buffer, lenp, ppos);
+}
+/* end of stub functions */
+#endif /* CONFIG_SYSCTL */
+
+
+/*
+ * Create/destroy watchdog threads as CPUs come and go:
+ */
+static int __cpuinit
+cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+	int hotcpu = (unsigned long)hcpu;
+
+	switch (action) {
+	case CPU_UP_PREPARE:
+	case CPU_UP_PREPARE_FROZEN:
+		if (watchdog_prepare_cpu(hotcpu))
+			return NOTIFY_BAD;
+		break;
+	case CPU_ONLINE:
+	case CPU_ONLINE_FROZEN:
+		if (watchdog_enable(hotcpu))
+			return NOTIFY_BAD;
+		break;
+#ifdef CONFIG_HOTPLUG_CPU
+	case CPU_UP_CANCELED:
+	case CPU_UP_CANCELED_FROZEN:
+		watchdog_disable(hotcpu);
+		break;
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+		watchdog_disable(hotcpu);
+		break;
+#endif /* CONFIG_HOTPLUG_CPU */
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata cpu_nfb = {
+	.notifier_call = cpu_callback
+};
+
+static int __init spawn_watchdog_task(void)
+{
+	void *cpu = (void *)(long)smp_processor_id();
+	int err;
+
+	if (no_watchdog)
+		return 0;
+
+	err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+	WARN_ON(err == NOTIFY_BAD);
+
+	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
+	register_cpu_notifier(&cpu_nfb);
+
+	atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
+
+	return 0;
+}
+early_initcall(spawn_watchdog_task);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e2e73cc..97a29e6 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -152,7 +152,7 @@ config DEBUG_SHIRQ
 	  points; some don't and need to be caught.
 
 config DETECT_SOFTLOCKUP
-	bool "Detect Soft Lockups"
+	bool
 	depends on DEBUG_KERNEL && !S390
 	default y
 	help
@@ -170,17 +170,27 @@ config DETECT_SOFTLOCKUP
 	   can be detected via the NMI-watchdog, on platforms that
 	   support it.)
 
-config NMI_WATCHDOG
-	bool "Detect Hard Lockups with an NMI Watchdog"
-	depends on DEBUG_KERNEL && PERF_EVENTS && PERF_EVENTS_NMI
+config LOCKUP_DETECTOR
+	bool "Detect Hard and Soft Lockups"
+	depends on DEBUG_KERNEL
+	default DETECT_SOFTLOCKUP
 	help
-	  Say Y here to enable the kernel to use the NMI as a watchdog
-	  to detect hard lockups.  This is useful when a cpu hangs for no
-	  reason but can still respond to NMIs.  A backtrace is displayed
-	  for reviewing and reporting.
+	  Say Y here to enable the kernel to act as a watchdog to detect
+	  hard and soft lockups.
+
+	  Softlockups are bugs that cause the kernel to loop in kernel
+	  mode for more than 60 seconds, without giving other tasks a
+	  chance to run.  The current stack trace is displayed upon
+	  detection and the system will stay locked up.
+
+	  Hardlockups are bugs that cause the CPU to loop in kernel mode
+	  for more than 60 seconds, without letting other interrupts have a
+	  chance to run.  The current stack trace is displayed upon detection
+	  and the system will stay locked up.
 
-	  The overhead should be minimal, just an extra NMI every few
-	  seconds.
+	  The overhead should be minimal.  A periodic hrtimer runs to
+	  generate interrupts and kick the watchdog task every 10-12 seconds.
+	  An NMI is generated every 60 seconds or so to check for hardlockups.
 
 config BOOTPARAM_SOFTLOCKUP_PANIC
 	bool "Panic (Reboot) On Soft Lockups"
-- 
1.6.5.2

Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Randy Dunlap]

On Tue, 20 Apr 2010 11:23:58 -0400 Don Zickus wrote:

> diff --git a/init/Kconfig b/init/Kconfig
> index 7331a16..98e3f5f 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -948,8 +948,11 @@ config PERF_USE_VMALLOC
>  
>  config PERF_EVENTS_NMI
>  	bool
> +	depends on PERF_EVENTS
>  	help
> -	  Arch has support for nmi_watchdog
> +	  Arch can generate an NMI using the perf event subsystem

Hi Don,

I realize that you didn't introduce Arch in this help text,
but can we eliminate him, please?  E.g.:

	  Platform can generate an NMI using the perf event subsystem.
or
	  System hardware can generate an NMI using the perf event subsystem.

> +	  Also has support for calculating cpu cycle events to

	                                   CPU

> +	  determine how many clock cycles in a given period

                                                     period.

>  
>  menu "Kernel Performance Events And Counters"


---
~Randy

Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Don Zickus]

On Tue, Apr 20, 2010 at 08:53:50AM -0700, Randy Dunlap wrote:
> On Tue, 20 Apr 2010 11:23:58 -0400 Don Zickus wrote:
> 
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 7331a16..98e3f5f 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -948,8 +948,11 @@ config PERF_USE_VMALLOC
> >  
> >  config PERF_EVENTS_NMI
> >  	bool
> > +	depends on PERF_EVENTS
> >  	help
> > -	  Arch has support for nmi_watchdog
> > +	  Arch can generate an NMI using the perf event subsystem
> 
> Hi Don,
> 
> I realize that you didn't introduce Arch in this help text,
> but can we eliminate him, please?  E.g.:

yup.

Thanks,
Don

Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Frederic Weisbecker]

Some minor things:


On Tue, Apr 20, 2010 at 11:23:58AM -0400, Don Zickus wrote:
> +#ifdef CONFIG_PERF_EVENTS_NMI
> +struct perf_event_attr wd_hw_attr = {
> +	.type		= PERF_TYPE_HARDWARE,
> +	.config		= PERF_COUNT_HW_CPU_CYCLES,
> +	.size		= sizeof(struct perf_event_attr),
> +	.pinned		= 1,
> +	.disabled	= 1,
> +};



Shouldn't it be static?


> +
> +/* Callback function for perf event subsystem */
> +void watchdog_overflow_callback(struct perf_event *event, int nmi,
> +		 struct perf_sample_data *data,
> +		 struct pt_regs *regs)
> +{
> +	int this_cpu = smp_processor_id();
> +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> +	char warn = per_cpu(watchdog_warn, this_cpu);



You can use __get_cpu_var() here



> +
> +	if (touch_ts == 0) {
> +		__touch_watchdog();
> +		return;
> +	}
> +
> +	/* check for a hardlockup
> +	 * This is done by making sure our timer interrupt
> +	 * is incrementing.  The timer interrupt should have
> +	 * fired multiple times before we overflow'd.  If it hasn't
> +	 * then this is a good indication the cpu is stuck
> +	 */
> +	if (is_hardlockup(this_cpu)) {
> +		/* only print hardlockups once */
> +		if (warn & HARDLOCKUP)
> +			return;
> +
> +		if (hardlockup_panic)
> +			panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> +		else
> +			WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> +
> +		per_cpu(watchdog_warn, this_cpu) = warn | HARDLOCKUP;



and here.



> +		return;
> +	}
> +
> +	per_cpu(watchdog_warn, this_cpu) = warn & ~HARDLOCKUP;
> +	return;
> +}
> +static void watchdog_interrupt_count(void)
> +{
> +	__get_cpu_var(hrtimer_interrupts)++;
> +}
> +#else
> +static void watchdog_interrupt_count(void) { return; }



Off case should be inline (although gcc will probably inline it by itself)



> +#endif /* CONFIG_PERF_EVENTS_NMI */
> +
> +/* watchdog kicker functions */
> +static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
> +{
> +	int this_cpu = smp_processor_id();
> +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);



__get_cpu_var

Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Don Zickus]

On Wed, Apr 21, 2010 at 07:27:33PM +0200, Frederic Weisbecker wrote:
> Some minor things:
> 
> 
> On Tue, Apr 20, 2010 at 11:23:58AM -0400, Don Zickus wrote:
> > +#ifdef CONFIG_PERF_EVENTS_NMI
> > +struct perf_event_attr wd_hw_attr = {
> > +	.type		= PERF_TYPE_HARDWARE,
> > +	.config		= PERF_COUNT_HW_CPU_CYCLES,
> > +	.size		= sizeof(struct perf_event_attr),
> > +	.pinned		= 1,
> > +	.disabled	= 1,
> > +};
> 
> 
> 
> Shouldn't it be static?

yes.  thanks.

> 
> 
> > +
> > +/* Callback function for perf event subsystem */
> > +void watchdog_overflow_callback(struct perf_event *event, int nmi,
> > +		 struct perf_sample_data *data,
> > +		 struct pt_regs *regs)
> > +{
> > +	int this_cpu = smp_processor_id();
> > +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> > +	char warn = per_cpu(watchdog_warn, this_cpu);
> 
> 
> 
> You can use __get_cpu_var() here

well, I already have this_cpu and need it later, I figured I would just
use it with per_cpu and save _get_cpu_var the work of re-running
smp_processor_id().

> 
> 
> 
> > +
> > +	if (touch_ts == 0) {
> > +		__touch_watchdog();
> > +		return;
> > +	}
> > +
> > +	/* check for a hardlockup
> > +	 * This is done by making sure our timer interrupt
> > +	 * is incrementing.  The timer interrupt should have
> > +	 * fired multiple times before we overflow'd.  If it hasn't
> > +	 * then this is a good indication the cpu is stuck
> > +	 */
> > +	if (is_hardlockup(this_cpu)) {
> > +		/* only print hardlockups once */
> > +		if (warn & HARDLOCKUP)
> > +			return;
> > +
> > +		if (hardlockup_panic)
> > +			panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> > +		else
> > +			WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
> > +
> > +		per_cpu(watchdog_warn, this_cpu) = warn | HARDLOCKUP;
> 
> 
> 
> and here.

same arguement as above.

