Re: [PACTH v1] kernel/hung_task.c: Dump all UNINTERUPTIBLE tasks

[Robert Foss]

On 2016-08-11 12:35 PM, Robert Foss wrote:
> On 2016-08-10 06:43 PM, Andrew Morton wrote:
> > On Tue,  2 Aug 2016 11:23:11 -0400 robert.foss@xxxxxxxxxxxxx wrote:
> >
> > > From: Aaron Durbin <adurbin@xxxxxxxxxxxx>
> > >
> > > When the panic path is taken for khungtaskd dump all
> > > tasks with the UNINTERUPTIBLE state. That way, any
> > > inter-dependent tasks that caused one another to hang
> > > will be saved in the crash output.
> > >
> > > ...
> > >
> > > --- a/kernel/hung_task.c
> > > +++ b/kernel/hung_task.c
> > > @@ -122,6 +122,8 @@ static void check_hung_task(struct task_struct
> > > *t, unsigned long timeout)
> > >      touch_nmi_watchdog();
> > >
> > >      if (sysctl_hung_task_panic) {
> > > +        /* Dump all tasks. */
> > > +        show_state_filter(TASK_UNINTERRUPTIBLE);
> > >          trigger_all_cpu_backtrace();
> > >          panic("hung_task: blocked tasks");
> > >      }
> >
> > Well, it's going to produce more gunk for the operator to read through
> > and understand.
> >
> > I'd like to hear a little more about the value of this change: what
> > particular problem prompted it, etc.
>
> It would indeed provide more gunk. What makes it useful is that is on
> enabled by default and enables rapid debugging of devices that are not
> physically accessible or accessible for debugging otherwise.
>
> So the primary usecase would be when a user of a device is seeing some
> issues and submits the logs from the device.
> Without any further action from the user, the problem could potentially
> be solved.

The debug output could be formatted better, would that make this patch 
more appealing?