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

[Vivek Goyal]

On Mon, Jun 26, 2006 at 11:51:52AM -0500, Miller, Mike (OS Dev) wrote:
[..]
> > kdump or taking crash dumps using the kexec on panic 
> > mechanism could be called a drivers worst nightmare.  In the 
> > latest distros this is becoming the way crash dump style 
> > information is captured.
> > 
> > Because the initial kernel is broken we do a jump into 
> > another kernel that is sufficient to record a crash dump.  
> > That second kernel initializes the hardware from whatever 
> > random state the first kernel left the drivers in.  That 
> > first kernel is not permitted to do any device shutdown activities.
> > 
> > The problem is that a command the running instance of the 
> > driver did not initiate completes.  At least if I read Vivek 
> > patch 2/2 correctly.
> > 
> > So we have three options.
> > - reset the card during initialization.
> > - handle the case of a command we did not initiate completing.
> > - mark the driver/card as impossibly hopeless for use in a crash
> >   dump scenario.
> > 
> > 
> > Eric
> 
> 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.
> 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.

That's the precise reason of introducing the "crashboot" command line
parameter. Driver authors can check against this condition and reset
the device and 99.9% of the users are not impacted.

Thanks
Vivek

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/