> 
> 
> 
> > +		return;
> > +	}
> > +
> > +	per_cpu(watchdog_warn, this_cpu) = warn & ~HARDLOCKUP;
> > +	return;
> > +}
> > +static void watchdog_interrupt_count(void)
> > +{
> > +	__get_cpu_var(hrtimer_interrupts)++;
> > +}
> > +#else
> > +static void watchdog_interrupt_count(void) { return; }
> 
> 
> 
> Off case should be inline (although gcc will probably inline it by itself)

yup.  thanks.

> 
> 
> 
> > +#endif /* CONFIG_PERF_EVENTS_NMI */
> > +
> > +/* watchdog kicker functions */
> > +static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
> > +{
> > +	int this_cpu = smp_processor_id();
> > +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> 
> 
> 
> __get_cpu_var

again same as above.

Thanks for the review.

Cheers,
Don

Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Frederic Weisbecker]

On Wed, Apr 21, 2010 at 01:50:21PM -0400, Don Zickus wrote:
> On Wed, Apr 21, 2010 at 07:27:33PM +0200, Frederic Weisbecker wrote:
> > Some minor things:
> > 
> > 
> > On Tue, Apr 20, 2010 at 11:23:58AM -0400, Don Zickus wrote:
> > > +#ifdef CONFIG_PERF_EVENTS_NMI
> > > +struct perf_event_attr wd_hw_attr = {
> > > +	.type		= PERF_TYPE_HARDWARE,
> > > +	.config		= PERF_COUNT_HW_CPU_CYCLES,
> > > +	.size		= sizeof(struct perf_event_attr),
> > > +	.pinned		= 1,
> > > +	.disabled	= 1,
> > > +};
> > 
> > 
> > 
> > Shouldn't it be static?
> 
> yes.  thanks.
> 
> > 
> > 
> > > +
> > > +/* Callback function for perf event subsystem */
> > > +void watchdog_overflow_callback(struct perf_event *event, int nmi,
> > > +		 struct perf_sample_data *data,
> > > +		 struct pt_regs *regs)
> > > +{
> > > +	int this_cpu = smp_processor_id();
> > > +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> > > +	char warn = per_cpu(watchdog_warn, this_cpu);
> > 
> > 
> > 
> > You can use __get_cpu_var() here
> 
> well, I already have this_cpu and need it later, I figured I would just
> use it with per_cpu and save _get_cpu_var the work of re-running
> smp_processor_id().



This is more about code clarity in fact. per_cpu() suggests we are
fetching something from another cpu.

This is a very minor issue though.

Re: [PATCH 1/6] [watchdog] combine nmi_watchdog and softlockup

[Don Zickus]

On Wed, Apr 21, 2010 at 10:24:21PM +0200, Frederic Weisbecker wrote:
> On Wed, Apr 21, 2010 at 01:50:21PM -0400, Don Zickus wrote:
> > On Wed, Apr 21, 2010 at 07:27:33PM +0200, Frederic Weisbecker wrote:
> > > Some minor things:
> > > 
> > > 
> > > On Tue, Apr 20, 2010 at 11:23:58AM -0400, Don Zickus wrote:
> > > > +#ifdef CONFIG_PERF_EVENTS_NMI
> > > > +struct perf_event_attr wd_hw_attr = {
> > > > +	.type		= PERF_TYPE_HARDWARE,
> > > > +	.config		= PERF_COUNT_HW_CPU_CYCLES,
> > > > +	.size		= sizeof(struct perf_event_attr),
> > > > +	.pinned		= 1,
> > > > +	.disabled	= 1,
> > > > +};
> > > 
> > > 
> > > 
> > > Shouldn't it be static?
> > 
> > yes.  thanks.
> > 
> > > 
> > > 
> > > > +
> > > > +/* Callback function for perf event subsystem */
> > > > +void watchdog_overflow_callback(struct perf_event *event, int nmi,
> > > > +		 struct perf_sample_data *data,
> > > > +		 struct pt_regs *regs)
> > > > +{
> > > > +	int this_cpu = smp_processor_id();
> > > > +	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
> > > > +	char warn = per_cpu(watchdog_warn, this_cpu);
> > > 
> > > 
> > > 
> > > You can use __get_cpu_var() here
> > 
> > well, I already have this_cpu and need it later, I figured I would just
> > use it with per_cpu and save _get_cpu_var the work of re-running
> > smp_processor_id().
> 
> 
> 
> This is more about code clarity in fact. per_cpu() suggests we are
> fetching something from another cpu.

ah gotcha.

> 
> This is a very minor issue though.

I have no problem changing it.

Cheers,
Don

[PATCH 2/6] [watchdog] convert touch_softlockup_watchdog to touch_watchdog

[Don Zickus]

Just a scripted conversion to remove touch_softlockup_watchdog.

Also converts the once case of touch_all_softlockup_watchdogs to
touch_all_watchdogs.

This is done as part of the removal of the old softlockup code and
transition to the new softlockup code.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 arch/ia64/kernel/time.c         |    2 +-
 arch/ia64/kernel/uncached.c     |    2 +-
 arch/ia64/xen/time.c            |    2 +-
 arch/mn10300/kernel/gdb-stub.c  |    2 +-
 arch/powerpc/kernel/swsusp_64.c |    2 +-
 arch/sparc/kernel/nmi.c         |    2 +-
 arch/x86/kernel/apic/nmi.c      |    2 +-
 arch/x86/xen/smp.c              |    2 +-
 drivers/ide/ide-iops.c          |    2 +-
 drivers/ide/ide-taskfile.c      |    2 +-
 drivers/mtd/nand/nand_base.c    |    4 ++--
 drivers/video/nvidia/nv_accel.c |    2 +-
 include/linux/nmi.h             |    7 +------
 include/linux/sched.h           |   26 ++++++++------------------
 kernel/kgdb.c                   |    6 +++---
 kernel/panic.c                  |    2 +-
 kernel/power/hibernate.c        |    2 +-
 kernel/sched.c                  |    2 +-
 kernel/sched_clock.c            |    2 +-
 kernel/sysctl.c                 |    9 ---------
 kernel/time/tick-sched.c        |    8 ++++----
 kernel/time/timekeeping.c       |    2 +-
 kernel/timer.c                  |    1 -
 kernel/watchdog.c               |   30 +-----------------------------
 24 files changed, 35 insertions(+), 88 deletions(-)

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index a35c661..e9f6a6f 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -368,7 +368,7 @@ ia64_init_itm (void)
 	paravirt_init_missing_ticks_accounting(smp_processor_id());
 
 	/* avoid softlock up message when cpu is unplug and plugged again. */
-	touch_softlockup_watchdog();
+	touch_watchdog();
 
 	/* Setup the CPU local timer tick */
 	ia64_cpu_local_tick();
diff --git a/arch/ia64/kernel/uncached.c b/arch/ia64/kernel/uncached.c
index a595823..d18107f 100644
--- a/arch/ia64/kernel/uncached.c
+++ b/arch/ia64/kernel/uncached.c
@@ -256,7 +256,7 @@ static int __init uncached_build_memmap(u64 uc_start, u64 uc_end, void *arg)
 	struct gen_pool *pool = uncached_pools[nid].pool;
 	size_t size = uc_end - uc_start;
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 
 	if (pool != NULL) {
 		memset((char *)uc_start, 0, size);
diff --git a/arch/ia64/xen/time.c b/arch/ia64/xen/time.c
index c1c5445..0fa7097 100644
--- a/arch/ia64/xen/time.c
+++ b/arch/ia64/xen/time.c
@@ -233,7 +233,7 @@ static void xen_local_tick_resume(void)
 {
 	/* Just trigger a tick.  */
 	ia64_cpu_local_tick();
-	touch_softlockup_watchdog();
+	touch_watchdog();
 }
 
 void
diff --git a/arch/mn10300/kernel/gdb-stub.c b/arch/mn10300/kernel/gdb-stub.c
index 41b1170..d639eae 100644
--- a/arch/mn10300/kernel/gdb-stub.c
+++ b/arch/mn10300/kernel/gdb-stub.c
@@ -1668,7 +1668,7 @@ done:
 	if (excep == EXCEP_NMI)
 		NMICR = NMICR_NMIF;
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 
 	local_irq_restore(epsw);
 	return 1;
diff --git a/arch/powerpc/kernel/swsusp_64.c b/arch/powerpc/kernel/swsusp_64.c
index 6f3f069..6f570bc 100644
--- a/arch/powerpc/kernel/swsusp_64.c
+++ b/arch/powerpc/kernel/swsusp_64.c
@@ -14,7 +14,7 @@
 void do_after_copyback(void)
 {
 	iommu_restore();
-	touch_softlockup_watchdog();
+	touch_watchdog();
 	mb();
 }
 
diff --git a/arch/sparc/kernel/nmi.c b/arch/sparc/kernel/nmi.c
index d242a73..a77875f 100644
--- a/arch/sparc/kernel/nmi.c
+++ b/arch/sparc/kernel/nmi.c
@@ -61,7 +61,7 @@ void touch_nmi_watchdog(void)
 		}
 	}
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 }
 EXPORT_SYMBOL(touch_nmi_watchdog);
 
diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index 5d47682..4fd1312 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -383,7 +383,7 @@ void touch_nmi_watchdog(void)
 	/*
 	 * Tickle the softlockup detector too:
 	 */
-	touch_softlockup_watchdog();
+	touch_watchdog();
 }
 EXPORT_SYMBOL(touch_nmi_watchdog);
 
