Re: [Fastboot] [PATCH] kdump: add a missing notifier before crashing

[Vivek Goyal <vgoyal@in.ibm.com>]

On Mon, Jun 19, 2006 at 10:49:32AM -0600, Eric W. Biederman wrote:
> Preben Traerup <Preben.Trarup@ericsson.com> writes:
> 
> > Strictly speaking for myself: Nothing.
> >
> > Mr. Akiyama Nobuyuk gave an example from his environment which is cluster
> > systems.
> > I was the one saying we in our Telco systems could use this feature too.
> >
> > The only thing Mr. Akiyama Nobuyuk and I have in common is we both would like to
> > do
> > something before crash dumping, simply because the less mess we will have to
> > cleanup
> > afterwards in the system taking over, the better.
> >
> > Mr. Akiyama Nobuyuk operates on SCSI devices to avoid filesystem corruptions.
> > My usage would be more like notifying external management to get traffic
> > redirected to server systems taking over.
> 
> Ok. That resolves some of my confusion.
> 
> After think this over here is my position.
> 
> There may be cases where it is warranted to add a call during crash_kexec.
> I have seen no evidence that the cases where we want something happening
> in crash_kexec are going to be at all common. It is my opinion anything
> added to the crash_kexec path needs a case by case review.
> 
> Therefore if something is needs to happen in the crash kexec path it
> should be a direct function call.  No pointers and no hooks.  Just call
> the function.
> 
> Patches that and add an explicit function call allow for case by case review
> and convey the message that you really don't want to do that, and that we
> are really dealing with an exceptional circumstance.
> 
> Does this sound like a reasonable position?

Sounds like trouble for modules. I am assuming that code to power down the
scsi disks/controller will be part of the driver, which is generally built
as a module and also assuming that powering down the disks is a valid
requirement after the crash.

After introducing an option to disable/enable crash notifiers from user
space I think now responsibility lies to with user. If he chooses to enable
the notifiers, he understands that there are chances that we never boot
into the next kernel and get lost in between. 

Thanks
Vivek