linux-kernel - Re: [PATCH] lockup_detector: Make DETECT_HUNT_TASK default depend on LOCKUP

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Date:	Sat, 7 Aug 2010 09:01:35 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] lockup_detector: Make DETECT_HUNT_TASK default depend on
 LOCKUP_DETECTOR


(Linus Cc:-ed)

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

> On Wed, Aug 04, 2010 at 09:53:03AM +0800, Li Zefan wrote:
> > CONFIG_DETECT_SOFTLOCKUP has been removed, so switch the
> > default value to LOCKUP_DETECTOR.
> > 
> > Also fix the help text of BOOT_PRINTK_DELAY.
> > 
> > Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> > ---
> 
> 
> Acked-by: Frederic Weisbecker <fweisbec@...il.com>
> 
> Thanks.

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.

So i turned off the new generic watchdog code's default intentionally - as it 
clearly does not cure cancer ;-)

I think distros will enable it, and most testers will as well. Those who dont 
enable it and run into a lockup have an easy option to enable.

Maybe a better change would be to make it more generally available - right now 
it's:

 config LOCKUP_DETECTOR
         bool "Detect Hard and Soft Lockups"
         depends on DEBUG_KERNEL && !S390

which means that it cannot be enabled when DEBUG_KERNEL is off.

So i think we should:

 - Remove the s390 hack and add an ARCH_HAS_LOCKUP_DETECTOR flag
 - Remove the DEBUG_KERNEL dependency

Hm?

Thanks,

	Ingo
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