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 563d205..b4cc3ff 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -60,7 +60,7 @@ static __cpuinit void cpu_bringup(void)
 	int cpu = smp_processor_id();
 
 	cpu_init();
-	touch_softlockup_watchdog();
+	touch_watchdog();
 	preempt_disable();
 
 	xen_enable_sysenter();
diff --git a/drivers/ide/ide-iops.c b/drivers/ide/ide-iops.c
index 222c1ef..cc493e2 100644
--- a/drivers/ide/ide-iops.c
+++ b/drivers/ide/ide-iops.c
@@ -524,7 +524,7 @@ int ide_wait_not_busy(ide_hwif_t *hwif, unsigned long timeout)
 		 */
 		if (stat == 0xff)
 			return -ENODEV;
-		touch_softlockup_watchdog();
+		touch_watchdog();
 		touch_nmi_watchdog();
 	}
 	return -EBUSY;
diff --git a/drivers/ide/ide-taskfile.c b/drivers/ide/ide-taskfile.c
index cc8633c..6382883 100644
--- a/drivers/ide/ide-taskfile.c
+++ b/drivers/ide/ide-taskfile.c
@@ -291,7 +291,7 @@ static void ide_pio_datablock(ide_drive_t *drive, struct ide_cmd *cmd,
 	if (cmd->tf_flags & IDE_TFLAG_IO_16BIT)
 		drive->io_32bit = 0;
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 
 	if (cmd->tf_flags & IDE_TFLAG_MULTI_PIO)
 		nr_bytes = min_t(unsigned, cmd->nleft, drive->mult_count << 9);
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 8f2958f..5ce4e3b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -445,7 +445,7 @@ static void panic_nand_wait_ready(struct mtd_info *mtd, unsigned long timeo)
 	for (i = 0; i < timeo; i++) {
 		if (chip->dev_ready(mtd))
 			break;
-		touch_softlockup_watchdog();
+		touch_watchdog();
 		mdelay(1);
 	}
 }
@@ -468,7 +468,7 @@ void nand_wait_ready(struct mtd_info *mtd)
 	do {
 		if (chip->dev_ready(mtd))
 			break;
-		touch_softlockup_watchdog();
+		touch_watchdog();
 	} while (time_before(jiffies, timeo));
 	led_trigger_event(nand_led_trigger, LED_OFF);
 }
diff --git a/drivers/video/nvidia/nv_accel.c b/drivers/video/nvidia/nv_accel.c
index ad6472a..ff2e5c4 100644
--- a/drivers/video/nvidia/nv_accel.c
+++ b/drivers/video/nvidia/nv_accel.c
@@ -73,7 +73,7 @@ static inline void nvidiafb_safe_mode(struct fb_info *info)
 {
 	struct nvidia_par *par = info->par;
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 	info->pixmap.scan_align = 1;
 	par->lockup = 1;
 }
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index abd48aa..425b12e 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -20,14 +20,10 @@ extern void touch_nmi_watchdog(void);
 extern void acpi_nmi_disable(void);
 extern void acpi_nmi_enable(void);
 #else
-#ifndef CONFIG_LOCKUP_DETECTOR
 static inline void touch_nmi_watchdog(void)
 {
-	touch_softlockup_watchdog();
+	touch_watchdog();
 }
-#else
-extern void touch_nmi_watchdog(void);
-#endif
 static inline void acpi_nmi_disable(void) { }
 static inline void acpi_nmi_enable(void) { }
 #endif
@@ -52,7 +48,6 @@ static inline bool trigger_all_cpu_backtrace(void)
 #endif
 
 #ifdef CONFIG_LOCKUP_DETECTOR
-int hw_nmi_is_cpu_stuck(struct pt_regs *);
 u64 hw_nmi_get_sample_period(void);
 extern int watchdog_enabled;
 struct ctl_table;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2455ff5..0c128ad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -307,23 +307,19 @@ extern void scheduler_tick(void);
 
 extern void sched_show_task(struct task_struct *p);
 
-#ifdef CONFIG_DETECT_SOFTLOCKUP
-extern void softlockup_tick(void);
-extern void touch_softlockup_watchdog(void);
-extern void touch_all_softlockup_watchdogs(void);
-extern int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
-				    void __user *buffer,
-				    size_t *lenp, loff_t *ppos);
+#ifdef CONFIG_LOCKUP_DETECTOR
+extern void touch_watchdog(void);
+extern void touch_all_watchdogs(void);
 extern unsigned int  softlockup_panic;
 extern int softlockup_thresh;
+extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
+				  void __user *buffer,
+				  size_t *lenp, loff_t *ppos);
 #else
-static inline void softlockup_tick(void)
-{
-}
-static inline void touch_softlockup_watchdog(void)
+static inline void touch_watchdog(void)
 {
 }
-static inline void touch_all_softlockup_watchdogs(void)
+static inline void touch_all_watchdogs(void)
 {
 }
 #endif
@@ -338,12 +334,6 @@ extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
 					 size_t *lenp, loff_t *ppos);
 #endif
 
-#ifdef CONFIG_LOCKUP_DETECTOR
-extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
-				  void __user *buffer,
-				  size_t *lenp, loff_t *ppos);
-#endif
-
 /* Attach to any functions which should be ignored in wchan output. */
 #define __sched		__attribute__((__section__(".sched.text")))
 
diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 2eb517e..15df969 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -596,7 +596,7 @@ static void kgdb_wait(struct pt_regs *regs)
 
 	/* Signal the primary CPU that we are done: */
 	atomic_set(&cpu_in_kgdb[cpu], 0);
-	touch_softlockup_watchdog();
+	touch_watchdog();
 	clocksource_touch_watchdog();
 	local_irq_restore(flags);
 }
@@ -1450,7 +1450,7 @@ acquirelock:
 	    (kgdb_info[cpu].task &&
 	     kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 		atomic_set(&kgdb_active, -1);
-		touch_softlockup_watchdog();
+		touch_watchdog();
 		clocksource_touch_watchdog();
 		local_irq_restore(flags);
 
@@ -1550,7 +1550,7 @@ kgdb_restore:
 	}
 	/* Free kgdb_active */
 	atomic_set(&kgdb_active, -1);
-	touch_softlockup_watchdog();
+	touch_watchdog();
 	clocksource_touch_watchdog();
 	local_irq_restore(flags);
 
diff --git a/kernel/panic.c b/kernel/panic.c
index c787333..eda8051 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -136,7 +136,7 @@ NORET_TYPE void panic(const char * fmt, ...)
 #endif
 	local_irq_enable();
 	for (i = 0; ; ) {
-		touch_softlockup_watchdog();
+		touch_watchdog();
 		i += panic_blink(i);
 		mdelay(1);
 		i++;
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index bbfe472..217929a 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -415,7 +415,7 @@ static int resume_target_kernel(bool platform_mode)
 	 */
 	swsusp_free();
 	restore_processor_state();
-	touch_softlockup_watchdog();
+	touch_watchdog();
 
 	sysdev_resume();
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 7266b91..2e82485 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6991,7 +6991,7 @@ void show_state_filter(unsigned long state_filter)
 			sched_show_task(p);
 	} while_each_thread(g, p);
 
-	touch_all_softlockup_watchdogs();
+	touch_all_watchdogs();
 
 #ifdef CONFIG_SCHED_DEBUG
 	sysrq_sched_debug_show();
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 5b49613..f98b3e4 100644
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -232,7 +232,7 @@ void sched_clock_idle_wakeup_event(u64 delta_ns)
 		return;
 
 	sched_clock_tick();
-	touch_softlockup_watchdog();
+	touch_watchdog();
 }
 EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 1083897..1fec781 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -827,15 +827,6 @@ static struct ctl_table kern_table[] = {
 		.extra1		= &zero,
 		.extra2		= &one,
 	},
-	{
-		.procname	= "softlockup_thresh",
-		.data		= &softlockup_thresh,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dosoftlockup_thresh,
-		.extra1		= &neg_one,
-		.extra2		= &sixty,
-	},
 #endif
 #ifdef CONFIG_DETECT_HUNG_TASK
 	{
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f992762..29035ac 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -147,7 +147,7 @@ static void tick_nohz_update_jiffies(ktime_t now)
 	tick_do_update_jiffies64(now);
 	local_irq_restore(flags);
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 }
 
 static void tick_nohz_stop_idle(int cpu, ktime_t now)
@@ -494,7 +494,7 @@ void tick_nohz_restart_sched_tick(void)
 		account_idle_ticks(ticks);
 #endif
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 	/*
 	 * Cancel the scheduled timer and restore the tick
 	 */
@@ -547,7 +547,7 @@ static void tick_nohz_handler(struct clock_event_device *dev)
 	 * do when we go busy again does not account too much ticks.
 	 */
 	if (ts->tick_stopped) {
-		touch_softlockup_watchdog();
+		touch_watchdog();
 		ts->idle_jiffies++;
 	}
 
@@ -708,7 +708,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 		 * when we go busy again does not account too much ticks.
 		 */
 		if (ts->tick_stopped) {
-			touch_softlockup_watchdog();
+			touch_watchdog();
 			ts->idle_jiffies++;
 		}
 		update_process_times(user_mode(regs));
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 7faaa32..661fc40 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -600,7 +600,7 @@ static int timekeeping_resume(struct sys_device *dev)
 	timekeeping_suspended = 0;
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 
-	touch_softlockup_watchdog();
+	touch_watchdog();
 
 	clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
 
diff --git a/kernel/timer.c b/kernel/timer.c
index c61a794..80c8da5 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1223,7 +1223,6 @@ void run_local_timers(void)
 {
 	hrtimer_run_queues();
 	raise_softirq(TIMER_SOFTIRQ);
-	softlockup_tick();
 }
 
 /*
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 6c87d7d..73529a8 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -125,7 +125,7 @@ void touch_watchdog(void)
 }
 EXPORT_SYMBOL(touch_watchdog);
 
-void touch_all_watchdog(void)
+void touch_all_watchdogs(void)
 {
 	int cpu;
 
@@ -144,25 +144,6 @@ void touch_nmi_watchdog(void)
 }
 EXPORT_SYMBOL(touch_nmi_watchdog);
 
