RE: [Fastboot] [RFC] [PATCH 2/2] kdump: cciss driver initialization issue fix

["Miller, Mike (OS Dev)" <Mike.Miller@hp.com>]

> -----Original Message-----
> From: Eric W. Biederman [mailto:ebiederm@xmission.com] 
> Sent: Monday, June 26, 2006 2:21 PM
> To: Miller, Mike (OS Dev)
> Cc: vgoyal@in.ibm.com; Maneesh Soni; Andrew Morton; 
> Neela.Kolli@engenio.com; linux-scsi@vger.kernel.org; 
> fastboot@lists.osdl.org; linux-kernel@vger.kernel.org
> Subject: Re: [Fastboot] [RFC] [PATCH 2/2] kdump: cciss driver 
> initialization issue fix
> 
> >> "Miller, Mike (OS Dev)" <Mike.Miller@hp.com> writes:
> >> 
> >> > Thanks Eric, that helps me understand. Section 8.2.2 of the
> >> open cciss
> >> > spec supports a reset message. Target 0x00 is the
> >> controller. We could
> >> > add this to the init routine to ensure the board is made 
> sane again 
> >> > but this would drastically increase init time under normal
> >> circumstances.
> >> 
> >> Where does the init time penalty come from? How large is the init 
> >> penalty?  I suspect it is from waiting for the scsi disks 
> to spin up.
> >> But I am just guessing in the dark.
> >
> > The penalty is in the firmware and self-test operations.
> 
> Ok.  Reasonable. Roughly long does that take? 1 millisecond? 1 second?
> 1 minute? 1 hour? 

Sorry, roughly 30 to 40 seconds. Maybe longer if the controller thinks
there's something wrong with the disks. Typically the disks are always
spinning so that delay is not an issue.

> 
> >> > And I suspect this is a hard reset, also. Not sure if that would 
> >> > negatively impact kdump. If there were some condition we 
> could test 
> >> > against and perform the reset when that condition is met it
> >> would not
> >> > impact 99.9% of users.
> >> 
> >> I am wondering if it is possible to look at the controller 
> and see if 
> >> it is in a bad state, (i.e. in some state besides just 
> coming out of 
> >> reset) and if so issue a reset.  If this really is a long 
> operation 
> >> that would be the ideal way to handle it.
> >
> > It's not really in a bad state at this time, is it? Maybe some 
> > commands hanging around.
> 
> Not bad as in broken.  But bad as in unexpected.  If it is 
> just a matter of outstanding commands we might even be able 
> to just ask the adapter to cancel all of the at initialization time.

We can't detect unexpected but we can discard everything at init.

> >
> > I was informed of the crashboot command line parameter. I can 
> > implement that as a test.
> 
> Sounds like a start.
> 
> >> Although it might simply be appropriate to handle commands 
> completing 
> >> you didn't start.  I am not at all familiar with that particular 
> >> piece of hardware so I can't make a good guess on what needs to 
> >> happen there.
> >
> > Not sure about doing this.
> 
> Well I would certainly print a warning.
> 
> Eric
> 
> 
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