watchdog: store the watchdog sample period as a variable
Currently getting the sample period is always thru a complex calculation: get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5). We can store the sample period as a variable, and set it as __read_mostly type. Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> Cc: Don Zickus <dzickus@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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2bf0a8f67f
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0f34c40091
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@ -31,6 +31,7 @@
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int watchdog_enabled = 1;
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int __read_mostly watchdog_thresh = 10;
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static int __read_mostly watchdog_disabled;
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static u64 __read_mostly sample_period;
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static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
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static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
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@ -116,7 +117,7 @@ static unsigned long get_timestamp(int this_cpu)
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return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
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}
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static u64 get_sample_period(void)
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static void set_sample_period(void)
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{
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/*
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* convert watchdog_thresh from seconds to ns
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@ -125,7 +126,7 @@ static u64 get_sample_period(void)
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* and hard thresholds) to increment before the
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* hardlockup detector generates a warning
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*/
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return get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
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sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
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}
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/* Commands for resetting the watchdog */
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@ -275,7 +276,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
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wake_up_process(__this_cpu_read(softlockup_watchdog));
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/* .. and repeat */
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hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
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hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
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if (touch_ts == 0) {
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if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
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@ -356,7 +357,7 @@ static void watchdog_enable(unsigned int cpu)
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hrtimer->function = watchdog_timer_fn;
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/* done here because hrtimer_start can only pin to smp_processor_id() */
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hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
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hrtimer_start(hrtimer, ns_to_ktime(sample_period),
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HRTIMER_MODE_REL_PINNED);
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/* initialize timestamp */
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@ -386,7 +387,7 @@ static int watchdog_should_run(unsigned int cpu)
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/*
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* The watchdog thread function - touches the timestamp.
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*
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* It only runs once every get_sample_period() seconds (4 seconds by
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* It only runs once every sample_period seconds (4 seconds by
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* default) to reset the softlockup timestamp. If this gets delayed
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* for more than 2*watchdog_thresh seconds then the debug-printout
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* triggers in watchdog_timer_fn().
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@ -519,6 +520,7 @@ int proc_dowatchdog(struct ctl_table *table, int write,
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if (ret || !write)
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return ret;
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set_sample_period();
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if (watchdog_enabled && watchdog_thresh)
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watchdog_enable_all_cpus();
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else
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@ -540,6 +542,7 @@ static struct smp_hotplug_thread watchdog_threads = {
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void __init lockup_detector_init(void)
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{
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set_sample_period();
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if (smpboot_register_percpu_thread(&watchdog_threads)) {
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pr_err("Failed to create watchdog threads, disabled\n");
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watchdog_disabled = -ENODEV;
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