-void touch_all_nmi_watchdog(void)
-{
-	touch_all_watchdog();
-}
-
-void touch_softlockup_watchdog(void)
-{
-	touch_watchdog();
-}
-
-void touch_all_softlockup_watchdogs(void)
-{
-	touch_all_watchdog();
-}
-
-void softlockup_tick(void)
-{
-}
-
 #ifdef CONFIG_PERF_EVENTS_NMI
 /* watchdog detector functions */
 static int is_hardlockup(int cpu)
@@ -510,15 +491,6 @@ int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 {
 	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 }
-
-/* stub functions */
-int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
-			     void __user *buffer,
-			     size_t *lenp, loff_t *ppos)
-{
-	return proc_dowatchdog_thresh(table, write, buffer, lenp, ppos);
-}
-/* end of stub functions */
 #endif /* CONFIG_SYSCTL */
 
 
-- 
1.6.5.2

Re: [PATCH 2/6] [watchdog] convert touch_softlockup_watchdog to touch_watchdog

[Frederic Weisbecker]

On Tue, Apr 20, 2010 at 11:23:59AM -0400, Don Zickus wrote:
> Just a scripted conversion to remove touch_softlockup_watchdog.
> 
> Also converts the once case of touch_all_softlockup_watchdogs to
> touch_all_watchdogs.
> 
> This is done as part of the removal of the old softlockup code and
> transition to the new softlockup code.
> 
> Signed-off-by: Don Zickus <dzickus@redhat.com>


In fact I worry a bit about this unification of watchdog touching.
When we touch the softlockup watchdog, do we also want to touch
the nmi watchdog?

Most of the time, I think we don't want to. We usually touch the
softlockup detector because we know we are abnormally delaying
the softlockup kthread from being scheduled, and if we are in such
situation, it means we are doing something in a sensitive context:
typically the kind of context favorable to create hardlockups...

But the opposite is right: if we touch the nmi watchdog: it means we
are abnormally delaying irqs, which means we also are abnormally
delaying the softlockup kthread from being scheduled, so if we
touch the nmi watchdog, we also want to touch the softlockup
detector.

Hence I guess we want to keep the current state:

- touch_nmi_watchdog() = touch softlockup and nmi watchdogs
- touch_softlockup_watchdog() = only touch softlockup watchdog

Re: [PATCH 2/6] [watchdog] convert touch_softlockup_watchdog to touch_watchdog

[Don Zickus]

On Wed, Apr 21, 2010 at 10:46:01PM +0200, Frederic Weisbecker wrote:
> On Tue, Apr 20, 2010 at 11:23:59AM -0400, Don Zickus wrote:
> > Just a scripted conversion to remove touch_softlockup_watchdog.
> > 
> > Also converts the once case of touch_all_softlockup_watchdogs to
> > touch_all_watchdogs.
> > 
> > This is done as part of the removal of the old softlockup code and
> > transition to the new softlockup code.
> > 
> > Signed-off-by: Don Zickus <dzickus@redhat.com>
> 
> 
> In fact I worry a bit about this unification of watchdog touching.
> When we touch the softlockup watchdog, do we also want to touch
> the nmi watchdog?
> 
> Most of the time, I think we don't want to. We usually touch the
> softlockup detector because we know we are abnormally delaying
> the softlockup kthread from being scheduled, and if we are in such
> situation, it means we are doing something in a sensitive context:
> typically the kind of context favorable to create hardlockups...
> 
> But the opposite is right: if we touch the nmi watchdog: it means we
> are abnormally delaying irqs, which means we also are abnormally
> delaying the softlockup kthread from being scheduled, so if we
> touch the nmi watchdog, we also want to touch the softlockup
> detector.
> 
> Hence I guess we want to keep the current state:
> 
> - touch_nmi_watchdog() = touch softlockup and nmi watchdogs
> - touch_softlockup_watchdog() = only touch softlockup watchdog

Hmm ok I see what you are saying.  A little tweak and I have this
compiled-tested only patch that I think satisifies you.

I didn't really touch the touch_nmi_watchdog() code in the kernel, so it
still calls a stub function in kernel/watchdog.c.  Add a boolean to that
path and I think it accomplishes the logic you are looking for.

Cheers,
Don


diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 9898c7c..c1a89ac 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -31,6 +31,7 @@ int watchdog_enabled;
 int __read_mostly softlockup_thresh = 60;
 
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
+static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 static DEFINE_PER_CPU(bool, watchdog_touch_sync);
@@ -147,6 +148,7 @@ void touch_watchdog_sync(void)
 
 void touch_nmi_watchdog(void)
 {
+	__get_cpu_var(watchdog_nmi_touch) = true;
 	touch_watchdog();
 }
 EXPORT_SYMBOL(touch_nmi_watchdog);
@@ -203,11 +205,10 @@ void watchdog_overflow_callback(struct perf_event *event, int nmi,
 		 struct pt_regs *regs)
 {
 	int this_cpu = smp_processor_id();
-	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
 	char warn = per_cpu(watchdog_warn, this_cpu);
 
-	if (touch_ts == 0) {
-		__touch_watchdog();
+	if (__get_cpu_var(watchdog_nmi_touch) == true) {
+		__get_cpu_var(watchdog_nmi_touch) = false;
 		return;
 	}
 

Re: [PATCH 2/6] [watchdog] convert touch_softlockup_watchdog to touch_watchdog

[Frederic Weisbecker]

On Wed, Apr 21, 2010 at 05:31:42PM -0400, Don Zickus wrote:
> On Wed, Apr 21, 2010 at 10:46:01PM +0200, Frederic Weisbecker wrote:
> > On Tue, Apr 20, 2010 at 11:23:59AM -0400, Don Zickus wrote:
> > > Just a scripted conversion to remove touch_softlockup_watchdog.
> > > 
> > > Also converts the once case of touch_all_softlockup_watchdogs to
> > > touch_all_watchdogs.
> > > 
> > > This is done as part of the removal of the old softlockup code and
> > > transition to the new softlockup code.
> > > 
> > > Signed-off-by: Don Zickus <dzickus@redhat.com>
> > 
> > 
> > In fact I worry a bit about this unification of watchdog touching.
> > When we touch the softlockup watchdog, do we also want to touch
> > the nmi watchdog?
> > 
> > Most of the time, I think we don't want to. We usually touch the
> > softlockup detector because we know we are abnormally delaying
> > the softlockup kthread from being scheduled, and if we are in such
> > situation, it means we are doing something in a sensitive context:
> > typically the kind of context favorable to create hardlockups...
> > 
> > But the opposite is right: if we touch the nmi watchdog: it means we
> > are abnormally delaying irqs, which means we also are abnormally
> > delaying the softlockup kthread from being scheduled, so if we
> > touch the nmi watchdog, we also want to touch the softlockup
> > detector.
> > 
> > Hence I guess we want to keep the current state:
> > 
> > - touch_nmi_watchdog() = touch softlockup and nmi watchdogs
> > - touch_softlockup_watchdog() = only touch softlockup watchdog
> 
> Hmm ok I see what you are saying.  A little tweak and I have this
> compiled-tested only patch that I think satisifies you.
> 
> I didn't really touch the touch_nmi_watchdog() code in the kernel, so it
> still calls a stub function in kernel/watchdog.c.  Add a boolean to that
> path and I think it accomplishes the logic you are looking for.
> 
> Cheers,
> Don


Yeah looks good.

Could you send this patch with a changelog and your sign-off?

Thanks!

> 
> 
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index 9898c7c..c1a89ac 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -31,6 +31,7 @@ int watchdog_enabled;
>  int __read_mostly softlockup_thresh = 60;
>  
>  static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
> +static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
>  static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
>  static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
>  static DEFINE_PER_CPU(bool, watchdog_touch_sync);
> @@ -147,6 +148,7 @@ void touch_watchdog_sync(void)
>  
>  void touch_nmi_watchdog(void)
>  {
> +	__get_cpu_var(watchdog_nmi_touch) = true;
>  	touch_watchdog();
>  }
>  EXPORT_SYMBOL(touch_nmi_watchdog);
> @@ -203,11 +205,10 @@ void watchdog_overflow_callback(struct perf_event *event, int nmi,
>  		 struct pt_regs *regs)
>  {
>  	int this_cpu = smp_processor_id();
> -	unsigned long touch_ts = per_cpu(watchdog_touch_ts, this_cpu);
>  	char warn = per_cpu(watchdog_warn, this_cpu);
>  
> -	if (touch_ts == 0) {
> -		__touch_watchdog();
> +	if (__get_cpu_var(watchdog_nmi_touch) == true) {
> +		__get_cpu_var(watchdog_nmi_touch) = false;
>  		return;
>  	}
>  

Re: [PATCH 2/6] [watchdog] convert touch_softlockup_watchdog to touch_watchdog

[Don Zickus]

On Wed, Apr 21, 2010 at 11:46:12PM +0200, Frederic Weisbecker wrote:
> > > Hence I guess we want to keep the current state:
> > > 
> > > - touch_nmi_watchdog() = touch softlockup and nmi watchdogs
> > > - touch_softlockup_watchdog() = only touch softlockup watchdog
> > 
> > Hmm ok I see what you are saying.  A little tweak and I have this
> > compiled-tested only patch that I think satisifies you.
> > 
> > I didn't really touch the touch_nmi_watchdog() code in the kernel, so it
> > still calls a stub function in kernel/watchdog.c.  Add a boolean to that
> > path and I think it accomplishes the logic you are looking for.
> > 
> > Cheers,
> > Don
> 
> 
> Yeah looks good.
> 
> Could you send this patch with a changelog and your sign-off?

I thought about including it when I refresh the patch series with the
other changes you suggested.  Do you prefer it to be separate?

