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SubjectRe: [PATCH] kernel/hung_task.c: Use continuously blocked time when reporting.
On Tue, Feb 26, 2019 at 10:58 AM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> Since commit a2e514453861dd39 ("kernel/hung_task.c: allow to set checking
> interval separately from timeout") added hung_task_check_interval_secs,
> setting a value different from hung_task_timeout_secs
>
> echo 0 > /proc/sys/kernel/hung_task_panic
> echo 120 > /proc/sys/kernel/hung_task_timeout_secs
> echo 5 > /proc/sys/kernel/hung_task_check_interval_secs
>
> causes confusing output as if the task was blocked for
> hung_task_timeout_secs seconds from the previous report.
>
> [ 399.395930] INFO: task kswapd0:75 blocked for more than 120 seconds.
> [ 405.027637] INFO: task kswapd0:75 blocked for more than 120 seconds.
> [ 410.659725] INFO: task kswapd0:75 blocked for more than 120 seconds.
> [ 416.292860] INFO: task kswapd0:75 blocked for more than 120 seconds.
> [ 421.932305] INFO: task kswapd0:75 blocked for more than 120 seconds.
>
> Although we could update t->last_switch_time after sched_show_task(t) if
> we want to report only every 120 seconds, reporting every 5 seconds might
> not be very bad for monitoring after a problematic situation has started.
> Thus, let's use continuously blocked time instead of updating previously
> reported time.
>
> [ 677.985011] INFO: task kswapd0:80 blocked for more than 122 seconds.
> [ 693.856126] INFO: task kswapd0:80 blocked for more than 138 seconds.
> [ 709.728075] INFO: task kswapd0:80 blocked for more than 154 seconds.
> [ 725.600018] INFO: task kswapd0:80 blocked for more than 170 seconds.
> [ 741.473133] INFO: task kswapd0:80 blocked for more than 186 seconds.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
> kernel/hung_task.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 4a91916..6429139 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -126,7 +126,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
> if (sysctl_hung_task_warnings > 0)
> sysctl_hung_task_warnings--;
> pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
> - t->comm, t->pid, timeout);
> + t->comm, t->pid, (jiffies - t->last_switch_time) / HZ);

Looks like an improvement to me.

Acked-by: Dmitry Vyukov <dvyukov@google.com>



> pr_err(" %s %s %.*s\n",
> print_tainted(), init_utsname()->release,
> (int)strcspn(init_utsname()->version, " "),
> --
> 1.8.3.1

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