Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks

Arjan van de Ven
2007-12-03T01:01:05Z

On Mon, 3 Dec 2007 01:07:41 +0100
Andi Kleen <andi@firstfloor.org> wrote:

> > We really need to get better diagnostics for the
> > bad-kernel-behavior-that-is-seen-as-bug cases. If we ever want to
> > get to the scenario where we have a more or less robust measure of
> > kernel quality (and we're not all that far off for several cases),
> > one thing
>
> One measure to kernel quality is to recover well from IO errors
> (like network problems or broken block devices)

yes. and this patch will flag cases that don't (yet) work well

>
> This patch will likely work against that by breaking error paths.

it won't break error paths, it will at most put a warning in the log.
It doesn't kill or otherwise damage the system or process.

>
> > This patch is a step in the right direction there, by quite a
> > lot.
> >
> > I really don't understand what your objection is to this patch...
> > is it that an enterprise distro can't ship with it on? (Which is
> > fine btw)
>
> Any distribution aimed at end users cannot ship with it on.

That's a pretty bold statement; assuming that the TASK_KILLABLE patch
is in, I don't see the problem.

And even if a distro doesn't turn it on, I still don't see a problem;
it's a diagnostics patch that people can turn on (even at runtime) if
they see problems.

> Also in general I have my doubts that the false positive:real bug
> ratio of this warning is well balanced.

I'll just have to disagree with you then; but both of us are making
wild guesses. Only one way to get the real false positive percentage.

> Just consider the original
> example of dead network servers. Even in my relatively small
> home network that that is a quite common occurrence. This patch
> will break that all by throwing random backtraces when this
> happens.

1) with TASK_KILLABLE that shouldn't happen
2) how does "throwing a backtrace" "break" things?

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