Cheers,
Don

Re: [PATCH 2/6] [watchdog] convert touch_softlockup_watchdog to touch_watchdog

[Frederic Weisbecker]

On Thu, Apr 22, 2010 at 09:20:25AM -0400, Don Zickus wrote:
> On Wed, Apr 21, 2010 at 11:46:12PM +0200, Frederic Weisbecker wrote:
> > > > Hence I guess we want to keep the current state:
> > > > 
> > > > - touch_nmi_watchdog() = touch softlockup and nmi watchdogs
> > > > - touch_softlockup_watchdog() = only touch softlockup watchdog
> > > 
> > > Hmm ok I see what you are saying.  A little tweak and I have this
> > > compiled-tested only patch that I think satisifies you.
> > > 
> > > I didn't really touch the touch_nmi_watchdog() code in the kernel, so it
> > > still calls a stub function in kernel/watchdog.c.  Add a boolean to that
> > > path and I think it accomplishes the logic you are looking for.
> > > 
> > > Cheers,
> > > Don
> > 
> > 
> > Yeah looks good.
> > 
> > Could you send this patch with a changelog and your sign-off?
> 
> I thought about including it when I refresh the patch series with the
> other changes you suggested.  Do you prefer it to be separate?


I was about to apply the series because there were mostly minor
things to fix.

But I would indeed prefer you repost a new series with the reviews
addressed, whatever this patch is a delta or a fixed existing one.
I will more likely forget things in the middle than you will.

Thanks.

[PATCH 3/6] [watchdog] remove old softlockup code

[Don Zickus]

Now that is no longer compiled or used, just remove it.

Also moves some of the code wrapped with DETECT_SOFTLOCKUP to the
LOCKUP_DETECTOR wrappers because that is the code that uses it now.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 kernel/softlockup.c |  278 ---------------------------------------------------
 kernel/sysctl.c     |   22 ++--
 2 files changed, 10 insertions(+), 290 deletions(-)
 delete mode 100644 kernel/softlockup.c

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
deleted file mode 100644
index d225790..0000000
--- a/kernel/softlockup.c
+++ /dev/null
@@ -1,278 +0,0 @@
-/*
- * Detect Soft Lockups
- *
- * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc.
- *
- * this code detects soft lockups: incidents in where on a CPU
- * the kernel does not reschedule for 10 seconds or more.
- */
-#include <linux/mm.h>
-#include <linux/cpu.h>
-#include <linux/nmi.h>
-#include <linux/init.h>
-#include <linux/delay.h>
-#include <linux/freezer.h>
-#include <linux/kthread.h>
-#include <linux/lockdep.h>
-#include <linux/notifier.h>
-#include <linux/module.h>
-#include <linux/sysctl.h>
-
-#include <asm/irq_regs.h>
-
-static DEFINE_SPINLOCK(print_lock);
-
-static DEFINE_PER_CPU(unsigned long, softlockup_touch_ts); /* touch timestamp */
-static DEFINE_PER_CPU(unsigned long, softlockup_print_ts); /* print timestamp */
-static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
-
-static int __read_mostly did_panic;
-int __read_mostly softlockup_thresh = 60;
-
-/*
- * Should we panic (and reboot, if panic_timeout= is set) when a
- * soft-lockup occurs:
- */
-unsigned int __read_mostly softlockup_panic =
-				CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
-
-static int __init softlockup_panic_setup(char *str)
-{
-	softlockup_panic = simple_strtoul(str, NULL, 0);
-
-	return 1;
-}
-__setup("softlockup_panic=", softlockup_panic_setup);
-
-static int
-softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
-{
-	did_panic = 1;
-
-	return NOTIFY_DONE;
-}
-
-static struct notifier_block panic_block = {
-	.notifier_call = softlock_panic,
-};
-
-/*
- * Returns seconds, approximately.  We don't need nanosecond
- * resolution, and we don't need to waste time with a big divide when
- * 2^30ns == 1.074s.
- */
-static unsigned long get_timestamp(int this_cpu)
-{
-	return cpu_clock(this_cpu) >> 30LL;  /* 2^30 ~= 10^9 */
-}
-
-static void __touch_softlockup_watchdog(void)
-{
-	int this_cpu = raw_smp_processor_id();
-
-	__raw_get_cpu_var(softlockup_touch_ts) = get_timestamp(this_cpu);
-}
-
-void touch_softlockup_watchdog(void)
-{
-	__raw_get_cpu_var(softlockup_touch_ts) = 0;
-}
-EXPORT_SYMBOL(touch_softlockup_watchdog);
-
-void touch_all_softlockup_watchdogs(void)
-{
-	int cpu;
-
-	/* Cause each CPU to re-update its timestamp rather than complain */
-	for_each_online_cpu(cpu)
-		per_cpu(softlockup_touch_ts, cpu) = 0;
-}
-EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
-
-int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
-			     void __user *buffer,
-			     size_t *lenp, loff_t *ppos)
-{
-	touch_all_softlockup_watchdogs();
-	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-}
-
-/*
- * This callback runs from the timer interrupt, and checks
- * whether the watchdog thread has hung or not:
- */
-void softlockup_tick(void)
-{
-	int this_cpu = smp_processor_id();
-	unsigned long touch_ts = per_cpu(softlockup_touch_ts, this_cpu);
-	unsigned long print_ts;
-	struct pt_regs *regs = get_irq_regs();
-	unsigned long now;
-
-	/* Is detection switched off? */
-	if (!per_cpu(softlockup_watchdog, this_cpu) || softlockup_thresh <= 0) {
-		/* Be sure we don't false trigger if switched back on */
-		if (touch_ts)
-			per_cpu(softlockup_touch_ts, this_cpu) = 0;
-		return;
-	}
-
-	if (touch_ts == 0) {
-		__touch_softlockup_watchdog();
-		return;
-	}
-
-	print_ts = per_cpu(softlockup_print_ts, this_cpu);
-
-	/* report at most once a second */
-	if (print_ts == touch_ts || did_panic)
-		return;
-
-	/* do not print during early bootup: */
-	if (unlikely(system_state != SYSTEM_RUNNING)) {
-		__touch_softlockup_watchdog();
-		return;
-	}
-
-	now = get_timestamp(this_cpu);
-
-	/*
-	 * Wake up the high-prio watchdog task twice per
-	 * threshold timespan.
-	 */
-	if (now > touch_ts + softlockup_thresh/2)
-		wake_up_process(per_cpu(softlockup_watchdog, this_cpu));
-
-	/* Warn about unreasonable delays: */
-	if (now <= (touch_ts + softlockup_thresh))
-		return;
-
-	per_cpu(softlockup_print_ts, this_cpu) = touch_ts;
-
-	spin_lock(&print_lock);
-	printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
-			this_cpu, now - touch_ts,
-			current->comm, task_pid_nr(current));
-	print_modules();
-	print_irqtrace_events(current);
-	if (regs)
-		show_regs(regs);
-	else
-		dump_stack();
-	spin_unlock(&print_lock);
-
-	if (softlockup_panic)
-		panic("softlockup: hung tasks");
-}
-
-/*
- * The watchdog thread - runs every second and touches the timestamp.
- */
-static int watchdog(void *__bind_cpu)
-{
-	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
-
-	sched_setscheduler(current, SCHED_FIFO, &param);
-
-	/* initialize timestamp */
-	__touch_softlockup_watchdog();
-
-	set_current_state(TASK_INTERRUPTIBLE);
-	/*
-	 * Run briefly once per second to reset the softlockup timestamp.
-	 * If this gets delayed for more than 60 seconds then the
-	 * debug-printout triggers in softlockup_tick().
-	 */
-	while (!kthread_should_stop()) {
-		__touch_softlockup_watchdog();
-		schedule();
-
-		if (kthread_should_stop())
-			break;
-
-		set_current_state(TASK_INTERRUPTIBLE);
-	}
-	__set_current_state(TASK_RUNNING);
-
-	return 0;
-}
-
-/*
- * Create/destroy watchdog threads as CPUs come and go:
- */
-static int __cpuinit
-cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
-{
-	int hotcpu = (unsigned long)hcpu;
-	struct task_struct *p;
-
-	switch (action) {
-	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
-		BUG_ON(per_cpu(softlockup_watchdog, hotcpu));
-		p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
-		if (IS_ERR(p)) {
-			printk(KERN_ERR "watchdog for %i failed\n", hotcpu);
-			return NOTIFY_BAD;
-		}
-		per_cpu(softlockup_touch_ts, hotcpu) = 0;
-		per_cpu(softlockup_watchdog, hotcpu) = p;
-		kthread_bind(p, hotcpu);
-		break;
-	case CPU_ONLINE:
-	case CPU_ONLINE_FROZEN:
-		wake_up_process(per_cpu(softlockup_watchdog, hotcpu));
-		break;
-#ifdef CONFIG_HOTPLUG_CPU
-	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
-		if (!per_cpu(softlockup_watchdog, hotcpu))
-			break;
-		/* Unbind so it can run.  Fall thru. */
-		kthread_bind(per_cpu(softlockup_watchdog, hotcpu),
-			     cpumask_any(cpu_online_mask));
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		p = per_cpu(softlockup_watchdog, hotcpu);
-		per_cpu(softlockup_watchdog, hotcpu) = NULL;
-		kthread_stop(p);
-		break;
-#endif /* CONFIG_HOTPLUG_CPU */
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block __cpuinitdata cpu_nfb = {
-	.notifier_call = cpu_callback
-};
-
-static int __initdata nosoftlockup;
-
-static int __init nosoftlockup_setup(char *str)
-{
-	nosoftlockup = 1;
-	return 1;
-}
-__setup("nosoftlockup", nosoftlockup_setup);
-
-static int __init spawn_softlockup_task(void)
-{
-	void *cpu = (void *)(long)smp_processor_id();
-	int err;
-
-	if (nosoftlockup)
-		return 0;
-
-	err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
-	if (err == NOTIFY_BAD) {
-		BUG();
-		return 1;
-	}
-	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
-	register_cpu_notifier(&cpu_nfb);
-
-	atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
-
-	return 0;
-}
-early_initcall(spawn_softlockup_task);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 1fec781..494e9a2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -99,7 +99,7 @@ extern int blk_iopoll_enabled;
 #endif
 
