linux-kernel - Re: OT: Re: System reboot triggered by just reading a device file....!?

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Date:	Sat, 24 Nov 2007 00:07:47 +0100
From:	devzero@....de
To:	Clemens Koller <clemens.koller@...gramm.de>
Cc:	Robert Hancock <hancockr@...w.ca>, linux-kernel@...r.kernel.org,
	Simon Arlott <simon@...e.lp0.eu>
Subject: Re: OT: Re: System reboot triggered by just reading a device file....!?

Hi Clemens, 

> 
> Hi, Roland!
> 
> Please don't top-post.

sorry!

>  > > [was: it would be easy to disable the kernel watchdog]
>  > thanks, but i know i could do this.
> 
> Good. I was also curious and just checked again. The watchdog subsystem
> is by default _disabled_ in the kernel configuration. If you use some
> distro's kernel, where they turned it on, complain to them!
> If you turned it on yourself, you are really on your own...
> the Kconfig help there is IMO sufficient and very clear and,
> "If unsure, say N". Hmm... sorry?!

whoops - sorry for that. i should have checked that, but i think i just didn`t expect some distro vendor to change that default.
sure i will complain to suse now. stopping getting on your nerves here, now.


>  > this thread is not meant to protect myself from this curiousity but it is meant
>  > to protect others. it`s a trap.
> 
> I guess I understand your position. But I don't see no way to improve
> the kernel in that point.
> Complain to the guys who enabled the watchdog / setup this trap for
> any reason.

sure. you`re completely right.


>  > i stepped into that.
>  > now i know that trap, so i can easily sidestep.
>  > it maybe very seldom that someone steps into this.
>  > but it may happen and then someone will have trouble and spend time on this.
>  > i think every admin can tell you about weird random reboots of his systems
>  > which he cannot explain what was the reason for it.
> 
> That's one possible way of "learning by doing suicide (tm);"

:)

>  > this maybe some of those reasons and this one could be avoided.
>  > i`m thinking of something simple like echo "now you`re armed" > /dev/watchdog
> 
> Read some details about watchdogs to get more background and why the
> watchdog is triggered so easily and why it's good this way.
> i.e: http://www.ganssle.com/watchdogs.pdf

thanks for your help and for that very useful link. that`s the very best stuff i every read about watchdogs!

regards
Roland

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