Messages in this thread | | | Date | Mon, 30 Jan 2023 11:28:29 +0100 | From | Petr Mladek <> | Subject | Re: [RFC PATCH] hung_task: show sysctl_hung_task_warnings |
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On Sun 2023-01-29 17:08:29, Weiping Zhang wrote: > Sorry for the late reply. > > On Fri, Jan 13, 2023 at 9:43 PM Petr Mladek <pmladek@suse.com> wrote: > > > > On Thu 2023-01-12 17:17:45, Weiping Zhang wrote: > > > This patch try to add more debug info to detect lost kernel log or no > > > hung task was detected. > > > > > > The user set 10 to the hung_task_timeout_secs, the kernel log: > > > > > > [ 3942.642220] INFO: task mount:19066 blocked for more than 10 seconds. > > > [ 3952.876768] INFO: task kworker/u81:0:7 blocked for more than 10 seconds. > > > [ 3952.877088] INFO: task scsi_eh_0:506 blocked for more than 10 seconds. > > > [ 3952.878212] INFO: task mount:19066 blocked for more than 10 seconds. > > > [ 3963.116805] INFO: task kworker/u81:0:7 blocked for more than 10 seconds. > > > [ 3963.117137] INFO: task scsi_eh_0:506 blocked for more than 10 seconds. > > > [ 3963.118275] INFO: task mount:19066 blocked for more than 10 seconds. > > > [ 3973.356837] INFO: task kworker/u81:0:7 blocked for more than 10 seconds. > > > [ 3973.357148] INFO: task scsi_eh_0:506 blocked for more than 10 seconds. > > > [ 3973.358247] INFO: task mount:19066 blocked for more than 10 seconds. > > Expect but no hung task log at this moment. > > > > [ 3993.836899] INFO: task kworker/u81:0:7 blocked for more than 10 seconds. > > > [ 3993.837238] INFO: task scsi_eh_0:506 blocked for more than 10 seconds. > > > [ 3993.838356] INFO: task mount:19066 blocked for more than 10 seconds. > > > > > > There is no any log at about 3983, it's hard to know if kernel log was > > > lost or there is no hung task was detected at that moment. So this patch > > > print sysctl_hung_task_warnings to distinguish the above two cases. > > > > > > Signed-off-by: Weiping Zhang <zhangweiping@didiglobal.com> > > > --- > > > kernel/hung_task.c | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > > > index c71889f3f3fc..ca917931473d 100644 > > > --- a/kernel/hung_task.c > > > +++ b/kernel/hung_task.c > > > @@ -127,8 +127,11 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > > > * complain: > > > */ > > > if (sysctl_hung_task_warnings) { > > > - if (sysctl_hung_task_warnings > 0) > > > + if (sysctl_hung_task_warnings > 0) { > > > sysctl_hung_task_warnings--; > > > + pr_err("sysctl_hung_task_warnings: %d\n", > > > + sysctl_hung_task_warnings); > > > + } > > > > It is too much noise. But it might make sense to report it when > > the counter gets down to zero. Something like: > > > > if (sysctl_hung_task_warnings) > > pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n"); > > > > and move this down after printing all the details for this hung task report. > I'm fine to print this warning when it gets down to 0.
I prefer this variant.
> The warning counter is useful to detect kernel log lost or not, if add > a new line to print this count is too noise, > how about append this counter at the end of the following line: > pr_err("INFO: task %s:%d blocked for more than %ld seconds, > sysctl_hung_task_warnings: %d\n", > t->comm, t->pid, (jiffies - t->last_switch_time) / HZ, > sysctl_hung_task_warnings);
Is it really important to print this on every line, please? IMHO, most people do not care. IMHO. it would add more harm (confusion, noise) than good.
Best Regards, Petr
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