 /* Constants used for minimum and  maximum */
-#ifdef CONFIG_DETECT_SOFTLOCKUP
+#ifdef CONFIG_LOCKUP_DETECTOR
 static int sixty = 60;
 static int neg_one = -1;
 #endif
@@ -713,6 +713,15 @@ static struct ctl_table kern_table[] = {
 		.extra1		= &neg_one,
 		.extra2		= &sixty,
 	},
+	{
+		.procname	= "softlockup_panic",
+		.data		= &softlockup_panic,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &one,
+	},
 #endif
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86) && !defined(CONFIG_LOCKUP_DETECTOR)
 	{
@@ -817,17 +826,6 @@ static struct ctl_table kern_table[] = {
 		.proc_handler	= proc_dointvec,
 	},
 #endif
-#ifdef CONFIG_DETECT_SOFTLOCKUP
-	{
-		.procname	= "softlockup_panic",
-		.data		= &softlockup_panic,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &zero,
-		.extra2		= &one,
-	},
-#endif
 #ifdef CONFIG_DETECT_HUNG_TASK
 	{
 		.procname	= "hung_task_panic",
-- 
1.6.5.2

[PATCH 4/6] [watchdog] remove nmi_watchdog.c file

[Don Zickus]

This file migrated to kernel/watchdog.c and then combined with
kernel/softlockup.c.  As a result kernel/nmi_watchdog.c is no longer
needed.  Just remove it.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 kernel/nmi_watchdog.c |  259 -------------------------------------------------
 1 files changed, 0 insertions(+), 259 deletions(-)
 delete mode 100644 kernel/nmi_watchdog.c

diff --git a/kernel/nmi_watchdog.c b/kernel/nmi_watchdog.c
deleted file mode 100644
index a79d211..0000000
--- a/kernel/nmi_watchdog.c
+++ /dev/null
@@ -1,259 +0,0 @@
-/*
- * Detect Hard Lockups using the NMI
- *
- * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
- *
- * this code detects hard lockups: incidents in where on a CPU
- * the kernel does not respond to anything except NMI.
- *
- * Note: Most of this code is borrowed heavily from softlockup.c,
- * so thanks to Ingo for the initial implementation.
- * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks
- * to those contributors as well.
- */
-
-#include <linux/mm.h>
-#include <linux/cpu.h>
-#include <linux/nmi.h>
-#include <linux/init.h>
-#include <linux/delay.h>
-#include <linux/freezer.h>
-#include <linux/lockdep.h>
-#include <linux/notifier.h>
-#include <linux/module.h>
-#include <linux/sysctl.h>
-
-#include <asm/irq_regs.h>
-#include <linux/perf_event.h>
-
-static DEFINE_PER_CPU(struct perf_event *, nmi_watchdog_ev);
-static DEFINE_PER_CPU(int, nmi_watchdog_touch);
-static DEFINE_PER_CPU(long, alert_counter);
-
-static int panic_on_timeout;
-
-void touch_nmi_watchdog(void)
-{
-	__raw_get_cpu_var(nmi_watchdog_touch) = 1;
-	touch_softlockup_watchdog();
-}
-EXPORT_SYMBOL(touch_nmi_watchdog);
-
-void touch_all_nmi_watchdog(void)
-{
-	int cpu;
-
-	for_each_online_cpu(cpu)
-		per_cpu(nmi_watchdog_touch, cpu) = 1;
-	touch_softlockup_watchdog();
-}
-
-static int __init setup_nmi_watchdog(char *str)
-{
-	if (!strncmp(str, "panic", 5)) {
-		panic_on_timeout = 1;
-		str = strchr(str, ',');
-		if (!str)
-			return 1;
-		++str;
-	}
-	return 1;
-}
-__setup("nmi_watchdog=", setup_nmi_watchdog);
-
-struct perf_event_attr wd_hw_attr = {
-	.type		= PERF_TYPE_HARDWARE,
-	.config		= PERF_COUNT_HW_CPU_CYCLES,
-	.size		= sizeof(struct perf_event_attr),
-	.pinned		= 1,
-	.disabled	= 1,
-};
-
-struct perf_event_attr wd_sw_attr = {
-	.type		= PERF_TYPE_SOFTWARE,
-	.config		= PERF_COUNT_SW_CPU_CLOCK,
-	.size		= sizeof(struct perf_event_attr),
-	.pinned		= 1,
-	.disabled	= 1,
-};
-
-void wd_overflow(struct perf_event *event, int nmi,
-		 struct perf_sample_data *data,
-		 struct pt_regs *regs)
-{
-	int cpu = smp_processor_id();
-	int touched = 0;
-
-	if (__get_cpu_var(nmi_watchdog_touch)) {
-		per_cpu(nmi_watchdog_touch, cpu) = 0;
-		touched = 1;
-	}
-
-	/* check to see if the cpu is doing anything */
-	if (!touched && hw_nmi_is_cpu_stuck(regs)) {
-		/*
-		 * Ayiee, looks like this CPU is stuck ...
-		 * wait a few IRQs (5 seconds) before doing the oops ...
-		 */
-		per_cpu(alert_counter, cpu) += 1;
-		if (per_cpu(alert_counter, cpu) == 5) {
-			if (panic_on_timeout)
-				panic("NMI Watchdog detected LOCKUP on cpu %d", cpu);
-			else
-				WARN(1, "NMI Watchdog detected LOCKUP on cpu %d", cpu);
-		}
-	} else {
-		per_cpu(alert_counter, cpu) = 0;
-	}
-
-	return;
-}
-
-static int enable_nmi_watchdog(int cpu)
-{
-	struct perf_event *event;
-	struct perf_event_attr *wd_attr;
-
-	event = per_cpu(nmi_watchdog_ev, cpu);
-	if (event && event->state > PERF_EVENT_STATE_OFF)
-		return 0;
-
-	if (event == NULL) {
-		/* Try to register using hardware perf events first */
-		wd_attr = &wd_hw_attr;
-		wd_attr->sample_period = hw_nmi_get_sample_period();
-		event = perf_event_create_kernel_counter(wd_attr, cpu, -1, wd_overflow);
-		if (IS_ERR(event)) {
-			/* hardware doesn't exist or not supported, fallback to software events */
-			printk(KERN_INFO "nmi_watchdog: hardware not available, trying software events\n");
-			wd_attr = &wd_sw_attr;
-			wd_attr->sample_period = NSEC_PER_SEC;
-			event = perf_event_create_kernel_counter(wd_attr, cpu, -1, wd_overflow);
-			if (IS_ERR(event)) {
-				printk(KERN_ERR "nmi watchdog failed to create perf event on %i: %p\n", cpu, event);
-				return -1;
-			}
-		}
-		per_cpu(nmi_watchdog_ev, cpu) = event;
-	}
-	perf_event_enable(per_cpu(nmi_watchdog_ev, cpu));
-	return 0;
-}
-
-static void disable_nmi_watchdog(int cpu)
-{
-	struct perf_event *event;
-
-	event = per_cpu(nmi_watchdog_ev, cpu);
-	if (event) {
-		perf_event_disable(per_cpu(nmi_watchdog_ev, cpu));
-		per_cpu(nmi_watchdog_ev, cpu) = NULL;
-		perf_event_release_kernel(event);
-	}
-}
-
-#ifdef CONFIG_SYSCTL
-/*
- * proc handler for /proc/sys/kernel/nmi_watchdog
- */
-int nmi_watchdog_enabled;
-
-int proc_nmi_enabled(struct ctl_table *table, int write,
-		     void __user *buffer, size_t *length, loff_t *ppos)
-{
-	int cpu;
-
-	if (!write) {
-		struct perf_event *event;
-		for_each_online_cpu(cpu) {
-			event = per_cpu(nmi_watchdog_ev, cpu);
-			if (event && event->state > PERF_EVENT_STATE_OFF) {
-				nmi_watchdog_enabled = 1;
-				break;
-			}
-		}
-		proc_dointvec(table, write, buffer, length, ppos);
-		return 0;
-	}
-
-	touch_all_nmi_watchdog();
-	proc_dointvec(table, write, buffer, length, ppos);
-	if (nmi_watchdog_enabled) {
-		for_each_online_cpu(cpu)
-			if (enable_nmi_watchdog(cpu)) {
-				printk(KERN_ERR "NMI watchdog failed configuration, "
-					" can not be enabled\n");
-			}
-	} else {
-		for_each_online_cpu(cpu)
-			disable_nmi_watchdog(cpu);
-	}
-	return 0;
-}
-
-#endif /* CONFIG_SYSCTL */
-
-/*
- * Create/destroy watchdog threads as CPUs come and go:
- */
-static int __cpuinit
-cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
-{
-	int hotcpu = (unsigned long)hcpu;
-
-	switch (action) {
-	case CPU_UP_PREPARE:
-	case CPU_UP_PREPARE_FROZEN:
-		per_cpu(nmi_watchdog_touch, hotcpu) = 0;
-		break;
-	case CPU_ONLINE:
-	case CPU_ONLINE_FROZEN:
-		if (enable_nmi_watchdog(hotcpu))
-			return NOTIFY_BAD;
-		break;
-#ifdef CONFIG_HOTPLUG_CPU
-	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
-		disable_nmi_watchdog(hotcpu);
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		break;
-#endif /* CONFIG_HOTPLUG_CPU */
-	}
-	return NOTIFY_OK;
-}
-
-static struct notifier_block __cpuinitdata cpu_nfb = {
-	.notifier_call = cpu_callback
-};
-
-static int __initdata nonmi_watchdog;
-
-static int __init nonmi_watchdog_setup(char *str)
-{
-	nonmi_watchdog = 1;
-	return 1;
-}
-__setup("nonmi_watchdog", nonmi_watchdog_setup);
-
-static int __init spawn_nmi_watchdog_task(void)
-{
-	void *cpu = (void *)(long)smp_processor_id();
-	int err;
-
-	if (nonmi_watchdog)
-		return 0;
-
-	printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
-
-	err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
-	if (err == NOTIFY_BAD) {
-		BUG();
-		return 1;
-	}
-	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
-	register_cpu_notifier(&cpu_nfb);
-
-	return 0;
-}
-early_initcall(spawn_nmi_watchdog_task);
-- 
1.6.5.2

