On Tue, Dec 04, 2012 at 06:58:42PM +0800, Chuansheng Liu wrote:
>
> Currently getting the sample period is always thru complex
> calculation: get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5).
> But just like the watchdog_thresh, which is not changed often.
>
> So we can store the sample period as a variable, and set it as
> __read_mostly type.
Seems safe and also helps the case of changing the value while running.
Now one has to disable/re-enable the watchdog to utilize the new value.
Acked-by: Don Zickus <dzic...@redhat.com>
>
> Signed-off-by: liu chuansheng <chuansheng....@intel.com>
> ---
> kernel/watchdog.c | 13 ++++++++-----
> 1 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/watchdog.c b/kernel/watchdog.c
> index dd4b80a..7a32b20 100644
> --- a/kernel/watchdog.c
> +++ b/kernel/watchdog.c
> @@ -31,6 +31,7 @@
> int watchdog_enabled = 1;
> int __read_mostly watchdog_thresh = 10;
> static int __read_mostly watchdog_disabled;
> +static u64 __read_mostly sample_period;
>
> static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
> static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
> @@ -116,7 +117,7 @@ static unsigned long get_timestamp(int this_cpu)
> return cpu_clock(this_cpu) >> 30LL; /* 2^30 ~= 10^9 */
> }
>
> -static u64 get_sample_period(void)
> +static void set_sample_period(void)
> {
> /*
> * convert watchdog_thresh from seconds to ns
> @@ -125,7 +126,7 @@ static u64 get_sample_period(void)
> * and hard thresholds) to increment before the
> * hardlockup detector generates a warning
> */
> - return get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
> + sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
> }
>
> /* Commands for resetting the watchdog */
> @@ -275,7 +276,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct
> hrtimer *hrtimer)
> wake_up_process(__this_cpu_read(softlockup_watchdog));
>
> /* .. and repeat */
> - hrtimer_forward_now(hrtimer, ns_to_ktime(get_sample_period()));
> + hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
>
> if (touch_ts == 0) {
> if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
> @@ -356,7 +357,7 @@ static void watchdog_enable(unsigned int cpu)
> hrtimer->function = watchdog_timer_fn;
>
> /* done here because hrtimer_start can only pin to smp_processor_id() */
> - hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
> + hrtimer_start(hrtimer, ns_to_ktime(sample_period),
> HRTIMER_MODE_REL_PINNED);
>
> /* initialize timestamp */
> @@ -383,7 +384,7 @@ static int watchdog_should_run(unsigned int cpu)
> /*
> * The watchdog thread function - touches the timestamp.
> *
> - * It only runs once every get_sample_period() seconds (4 seconds by
> + * It only runs once every 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().
> @@ -516,6 +517,7 @@ int proc_dowatchdog(struct ctl_table *table, int write,
> if (ret || !write)
> return ret;
>
> + set_sample_period();
> if (watchdog_enabled && watchdog_thresh)
> watchdog_enable_all_cpus();
> else
> @@ -537,6 +539,7 @@ static struct smp_hotplug_thread watchdog_threads = {
>
> void __init lockup_detector_init(void)
> {
> + set_sample_period();
> if (smpboot_register_percpu_thread(&watchdog_threads)) {
> pr_err("Failed to create watchdog threads, disabled\n");
> watchdog_disabled = -ENODEV;
> --
> 1.7.0.4
>
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
