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DateSun, 8 Aug 2010 23:23:11 +0200
FromIngo Molnar <>
SubjectRe: [PATCH] lockup_detector: Make DETECT_HUNT_TASK default depend on LOCKUP_DETECTOR

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> > The thing is, CONFIG_DETECT_SOFTLOCKUP was default-y before, so many
> > people had it enabled [and had it forced-enabled if DEBUG_KERNEL was off],
> > even if they didnt really want or need it.
>
> Hmm. It was:
>
> config DETECT_SOFTLOCKUP
> bool "Detect Soft Lockups"
> depends on DEBUG_KERNEL && !S390
> default y
>
> It means it's default enabled only if DEBUG_KERNEL, right? Then if you don't
> select CONFIG_DEBUG_KERNEL, it's fine as it won't be selected.

Indeed, you are right.

Anyway, i think the general point remains: i'm not sure we should
default-enable this feature.

> But I agree with you. There is a bunch of config options for which selection
> is a duty when you are a kernel developer: PROVE_LOCKING, DETECT_HUNG_TASK,
> DEBUG_PREEMPT, PROVE_RCU, etc... Because they all show (or prove we can
> have) bugs that one might miss without these options. Softlockups are rarely
> part of them because even without the lockup detector enabled, you'll
> observe something is wrong.

Note that it's now detecting all kinds of lockups: softlockups, hard lockups
and even unkillable hung tasks.

Ingo


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