[PATCH 5/6] [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier

[Don Zickus]

As part of the transition of the nmi watchdog to something more generic,
the trigger_all_cpu_backtrace code is getting left behind.  Put it in its
own die_notifier so it can still be used.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 arch/x86/kernel/apic/hw_nmi.c |   65 ++++++++++++++++++++++++++++++++---------
 1 files changed, 51 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 79425f9..19d3435 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -17,6 +17,10 @@
 #include <linux/cpumask.h>
 #include <linux/kernel_stat.h>
 #include <asm/mce.h>
+#include <linux/kdebug.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+
 
 #include <linux/nmi.h>
 #include <linux/module.h>
@@ -54,20 +58,6 @@ int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
 	unsigned int sum;
 	int cpu = smp_processor_id();
 
-	/* FIXME: cheap hack for this check, probably should get its own
-	 * die_notifier handler
-	 */
-	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
-		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
-
-		spin_lock(&lock);
-		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
-		show_regs(regs);
-		dump_stack();
-		spin_unlock(&lock);
-		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
-	}
-
 	/* if we are doing an mce, just assume the cpu is not stuck */
 	/* Could check oops_in_progress here too, but it's safer not to */
 	if (mce_in_progress())
@@ -109,6 +99,53 @@ void arch_trigger_all_cpu_backtrace(void)
 		mdelay(1);
 	}
 }
+
+static int __kprobes
+arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
+			 unsigned long cmd, void *__args)
+{
+	struct die_args *args = __args;
+	struct pt_regs *regs;
+	int cpu = smp_processor_id();
+
+	switch (cmd) {
+	case DIE_NMI:
+	case DIE_NMI_IPI:
+		break;
+
+	default:
+		return NOTIFY_DONE;
+	}
+
+	regs = args->regs;
+
+	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
+		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
+
+		spin_lock(&lock);
+		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
+		show_regs(regs);
+		dump_stack();
+		spin_unlock(&lock);
+		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
+		return NOTIFY_STOP;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static __read_mostly struct notifier_block backtrace_notifier = {
+	.notifier_call          = arch_trigger_all_cpu_backtrace_handler,
+	.next                   = NULL,
+	.priority               = 1
+};
+
+static int __init register_trigger_all_cpu_backtrace(void)
+{
+	register_die_notifier(&backtrace_notifier);
+	return 0;
+}
+early_initcall(register_trigger_all_cpu_backtrace);
 #endif
 
 /* STUB calls to mimic old nmi_watchdog behaviour */
-- 
1.6.5.2

Re: [PATCH 5/6] [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier

[Frederic Weisbecker]

On Tue, Apr 20, 2010 at 11:24:02AM -0400, Don Zickus wrote:
> As part of the transition of the nmi watchdog to something more generic,
> the trigger_all_cpu_backtrace code is getting left behind.  Put it in its
> own die_notifier so it can still be used.
> 
> Signed-off-by: Don Zickus <dzickus@redhat.com>
> ---
>  arch/x86/kernel/apic/hw_nmi.c |   65 ++++++++++++++++++++++++++++++++---------
>  1 files changed, 51 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
> index 79425f9..19d3435 100644
> --- a/arch/x86/kernel/apic/hw_nmi.c
> +++ b/arch/x86/kernel/apic/hw_nmi.c
> @@ -17,6 +17,10 @@
>  #include <linux/cpumask.h>
>  #include <linux/kernel_stat.h>
>  #include <asm/mce.h>
> +#include <linux/kdebug.h>
> +#include <linux/notifier.h>
> +#include <linux/kprobes.h>
> +
>  
>  #include <linux/nmi.h>
>  #include <linux/module.h>
> @@ -54,20 +58,6 @@ int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
>  	unsigned int sum;
>  	int cpu = smp_processor_id();
>  
> -	/* FIXME: cheap hack for this check, probably should get its own
> -	 * die_notifier handler
> -	 */
> -	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> -		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
> -
> -		spin_lock(&lock);
> -		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
> -		show_regs(regs);
> -		dump_stack();
> -		spin_unlock(&lock);
> -		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
> -	}
> -
>  	/* if we are doing an mce, just assume the cpu is not stuck */
>  	/* Could check oops_in_progress here too, but it's safer not to */
>  	if (mce_in_progress())
> @@ -109,6 +99,53 @@ void arch_trigger_all_cpu_backtrace(void)
>  		mdelay(1);
>  	}
>  }
> +
> +static int __kprobes
> +arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
> +			 unsigned long cmd, void *__args)
> +{
> +	struct die_args *args = __args;
> +	struct pt_regs *regs;
> +	int cpu = smp_processor_id();
> +
> +	switch (cmd) {
> +	case DIE_NMI:
> +	case DIE_NMI_IPI:
> +		break;
> +
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +
> +	regs = args->regs;
> +
> +	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> +		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
> +
> +		spin_lock(&lock);



This should be an arch_spin_lock(), so that it won't sleep with rt mutex.


In fact this whole function can be moved to generic code, right?



> +		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
> +		show_regs(regs);
> +		dump_stack();
> +		spin_unlock(&lock);
> +		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
> +		return NOTIFY_STOP;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static __read_mostly struct notifier_block backtrace_notifier = {
> +	.notifier_call          = arch_trigger_all_cpu_backtrace_handler,
> +	.next                   = NULL,
> +	.priority               = 1
> +};
> +
> +static int __init register_trigger_all_cpu_backtrace(void)
> +{
> +	register_die_notifier(&backtrace_notifier);
> +	return 0;
> +}
> +early_initcall(register_trigger_all_cpu_backtrace);
>  #endif
>  
>  /* STUB calls to mimic old nmi_watchdog behaviour */
> -- 
> 1.6.5.2
> 

Re: [PATCH 5/6] [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier

[Don Zickus]

On Wed, Apr 21, 2010 at 11:00:04PM +0200, Frederic Weisbecker wrote:
> On Tue, Apr 20, 2010 at 11:24:02AM -0400, Don Zickus wrote:
> > As part of the transition of the nmi watchdog to something more generic,
> > the trigger_all_cpu_backtrace code is getting left behind.  Put it in its
> > own die_notifier so it can still be used.
> > 
> > Signed-off-by: Don Zickus <dzickus@redhat.com>
> > ---
> >  arch/x86/kernel/apic/hw_nmi.c |   65 ++++++++++++++++++++++++++++++++---------
> >  1 files changed, 51 insertions(+), 14 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
> > index 79425f9..19d3435 100644
> > --- a/arch/x86/kernel/apic/hw_nmi.c
> > +++ b/arch/x86/kernel/apic/hw_nmi.c
> > @@ -17,6 +17,10 @@
> >  #include <linux/cpumask.h>
> >  #include <linux/kernel_stat.h>
> >  #include <asm/mce.h>
> > +#include <linux/kdebug.h>
> > +#include <linux/notifier.h>
> > +#include <linux/kprobes.h>
> > +
> >  
> >  #include <linux/nmi.h>
> >  #include <linux/module.h>
> > @@ -54,20 +58,6 @@ int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
> >  	unsigned int sum;
> >  	int cpu = smp_processor_id();
> >  
> > -	/* FIXME: cheap hack for this check, probably should get its own
> > -	 * die_notifier handler
> > -	 */
> > -	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> > -		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
> > -
> > -		spin_lock(&lock);
> > -		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
> > -		show_regs(regs);
> > -		dump_stack();
> > -		spin_unlock(&lock);
> > -		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
> > -	}
> > -
> >  	/* if we are doing an mce, just assume the cpu is not stuck */
> >  	/* Could check oops_in_progress here too, but it's safer not to */
> >  	if (mce_in_progress())
> > @@ -109,6 +99,53 @@ void arch_trigger_all_cpu_backtrace(void)
> >  		mdelay(1);
> >  	}
> >  }
> > +
> > +static int __kprobes
> > +arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
> > +			 unsigned long cmd, void *__args)
> > +{
> > +	struct die_args *args = __args;
> > +	struct pt_regs *regs;
> > +	int cpu = smp_processor_id();
> > +
> > +	switch (cmd) {
> > +	case DIE_NMI:
> > +	case DIE_NMI_IPI:
> > +		break;
> > +
> > +	default:
> > +		return NOTIFY_DONE;
> > +	}
> > +
> > +	regs = args->regs;
> > +
> > +	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> > +		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
> > +
> > +		spin_lock(&lock);
> 
> 
> 
> This should be an arch_spin_lock(), so that it won't sleep with rt mutex.

ok, I just copied and pasted what was there currently.

> 
> 
> In fact this whole function can be moved to generic code, right?

generic for x86, yes.  Ingo stuck in the nmi.c code awhile ago.  This code
just needs a home somewhere.  I really don't care where.

