*
* 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
+ * Note: Most of this code is borrowed heavily from the original softlockup
+ * detector, so thanks to Ingo for the initial implementation.
+ * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
* to those contributors as well.
*/
+#define pr_fmt(fmt) "NMI watchdog: " fmt
+
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/nmi.h>
#include <linux/perf_event.h>
int watchdog_enabled = 1;
-int __read_mostly softlockup_thresh = 60;
+int __read_mostly watchdog_thresh = 10;
static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
__setup("nosoftlockup", nosoftlockup_setup);
/* */
+/*
+ * Hard-lockup warnings should be triggered after just a few seconds. Soft-
+ * lockups can have false positives under extreme conditions. So we generally
+ * want a higher threshold for soft lockups than for hard lockups. So we couple
+ * the thresholds with a factor: we make the soft threshold twice the amount of
+ * time the hard threshold is.
+ */
+static int get_softlockup_thresh(void)
+{
+ return watchdog_thresh * 2;
+}
/*
* Returns seconds, approximately. We don't need nanosecond
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
+ * convert watchdog_thresh from seconds to ns
+ * the divide by 5 is to give hrtimer several chances (two
+ * or three with the current relation between the soft
+ * and hard thresholds) to increment before the
+ * hardlockup detector generates a warning
*/
- return softlockup_thresh * (NSEC_PER_SEC / 5);
+ return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
}
/* Commands for resetting the watchdog */
unsigned long now = get_timestamp(smp_processor_id());
/* Warn about unreasonable delays: */
- if (time_after(now, touch_ts + softlockup_thresh))
+ if (time_after(now, touch_ts + get_softlockup_thresh()))
return now - touch_ts;
return 0;
}
#ifdef CONFIG_HARDLOCKUP_DETECTOR
+
static struct perf_event_attr wd_hw_attr = {
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
};
/* Callback function for perf event subsystem */
-static void watchdog_overflow_callback(struct perf_event *event, int nmi,
+static void watchdog_overflow_callback(struct perf_event *event,
struct perf_sample_data *data,
struct pt_regs *regs)
{
if (__this_cpu_read(soft_watchdog_warn) == true)
return HRTIMER_RESTART;
- printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
+ printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
print_modules();
*/
static int watchdog(void *unused)
{
- static struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+ struct sched_param param = { .sched_priority = 0 };
struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
- sched_setscheduler(current, SCHED_FIFO, ¶m);
-
/* initialize timestamp */
__touch_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 watchdog_timer_fn().
+ * Run briefly (kicked by the hrtimer callback function) once every
+ * get_sample_period() seconds (4 seconds by default) to reset the
+ * softlockup timestamp. If this gets delayed for more than
+ * 2*watchdog_thresh seconds then the debug-printout triggers in
+ * watchdog_timer_fn().
*/
while (!kthread_should_stop()) {
__touch_watchdog();
set_current_state(TASK_INTERRUPTIBLE);
}
+ /*
+ * Drop the policy/priority elevation during thread exit to avoid a
+ * scheduling latency spike.
+ */
__set_current_state(TASK_RUNNING);
-
+ sched_setscheduler(current, SCHED_NORMAL, ¶m);
return 0;
}
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, NULL, watchdog_overflow_callback);
+ wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
+
+ /* Try to register using hardware perf events */
+ event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
if (!IS_ERR(event)) {
- printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
+ pr_info("enabled, takes one hw-pmu counter.\n");
goto out_save;
}
/* vary the KERN level based on the returned errno */
if (PTR_ERR(event) == -EOPNOTSUPP)
- printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
+ pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
else if (PTR_ERR(event) == -ENOENT)
- printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
+ pr_warning("disabled (cpu%i): hardware events not enabled\n",
+ cpu);
else
- printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
+ pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
+ cpu, PTR_ERR(event));
return PTR_ERR(event);
/* success path */
#endif /* CONFIG_HARDLOCKUP_DETECTOR */
/* prepare/enable/disable routines */
-static int watchdog_prepare_cpu(int cpu)
+static void 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)
/* create the watchdog thread */
if (!p) {
- p = kthread_create(watchdog, (void *)(unsigned long)cpu, "watchdog/%d", cpu);
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+ p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
if (IS_ERR(p)) {
- printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
+ pr_err("softlockup watchdog for %i failed\n", cpu);
if (!err) {
/* if hardlockup hasn't already set this */
err = PTR_ERR(p);
}
goto out;
}
+ sched_setscheduler(p, SCHED_FIFO, ¶m);
kthread_bind(p, cpu);
per_cpu(watchdog_touch_ts, cpu) = 0;
per_cpu(softlockup_watchdog, cpu) = p;
}
}
+/* sysctl functions */
+#ifdef CONFIG_SYSCTL
static void watchdog_enable_all_cpus(void)
{
int cpu;
watchdog_enabled = 1;
if (!watchdog_enabled)
- printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
+ pr_err("failed to be enabled on some cpus\n");
}
}
-/* sysctl functions */
-#ifdef CONFIG_SYSCTL
/*
- * proc handler for /proc/sys/kernel/nmi_watchdog
+ * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
*/
-int proc_dowatchdog_enabled(struct ctl_table *table, int write,
- void __user *buffer, size_t *length, loff_t *ppos)
+int proc_dowatchdog(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
{
- proc_dointvec(table, write, buffer, length, ppos);
+ int ret;
- if (write) {
- if (watchdog_enabled)
- watchdog_enable_all_cpus();
- else
- watchdog_disable_all_cpus();
- }
- return 0;
-}
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (ret || !write)
+ goto out;
-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);
+ if (watchdog_enabled && watchdog_thresh)
+ watchdog_enable_all_cpus();
+ else
+ watchdog_disable_all_cpus();
+
+out:
+ return ret;
}
#endif /* CONFIG_SYSCTL */
cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
int hotcpu = (unsigned long)hcpu;
- int err = 0;
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- err = watchdog_prepare_cpu(hotcpu);
+ watchdog_prepare_cpu(hotcpu);
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
if (watchdog_enabled)
- err = watchdog_enable(hotcpu);
+ watchdog_enable(hotcpu);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_UP_CANCELED:
Code Review / linux-2.6.git / blobdiff