Cheers,
Don

Re: [PATCH 5/6] [x86] watchdog: move trigger_all_cpu_backtrace to its own die_notifier

[Frederic Weisbecker]

On Wed, Apr 21, 2010 at 05:10:12PM -0400, Don Zickus wrote:
> On Wed, Apr 21, 2010 at 11:00:04PM +0200, Frederic Weisbecker wrote:
> > On Tue, Apr 20, 2010 at 11:24:02AM -0400, Don Zickus wrote:
> > > As part of the transition of the nmi watchdog to something more generic,
> > > the trigger_all_cpu_backtrace code is getting left behind.  Put it in its
> > > own die_notifier so it can still be used.
> > > 
> > > Signed-off-by: Don Zickus <dzickus@redhat.com>
> > > ---
> > >  arch/x86/kernel/apic/hw_nmi.c |   65 ++++++++++++++++++++++++++++++++---------
> > >  1 files changed, 51 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
> > > index 79425f9..19d3435 100644
> > > --- a/arch/x86/kernel/apic/hw_nmi.c
> > > +++ b/arch/x86/kernel/apic/hw_nmi.c
> > > @@ -17,6 +17,10 @@
> > >  #include <linux/cpumask.h>
> > >  #include <linux/kernel_stat.h>
> > >  #include <asm/mce.h>
> > > +#include <linux/kdebug.h>
> > > +#include <linux/notifier.h>
> > > +#include <linux/kprobes.h>
> > > +
> > >  
> > >  #include <linux/nmi.h>
> > >  #include <linux/module.h>
> > > @@ -54,20 +58,6 @@ int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
> > >  	unsigned int sum;
> > >  	int cpu = smp_processor_id();
> > >  
> > > -	/* FIXME: cheap hack for this check, probably should get its own
> > > -	 * die_notifier handler
> > > -	 */
> > > -	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> > > -		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
> > > -
> > > -		spin_lock(&lock);
> > > -		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);
> > > -		show_regs(regs);
> > > -		dump_stack();
> > > -		spin_unlock(&lock);
> > > -		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
> > > -	}
> > > -
> > >  	/* if we are doing an mce, just assume the cpu is not stuck */
> > >  	/* Could check oops_in_progress here too, but it's safer not to */
> > >  	if (mce_in_progress())
> > > @@ -109,6 +99,53 @@ void arch_trigger_all_cpu_backtrace(void)
> > >  		mdelay(1);
> > >  	}
> > >  }
> > > +
> > > +static int __kprobes
> > > +arch_trigger_all_cpu_backtrace_handler(struct notifier_block *self,
> > > +			 unsigned long cmd, void *__args)
> > > +{
> > > +	struct die_args *args = __args;
> > > +	struct pt_regs *regs;
> > > +	int cpu = smp_processor_id();
> > > +
> > > +	switch (cmd) {
> > > +	case DIE_NMI:
> > > +	case DIE_NMI_IPI:
> > > +		break;
> > > +
> > > +	default:
> > > +		return NOTIFY_DONE;
> > > +	}
> > > +
> > > +	regs = args->regs;
> > > +
> > > +	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> > > +		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
> > > +
> > > +		spin_lock(&lock);
> > 
> > 
> > 
> > This should be an arch_spin_lock(), so that it won't sleep with rt mutex.
> 
> ok, I just copied and pasted what was there currently.
> 
> > 
> > 
> > In fact this whole function can be moved to generic code, right?
> 
> generic for x86, yes.  Ingo stuck in the nmi.c code awhile ago.  This code
> just needs a home somewhere.  I really don't care where.


Ah right, this is x86 only, sorry.

[PATCH 6/6] [x86] watchdog: cleanup hw_nmi.c cruft

[Don Zickus]

The design of the hardlockup watchdog has changed and cruft was left
behind in the hw_nmi.c file.  Just remove the code that isn't used
anymore.

Signed-off-by: Don Zickus <dzickus@redhat.com>
---
 arch/x86/kernel/apic/hw_nmi.c |   58 -----------------------------------------
 1 files changed, 0 insertions(+), 58 deletions(-)

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 19d3435..1454dd2 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -9,74 +9,16 @@
  *
  */
 
-#include <asm/apic.h>
-#include <linux/smp.h>
 #include <linux/cpumask.h>
-#include <linux/sched.h>
-#include <linux/percpu.h>
-#include <linux/cpumask.h>
-#include <linux/kernel_stat.h>
-#include <asm/mce.h>
 #include <linux/kdebug.h>
 #include <linux/notifier.h>
 #include <linux/kprobes.h>
-
-
 #include <linux/nmi.h>
 #include <linux/module.h>
 
 /* For reliability, we're prepared to waste bits here. */
 static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
 
-static DEFINE_PER_CPU(unsigned, last_irq_sum);
-
-/*
- * 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)
-{
-	unsigned int irqs = per_cpu(irq_stat, cpu).irq0_irqs;
-
-#if defined(CONFIG_X86_LOCAL_APIC)
-	irqs += per_cpu(irq_stat, cpu).apic_timer_irqs;
-#endif
-
-	return irqs;
-}
-
-static inline int mce_in_progress(void)
-{
-#if defined(CONFIG_X86_MCE)
-	return atomic_read(&mce_entry) > 0;
-#endif
-	return 0;
-}
-
-int hw_nmi_is_cpu_stuck(struct pt_regs *regs)
-{
-	unsigned int sum;
-	int cpu = smp_processor_id();
-
-	/* if we are doing an mce, just assume the cpu is not stuck */
-	/* Could check oops_in_progress here too, but it's safer not to */
-	if (mce_in_progress())
-		return 0;
-
-	/* We determine if the cpu is stuck by checking whether any
-	 * interrupts have happened since we last checked.  Of course
-	 * an nmi storm could create false positives, but the higher
-	 * level logic should account for that
-	 */
-	sum = get_timer_irqs(cpu);
-	if (__get_cpu_var(last_irq_sum) == sum) {
-		return 1;
-	} else {
-		__get_cpu_var(last_irq_sum) = sum;
-		return 0;
-	}
-}
-
 u64 hw_nmi_get_sample_period(void)
 {
 	return (u64)(cpu_khz) * 1000 * 60;
-- 
1.6.5.2

[PATCH 7/6] [watchdog] resolve softlockup.c conflicts

[Don Zickus]

My changes with the softlockup code uses an older version of softlockup.c.
A couple of commits have been committed that were not on the branch I am
using.  This patch resolves those conflicts.

Commit 8c2eb4 softlockup: Stop spurious softlockup messages due to overflow
       d6ad3e softlockup: Add sched_clock_tick() to avoid kernel warning on kgdb resume

Conflicts:

	include/linux/sched.h
	kernel/kgdb.c
	kernel/softlockup.c

Signed-off-by: Don Zickus <dzickus@redhat.com>

--

Hi Ingo,

If there is a better way to deal with these conflicts please let me know.

---
 include/linux/sched.h |    4 ++++
 kernel/kgdb.c         |    6 +++---
 kernel/watchdog.c     |   17 ++++++++++++++++-
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0c128ad..e039e22 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -310,6 +310,7 @@ extern void sched_show_task(struct task_struct *p);
 #ifdef CONFIG_LOCKUP_DETECTOR
 extern void touch_watchdog(void);
 extern void touch_all_watchdogs(void);
+extern void touch_watchdog_sync(void);
 extern unsigned int  softlockup_panic;
 extern int softlockup_thresh;
 extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
@@ -322,6 +323,9 @@ static inline void touch_watchdog(void)
 static inline void touch_all_watchdogs(void)
 {
 }
+static inline void touch_watchdog_sync(void)
+{
+}
 #endif
 
 #ifdef CONFIG_DETECT_HUNG_TASK
diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 15df969..da98119 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -596,7 +596,7 @@ static void kgdb_wait(struct pt_regs *regs)
 
 	/* Signal the primary CPU that we are done: */
 	atomic_set(&cpu_in_kgdb[cpu], 0);
-	touch_watchdog();
+	touch_watchdog_sync();
 	clocksource_touch_watchdog();
 	local_irq_restore(flags);
 }
@@ -1450,7 +1450,7 @@ acquirelock:
 	    (kgdb_info[cpu].task &&
 	     kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 		atomic_set(&kgdb_active, -1);
-		touch_watchdog();
+		touch_watchdog_sync();
 		clocksource_touch_watchdog();
 		local_irq_restore(flags);
 
@@ -1550,7 +1550,7 @@ kgdb_restore:
 	}
 	/* Free kgdb_active */
 	atomic_set(&kgdb_active, -1);
-	touch_watchdog();
+	touch_watchdog_sync();
 	clocksource_touch_watchdog();
 	local_irq_restore(flags);
 
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 73529a8..9898c7c 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -33,6 +33,7 @@ int __read_mostly softlockup_thresh = 60;
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
+static DEFINE_PER_CPU(bool, watchdog_touch_sync);
 #define HARDLOCKUP	1
 #define SOFTLOCKUP	2
 static DEFINE_PER_CPU(char, watchdog_warn);
@@ -138,6 +139,12 @@ void touch_all_watchdogs(void)
 		per_cpu(watchdog_touch_ts, cpu) = 0;
 }
 
+void touch_watchdog_sync(void)
+{
+	__raw_get_cpu_var(watchdog_touch_sync) = true;
+	__raw_get_cpu_var(watchdog_touch_ts) = 0;
+}
+
 void touch_nmi_watchdog(void)
 {
 	touch_watchdog();
@@ -163,7 +170,7 @@ static int is_softlockup(unsigned long touch_ts, int cpu)
 	unsigned long now = get_timestamp(cpu);
 
 	/* Warn about unreasonable delays: */
-	if (now > (touch_ts + softlockup_thresh))
+	if (time_after(now, touch_ts + softlockup_thresh))
 		return now - touch_ts;
 
 	return 0;
@@ -254,6 +261,14 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 	hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
 
 	if (touch_ts == 0) {
+		if (unlikely(per_cpu(watchdog_touch_sync, this_cpu))) {
+			/*
+			 * If the time stamp was touched atomically
+			 * make sure the scheduler tick is up to date.
+			 */
+			per_cpu(watchdog_touch_sync, this_cpu) = false;
+			sched_clock_tick();
+		}
 		__touch_watchdog();
 		return HRTIMER_RESTART;
 	}
-- 
1.6.5.2